Determinants of temporal variability in NHEXAS-Maryland environmental concentrations, exposures, and biomarkers

Personal PM2.5-bound PAH exposure and lung function in healthy office workers: A pilot study in Beijing and Baoding, China

The effect of short-term exposure to polycyclic aromatic hydrocarbons (PAHs) on the respiratory system among healthy residents is unclear. Beijing and Baoding are typical polluted cities in China, and there is little research on PAH exposure and its health effects at the individual level. Fourteen healthy female office workers were recruited in urban Beijing and Baoding, China, in 2019. The personal exposure to fine particulate matter (PM_2.5)-bound PAHs and lung function were seasonally monitored. The relationships between PAH exposure and lung function were determined by a generalized mixed linear model. Subjects were exposed to high levels of PAH, in which the benzo[a]pyrene (BaP) level (1.26 ng/m³) was over than Chinese national indoor standard (1 ng/m³). All PAHs concentration was higher in winter than that in summer and autumn. Only benz[a]anthracene (BaA) and chrysene (Chr) exposure showed weak relations with decreased lung function, i.e., a 0.58% and 0.73% decrease in peak expiratory flow at lag 2 day, respectively (p < 0.05). PAHs may not be suitable exposure indicators for short-term change in lung function. Our findings highlight the importance of reducing PAH pollution for public respiratory health protection in heavy-polluted cities of China. This pilot study also provides experience on personal PAH assessment such as estimation of the number of repeated measurements required, which is helpful to determine the relationship between PAH exposure and health effect.

Blood metal/metalloid concentration of male subjects undergoing IVF/ICSI treatment outcomes: A prospective cohort study

BACKGROUND

Previous epidemiology studies reported that heavy metal/metalloid exposure is associated with the impairment of semen quality. However, it is still not clear whether the in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) treatment outcome will be affected after the heavy metal/metalloid exposure of the male partners.

METHODS

A prospective cohort study with a 2-year followed-up was conducted in a tertiary IVF center. A total of 111 couples undergoing IVF/ICSI treatment were initially recruited from November 2015 to November 2016. Male blood concentrations of heavy metal/metalloid including Ca, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Mo, Cd, Hg, and Pb were measured by inductively coupled plasma mass spectrometry, and the lab and pregnancy outcome data were followed up. The associations between male blood heavy metal/metalloid concentration and the clinical outcomes were analyzed by Poisson regression analysis.

RESULTS

Our results showed that none of the heavy metal/metalloid of male partners we investigated are significantly associated with the oocyte fertilization and good embryo (P ≥ 0.05); however, antral follicle count (AFC) was a protective factor for the oocyte fertilization (RR: 1.07, 95 % CI: 1.04-1.10). The blood Fe concentration of the male partner was positively associated (P < 0.05) with pregnancy in the first fresh cycle (RR:170.93, 95 % CI: 4.13-7082.04), cumulative pregnancy (RR: 23.61, 95 % CI: 3.25-171.64) and cumulative live birth (RR: 36.42, 95 % CI: 1.21-1092.54). In the first frozen embryo cycles, pregnancy was significantly associated (P < 0.05) with the blood Mn (RR: 0.01, 95 % CI:0.00-0.11) and Se concentration (RR: 0.01, 95 % CI:8.25 E-5-0.47) and female age (RR: 0.86, 95 % CI:0.75-0.99); live birth was significantly associated (P < 0.05) with the blood Mn concentration (RR: 0.00, 95 % CI: 1.14E-7-0.51).

CONCLUSIONS

Our results suggested that the higher male blood Fe concentration was positively associated with pregnancy in the fresh embryo transfer cycle, cumulative pregnancy, and cumulative live birth, whereas the higher male blood Mn and Se concentration were associated with lower chance of pregnancy and live birth in the frozen embryo transfer cycle. However, the underline mechanism of this finding still needs further investigation.

Characteristics and determinants of personal exposure to typical air pollutants: A pilot study in Beijing and Baoding, China

Personal exposure to fine particulate matter (PM_2.5), nitrogen oxides (NO_x, NO₂ and NO), ozone (O₃) and sulfur dioxide (SO₂) was repeatedly measured among fourteen office workers in Beijing and Baoding, China in summer, autumn and winter of 2019. Time-activity patterns were simultaneously recorded. Determinants of personal air pollution exposure were investigated for each pollutant via a linear mixed effect model. The personal concentrations of PM_2.5, NO₂, NO and O₃ were higher in autumn and winter than those in summer. A decreasing trend was found in the personal PM_2.5 level for a typical indoor population in Beijing, indicating that particulate pollution was effectively controlled in Beijing and its surrounding area. The personal levels of PM_2.5, NO₂, and O₃ were weakly correlated with those monitored at ambient stations and were lower than the respective ambient levels except for PM_2.5 in summer and NO₂ in winter. This pilot study showed that the indoor air environment, ambient pollution, traffic-related variables and temperature were significant exposure sources for office workers. Our study highlighted the significance of controlling traffic emissions and improving the workplace air quality to protect the health of office workers. More importantly, we demonstrated the feasibility of model development for personal air pollution exposure prediction.

Associations of Heavy Metals with Activities of Daily Living Disability: An Epigenome-Wide View of DNA Methylation and Mediation Analysis

BACKGROUND

Exposure to heavy metals has been reported to be associated with multiple diseases. However, direct associations and potential mechanisms of heavy metals with physical disability remain unclear.

OBJECTIVES

We aimed to quantify associations of heavy metals with physical disability and further explore the potential mechanisms of DNA methylation on the genome scale.

METHODS

A cross-sectional study of 4,391 older adults was conducted and activities of daily living (ADL) disability were identified using a 14-item scale questionnaire including basic and instrumental activities to assess the presence of disability (yes or no) rated on a scale of dependence. Odds ratios (ORs) and 95% confidence intervals (CI) were estimated to quantify associations between heavy metals and ADL disability prevalence using multivariate logistic regression and Bayesian kernel machine regression (BKMR) models. Whole blood-derived DNA methylation was measured using the HumanMethylationEPIC BeadChip array. An ADL disability-related epigenome-wide DNA methylation association study (EWAS) was performed among 212 sex-matched ADL disability cases and controls, and mediation analysis was further applied to explore potential mediators of DNA methylation.

RESULTS

Each 1-standard deviation (SD) higher difference in log10-transformed manganese, copper, arsenic, and cadmium level was significantly associated with a 14% (95% CI: 1.05, 1.24), 16% (95% CI:1.07, 1.26), 22% (95% CI:1.13, 1.33), and 15% (95% CI:1.06, 1.26) higher odds of ADL disability, which remained significant in the multiple-metal and BKMR models. A total of 85 differential DNA methylation sites were identified to be associated with ADL disability prevalence, among which methylation level at cg220000984 and cg23012519 (annotated to IRGM and PKP3) mediated 31.0% and 31.2% of manganese-associated ADL disability prevalence, cg06723863 (annotated to ESRP2) mediated 32.4% of copper-associated ADL disability prevalence, cg24433124 (nearest to IER3) mediated 15.8% of arsenic-associated ADL disability prevalence, and cg07905190 and cg17485717 (annotated to FREM1 and TCP11L1) mediated 21.5% and 30.5% of cadmium-associated ADL disability prevalence (all p<0.05).

DISCUSSION

Our findings suggested that heavy metals contributed to higher prevalence of ADL disability and that locus-specific DNA methylation are partial mediators, providing potential biomarkers for further cellular mechanism studies. https://doi.org/10.1289/EHP10602.

Spatio-temporal assessment of pregnant women exposure to chlorpyrifos at a regional scale

BACKGROUND

The aim of this study was to use an integrated exposure assessment approach, combining spatiotemporal modeling of environmental exposure and fate of the chemical to assess the exposure of vulnerable populations. In this study, chlorpyrifos exposure of pregnant women in Picardy was evaluated at a regional scale during 1 year. This approach provided a mapping of exposure indicators of pregnant women to chlorpyrifos over fine spatial and temporal resolutions using a GIS environment.

METHODS

Fate and transport models (emission, atmospheric dispersion, multimedia exposure, PBPK) were combined with environmental databases in a GIS environment. Quantities spread over agricultural fields were simulated and integrated into a modeling chain coupling models. The fate and transport of chlorpyrifos was characterized by an atmospheric dispersion statistical metamodel and the dynamiCROP model. Then, the multimedia model Modul'ERS was used to predict chlorpyrifos daily exposure doses which were integrated in a PBPK model to compute biomarker of exposure (TCPy urinary concentrations). For the concentration predictions, two scenarios (lower bound and upper bound) were built.

RESULTS

At fine spatio-temporal resolutions, the cartography of biomarkers in the lower bound scenario clearly highlights agricultural areas. In these maps, some specific areas and hotspots appear as potentially more exposed specifically during application period. Overall, predictions were close to biomonitoring data and ingestion route was the main contributor to chlorpyrifos exposure.

CONCLUSIONS

This study demonstrated the feasibility of an integrated approach for the evaluation of chlorpyrifos exposure which allows the comparison between modeled predictions and biomonitoring data.

Identifying Jurisdictions at Risk of Containing Housing Units With Deteriorated Paint: Results and Targeting Implications for the US Department of Housing and Urban Development

CONTEXT

The US Department of Housing and Urban Development provides millions in annual funding to make low-income housing lead safe, but funds are limited relative to need. To adequately target efforts, local program administrators must identify neighborhoods that are the most "at risk" of residential lead exposure; however, no federal agency currently provides a public data set for this use.

OBJECTIVES

To examine pre-1980 households with large areas of deteriorated paint, a significant and common predictor of lead dust, and identify high-risk jurisdictions. To highlight the potential use of a newly available data set for strategic lead poisoning prevention and targeting.

DESIGN

Microdata from the 2011 American Housing Survey and the 2009-2013 American Community Survey were used to develop a household-level predicted risk metric that identifies housing units at risk of containing large areas of deteriorated paint. Predicted risk, defined as the mean predicted percentage of occupied housing units at risk of containing deteriorated paint within a given jurisdiction, was summarized by state, county, and tract.

SETTING

National, all occupied housing units.

PARTICIPANTS

Occupied housing units summarized by household (n = 9 363 000), census tract (n = 72 235), county (n = 3143), and state (n = 51).

MAIN OUTCOME MEASURE

Housing units built prior to 1980 with a large area of deteriorated paint.

RESULTS

New York, Rhode Island, New Jersey, Massachusetts, and Pennsylvania had the highest predicted percentage of at-risk households (range: 2.52%-2.90%). County-level and tract-level estimates are the most useful when examining a predefined jurisdiction; New York state was presented as a case study. County-level quartile risk scores revealed Albany as an at-risk jurisdiction. Tract-level quartile risk scores further identified at-risk neighborhoods in northeastern Albany.

CONCLUSIONS

Findings can help housing and health policy makers identify and target geographic areas with a high probability of households at risk of potential exposure to deteriorated lead-based paint.

Combined exposure to multiple metals and cognitive function in older adults

Single toxic metal exposure has been reported to be associated with impaired cognitive function, but less is known about the effects of combined exposure to multiple metals. The aim of the study was to investigate the potential associations and interactions of multiple metals with cognitive function in older adults using multi-pollutants approach. A cross-sectional study was conducted in a total of 2879 participants aged ≥ 60 years old. We systematically measured levels of 22 blood metals and used the Mini-Mental State Examination (MMSE) to assess the cognitive function. The least absolute shrinkage and selection operator (LASSO) penalized regression was applied to identify independently main metals. Adjusted estimates of cognitive function with selected metals were investigated by generalized linear regression in the multi-metal model. We found that calcium, titanium, vanadium, copper, zinc, arsenic, selenium, rubidium, molybdenum, cadmium, barium, and lead were independently identified based on LASSO penalized regression. The multi-metal model showed a higher MMSE of 0.384 (95% CI: 0.122-0.646) for a 1-SD increment in log-transformed rubidium and a lower MMSE of 0.460 (95% CI: - 0.706 to - 0.214) for a 1-SD increment in log-transformed cadmium (P < 0.05). The significantly negative associations between cadmium and cognitive function were attenuated to null accompanying with increasing concentrations of rubidium (P _interaction = 0.256). Our findings suggested that blood rubidium and cadmium were mainly associated with cognitive function when accounting for co-exposure to other metals and higher level of rubidium appeared to attenuate the toxic effects of cadmium on cognitive function in older adults.

Temporal variability of indoor dust concentrations of semivolatile organic compounds

The determinants of the temporal variability of indoor dust concentrations of semivolatile organic compounds (SVOCs) remain mostly unexplored. We examined temporal variability of dust concentrations and factors affecting dust concentrations for a wide range of SVOCs. We collected dust samples three times from 29 California homes during a period of 22 months and quantified concentrations of 47 SVOCs in 87 dust samples. We computed intraclass correlation coefficients (ICCs) using three samples collected within the same house. We calculated correlation coefficients (r) between two seasons with similar climate (spring and fall) and between two seasons with opposite climate (summer and winter). Among 26 compounds that were detected in more than 50% of the samples at all three visits, 20 compounds had ICCs above 0.50 and 6 compounds had ICCs below 0.50. For 19 out of 26 compounds, correlation coefficients between spring and fall (r = 0.48-0.98) were higher than those between summer and winter (r = 0.09-0.92), implying seasonal effects on dust concentrations. Our study showed that within-home temporal variability of dust concentrations was small (ICC > 0.50) for most SVOCs, but dust concentrations may vary over time for some SVOCs with seasonal variations in source rates, such as product use.

Associations between blood metal/ metalloid concentration and human semen quality and sperm function: A cross-sectional study in Hong Kong

BACKGROUND

The association between metal/metalloid exposure on human sperm quality is still inconclusive. There is a lack of data on the effect of metal/metalloid on sperm function.

METHODS

The aim of this study was to clarify the association between blood metal/metalloid concentration and traditional and functional sperm parameters, the blood concentration of Pb, Hg, Cd, As, Ni, Mo, Zn, Cu, Se, Fe, Mg, Cr and Ca of 288 men in Hong Kong were assessed by inductively coupled plasma-mass spectrometry, and sperm parameters including sperm concentration, motility, morphology, vitality, total sperm count, total motile sperm count, sperm DNA fragmentation and sperm acrosome reaction were measured. Demographic and lifestyle questionnaires were also provided for all participants. Multivariable linear regression analysis was performed to test the association between blood metal/ metalloid concentration and semen parameters after adjusting for relevant confounding variables.

RESULTS

The results showed that moderate to high level of blood Pb concentration (>27.19 μg/L) appeared to be negatively associated with sperm morphology (P < 0.05); high level of blood Cd concentration (>1.44 μg/L) was negatively associated with sperm acrosome reaction (P < 0.05); Mo was positively associated with semen volume (P < 0.05), however, high level of blood Mo concentration (>13.52 μg/L) was negatively associated with sperm vitality (P < 0.05); high level of blood Zn concentration (>6.20 mg/L) was positively associated with sperm vitality (P < 0.05); moderate level of blood Fe concentration (526.89-566.63 mg/L) was positively associated with sperm acrosome reaction (P < 0.05); moderate level of blood Ca concentration (55.92-66.10 mg/L) was positively associated with semen volume (P < 0.05); however, lower level of blood Ca concentration (45.90-55.92 mg/L) was negatively associated with sperm morphology (P < 0.05).

CONCLUSIONS

Our results suggested that the sperm function could be affected by blood Cd and Fe concentration and traditional sperm parameters could be affected by blood concentration of Mo, Zn, Pb and Ca.

The associations of multiple metals mixture with accelerated DNA methylation aging

Aging is a leading cause of mortality for the elderly and DNA methylation age is reported to be predictive of biological aging. However, few studies have investigated the associations between multiple metals exposure and accelerated aging in the elderly. We performed a pilot study of 288 elderly participants aged 50-115 years and measured genome-wide DNA methylation and 22 blood metals concentrations. Measures of DNA methylation age were estimated using CpGs from Illumina HumanMethylation EPIC BeadChip. Linear mixed regression and Bayesian kernel machine regression (BKMR) models were used to estimate the individual and overall associations between multiple metals and accelerated methylation aging. Single metal models revealed that each 1-standard deviance (SD) increase in log-transformed vanadium, cobalt, nickel, zinc, arsenic, and barium was associated with a -2.256, -1.318, 1.004, -1.926, 1.910 and -1.356 changes in ΔAge, respectively; meanwhile, for aging rate, the change was -0.019, -0.013, 0.010, -0.018, 0.023, and -0.012, respectively (all P < 0.05). The BKMR models showed reverse U-shaped associations of the overall metals mixture with ΔAge and aging rate. Downward trends of ΔAge and aging rate were observed for increasing quantiles of essential metals mixture, but upward trends were observed for non-essential metals mixture. Further individual analysis of the BKMR revealed that the 95% confidence interval of ΔAge and aging rate associated with vanadium, zinc, and arsenic did not cross 0, when other metals concentrations set at 25th, 50th, and 75th percentile. Our findings suggest reverse U-shaped associations of the overall metals mixture with accelerated methylation aging for the first time, and vanadium, zinc, and arsenic may be major contributors driving the associations.

Evaluation of 1-year urinary excretion of eight metabolites of synthetic pyrethroids, chlorpyrifos, and neonicotinoids

Synthetic pyrethroids, chlorpyrifos, and neonicotinoids are representatives of non-persistent insecticides ubiquitously used against insects all over the world. Their widespread use causes prevalent exposure to these compounds, which may be hazardous to human health. The insecticides have short biological half-lives and are mostly excreted in urine within 24 h after entering the human body; thus, the urinary concentration of their metabolites is highly dependent on the time elapsed between exposure and sample collection. Considering the within-day fluctuations in urinary concentration, one randomly collected sample may cause misclassification of long-term exposure. We evaluated the variability of excretion of eight insecticide metabolites in 24-h urine samples collected from 14 volunteers once or twice per month over 12 consecutive months. High detection frequency above 70% for non-specific metabolites of pyrethroid, chlorpyrifos, and neonicotinoids confirmed widespread exposure to these insecticides in the studied population. A long-term variability of exposure was assessed based on intraclass correlation coefficient (ICC). We found relatively low variability of excretion for non-specific pyrethroid metabolites and 3,5,6-trichloro-2-pyridinol (ICC > 0.75), but poor repeatability for 6-chloronicotinic acid. Constantly higher ICCs were observed for daily excretion than for unadjusted concentrations. Seasonal differences were observed for 3,5,6-trichloro-2-pyridinol and 6-chloronicotinic acid, with the highest and the lowest median concentration, respectively, in the summer. Due to high ICC values and lack of seasonal variations, one 24-h urine sample was considered sufficient to characterize long-term excretion of non-specific pyrethroid metabolites in non-occupationally exposed population. In addition, we calculated the daily intake (DI) for cypermethrin, permethrin, deltamethrin, and chlorpyrifos. The estimated DI values were mostly below the acceptable daily intake, which indicates that the evaluated exposure is non-hazardous to the population.

Polycyclic aromatic hydrocarbons (PAHs) levels in urine samples collected in a subarctic region of the Northwest Territories, Canada

Traditional food consumption for Indigenous peoples is associated with improved nutrition and health but can also pose potential risks via exposure to contaminants. Polycyclic aromatic hydrocarbons (PAHs) are compounds of interest due to their widespread presence (e.g., their metabolites are detected in up to 100% of the Canadian population) and their toxicological potential. To better understand the range of exposures faced by Indigenous populations in northern Canada and to address a contaminant of emerging concern identified by the Arctic Monitoring and Assessment Programme, a multi-year biomonitoring study investigated levels of PAH exposure in subarctic First Nations communities of the Northwest Territories, Canada. Secondary data analysis of banked samples from a subset of the cross-sectional study was done. PAHs and cotinine markers in the urine samples (n = 97) of participants from two regions from the Mackenzie Valley (Dehcho and Sahtú) was completed by liquid and gas chromatography coupled with mass spectrometry. Also, participants completed a 24-hr recall food survey. When compared according to age/sex categories, the GM of several biomarkers (1-hydroxypyrene, 1-naphthol, 2-hydroxyfluorene, 2-hydroxyphenanthrene, 2-naphthol, 3-hydroxyfluorene, 3-hydroxyphenanthrene, 4-hydroxyphenanthrene, 9-hydroxyfluorene, 9-hydroxyphenanthrene) appeared higher than observed for the general Canadian population. The PAHs levels observed were, however, below clinical levels associated with adverse health outcomes. Altogether, these elevated biomarkers are metabolites of pyrene, naphthalene, fluorene and phenanthrene. Statistically significant non-parametric associations were observed between several biomarkers and i) the consumption of cooked meat in the last 24 h; and, ii) smoking status (self-reported status and adjusted on urine cotinine level). This work is the first to report PAH levels in a northern Canadian population and provides local baseline data for monitoring the effects of changes to climate and lifestyle over time. These findings will support regional and territorial decision makers in identifying environmental health priorities.

Calibrating an agent-based model of longitudinal human activity patterns using the Consolidated Human Activity Database

Patterns of human behavior over extended periods of time are important for characterizing human exposure to hazardous chemicals. Because longitudinal behavior patterns for an individual are difficult to obtain, exposure-assessors have characterized such patterns by linking daily records from multiple individuals. In an earlier publication, we developed an alternative strategy that was based on agent-based simulation modeling. Specifically, we created a software program, Agent-Based Model of Human Activity Patterns (ABMHAP), that generates year-long longitudinal behavior patterns. In this paper, we both calibrate and evaluate ABMHAP using human behavior data from the U.S. Environmental Protection Agency's Consolidated Human Activity Database (CHAD). We use the longitudinal data (data on individuals' activities over multiple days) in CHAD to parameterize ABMHAP, and we use single-day behavior data from CHAD to evaluate ABMHAP predictions. We evaluate ABMHAP's ability to simulate sleeping, eating, commuting, and working (or attending school) for four populations: working adults, nonworking adults, school-age children, and preschool children. The results demonstrate that ABMHAP, when parameterized with empirical data, can capture both interindividual and intraindividual variation in behaviors in different types of individuals. We propose that simulating annual activity patterns via ABMHAP may allow exposure-assessors to characterize exposure-related behavior in ways not possible with traditional survey methods.

Simulating exposure-related behaviors using agent-based models embedded with needs-based artificial intelligence

Exposure to a chemical is a critical consideration in the assessment of risk, as it adds real-world context to toxicological information. Descriptions of where and how individuals spend their time are important for characterizing exposures to chemicals in consumer products and in indoor environments. Herein we create an agent-based model (ABM) that simulates longitudinal patterns in human behavior. By basing the ABM upon an artificial intelligence (AI) system, we create agents that mimic human decisions on performing behaviors relevant for determining exposures to chemicals and other stressors. We implement the ABM in a computer program called the Agent-Based Model of Human Activity Patterns (ABMHAP) that predicts the longitudinal patterns for sleeping, eating, commuting, and working. We then show that ABMHAP is capable of simulating behavior over extended periods of time. We propose that this framework, and models based on it, can generate longitudinal human behavior data for use in exposure assessments.

Temporal variability in urinary pesticide concentrations in repeated-spot and first-morning-void samples and its association with oxidative stress in healthy individuals

Exposure of humans to pesticides is widespread. Measurement of urinary levels of pesticides and their metabolites is often used in the assessment of body burdens and exposure doses to these chemicals. An understanding of temporal variability in urinary levels of pesticides within individuals is critical for accurate exposure assessment. We examined within- and between-individual variability in concentrations of nine organophosphate and pyrethroid insecticides as well as two phenoxy herbicides in urine collected consecutively for up to 44 days from 19 individuals. Seven oxidative stress biomarkers also were measured in urine samples to elucidate their relationship with pesticide exposure. Intraclass correlation coefficients (ICCs) were calculated to assess reproducibility in urinary pesticide concentrations from repeated measures. Sensitivity and specificity analyses were performed to evaluate the suitability of spot urine to characterize average exposures. Data analysis was further limited to seven pesticides and their metabolites, which had a detection frequency of >60%. Poor reproducibility was found for the seven pesticides and their metabolites in both spot (ICCs ≤0.24) and first-morning-void (FMV) samples (ICCs <0.38) collected during the 44-day study period. Use of single-spot or FMV sample to classify high (top 33%) concentrations showed high specificities (0.73-0.85) but low sensitivities (0.45-0.70). The minimum number of samples (k) required per individual to estimate participant-specific mean value for pesticides (within 20% of the "true" values) were 28-140 and 18-119 for spot and FMV samples, respectively. Repeated longitudinal measurements of these pesticides and their metabolites in urine showed considerable within-individual variability in both spot and FMV samples. Urinary concentrations of seven pesticides and their metabolites were significantly correlated with oxidative damage to lipids, proteins, and DNA.

The Fort Collins commuter study: Variability in personal exposure to air pollutants by microenvironment

This study investigated the role of microenvironment on personal exposures to black carbon (BC), fine particulate mass (PM2.5 ), carbon monoxide (CO), and particle number concentration (PNC) among adult residents of Fort Collins, Colorado, USA. Forty-four participants carried a backpack containing personal monitoring instruments for eight nonconsecutive 24-hour periods. Exposures were apportioned into five microenvironments: Home, Work, Transit, Eateries, and Other. Personal exposures exhibited wide heterogeneity that was dominated by within-person variability (both day-to-day and between microenvironment variability). Linear mixed-effects models were used to compare mean personal exposures in each microenvironment, while accounting for possible within-person correlation. Mean personal exposures during Transit and at Eateries tended to be higher than exposures at Home, where participants spent the majority of their time. Compared to Home, mean exposures to BC in Transit were, on average, 129% [95% confidence interval: 101% 162%] higher and exposures to PNC were 180% [101% 289%] higher in Eateries.

Determinants of personal exposure to fine particulate matter (PM2.5) in adult subjects in Hong Kong

Personal monitoring for fine particulate matter (PM_2.5) was conducted for adults (48 subjects, 18-63years of age) in Hong Kong during the summer and winter of 2014-2015. All filters were analyzed for PM_2.5 mass and constituents (including carbonaceous aerosols, water-soluble ions, and elements). We found that season (p=0.02) and occupation (p<0.001) were significant factors affecting the strength of the personal-ambient PM_2.5 associations. We applied mixed-effects models to investigate the determinants of personal exposure to PM_2.5 mass and constituents, along with within- and between-individual variance components. Ambient PM_2.5 was the dominant predictor of (R²=0.12-0.59, p<0.01) and the largest contributor (>37.3%) to personal exposures for PM_2.5 mass and most components. For all subjects, a one-unit (2.72μg/m³) increase in ambient PM_2.5 was associated with a 0.75μg/m³ (95% CI: 0.59-0.94μg/m³) increase in personal PM_2.5 exposure. The adjusted mixed-effects models included information extracted from individual's activity diaries as covariates. The results showed that season, occupation, time indoors at home, in transit, and cleaning were significant determinants for PM_2.5 components in personal exposure (R²_β=0.06-0.63, p<0.05), contributing to 3.0-70.4% of the variability. For one-hour extra time spent at home, in transit, and cleaning an average increase of 1.7-3.6% (ammonium, sulfate, nitrate, sulfur), 2.7-12.3% (elemental carbon, ammonium, titanium, iron), and 8.7-19.4% (ammonium, magnesium ions, vanadium) in components of personal PM_2.5 were observed, respectively. In this research, the within-individual variance component dominated the total variability for all investigated exposure data except PM_2.5 and EC. Results from this study indicate that performing long-term personal monitoring is needed for examining the associations of mass and constituents of personal PM_2.5 with health outcomes in epidemiological studies by describing the impacts of individual-specific data on personal exposures.

Comparison of gaseous polycyclic aromatic hydrocarbon metabolites according to their specificity as biomarkers of occupational exposure: Selection of 2-hydroxyfluorene and 2-hydroxyphenanthrene

Exposure to Polycyclic Aromatic Hydrocarbons (PAHs) occurs by respiratory, digestive and dermal absorption. Biomonitoring takes all pathways into account but sensitive and specific biomarkers are required. Different gaseous PAHs metabolites were used due to their abundance in the atmospheric mixtures but none of them were selected as better biomarker than the others. To identify the best candidates for assessing occupational airborne exposure, relation between atmospheric levels of Naphtalene, Fluorene and Phenanthrene and urinary metabolites concentrations was studied in a carbon electrode workers group. Linear mixed effects models were built to select explanatory variables and estimate variance component. Urinary creatinine was a predictor of metabolites levels confirming the importance of diuresis for interpreting results. High significance of pre-shift sampling time combined with positive coefficients of post-shift indicated that urine should be sampled at the end of the workday in association with pre-shift urine to avoid misinterpretations. Among the 10 metabolites studied, urinary 2-hydroxyfluorene and 2-hydroxyphenanthrene showed the highest increase of variance explained by models after inclusion of individual atmospheric levels as explanatory variable. Priority could be given to 2-hydroxyfluorene due to higher excretion levels than 2-hydroxyphenanthrene.

Polycyclic aromatic hydrocarbons (PAHs) in indoor dust samples from Cities of Jeddah and Kuwait: Levels, sources and non-dietary human exposure

This study reports levels and profiles of polycyclic aromatic hydrocarbons (PAHs) in dust samples collected from three different microenvironments (cars, air conditioner (AC) filters and household floor dust) of Jeddah, Saudi Arabia (KSA) and Kuwait. To the best of our knowledge, this is first study reporting PAHs in indoor microenvironments of KSA, which makes these findings important. Benzo(b)fluoranthene (BbF), benzo(a)pyrene (BaP), phenanthrene (Phe), and pyrene (Pyr) were found to be the major chemicals in dust samples from all selected microenvironments. ΣPAHs occurred at median concentrations (ng/g) of 3450, 2200, and 2650 in Saudi AC filter, car and household floor dust, respectively. The median levels (ng/g) of ΣPAHs in Kuwaiti car (950) and household floor (1675) dust samples were lower than Saudi dust. The PAHs profile in Saudi dust was dominated by high molecular weight (HMW) (4-5 ring) PAHs while in Kuwaiti dust 3 ring PAHs have marked contribution. BaP equivalent, a marker for carcinogenic PAHs, was high in Saudi household floor and AC filter dust with median levels (ng/g) of 370 and 455, respectively. Different exposure scenarios, using 5th percentile, median, mean, and 95th percentile levels, were estimated for adults and toddlers. For Saudi and Kuwaiti toddlers worst exposure scenario of ΣPAHs was calculated at 175 and 85ng/kg body weight/day (ng/kgbw/d), respectively. For Saudi toddlers, the calculated worst exposure scenarios for carcinogenic BaP (27.7) and BbF (29.3ng/kgbw/d) was 2-4 times higher than Kuwaiti toddlers. This study is based on small number of samples which necessitate more detailed studies for better understanding of dynamics of PAHs in the indoor environments of this region. Nevertheless, our finding supports the ongoing exposure of organic pollutants to population that accumulates indoor.

Urinary microRNAs as potential biomarkers of pesticide exposure

MicroRNAs (miRNAs) are post-transcriptional regulators that silence messenger RNAs. Because miRNAs are stable at room temperature and long-lived, they have been proposed as molecular biomarkers to monitor disease and exposure status. While urinary miRNAs have been used clinically as potential diagnostic markers for kidney and bladder cancers and other diseases, their utility in non-clinical settings has yet to be fully developed. Our goal was to investigate the potential for urinary miRNAs to act as biomarkers of pesticide exposure and early biological response by identifying the miRNAs present in urine from 27 parent/child, farmworker/non-farmworker pairs (16FW/11NFW) collected during two agricultural seasons (thinning and post-harvest) and characterizing the between- and within-individual variability of these miRNA epigenetic regulators. MiRNAs were isolated from archived urine samples and identified using PCR arrays. Comparisons were made between age, households, season, and occupation. Of 384 miRNAs investigated, 297 (77%) were detectable in at least one sample. Seven miRNAs were detected in at least 50% of the samples, and one miRNA was present in 96% of the samples. Principal components and hierarchical clustering analyses indicate significant differences in miRNA profiles between farmworker and non-farmworker adults as well as between seasons. Six miRNAs were observed to be positively associated with farmworkers status during the post-harvest season. Expression of five of these miRNA trended towards a positive dose response relationship with organophosphate pesticide metabolites in farmworkers. These results suggest that miRNAs may be novel biomarkers of pesticide exposure and early biological response.

Biomonitoring of blood heavy metals and reproductive hormone level related to low semen quality

Reproductive hormones and exposure to environmental metals are correlated with low-quality semen. The aim of this study was to evaluate the levels of heavy metals and reproductive hormones in the blood in addition to other relevant factors to clarify the relationship between these factors and semen quality. We recruited 154 male participants from a reproductive medical center. All participants were provided with a questionnaire on lifestyle implementation. The levels of metals in the blood were determined using inductively coupled plasma-mass spectrometry. The levels of hormones in the blood were determined using an automatic gamma counter. Multiple logistic regression analyses were conducted to predict the effects of statistically significant risk factors on semen quality by adjusting for relevant confounders and modifiers. After adjusting for the age, education level, and related factors in the multiple logistic regression analyses, we observed that the increased blood Pb levels were significantly and positively associated with low semen quality. High blood Pb levels (>50 μg/L) had an 11-fold risk of low semen quality. Our results suggest that progressive motility sperm may be a sensitive indicator of the semen quality among all the semen parameters in Taiwan.

Dust metal loadings and the risk of childhood acute lymphoblastic leukemia

We evaluated the relationship between the risk of childhood acute lymphoblastic leukemia (ALL) and the levels of metals in carpet dust. A dust sample was collected from the homes of 142 ALL cases and 187 controls participating in the California Childhood Leukemia Study using a high volume small surface sampler (2001-2006). Samples were analyzed using microwave-assisted acid digestion in combination with inductively coupled plasma mass spectrometry for arsenic, cadmium, chromium, copper, lead, nickel, tin, tungsten, and zinc. Eight metals were detected in at least 85% of the case and control homes; tungsten was detected in <15% of homes. Relationships between dust metal loadings (μg metal per m(2) carpet) and ALL risk were modeled using multivariable logistic regression, adjusting for the child's age, sex, and race/ethnicity and confounders, including household annual income. A doubling of dust metal loadings was not associated with significant changes in ALL risk (odds ratio (95% confidence interval): arsenic: 0.96 (0.86, 1.07), cadmium: 0.92 (0.81, 1.05), chromium: 1.01 (0.90, 1.14), copper: 0.97 (0.91, 1.03), lead: 1.01 (0.93, 1.10), nickel: 0.95 (0.82, 1.09), tin: 0.96 (0.86, 1.08), and zinc: 0.94 (0.84, 1.05)). Our findings do not support the hypothesis that metals in carpet dust are risk factors for childhood ALL.

Spatiotemporal analysis and human exposure assessment on polycyclic aromatic hydrocarbons in indoor air, settled house dust, and diet: A review

This review summarizes the published literature on the presence of polycyclic aromatic hydrocarbons (PAH) in indoor air, settled house dust, and food, and highlights geographical and temporal trends in indoor PAH contamination. In both indoor air and dust, ΣPAH concentrations in North America have decreased over the past 30 years with a halving time of 6.7±1.9years in indoor air and 5.0±2.3 years in indoor dust. In contrast, indoor PAH concentrations in Asia have remained steady. Concentrations of ΣPAH in indoor air are significantly (p<0.01) higher in Asia than North America. In studies recording both vapor and particulate phases, the global average concentration in indoor air of ΣPAH excluding naphthalene is between 7 and 14,300 ng/m(3). Over a similar period, the average ΣPAH concentration in house dust ranges between 127 to 115,817ng/g. Indoor/outdoor ratios of atmospheric concentrations of ΣPAH have declined globally with a half-life of 6.3±2.3 years. While indoor/outdoor ratios for benzo[a]pyrene toxicity equivalents (BaPeq) declined in North America with a half-life of 12.2±3.2 years, no significant decline was observed when data from all regions were considered. Comparison of the global database, revealed that I/O ratios for ΣPAH (average=4.3±1.3), exceeded significantly those of BaPeq (average=1.7±0.4) in the same samples. The significant decline in global I/O ratios suggests that indoor sources of PAH have been controlled more effectively than outdoor sources. Moreover, the significantly higher I/O ratios for ΣPAH compared to BaPeq, imply that indoor sources of PAH emit proportionally more of the less carcinogenic PAH than outdoor sources. Dietary exposure to PAH ranges from 137 to 55,000 ng/day. Definitive spatiotemporal trends in dietary exposure were precluded due to relatively small number of relevant studies. However, although reported in only one study, PAH concentrations in Chinese diets exceeded those in diet from other parts of the world, a pattern consistent with the spatial trends observed for concentrations of PAH in indoor air. Evaluation of human exposure to ΣPAH via inhalation, dust and diet ingestion, suggests that while intake via diet and inhalation exceeds that via dust ingestion; all three pathways contribute and merit continued assessment.

The Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort study: assessment of environmental exposures

The Canadian Healthy Infant Longitudinal Development birth cohort was designed to elucidate interactions between environment and genetics underlying development of asthma and allergy. Over 3600 pregnant mothers were recruited from the general population in four provinces with diverse environments. The child is followed to age 5 years, with prospective characterization of diverse exposures during this critical period. Key exposure domains include indoor and outdoor air pollutants, inhalation, ingestion and dermal uptake of chemicals, mold, dampness, biological allergens, pets and pests, housing structure, and living behavior, together with infections, nutrition, psychosocial environment, and medications. Assessments of early life exposures are focused on those linked to inflammatory responses driven by the acquired and innate immune systems. Mothers complete extensive environmental questionnaires including time-activity behavior at recruitment and when the child is 3, 6, 12, 24, 30, 36, 48, and 60 months old. House dust collected during a thorough home assessment at 3-4 months, and biological specimens obtained for multiple exposure-related measurements, are archived for analyses. Geo-locations of homes and daycares and land-use regression for estimating traffic-related air pollution complement time-activity-behavior data to provide comprehensive individual exposure profiles. Several analytical frameworks are proposed to address the many interacting exposure variables and potential issues of co-linearity in this complex data set.

Association between environmental exposure to cadmium and human semen quality

Cadmium (Cd) is a heavy metal with toxicant to reproductive functions. The aim of this study was to explore the effects of environmental exposure to Cd on human semen quality. A total of 587 men from the general population, aged from 20 to 59 years old, and without occupational exposure to Cd were recruited from three provinces in China to participate in the study. The median of serum Cd was 1.9 μg/L (P25-P75:1.1-2.9). In case Cd was less than or equal to 6.3 μg/L (P95) and the semen parameters were logarithmically transformed, the inverse associations between Cd and semen volume (-0.03 ± 0.007), progressive motility (-0.01 ± 0.004), and sperm morphology (-0.04 ± 0.004) were found across the whole group, after adjusting for age group, occupation, season of semen sample collection, abstinence intervals, smoking, alcohol drinking, and body mass index. Our findings indicate that higher Cd may reduce the semen volume, progressive motility, and morphology among men without occupational exposure to Cd.

Effect measure modification of blood lead-air lead slope factors

There is abundant literature finding that susceptibility factors, including race and ethnicity, age, and housing, directly influence blood lead levels. No study has explored how susceptibility factors influence the blood lead-air lead relationship nationally. The objective is to evaluate whether susceptibility factors act as effect measure modifiers on the blood lead-air lead relationship. Participant level blood lead data from the 1999 to 2008 National Health and Nutrition Examination Survey were merged with air lead data from the US Environmental Protection Agency. Linear mixed effects models were run with and without an air lead interaction term for age group, sex, housing age, or race/ethnicity to determine whether these factors are effect measure modifiers for all ages combined and for five age brackets. Age group and race/ethnicity were determined to be effect measure modifiers in the all-age model and for some age groups. Being a child (1-5, 6-11, and 12-19 years) or of Mexican-American ethnicity increased the effect estimate. Living in older housing (built before 1950) decreased the effect estimate for all models except for the 1-5-year group, where older housing was an effect measure modifier. These results are consistent with the peer-reviewed literature of time-activity patterns, ventilation, and toxicokinetics.

Drinking water studies: a review on heavy metal, application of biomarker and health risk assessment (a special focus in Malaysia)

Malaysia has abundant sources of drinking water from river and groundwater. However, rapid developments have deteriorated quality of drinking water sources in Malaysia. Heavy metal studies in terms of drinking water, applications of health risk assessment and bio-monitoring in Malaysia were reviewed from 2003 to 2013. Studies on heavy metal in drinking water showed the levels are under the permissible limits as suggested by World Health Organization and Malaysian Ministry of Health. Future studies on the applications of health risk assessment are crucial in order to understand the risk of heavy metal exposure through drinking water to Malaysian population. Among the biomarkers that have been reviewed, toenail is the most useful tool to evaluate body burden of heavy metal. Toenails are easy to collect, store, transport and analysed. This review will give a clear guidance for future studies of Malaysian drinking water. In this way, it will help risk managers to minimize the exposure at optimum level as well as the government to formulate policies in safe guarding the population.

Associations between self-reported pest treatments and pesticide concentrations in carpet dust

BACKGROUND

Recent meta-analyses demonstrate an association between self-reported residential pesticide use and childhood leukemia risk. Self-reports may suffer from recall bias and provide information only on broad pesticide categories. We compared parental self-reported home and garden pest treatments to pesticides measured in carpet dust.

METHODS

Parents of 277 children with leukemia and 306 controls in Northern and Central California (2001-2007) were asked about insect and weed treatments during the previous year. Carpet dust samples were analyzed for 47 pesticides. We present results for the 7 insecticides (carbaryl, propoxur, chlorpyrifos, diazinon, cyfluthrin, cypermethrin, permethrin), 5 herbicides (2,4-dichlorophenoxyacetic acid [2,4-D], chlorthal, dicamba, mecoprop, simazine), and 1 synergist (piperonyl butoxide) that were present in home and garden products during the study period and were detected in ≥25% of carpet dust samples. We constructed linear regression models for the relative change in pesticide concentrations associated with self-reported treatment of pest types in cases and controls separately and combined, adjusting for demographics, housing characteristics, and nearby agricultural pesticide applications.

RESULTS

Several self-reported treatments were associated with pesticide concentrations in dust. For example, households with flea/tick treatments had 2.3 (95% Confidence Interval [CI]: 1.4, 3.7) times higher permethrin concentrations than households not reporting this treatment. Households reporting treatment for ants/cockroaches had 2.5 (95% CI: 1.5, 4.2) times higher cypermethrin levels than households not reporting this treatment. Weed treatment by a household member was associated with 1.9 (1.4, 2.6), 2.2 (1.6, 3.1), and 2.8 (2.1, 3.7) times higher dust concentrations of dicamba, mecoprop, and 2,4-D, respectively. Weed treatments by professional applicators were null/inversely associated with herbicide concentrations in dust. Associations were generally similar between cases and controls and were consistent with pesticide active ingredients in these products during the study time period.

CONCLUSIONS

Consistency between self-reported pest treatments, concentrations in dust, and pesticides in products lends credibility to the exposure assessment methods and suggests that differential recall by case-control status is minimal.

Temporal variation of residential pesticide use and comparison of two survey platforms: a longitudinal study among households with young children in Northern California

BACKGROUND

Pesticide use patterns are essential inputs into human pesticide exposure models. Currently, data included for modeling purposes have mostly been collected in cross-sectional surveys. However, it is questionable whether responses to one-time surveys are representative of pesticide use over longer periods, which is needed for assessment of health impact. This study was designed to evaluate population-wide temporal variations and within-household variations in reported residential pesticide use patterns and to compare alternative pesticide data collection methods - web surveys versus telephone interviews.

METHOD

A total of 481 households in Northern California provided up to 3 annual telephone interviews on residential pesticide use; 182 of these households provided up to 6 quarterly web surveys that covered the same topics for some of the same time periods. Information on frequency and areas of application were collected for outdoor and indoor sprays, indoor foggers, professional applications, and behind-the-neck treatments for pets. Population-wide temporal variation and within-household consistency were examined both within telephone surveys and within web surveys, and quantified using Generalized Estimating Equations and Mixed Effect Modeling. Reporting between the two methods, the telephone survey and the web survey, was also compared.

RESULTS

Use prevalence of outdoor sprays across the population reported in both the annual telephone surveys and the quarterly web surveys decreased over time, as did behind-the-neck treatment of pets reported in the quarterly web survey. Similarly, frequencies of use of these products decreased in the quarterly web surveys. Indoor sprays showed no statistically significant population-wide temporal variation in either survey. Intraclass correlation coefficients indicated consistent use within a household for behind-the-neck treatment on pets and outdoor sprays but great variability for the use of indoor sprays. Indoor sprays were most consistently applied in the bathroom and kitchen. Outdoor sprays were consistently more often applied by male household members, while indoor sprays were not. The two survey approaches obtained fairly similar results on the prevalence of using pesticides, but found discrepancies in use frequencies. In addition, the number of products purchased was positively correlated with application frequency for outdoor sprays (R = 0.51, p = 0.0005) but not for indoor sprays.

CONCLUSIONS

In this population, repeated surveys are necessary either to obtain a reliable estimate of the average household use of pesticides or to project potential temporal changes of pesticide use. Web surveys could collect comparable data to traditional telephone surveys for some information. However, researchers need to consider the internet acceptability among the target population and balance lower participant burden against the need for sufficiently accurate time-varying measurement, to improve subject retention in longitudinal surveys.

Urinary 3,5,6-trichloro-2-pyridinol (TCPY) in pregnant women from Mexico City: distribution, temporal variability, and relationship with child attention and hyperactivity

Attention Deficit Hyperactivity Disorder (ADHD) is the most commonly diagnosed and studied cognitive and behavioral disorder in school-age children. The etiology of ADHD and ADHD-related behavior is unclear, but genetic and environmental factors, such as pesticides, have been hypothesized. The objective of this study was to investigate the relationship between in utero exposure to chlorpyrifos, chlorpyrifos-methyl, and/or 3,5,6-trichloro-2-pyridinol (TCPY) and ADHD in school-age Mexican children using TCPY as a biomarker of exposure. The temporal reliability of repeated maternal urinary TCPY concentrations across trimesters was also explored (N=21). To explore associations with ADHD-related outcomes in children, third trimester urinary TCPY concentrations in were measured in 187 mother-child pairs from a prospective birth cohort. Child neurodevelopment in children 6-11 years of age was assessed using Conners' Parental Rating Scales-Revised (CRS-R), Conners' Continuous Performance Test (CPT), and Behavior Assessment System for Children-2 (BASC-2). Multivariable linear regression models were used to test relationships for all children combined and also stratified by sex. Intraclass correlation coefficients (ICC) calculations were based on a random effects model. The ICC was 0.41 for uncorrected TCPY, and ranged from 0.29 to 0.32 for specific gravity-corrected TCPY. We did not observe any statistically significant associations between tertiles of maternal TCPY concentrations and ADHD-related outcomes in children. However, compared to the lowest tertile we found suggestive evidence for increased ADHD index in the highest TCPY tertile in boys (β=5.55 points; 95% CI (-0.19, 11.3); p=0.06) and increased attention problems for the middle tertile in girls (β=5.81 points; 95% CI (-0.75, 12.4); p=0.08). Considering the continued widespread agricultural and possible residential use of chlorpyrifos and chlorpyrifos-methyl in Mexico and the educational implications of cognitive and behavior deficits, these relationships deserve further study.

A new exposure metric for traffic-related air pollution? An analysis of determinants of hopanes in settled indoor house dust

BACKGROUND

Exposure to traffic-related air pollution (TRAP) can adversely impact health but epidemiologic studies are limited in their abilities to assess long-term exposures and incorporate variability in indoor pollutant infiltration.

METHODS

In order to examine settled house dust levels of hopanes, engine lubricating oil byproducts found in vehicle exhaust, as a novel TRAP exposure measure, dust samples were collected from 171 homes in five Canadian cities and analyzed by gas chromatography-mass spectrometry. To evaluate source contributions, the relative abundance of the highest concentration hopane monomer in house dust was compared to that in outdoor air. Geographic variables related to TRAP emissions and outdoor NO2 concentrations from city-specific TRAP land use regression (LUR) models were calculated at each georeferenced residence location and assessed as predictors of variability in dust hopanes.

RESULTS

Hopanes relative abundance in house dust and ambient air were significantly correlated (Pearson's r=0.48, p<0.05), suggesting that dust hopanes likely result from traffic emissions. The proportion of variance in dust hopanes concentrations explained by LUR NO2 was less than 10% in Vancouver, Winnipeg and Toronto while the correlations in Edmonton and Windsor explained 20 to 40% of the variance. Modeling with household factors such as air conditioning and shoe removal along with geographic predictors related to TRAP generally increased the proportion of explained variability (10-80%) in measured indoor hopanes dust levels.

CONCLUSIONS

Hopanes can consistently be detected in house dust and may be a useful tracer of TRAP exposure if determinants of their spatiotemporal variability are well-characterized, and when home-specific factors are considered.

Polycyclic aromatic hydrocarbons in residential dust: sources of variability

BACKGROUND

There is interest in using residential dust to estimate human exposure to environmental contaminants.

OBJECTIVES

We aimed to characterize the sources of variability for polycyclic aromatic hydrocarbons (PAHs) in residential dust and provide guidance for investigators who plan to use residential dust to assess exposure to PAHs.

METHODS

We collected repeat dust samples from 293 households in the Northern California Childhood Leukemia Study during two sampling rounds (from 2001 through 2007 and during 2010) using household vacuum cleaners, and measured 12 PAHs using gas chromatography-mass spectrometry. We used a random- and a mixed-effects model for each PAH to apportion observed variance into four components and to identify sources of variability.

RESULTS

Median concentrations for individual PAHs ranged from 10 to 190 ng/g of dust. For each PAH, total variance was apportioned into regional variability (1-9%), intraregional between-household variability (24-48%), within-household variability over time (41-57%), and within-sample analytical variability (2-33%). Regional differences in PAH dust levels were associated with estimated ambient air concentrations of PAH. Intraregional differences between households were associated with the residential construction date and the smoking habits of residents. For some PAHs, a decreasing time trend explained a modest fraction of the within-household variability; however, most of the within-household variability was unaccounted for by our mixed-effects models. Within-household differences between sampling rounds were largest when the interval between dust sample collections was at least 6 years in duration.

CONCLUSIONS

Our findings indicate that it may be feasible to use residential dust for retrospective assessment of PAH exposures in studies of health effects.

Temporal variability of pesticide concentrations in homes and implications for attenuation bias in epidemiologic studies

BACKGROUND

Residential pesticide exposure has been linked to adverse health outcomes in adults and children. High-quality exposure estimates are critical for confirming these associations. Past epidemiologic studies have used one measurement of pesticide concentrations in carpet dust to characterize an individual's average long-term exposure. If concentrations vary over time, this approach could substantially misclassify exposure and attenuate risk estimates.

OBJECTIVES

We assessed the repeatability of pesticide concentrations in carpet dust samples and the potential attenuation bias in epidemiologic studies relying on one sample.

METHODS

We collected repeated carpet dust samples (median = 3; range, 1-7) from 21 homes in Fresno County, California, during 2003-2005. Dust was analyzed for 13 pesticides using gas chromatography-mass spectrometry. We used mixed-effects models to estimate between- and within-home variance. For each pesticide, we computed intraclass correlation coefficients (ICCs) and the estimated attenuation of regression coefficients in a hypothetical case-control study collecting a single dust sample.

RESULTS

The median ICC was 0.73 (range, 0.37-0.95), demonstrating higher between-home than within-home variability for most pesticides. The expected magnitude of attenuation bias associated with using a single dust sample was estimated to be ≤ 30% for 7 of the 13 compounds evaluated.

CONCLUSIONS

For several pesticides studied, use of one dust sample to represent an exposure period of approximately 2 years would not be expected to substantially attenuate odds ratios. Further study is needed to determine if our findings hold for longer exposure periods and for other pesticides.

Human exposures to PAHs: an eastern United States pilot study

Personal exposure monitoring for select polycyclic aromatic hydrocarbons (PAHs) was performed as part of the National Human Exposure Assessment Survey (NHEXAS) Pilot Study in Baltimore, MD and in four surrounding counties (NHEXAS-Maryland). An objective of this effort was to establish environmental exposure estimates for non-scripted subpopulations involved in their normal activities. Participants, children, and adults (ages 13-84) were randomly selected from urban, suburban, and rural areas near Baltimore. Twenty-four hour PM(10) sample collections (~5.8 m(3)) were performed using personal environmental monitors. Monitoring was performed for 47 households and 6 sampling Cycles during 1995-1996. A total of 233 personal air samples were available from the participants with eight PAHs speciated (e.g., chrysene, benzo(a)pyrene) as well as an aggregate grouping (total carcinogenic PAHs). Results indicate that ~50% of the selected samples had detectable concentrations for 3 to 5 of the individual PAHs depending upon spatial setting. Noted differences were observed between exposure concentrations from individuals living in rural areas as compared to urban/suburban environments. Mean benzo(a)pyrene concentrations were observed to be 0.10 ng/m(3) across the entire sampling population. This represented a value well below the World Health Organization's 1.0 ng/m(3) ambient air guideline for this PAH.

Neurobehavioral assessment of mice following repeated postnatal exposure to chlorpyrifos-oxon

Chlorpyrifos (CPF), one of the most widely-used organophosphorus (OP) insecticides in agriculture, is degraded in the field to its oxon form, chlorpyrifos-oxon (CPO), which can represent a significant contaminant in exposures to adults and children. CPO is also responsible for the acetylcholinesterase (AChE) inhibition associated with CPF exposures; CPF is converted by liver CYP450 enzymes to CPO, which binds to and inhibits AChE and other serine active-site esterases, lipases and proteases. Young children represent a particularly susceptible population for exposure to CPF and CPO, in part because levels of the plasma enzyme, paraoxonase (PON1), which hydrolyzes CPO, are very low during early development. While a number of studies have demonstrated developmental neurotoxicity associated with CPF exposure, including effects at or below the threshold levels for AChE inhibition, it is unclear whether these effects were due directly to CPF or to its active metabolite, CPO. PON1 knockout (PON1-/-) mice, which lack PON1, represent a highly sensitive mouse model for toxicity associated with exposure to CPF or CPO. To examine the neurobehavioral consequences of CPO exposure during postnatal development, PON1-/- mice were exposed daily from PND 4 to PND 21 to CPO at 0.15, 0.18, or 0.25 mg/kg/d. A neurobehavioral test battery did not reveal significant effects of CPO on early reflex development, motor coordination, pre-pulse inhibition of startle, startle amplitude, open field behavior, or learning and memory in the contextual fear conditioning, Morris water maze, or water radial-arm maze tests. However, body weight gain and startle latency were significantly affected by exposure to 0.25 mg/kg/d CPO. Additionally, from PNDs 15-20 the mice exposed repeatedly to CPO at all three doses exhibited a dose-related transient hyperkinesis in the 20-min period following CPO administration, suggesting possible effects on catecholaminergic neurotransmission. Our previous study demonstrated wide-ranging effects of neonatal CPO exposure on gene expression in the brain and on brain AChE inhibition, and modulation of both of these effects by the PON1(Q192R) polymorphism. The current study indicates that the neurobehavioral consequences of these effects are more elusive, and suggests that alternative neurobehavioral tests might be warranted, such as tests of social interactions, age-dependent effects on learning and memory, or tests designed specifically to assess dopaminergic or noradrenergic function.

Have regulatory efforts to reduce organophosphorus insecticide exposures been effective?

BACKGROUND

The Food Quality Protection Act (FQPA) was signed into law in 1996 to strengthen the regulation of pesticide tolerances in food. Organophosphorus (OP) insecticides were the first group of pesticides reviewed by the U.S. Environmental Protection Agency (EPA) under the new law.

OBJECTIVE

Our goal was to determine whether urinary concentrations of dialkylphosphate (DAP) metabolites of OP pesticides declined between the National Health and Nutrition Examination Survey (NHANES) III and NHANES 1999-2004.

METHODS

Using mass spectrometry-based methods, we analyzed urine samples from a nationally representative sample of 2,874 adults 20-59 years of age in NHANES 1999-2004 and samples from a non-nationally representative sample of 197 adult participants for NHANES III (1988-1994) for six common DAP metabolites of OP pesticides.

RESULTS

Median urinary DAP concentrations decreased by more than half between NHANES III and NHANES 2003-2004. Reductions of about 50%-90% were also observed for 95th percentile concentrations of five of the six metabolites. Frequencies of detection (FODs) decreased in all six metabolites (< 50% reduction). On average, median and 95th percentile concentrations and FODs showed a larger decrease in diethylphosphate metabolites than dimethylphosphate metabolites.

CONCLUSIONS

Human exposure to OP insecticides as assessed by urinary DAP concentrations has decreased since the implementation of the FQPA, although we cannot be certain that U.S. EPA actions in response to the FQPA directly caused the decrease in DAP concentrations.

Carpet-dust chemicals as measures of exposure: Implications of variability

BACKGROUND

There is increasing interest in using chemicals measured in carpet dust as indicators of chemical exposures. However, investigators have rarely sampled dust repeatedly from the same households and therefore little is known about the variability of chemical levels that exist within and between households in dust samples.

RESULTS

We analyzed 9 polycyclic aromatic hydrocarbons, 6 polychlorinated biphenyls, and nicotine in 68 carpet-dust samples from 21 households in agricultural communities of Fresno County, California collected from 2003-2005. Chemical concentrations (ng per g dust) ranged from < 2-3,609 for 9 polycyclic aromatic hydrocarbons, from < 1-150 for 6 polychlorinated biphenyls, and from < 20-7,776 for nicotine. We used random-effects models to estimate variance components for concentrations of each of these carpet-dust chemicals and calculated the variance ratio, λ, defined as the ratio of the within-household variance component to the between-household variance component. Subsequently, we used the variance ratios calculated from our data, to illustrate the potential effect of measurement error on the attenuation of odds ratios in hypothetical case-control studies. We found that the median value of the estimated variance ratios was 0.33 (range: 0.13-0.72). Correspondingly, in case-control studies of associations between these carpet-dust chemicals and disease, given the collection of only one measurement per household and a hypothetical odds ratio of 1.5, we expect that the observed odds ratios would range from 1.27 to 1.43. Moreover, for each of the chemicals analyzed, the collection of three repeated dust samples would limit the expected magnitude of odds ratio attenuation to less than 20%.

CONCLUSIONS

Our findings suggest that attenuation bias should be relatively modest when using these semi-volatile carpet-dust chemicals as exposure surrogates in epidemiologic studies.

Carpet-dust chemicals as measures of exposure: Implications of variability

BACKGROUND

There is increasing interest in using chemicals measured in carpet dust as indicators of chemical exposures. However, investigators have rarely sampled dust repeatedly from the same households and therefore little is known about the variability of chemical levels that exist within and between households in dust samples.

RESULTS

We analyzed 9 polycyclic aromatic hydrocarbons, 6 polychlorinated biphenyls, and nicotine in 68 carpet-dust samples from 21 households in agricultural communities of Fresno County, California collected from 2003-2005. Chemical concentrations (ng per g dust) ranged from < 2-3,609 for 9 polycyclic aromatic hydrocarbons, from < 1-150 for 6 polychlorinated biphenyls, and from < 20-7,776 for nicotine. We used random-effects models to estimate variance components for concentrations of each of these carpet-dust chemicals and calculated the variance ratio, λ, defined as the ratio of the within-household variance component to the between-household variance component. Subsequently, we used the variance ratios calculated from our data, to illustrate the potential effect of measurement error on the attenuation of odds ratios in hypothetical case-control studies. We found that the median value of the estimated variance ratios was 0.33 (range: 0.13-0.72). Correspondingly, in case-control studies of associations between these carpet-dust chemicals and disease, given the collection of only one measurement per household and a hypothetical odds ratio of 1.5, we expect that the observed odds ratios would range from 1.27 to 1.43. Moreover, for each of the chemicals analyzed, the collection of three repeated dust samples would limit the expected magnitude of odds ratio attenuation to less than 20%.

CONCLUSIONS

Our findings suggest that attenuation bias should be relatively modest when using these semi-volatile carpet-dust chemicals as exposure surrogates in epidemiologic studies.

Categorizing biomarkers of the human exposome and developing metrics for assessing environmental sustainability

The concept of maintaining environmental sustainability broadly encompasses all human activities that impact the global environment, including the production of energy, use and management of finite resources such as petrochemicals, metals, food production (farmland, fresh and ocean waters), and potable water sources (rivers, lakes, aquifers), as well as preserving the diversity of the surrounding ecosystems. The ultimate concern is how one can manage Spaceship Earth in the long term to sustain the life, health, and welfare of the human species and the planet's flora and fauna. On a more intimate scale, one needs to consider the human interaction with the environment as expressed in the form of the exposome, which is defined as all exogenous and endogenous exposures from conception onward, including exposures from diet, lifestyle, and internal biology, as a quantity of critical interest to disease etiology. Current status and subsequent changes in the measurable components of the exposome, the human biomarkers, could thus conceivably be used to assess the sustainability of the environmental conditions with respect to human health. The basic theory is that a shift away from sustainability will be reflected in outlier measurements of human biomarkers. In this review, the philosophy of long-term environmental sustainability is explored in the context of human biomarker measurements and how empirical data can be collected and interpreted to assess if solutions to existing environmental problems might have unintended consequences. The first part discusses four conventions in the literature for categorizing environmental biomarkers and how different types of biomarker measurements might fit into the various grouping schemes. The second part lays out a sequence of data management strategies to establish statistics and patterns within the exposome that reflect human homeostasis and how changes or perturbations might be interpreted in light of external environmental stressors. The underlying concept is to identify probative outliers from the "unremarkable exposome" in individuals or subpopulations that could be used for discerning deviations from the healthy environment, much like current diagnostic medicine uses batteries of blood and urine tests to screen for preclinical disease conditions. Such empirically derived human in vivo data could subsequently be integrated into high-throughput in vitro and in silico testing of environmental and manufactured chemicals to support real-world toxicity evaluations.

Estimating exposures to indoor contaminants using residential dust

Residential dust has been used as a medium for assessing human exposures to a constellation of indoor contaminants including radionuclides, persistent organic pollutants, metals, allergens, and tobacco smoke. Here, we review and comment on investigations of household dust levels of particular analytes of health significance, namely polybrominated diphenyl ethers, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons. In doing so, we not only describe methods for collecting and analyzing residential dust, but also describe global patterns in dust levels. Aside from geographic location, we discuss several potential determinants for dust levels of these contaminants. We also review previous estimates of the contribution of dust to overall intake of these three chemical classes and show how residential-dust measurements could be useful in either augmenting or replacing questionnaire-based assessment of human exposures in epidemiological studies. We conclude our review with a discussion of the current gaps in knowledge of worldwide dust levels and suggestions for how residential-dust measurements could be used to describe human exposures to chemicals in developing countries.

A biomonitoring framework to support exposure and risk assessments

BACKGROUND

Biomonitoring is used in exposure and risk assessments to reduce uncertainties along the source-to-outcome continuum. Specifically, biomarkers can help identify exposure sources, routes, and distributions, and reflect kinetic and dynamic processes following exposure events. A variety of computational models now utilize biomarkers to better understand exposures at the population, individual, and sub-individual (target) levels. However, guidance is needed to clarify biomonitoring use given available measurements and models.

OBJECTIVE

This article presents a biomonitoring research framework designed to improve biomarker use and interpretation in support of exposure and risk assessments.

DISCUSSION

The biomonitoring research framework is based on a modified source-to-outcome continuum. Five tiers of biomonitoring analyses are included in the framework, beginning with simple cross-sectional and longitudinal analyses, and ending with complex analyses using various empirical and mechanistic models. Measurements and model requirements of each tier are given, as well as considerations to enhance analyses. Simple theoretical examples are also given to demonstrate applications of the framework for observational exposure studies.

CONCLUSION

This biomonitoring framework can be used as a guide for interpreting existing biomarker data, designing new studies to answer specific exposure- and risk-based questions, and integrating knowledge across scientific disciplines to better address human health risks.

Interpersonal and temporal variability of urinary cotinine in elderly subjects

Although a single measurement of urinary cotinine is often used for biological monitoring, the validity of this measurement for estimating long-term exposure has not been well evaluated. The purpose of this study was to determine the efficacy of using a single measurement per person to estimate long-term smoking exposure in an elderly population. Analysis was conducted using a cohort of elderly subjects for whom multiple urinary cotinine measurements had been collected over eight weeks. The mixed-effects model of urinary cotinine indicated that interpersonal variability was greater than temporal variability. The efficacy of using single measurements to track the mean long-term exposure of a population is supported by the relatively consistent population averages. The classification of high and low exposure groups using a single measurement or using eight measurements produced similar group distributions. When using cut-off levels of 20 and 100 μg cotinine/g creatinine, 9.3% and 5.6% of individual exposures were misclassified, respectively, when using a single measurement. Urinary cotinine can be a useful biomarker for characterizing exposure to tobacco smoke. Although the incidence of misclassification decreased with an increase in the number of measurements, a single measurement of the urinary cotinine level may accurately represent long-term exposure to tobacco smoke.

Variability of environmental exposure to fine particles, black smoke, and trace elements among a Swedish population

Mixed-effects models were used to estimate within-person and between-person variance components, and some determinants of environmental exposure to particulate matter (PM(2.5)), black smoke (BS) and trace elements (Cl, K, Ca, Ti, Fe, Ni, Cu, Zn, and Pb) for personal measurements from 30 adult subjects in Gothenburg, Sweden. The within-person variance component dominated the total variability for all investigated compounds except for PM(2.5) and Zn (in which the variance components were about equal). Expressed as fold ranges containing 95% of the underlying distributions, the within-person variance component ranged between 5-fold and 39-fold (median: sixfold), whereas the between-person variance component was always <sixfold (median: threefold). The relatively large within-person variance components can lead to attenuation bias in exposure-response relationships and point to the importance of obtaining repeated samples of PM exposure from study subjects in epidemiological investigations of urban air pollution. On the basis of the variance components estimated for the various particulate species, between 3 and 39 repeated measurements per subject would be required to limit attenuation bias to 20%. Significant determinants for personal exposure levels were urban background air concentrations (PM(2.5), BS, Cl, Zn, and Pb), cigarette smoking (PM(2.5), BS, K, and Ti), season (PM(2.5), Fe, and Pb), and the time spent outdoors or in traffic (Fe).

Organophosphate pesticide metabolite levels in pre-school children in an agricultural community: within- and between-child variability in a longitudinal study

This study characterized the within- and between-child variability in dimethylthiophosphate (DMTP) levels in the urine of 44 children living in an agricultural community in central Washington State in December 1997 and 1999. The goal of this analysis was to investigate these variability components during periods when organophosphate pesticides were and were not actively applied to orchards in that community. Each child provided between 10 and 26 biweekly urine samples over a 21-month period, and these samples were analyzed for six dialkylphosphate (DAP) metabolites common to organophosphate pesticides, including DMTP. Previous analysis of this dataset found that DAP concentrations were elevated during months when organophosphate pesticides were applied to orchards in this region. The current analysis demonstrates that the within-child component of day-to-day variability was much greater than the between-child component of variability by a factor of 3-7 across the DAP metabolites that were analyzed. Therefore, organophosphate pesticide exposure appeared to vary more than 3 times from day-to-day than from child-to-child. This finding has important implications for epidemiologic and exposure pathways research, since accounting for within-child variability may increase the power of a study and allow for the detection of differences that would not otherwise be possible without an analysis that separates out the within-child variability.

Determinants of agricultural pesticide concentrations in carpet dust

BACKGROUND

Residential proximity to agricultural pesticide applications has been used as a surrogate for exposure in epidemiologic studies, although little is known about the relationship with levels of pesticides in homes.

OBJECTIVE

We identified determinants of concentrations of agricultural pesticides in dust.

METHODS

We collected samples of carpet dust and mapped crops within 1,250 m of 89 residences in California. We measured concentrations of seven pesticides used extensively in agriculture (carbaryl, chlorpyrifos, chlorthal-dimethyl, diazinon, iprodione, phosmet, and simazine). We estimated use of agricultural pesticides near residences from a statewide database alone and by linking the database with crop maps. We calculated the density of pesticide use within 500 and 1,250 m of residences for 180, 365, and 730 days before collection of dust and evaluated relationships between agricultural pesticide use estimates and pesticide concentrations in carpet dust.

RESULTS

For five of the seven pesticides evaluated, residences with use of agricultural pesticides within 1,250 m during the previous 365 days had significantly higher concentrations of pesticides than did residences with no nearby use. The highest correlation with concentrations of pesticides was generally for use reported within 1,250 m of the residence and 730 days before sample collection. Regression models that also accounted for occupational and home use of pesticides explained only a modest amount of the variability in pesticide concentrations (4-28%).

CONCLUSIONS

Agricultural pesticide use near residences was a significant determinant of concentrations of pesticides in carpet dust for five of seven pesticides evaluated.

Review of pesticide urinary biomarker measurements from selected US EPA children's observational exposure studies

Children are exposed to a wide variety of pesticides originating from both outdoor and indoor sources. Several studies were conducted or funded by the EPA over the past decade to investigate children’s exposure to organophosphate and pyrethroid pesticides and the factors that impact their exposures. Urinary metabolite concentration measurements from these studies are consolidated here to identify trends, spatial and temporal patterns, and areas where further research is required. Namely, concentrations of the metabolites of chlorpyrifos (3,5,6-trichloro-2-pyridinol or TCPy), diazinon (2-isopropyl-6-methyl-4-pyrimidinol or IMP), and permethrin (3-phenoxybenzoic acid or 3-PBA) are presented. Information on the kinetic parameters describing absorption and elimination in humans is also presented to aid in interpretation. Metabolite concentrations varied more dramatically across studies for 3-PBA and IMP than for TCPy, with TCPy concentrations about an order of magnitude higher than the 3-PBA concentrations. Temporal variability was high for all metabolites with urinary 3-PBA concentrations slightly more consistent over time than the TCPy concentrations. Urinary biomarker levels provided only limited evidence of applications. The observed relationships between urinary metabolite levels and estimates of pesticide intake may be affected by differences in the contribution of each exposure route to total intake, which may vary with exposure intensity and across individuals.