Effects of exposure measurement error on particle matter epidemiology: a simulation using data from a panel study in Baltimore, MD

Inflammatory and oxidative stress responses of healthy elders to solar-assisted large-scale cleaning system (SALSCS) and changes in ambient air pollution: A quasi-interventional study in Xi'an, China

An outdoor solar assisted large-scale cleaning system (SALSCS) was constructed to mitigate the levels of fine particulate matter (PM_2.5) in urban areas of Xi'an China, providing a quasi-experimental opportunity to examine the biologic responses to the changes in pollution level. We conducted this outdoor SALSCS based real-world quasi-interventional study to examine the associations of the SALSCS intervention and changes in air pollution levels with the biomarkers of systemic inflammation and oxidative stress in healthy elders. We measured the levels of 8-hydrox-2-deoxyguanosine (8-OHdG), Interlukin-6 (IL-6), as well as tumor necrosis factor alpha (TNF-α) from urine samples, and IL-6 from saliva samples of 123 healthy retired participants from interventional/control residential areas in two sampling campaigns. We collected daily 24-h PM_2.5 samples in two residential areas during the study periods using mini-volume samplers. Data on PM₁₀, gaseous pollutants and weather factors were collected from the nearest national air quality monitoring stations. We used linear mixed-effect models to examine the percent change in each biomarker associated with the SALSCS intervention and air pollution levels, after adjusting for time trend, seasonality, weather factors and personal characteristics. Results showed that the SALSCS intervention was significantly associated with decreases in the geometric mean of biomarkers by 47.6% (95% confidence interval: 16.5-67.2%) for 8-OHdG, 66% (31.0-83.3%) for TNF-α, 41.7% (0.2-65.9%) and 43.4% (13.6-62.9%) for urinary and salivary IL-6, respectively. An inter-quartile range increase of ambient PM_2.5 exposure averaged on the day of the collection of bio-samples and the day before (34.1 μg/m³) was associated, albeit non-significantly so, with 22.8%-37.9% increases in the geometric mean of these biomarkers. This study demonstrated that the SALSCS intervention and decreased ambient air pollution exposure results in lower burden of systemic inflammation and oxidative stress in older adults.

Ambient air pollution and low temperature associated with case fatality of COVID-19: A nationwide retrospective cohort study in China

The evidence for the effects of environmental factors on COVID-19 case fatality remains controversial, and it is crucial to understand the role of preventable environmental factors in driving COVID-19 fatality. We thus conducted a nationwide cohort study to estimate the effects of environmental factors (temperature, particulate matter [PM_2.5, PM₁₀], sulfur dioxide [SO₂], nitrogen dioxide [NO₂], and ozone [O₃]) on COVID-19 case fatality. A total of 71,808 confirmed COVID-19 cases were identified and followed up for their vital status through April 25, 2020. Exposures to ambient air pollution and temperature were estimated by linking the city- and county-level monitoring data to the residential community of each participant. For each participant, two windows were defined: the period from symptom onset to diagnosis (exposure window I) and the period from diagnosis date to date of death/recovery or end of the study period (exposure window II). Cox proportional hazards models were used to estimate the associations between these environmental factors and COVID-19 case fatality. COVID-19 case fatality increased in association with environmental factors for the two exposure windows. For example, each 10 μg/m³ increase in PM_2.5, PM₁₀, O₃, and NO₂ in window I was associated with a hazard ratio of 1.11 (95% CI 1.09, 1.13), 1.10 (95% CI 1.08, 1.13), 1.09 (95 CI 1.03, 1.14), and 1.27 (95% CI 1.19, 1.35) for COVID-19 fatality, respectively. A significant effect was also observed for low temperature, with a hazard ratio of 1.03 (95% CI 1.01, 1.04) for COVID-19 case fatality per 1°C decrease. Subgroup analysis indicated that these effects were stronger in the elderly, as well as in those with mild symptoms and living in Wuhan or Hubei. Overall, the sensitivity analyses also yielded consistent estimates. Short-term exposure to ambient air pollution and low temperature during the illness would play a nonnegligible part in causing case fatality due to COVID-19. Reduced exposures to high concentrations of PM_2.5, PM₁₀, O₃, SO₂, and NO₂ and low temperature would help improve the prognosis and reduce public health burden.

Ambient PM2.5 species and ultrafine particle exposure and their differential metabolomic signatures

BACKGROUND

The metabolomic signatures of short- and long-term exposure to PM_2.5 have been reported and linked to inflammation and oxidative stress. However, little is known about the relative contribution of the specific PM_2.5 species (hence sources) that drive these metabolomic signatures.

OBJECTIVES

We aimed to determine the relative contribution of the different species of PM_2.5 exposure to the perturbed metabolic pathways related to changes in the plasma metabolome.

METHODS

We performed mass-spectrometry based metabolomic profiling of plasma samples among men from the Normative Aging Study to identify metabolic pathways associated with PM_2.5 species. The exposure windows included short-term (one, seven-, and thirty-day moving average) and long-term (one year moving average). We used linear mixed-effect regression with subject-specific intercepts while simultaneously adjusting for PM_2.5, NO₂, O₃, temperature, relative humidity, and covariates and correcting for multiple testing. We also used independent component analysis (ICA) to examine the relative contribution of patterns of PM_2.5 species.

RESULTS

Between 2000 and 2016, 456 men provided 648 blood samples, in which 1158 metabolites were quantified. We chose 305 metabolites for the short-term and 288 metabolites for the long-term exposure in this analysis that were significantly associated (p-value < 0.01) with PM_2.5 to include in our PM_2.5 species analysis. On average, men were 75.0 years old and their body mass index was 27.7 kg/m². Only 3% were current smokers. In the adjusted models, ultrafine particles (UFPs) were the most significant species of short-term PM_2.5 exposure followed by nickel, vanadium, potassium, silicon, and aluminum. Black carbon, vanadium, zinc, nickel, iron, copper, and selenium were the significant species of long-term PM_2.5 exposure. We identified several metabolic pathways perturbed with PM_2.5 species including glycerophospholipid, sphingolipid, and glutathione. These pathways are involved in inflammation, oxidative stress, immunity, and nucleic acid damage and repair. Results were overlapped with the ICA.

CONCLUSIONS

We identified several significant perturbed plasma metabolites and metabolic pathways associated with exposure to PM_2.5 species. These species are associated with traffic, fuel oil, and wood smoke. This is the largest study to report a metabolomic signature of PM_2.5 species' exposure and the first to use ICA.

Metabolomic signatures of the long-term exposure to air pollution and temperature

BACKGROUND

Long-term exposures to air pollution has been reported to be associated with inflammation and oxidative stress. However, the underlying metabolic mechanisms remain poorly understood.

OBJECTIVES

We aimed to determine the changes in the blood metabolome and thus the metabolic pathways associated with long-term exposure to outdoor air pollution and ambient temperature.

METHODS

We quantified metabolites using mass-spectrometry based global untargeted metabolomic profiling of plasma samples among men from the Normative Aging Study (NAS). We estimated the association between long-term exposure to PM2.5, NO2, O3, and temperature (annual average of central site monitors) with metabolites and their associated metabolic pathways. We used multivariable linear mixed-effect regression models (LMEM) while simultaneously adjusting for the four exposures and potential confounding and correcting for multiple testing. As a reduction method for the intercorrelated metabolites (outcome), we further used an independent component analysis (ICA) and conducted LMEM with the same exposures.

RESULTS

Men (N = 456) provided 648 blood samples between 2000 and 2016 in which 1158 metabolites were quantified. On average, men were 75.0 years and had an average body mass index of 27.7 kg/m2. Almost all men (97%) were not current smokers. The adjusted analysis showed statistically significant associations with several metabolites (58 metabolites with PM2.5, 15 metabolites with NO2, and 6 metabolites with temperature) while no metabolites were associated with O3. One out of five ICA factors (factor 2) was significantly associated with PM2.5. We identified eight perturbed metabolic pathways with long-term exposure to PM2.5 and temperature: glycerophospholipid, sphingolipid, glutathione, beta-alanine, propanoate, and purine metabolism, biosynthesis of unsaturated fatty acids, and taurine and hypotaurine metabolism. These pathways are related to inflammation, oxidative stress, immunity, and nucleic acid damage and repair.

CONCLUSIONS

Using a global untargeted metabolomic approach, we identified several significant metabolites and metabolic pathways associated with long-term exposure to PM2.5, NO2 and temperature. This study is the largest metabolomics study of long-term air pollution, to date, the first study to report a metabolomic signature of long-term temperature exposure, and the first to use ICA in the analysis of both.

Differentiating the effects of ambient fine and coarse particles on mortality from cardiopulmonary diseases: A nationwide multicity study

BACKGROUND

Both inhalable particles (PM₁₀) and fine particles (PM_2.5) are regulated in various countries mainly due to their adverse health effects. However, there is increasing evidence that PM_2.5 might be responsible for these effects and coarse particles (PM_c) plays little role in adverse health effects, if so, it might be not necessary to monitor PM₁₀.

METHODS

In this study, we conducted a time-series analysis using a generalized additive model to explore the effects of PM_2.5, PM_c, and PM₁₀ on mortality from ischemic heart disease (IHD) and chronic obstructive pulmonary disease (COPD) in 96 Chinese cities during 2013-2016. The mortality number and attributable fraction were further estimated using the national air quality standard and WHO's guideline as the reference.

RESULTS

We observed significant effects of PM_2.5 on IHD and COPD mortality; each 10 ug/m³ increase in lag₀₁ PM_2.5 was associated with a 0.26% (95% CI: 0.17%, 0.34%) increase in IHD mortality and a 0.19% (95% CI: 0.09%, 0.29%) increase in COPD mortality. We also found significant effects of PM_c and PM₁₀ on mortality from IHD and COPD, but the magnitudes of effects were weaker than those of PM_2.5. The results were robust when adjusting for co-pollutants and altering model parameters. We further estimated that about 1.27% (95% CI: 0.29%, 2.30%) of IHD mortality and 1.25% (95% CI: 0.08%, 2.46%) of COPD mortality could be attributable to PM_2.5 exposure using WHO's guideline (25 ug/m³) as a reference, corresponding to 15,337 (95% CI: 3,375, 27,842) mortalities from IHD and 5,653 (95% CI: 379, 11,152) COPD mortalities in the 96 cities. Across all of China, almost fifty thousand cases of IHD mortality and twenty thousand cases of COPD mortality might be avoidable if the PM_2.5 concentration declined to the WHO guideline.

CONCLUSIONS

Our study indicates that short-term exposure to PM_2.5 could be an important risk factor of mortality from IHD and COPD, and substantial cardiopulmonary mortality could be avoidable by reducing daily PM_2.5 concentrations. It is nonnegligible to consider the role of PM_c in triggering in cardiopulmonary mortality. And it could be necessary to continue monitoring PM₁₀ in the study regions due to the adverse effects of PM_c.

Ambient air pollution exposure associated with glucose homeostasis during pregnancy and gestational diabetes mellitus

BACKGROUND

To investigate the effects of air pollution exposure during pregnancy on the indicators of glucose homeostasis and gestational diabetes mellitus (GDM).

METHODS

We conducted a birth cohort study in Foshan, China during 2015-2019. Oral glucose tolerance test (OGTT) was administered to each participant during pregnancy. GDM was defined according to the International Association of Diabetes and Pregnancy Study Groups criteria (IADPSG). Air pollutant (fine particulate matter (PM_2.5), particulate matter with an aerodynamic diameter of 10 μm or less (PM₁₀), sulfate dioxide (SO₂), nitrogen dioxide (NO₂) and ozone (O₃)) concentrations from the air monitoring stations in Foshan were used to estimate individual air pollutant exposure during the first two trimesters. Linear and logistic regression models were employed to estimate the associations between air pollution exposure during the first two trimesters and OGTT glucose levels and GDM.

RESULTS

Of 12,842 pregnant women, 3055 (23.8%) had GDM. A 10 μg/m³ increase in PM_2.5, PM₁₀ and SO₂ during trimester 1, trimester 2 and two trimesters were associated with 0.07 mmol/L to 0.29 mmol/L increment in OGTT-fasting glucose levels in single-pollutant model. A 10 μg/m³ increase in NO₂ and O₃ during two trimesters were associated with 0.15 mmol/L and 0.12 mmol/L decrease in OGTT-fasting glucose in single-pollutant model. However, no significant or weaker effects of O₃ during two trimesters on OGTT-fasting glucose were observed in two-pollutant models. Moreover, exposure to PM_2.5, PM₁₀ and SO₂ were associated with increased risk of GDM in both single- and two-pollutant models.

CONCLUSIONS

Our study suggests PM_2.5, PM₁₀ and SO₂ exposure during the first two trimesters might increase the risk of GDM.

PM2.5 and NO2 exposure errors using proxy measures, including derived personal exposure from outdoor sources: A systematic review and meta-analysis

BACKGROUND

The use of proxy exposure estimates for PM_2.5 and NO₂ in air pollution studies instead of personal exposures, introduces measurement error, which can produce biased epidemiological effect estimates. Most studies consider total personal exposure as the gold standard. However, when studying the effects of ambient air pollution, personal exposure from outdoor sources is the exposure of interest.

OBJECTIVES

We assessed the magnitude and variability of exposure measurement error by conducting a systematic review of the differences between personal exposures from outdoor sources and the corresponding measurements for ambient concentrations in order to increase understanding of the measurement error structures of the pollutants.

DATA SOURCES AND ELIGIBILITY CRITERIA

We reviewed the literature (ISI Web of Science, Medline, 2000-2016) for English language studies (in any age group in any location (NO₂) or Europe and North America (PM_2.5)) that reported repeated measurements over time both for personal and ambient PM_2.5 or NO₂ concentrations. Only a few studies reported personal exposure from outdoor sources. We also collected data for infiltration factors and time-activity patterns of the individuals in order to estimate personal exposures from outdoor sources in every study.

STUDY APPRAISAL AND SYNTHESIS METHODS

Studies using modelled rather than monitored exposures were excluded. Type of personal exposure monitor was assessed. Random effects meta-analysis was conducted to quantify exposure error as the mean difference between "true" and proxy measures.

RESULTS

Thirty-two papers for PM_2.5 and 24 for NO₂ were identified. Outdoor sources were found to contribute 44% (range: 33-55%) of total personal exposure to PM_2.5 and 74% (range: 57-88%) to NO₂. Overall estimates of personal exposure (24-hour averages) from outdoor sources were 9.3 μg/m³ and 12.0 ppb for PM_2.5 and NO₂ respectively, while the corresponding difference between these exposures and the ambient concentrations (i.e. the measurement error) was 5.72 μg/m³ and 7.17 ppb. Our findings indicated also higher error variability for NO₂ than PM_2.5. Large heterogeneity was observed which was not explained sufficiently by geographical location or age group of the study sample.

LIMITATIONS, CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Relying only on information available in published studies led to some limitations: the contribution of outdoor sources to total personal exposure for NO₂ had to be inferred, individual variation in exposure misclassification was unavailable and instrument error could not be addressed. The larger magnitude and variability of errors for NO₂ compared with PM_2.5 has implications for biases in the health effect estimates of multi-pollutant epidemiological models. Results suggest that further research is needed regarding personal exposure studies and measurement error bias in epidemiological models.

Short-term and long-term effects of PM2.5 on acute nasopharyngitis in 10 communities of Guangdong, China

OBJECTIVES

We aimed to assess the effects of short-term and long-term exposure to ambient fine particle matter (PM_2.5) on acute nasopharyngitis.

METHODS

A total of 9468 participants aged 18 years and above were recruited from 10 communities in four cities of Guangdong, China during the baseline survey in 2014, and they were followed-up from January 2015 to December 2016. Air pollution exposure was assessed based on the daily concentrations (short-term) and annual concentrations (long-term) of the nearby air monitoring station and the survey date. A mixed-effect logistic model and Cox proportional hazards model were used to quantify the short-term and long-term associations after adjustment for potential confounding factors.

RESULTS

Significantly positive associations were found between both short-term and long-term exposures of PM_2.5 and acute nasopharyngitis. The adjusted odds ratio was 1.15 (95% CI: 1.07, 1.23) for each 10 μg/m³ increase in daily PM_2.5 at lag2 day (short-term effects), and the hazard risk was 1.18 (95% CI: 1.10, 1.25) for each 10 μg/m³ increase in annual PM_2.5 (long-term effects). Stronger associations between short-term PM_2.5 exposure and acute nasopharyngitis were observed among men (OR = 1.10; 95% CI: 1.04, 1.17) and participants aged above 65 years (OR = 1.13; 95% CI: 1.04, 1.23) in the stratified analyses. No significant association was found in women (OR = 1.00; 95% CI: 0.92, 1.10) or young participants ≤65 years (OR = 0.96; 95% CI: 0.88, 1.04). However, for the long-term exposure, the hazard risk was higher for participants younger than 65 years (OR = 1.22; 95% CI: 1.12, 1.32) than the older group (OR = 1.11; 95% CI: 1.00, 1.24).

CONCLUSION

This study indicates that both short-term and long-term exposures to higher concentrations of PM_2.5 could increase the risk of acute nasopharyngitis.

Estimation of personal exposure to fine particles (PM2.5) of ambient origin for healthy adults in Hong Kong

Personal exposure and ambient fine particles (PM_2.5) measurements for 13 adult subjects (ages 19-57) were conducted in Hong Kong between April 2014 and June 2015. Six to 21 personal samples (mean = 19) per subject were obtained throughout the study period. Samples were analyzed for mass by gravimetric analysis, and 19 elements (from Na to Pb) were analyzed using X-Ray Fluorescence. Higher subject-specific correlations between personal and ambient sulfur (r_s = 0.92; p < 0.001) were found as compared to PM_2.5 mass (r_s = 0.79; p < 0.001) and other elements (0.06 < r_s < 0.86). Personal vs. ambient sulfur regression yielded an average exposure factor (F_pex) of 0.73 ± 0.02, supporting the use of sulfur as a surrogate to estimate personal exposure to PM_2.5 of ambient origin (E_a). E_a accounted for 41-82% and 57-73% of total personal PM_2.5 exposures (P) by season and by subject, respectively. The importance of both E_a and non-ambient exposures (E_na, 11.2 ± 5.6 μg/m³; 32.5 ± 10.9%) are noted. Mixed-effects models were applied to estimate the relationships between ambient PM_2.5 concentrations and their corresponding exposure variables (E_a, P). Higher correlations for E_a (0.90; p < 0.001) than for P (0.58; p < 0.01) were found. A calibration coefficient < 1 suggests an attenuation of 22% (ranging 16-28%) of the true effect estimates when using average ambient concentrations at central monitoring stations as surrogates for E_a. Stationary ambient data can be used to assess population exposure only if PM exposure is dominated by E_a.

Short-term effects of fine particulate matter on non-accidental and circulatory diseases mortality: A time series study among the elder in Changchun

Background and objectives

Fine particulate matter (PM_2.5, particulate matter with an aerodynamic diameter less than or equal to 2.5 μm) has multiple adverse effects on human health, especially on the respiratory and circulatory system. The purpose of this study was to evaluate the short-term effect of PM_2.5 on the mortality risk of non-accidental and circulatory diseases, and to explore the potential effect modification by sex, education and death location.

Methods

We collected daily mortality counts of Changchun (China) residents, daily meteorology and air pollution data, from January 1, 2014, to January 1, 2017. We focused on the elderly (≥65 years old) population who died from non-accidental causes and circulatory diseases, and stratified them by sex, education, and death location. A generalized additive Poisson regression model (GAM) was used to analyse the impact of air pollutants on mortality. We fit single pollutant models to examine PM_2.5 effects with different lag structures of single-day (distributed lag:lag0-lag3) and multi-day (moving average lag: lag01-lag03). To test the sensitivity of the model, a multi-pollutant model was established when the PM_2.5 effect was strongest.

Results

In the single pollutant models, an increment of PM_2.5 by 10 μg/m³ at lag0-3 was associated with a 0.385% (95% CI: 0.069% to 0.702%) increase in daily non-accidental mortality and a 0.442% (95% CI: 0.038% to 0.848%) increase in daily circulatory disease mortality. NO₂ (lag1) and O₃ (lag0, lag1, lag2, lag01,lag02, lag03) were associated with daily non-accidental death and NO₂ (lag1, lag3, lag03) and O₃ (lag0, lag1, lag01,lag02, lag03) were associated with daily circulatory disease mortality. In the co-pollutant models, the risk estimates for PM_2.5 changed slightly. The excess mortality risk of non-accidental and circulatory diseases was higher for women, people with low education, and died outside hospital.

Conclusions

We found that short-term exposure to PM_2.5 increased the mortality risk of non-accidental and circulatory diseases among the elderly in Changchun. Women, people with low education and died outside hospital are more susceptible to PM_2.5. NO₂ and O₃ were also associated with an increase in mortality from non-accidental and circulatory diseases and the O₃ is a high effect.

Short-term effects of fine and coarse particles on deaths in Hong Kong elderly population: An analysis of mortality displacement

BACKGROUND

While numerous studies worldwide have evaluated the short-term associations of fine and coarse particulate matter (PM) air pollution with mortality and morbidity, these studies may be susceptible to short-term harvesting effect. We aimed to investigate the short-term association between mortality and PM with aerodynamic diameter less than 2.5 μm (PM_2.5) and those between 2.5 and 10 μm (PMc) within a month prior to death, and assess the mortality displacement by PM_2.5 and PMc among elderly population in Hong Kong.

METHODS

We obtained air pollution data from January 2011 to December 2015 from Environmental Protection Department, and daily cause-specific mortality data from Census and Statistical Department of Hong Kong. We performed generalized additive distributed lag model to examine the acute, delayed and long-lasting effects of PM_2.5 and PMc within one month on mortality.

RESULTS

We observed a statistically significant association of PM_2.5 and PMc exposure over lags 0-6 days with all natural mortality and cardio-respiratory mortality. The overall cumulative effect of PM_2.5 over 0-30 lag days was 3.44% (95% CI: 0.30-6.67%) increase in all natural mortality and 6.90% (95% CI: 0.58-13.61%) increase of circulatory mortality, which suggested the absence of mortality displacement by PM_2.5. On the other hand, no significant cumulative association with mortality was found for PMc over 0-30 lag exposure window, and thus mortality displacement by PMc cannot be ruled out. Findings remained robust in various sensitivity analyses.

CONCLUSIONS

We found adverse effect of both PM_2.5 and PMc exposure within one week prior to death. While there was no evidence of mortality displacement in the association of PM_2.5 exposure over one month prior with all natural and circulatory mortality, mortality displacement by PMc cannot be ruled out. PM_2.5 may contribute more to the longer term effect of particulate matter than PMc.

Lagged Influence of Fine Particulate Matter and Geographic Disparities on Clinic Visits for Children's Asthma in Taiwan

Recent studies have revealed the influence of fine particulate matter (PM_2.5) on increased medication use, hospital admission, and emergency room visits for asthma attack in children, but the lagged influence of PM_2.5 on children’s asthma and geographic disparities of children’s asthma have rarely been discussed simultaneously. This study investigated the documented diagnosis of children’s asthma in clinic visits for children aged less than 15 years old that were associated with PM_2.5 in two counties located in west-central Taiwan during 2005–2010. The result shows that PM_2.5 had a significant lagged effect on children’s asthma for up to 6 days. A significantly higher relative risk for children’s asthma was more likely to happen at 2-day lag compared to the present day when PM_2.5 increased from 36.17 μg/m³ to 81.26 μg/m³. Considering all lagged effects, the highest relative risk for children’s asthma was 1.08 (95% CI = 1.05, 1.11) as PM_2.5 increased as high as 64.66 μg/m³. In addition, geographic disparities of children’s asthma were significant, and 47.83% of areas were identified to have children vulnerable to asthma. To sum up, our findings can serve as a valuable reference for the implementation of an early warning to governmental agencies about a susceptible population of children.

Short-term effects of fine particulate matter on acute myocardial infraction mortality and years of life lost: A time series study in Hong Kong

Previous studies have applied years of life lost (YLL) as a complementary indicator to assess the short-term effect of the air pollution on the health burden from all-cause mortality, but sparsely focused on individual diseases such as acute myocardial infraction (AMI). In this study, we aimed to conduct a time-series analysis to evaluate short-term effects of fine particulate matter (PM_2.5) on mortality and YLL from AMI in Hong Kong from 2011 to 2015, and explore the potential effect modifiers including sex and age by subgroup analysis. We applied generalized additive Poisson and Gaussian regression model for daily death count and YLL, respectively. We found that 10μg/m³ increment in concentration of PM_2.5 lasting for two days (lag₀₁) was associated with a 2.35% (95% CI 0.38% to 4.36%) increase in daily mortality count and a 1.69 (95% CI 0.01 to 3.37) years increase in YLL from AMI. The association between PM_2.5 and AMI mortality count was stronger among women and older people than men and young people, respectively. We concluded that acute exposure to PM_2.5 may increase the risk of mortality and YLL from AMI in Hong Kong and this effect can be modified by age and gender. These findings add to the evidence base for public health policy formulation and resource allocation.

Acute exposure to fine particulate matter and cardiovascular hospital emergency room visits in Beijing, China

Fine particulate matter (PM_2.5) air pollution outbreaks have recently occurred frequently in China. However, evidence of the associations between short-term exposure to PM_2.5 and cardiovascular morbidity is still limited in China. This study aimed to evaluate the associations between PM_2.5 and hospital emergency room visits (ERVs) for cardiovascular diseases in urban areas in Beijing. Daily counts of cardiovascular ERVs were collected from ten large general hospitals from Jan 1 to Dec 31, 2013. Air pollution data were obtained from the Beijing Environmental Protection Bureau including 17 monitoring stations. A generalized additive Poisson model was used to examine the associations between PM_2.5 and cardiovascular ERVs after controlling for seasonality, day of the week, public holidays, influenza outbreaks, and weather conditions. In total, there were 56,221 cardiovascular ERVs during the study period. The daily mean PM_2.5 concentration was 102.1 μg/m³, ranging from 6.7 μg/m³ to 508.5 μg/m³. Per 10 μg/m³ increase in PM_2.5 was associated with a 0.14% (95% confidence interval [CI]: 0.01%-0.27%) increase in cardiovascular ERVs at lag₃. Cumulative delayed estimates were greatest at lag_0-5 (0.30%, 95% CI: 0.09%-0.52%). The estimates of percentage change in daily ERVs per 10 μg/m³ increase in PM_2.5 were 0.56% (95%CI: 0.16%-0.95%) for ischemic heart disease (IHD) at lag_0-1, 0.81% (95%CI: 0.05%-1.57%) for heart rhythm disturbances (HRD) at lag_0-1 and 1.21% (95%CI: 0.27%-2.15%) for heart failure (HF) at lag₀, respectively. The effects of PM_2.5 on IHD ERVs during high temperature days (>11.01 °C) were significantly higher than that on low temperature days (≤11.01 °C) at lag₀, lag_0-1, lag_0-3 and lag_0-5 (P < 0.05). The study suggests that PM_2.5 has acute impacts on cardiovascular ERVs in Beijing, especially on IHD, HRD and HF. The effects of PM_2.5 on IHD ERVs vary by temperature.

Mortality benefits of vigorous air quality improvement interventions during the periods of APEC Blue and Parade Blue in Beijing, China

Vigorous air pollution control measures were implemented during the 2014 Asia-Pacific Economic Cooperation and a large-scale military parade (described here as "APEC Blue" and "Parade Blue" periods) in Beijing, China. A natural experiment was conducted in a health impact assessment framework to estimate the number of deaths attributable to PM_2.5, using concentration-response functions derived from previous studies conducted in Beijing, combined with the differences in PM_2.5 concentrations between intervention and reference periods. Substantial reductions in daily PM_2.5 concentrations were observed during both intervention periods. Using the same dates from the prior year as a reference, daily PM_2.5 concentration decreased from 98.57 μg/m³ to 47.53 μg/m³ during "APEC Blue", and from 59.15 μg/m³ to 17.07 μg/m³ during the "Parade Blue". We estimated that 39-63 all-cause deaths (21-51 cardiovascular, 6-13 respiratory deaths) have been prevented during the APEC period; and 41-65 deaths (22-52 cardiovascular, 6-13 respiratory deaths) have been prevented during the Parade period. This study shows that substantial mortality reductions could be achieved by implementing stringent air pollution mitigation measures.

Short-term exposure to ambient particulate matter and emergency ambulance dispatch for acute illness in Japan

Short-term exposure to air pollution may be linked to negative health outcomes that require an emergency medical response. However, few studies have been undertaken on this phenomenon to date. The aim of this study therefore was to examine the association between short-term exposure to ambient suspended particulate matter (SPM) and emergency ambulance dispatches (EADs) for acute illness in Japan. Daily EAD data, daily mean SPM and meteorological data were obtained for four prefectures in the Kanto region of Japan for the period from 2007 to 2011. The area-specific association between daily EAD for acute illness and SPM was explored using generalized linear models while controlling for ambient temperature, relative humidity, seasonality, long-term trends, day of the week and public holidays. Stratified analyses were conducted to evaluate the modifying effects of age, sex and medical conditions. Area-specific estimates were combined using meta-analyses. For the total study period the mean level of SPM was 23.7μg/m(3). In general, higher SPM was associated with a significant increase in EAD for acute illness [estimated pooled relative risk (RR): 1.008, 95% CI: 1.007 to 1.010 per 10μg/m(3) increase in SPM at lag 0-1]. The effects of SPM on EAD for acute illness were significantly greater for moderate/mild medical conditions (e.g. cases that resulted in <3weeks hospitalization or no hospitalization) when compared to severe medical conditions (e.g. critical cases, and cases that led to >3weeks hospitalization or which resulted in death). Using EAD data, this study has shown the adverse health effects of ambient air pollution. This highlights the importance of reducing the level of air pollution in order to maintain population health and well-being.

Risk of Cardiovascular Hospitalizations from Exposure to Coarse Particulate Matter (PM10) Below the European Union Safety Threshold

The association between exposure to air pollution and acute cardiovascular (CV) events is well documented; however, limited data are available evaluating the public health safety of various "doses" of particular matter (PM) below currently accepted safety thresholds. We explored the cross-sectional association between PM with aerodynamic diameter <10 μm (PM10) and daily CV hospitalizations in Brescia, Italy, using Poisson regression models adjusted for age, gender, and meteorologic indices. Average daily exposure to PM10 obtained from arithmetic means of air pollution data were captured by 4 selected monitoring stations. PM10 data were expressed as daily means (lag 0-day) or 3-day moving averages (lag 3-day) and categorized according to the European Union daily limit value of 50 μg/m(3). From September 2004 to September 2007, data from 6,000 acute CV admissions to a tertiary referral center were collected. An increase of 1 μg/m(3) PM10 at lag 0-day was independently associated with higher rates of acute hospitalizations for composite CV-related events (relative risk [RR] 1.004, 95% confidence interval [CI] 1.002 to 1.006), acute heart failure (RR 1.004, 95% CI 1.001 to 1.008), acute coronary syndromes (RR 1.002, 95% CI 0.999 to 1.005), malignant ventricular arrhythmias (RR 1.004, 95% CI 0.999 to 1.010), and atrial fibrillation (RR 1.008, 95% CI 1.003 to 1.012). Similar results were obtained using PM10 lag 3-day data. The excess PM10 CV hospitalization risk (by lag 0-day and lag 3-day) did not vary significantly above and below the 50 μg/m(3) safety threshold or by age and gender. In conclusion, increased levels of PM10, even below the current limits set by the European Union, were associated with excess risk for admissions for acute CV events.

Estimating risk of emergency room visits for asthma from personal versus fixed site measurements of NO2

BACKGROUND

We examined the impact of data source and exposure measurement error for ambient NO2 on risk estimates derived from a case-crossover study of emergency room visits for asthma in Windsor, Canada between 2002 and 2009.

METHODS

Paired personal and fixed-site NO2 data were available from an independent population (47 children and 48 adults) in Windsor between 2005 and 2006. We used linear regression to estimate the relationship and measurement error variance induced between fixed site and personal measurements of NO2, and through a series of simulations, evaluated the potential for a Bayesian model to adjust for this change in scale and measurement error. Finally, we re-analyzed data from the previous case-crossover study adjusting for the estimated change in slope and measurement error.

RESULTS

Correlations between paired NO2 measurements were weak (R(2)≤0.08) and slopes were far from unity (0.0029≤β≤0.30). Adjusting the previous case-crossover analysis suggested a much stronger association between personal NO2 (per 1ppb) (Odds Ratio (OR)=1.276, 95% Credible Interval (CrI): 1.034, 1.569) and emergency room visits for asthma among children relative to the fixed-site estimate (OR=1.024, 95% CrI 1.004-1.045).

CONCLUSIONS

Our findings suggest that risk estimates based on fixed-site NO2 concentrations may differ substantially from estimates based on personal exposures if the change in scale and/or measurement error is large. In practice, one must always keep the scale being used in mind when interpreting risk estimates and not assume that coefficients for ambient concentrations reflect risks at the personal level.

The effects of PM2.5 and its components from indoor and outdoor sources on cough and wheeze symptoms in asthmatic children

Particulate matter with aerodynamic diameter <2.5 μm (PM2.5) is associated with asthma exacerbation. In the Children's Air Pollution Asthma Study, we investigated the longitudinal association of PM2.5 and its components from indoor and outdoor sources with cough and wheeze symptoms in 36 asthmatic children. The sulfur tracer method was used to estimate infiltration factors. Mixed proportional odds models for an ordinal response were used to relate daily cough and wheeze scores to PM2.5 exposures. The odds ratio associated with being above a given symptom score for a SD increase in PM2.5 from indoor sources (PMIS) was 1.24 (95% confidence interval: 0.92-1.68) for cough and 1.63 (1.11-2.39) for wheeze. Ozone was associated with wheeze (1.82, 1.19-2.80), and cough was associated with indoor PM2.5 components from outdoor sources (denoted with subscript "OS") bromine (BrOS: 1.32, 1.05-1.67), chlorine (ClOS: 1.27, 1.02-1.59) and pyrolyzed organic carbon (OPOS: 1.49, 1.12-1.99). The highest effects were seen in the winter for cough with sulfur (SOS: 2.28, 1.01-5.16) and wheeze with organic carbon fraction 2 (OC2OS: 7.46, 1.19-46.60). Our results indicate that exposure to components originating from outdoor sources of photochemistry, diesel and fuel oil combustion is associated with symptom's exacerbation, especially in the winter. PM2.5 mass of indoor origin was more strongly associated with wheeze than with cough.

Sources of indoor air pollution in New York City residences of asthmatic children

Individuals spend ∼90% of their time indoors in proximity to sources of particulate and gaseous air pollutants. The sulfur tracer method was used to separate indoor concentrations of particulate matter (PM) PM2.5 mass, elements and thermally resolved carbon fractions by origin in New York City residences of asthmatic children. Enrichment factors relative to sulfur concentrations were used to rank species according to the importance of their indoor sources. Mixed effects models were used to identify building characteristics and resident activities that contributed to observed concentrations. Significant indoor sources were detected for OC1, Cl, K and most remaining OC fractions. We attributed 46% of indoor PM2.5 mass to indoor sources related to OC generation indoors. These sources include cooking (NO2, Si, Cl, K, OC4 and OP), cleaning (most OC fractions), candle/incense burning (black carbon, BC) and smoking (K, OC1, OC3 and EC1). Outdoor sources accounted for 28% of indoor PM2.5 mass, mainly photochemical reaction products, metals and combustion products (EC, EC2, Br, Mn, Pb, Ni, Ti, V and S). Other indoor sources accounted for 26% and included re-suspension of crustal elements (Al, Zn, Fe, Si and Ca). Indoor sources accounted for ∼72% of PM2.5 mass and likely contributed to differences in the composition of indoor and outdoor PM2.5 exposures.

Associations between summertime ambient pollutants and respiratory morbidity in New York City: comparison of results using ambient concentrations versus predicted exposures

Epidemiological analyses of air quality often estimate human exposure from ambient monitoring data, potentially leading to exposure misclassification and subsequent bias in estimated health risks. To investigate this, we conducted a case-crossover study of summertime ambient ozone and fine particulate matter (PM(2.5)) levels and daily respiratory hospitalizations in New York City during 2001-2005. Comparisons were made between associations estimated using two pollutant exposure metrics: observed concentrations and predicted exposures from the EPA's Stochastic Human Exposure and Dose Simulation (SHEDS) model. Small, positive associations between interquartile range mean ozone concentrations and hospitalizations were observed and were strongest for 0-day lags (hazard ratio (HR)=1.013, 95% confidence interval (CI): 0.998, 1.029) and 3-day lags (HR=1.006, 95% CI: 0.991, 1.021); applying mean predicted ozone exposures yielded similar results. PM(2.5) was also associated with admissions, strongest at 2- and 4-day lags, with few differences between exposure metrics. Subgroup analyses support recognized sociodemographic differences in concentration-related hospitalization risk, whereas few inter-stratum variations were observed in relation to SHEDS exposures. Predicted exposures for these spatially homogenous pollutants were similar across sociodemographic strata, therefore SHEDS predictions coupled with the case-crossover design may have masked observable heterogeneity in risks. However, significant effect modification was found for subjects in the top exposure-to-concentration ratio tertiles, suggesting risks may increase as a consequence of infiltration or greater exposure to outdoor air.

Effects of coarse particulate matter on emergency hospital admissions for respiratory diseases: a time-series analysis in Hong Kong

BACKGROUND

Many epidemiological studies have linked daily counts of hospital admissions to particulate matter (PM) with an aerodynamic diameter ≤ 10 μm (PM10) and ≤ 2.5 μm (PM2.5), but relatively few have investigated the relationship of hospital admissions with coarse PM (PMc; 2.5-10 μm aerodynamic diameter).

OBJECTIVES

We conducted this study to estimate the health effects of PMc on emergency hospital admissions for respiratory diseases in Hong Kong after controlling for PM2.5 and gaseous pollutants.

METHODS

We conducted a time-series analysis of associations between daily emergency hospital admissions for respiratory diseases in Hong Kong from January 2000 to December 2005 and daily PM2.5 and PMc concentrations. We estimated PMc concentrations by subtracting PM2.5 from PM10 measurements. We used generalized additive models to examine the relationship between PMc (single- and multiday lagged exposures) and hospital admissions adjusted for time trends, weather conditions, influenza outbreaks, PM2.5, and gaseous pollutants (nitrogen dioxide, sulfur dioxide, and ozone).

RESULTS

A 10.9-μg/m(3) (interquartile range) increase in the 4-day moving average concentration of PMc was associated with a 1.94% (95% confidence interval: 1.24%, 2.64%) increase in emergency hospital admissions for respiratory diseases that was attenuated but still significant after controlling for PM2.5. Adjusting for gaseous pollutants and altering models assumptions had little influence on PMc effect estimates.

CONCLUSION

PMc was associated with emergency hospital admissions for respiratory diseases in Hong Kong independent of PM2.5 and gaseous pollutants. Further research is needed to evaluate health effects of different components of PMc.

Measurement error in environmental epidemiology and the shape of exposure-response curves

Both classical and Berkson exposure measurement errors as encountered in environmental epidemiology data can result in biases in fitted exposure-response relationships that are large enough to affect the interpretation and use of the apparent exposure-response shapes in risk assessment applications. A variety of sources of potential measurement error exist in the process of estimating individual exposures to environmental contaminants, and the authors review the evaluation in the literature of the magnitudes and patterns of exposure measurement errors that prevail in actual practice. It is well known among statisticians that random errors in the values of independent variables (such as exposure in exposure-response curves) may tend to bias regression results. For increasing curves, this effect tends to flatten and apparently linearize what is in truth a steeper and perhaps more curvilinear or even threshold-bearing relationship. The degree of bias is tied to the magnitude of the measurement error in the independent variables. It has been shown that the degree of bias known to apply to actual studies is sufficient to produce a false linear result, and that although nonparametric smoothing and other error-mitigating techniques may assist in identifying a threshold, they do not guarantee detection of a threshold. The consequences of this could be great, as it could lead to a misallocation of resources towards regulations that do not offer any benefit to public health.

Windsor, Ontario Exposure Assessment Study: Design and Methods Validation of Personal, Indoor, and Outdoor Air Pollution Monitoring

The Windsor, Ontario Exposure Assessment Study evaluated the contribution of ambient air pollutants to personal and indoor exposures of adults and asthmatic children living in Windsor, Ontario, Canada. In addition, the role of personal, indoor, and outdoor air pollution exposures upon asthmatic children's respiratory health was assessed. Several active and passive sampling methods were applied, or adapted, for personal, indoor, and outdoor residential monitoring of nitrogen dioxide, volatile organic compounds, particulate matter (PM; PM ≤ 2.5 μm [PM_2.5] and ≤ 10 μm [PM₁₀] in aerodynamic diameter),elemental carbon, ultrafine particles, ozone, air exchange rates, allergens in settled dust, and particulate-associated metals. Participants completed five consecutive days of monitoring during the winter and summer of 2005 and 2006. During 2006, in addition to undertaking the air pollution measurements, asthmatic children completed respiratory health measurements (including peak flow meter tests and exhaled breath condensate) and tracked respiratory symptoms in a diary. Extensive quality assurance and quality control steps were implemented, including the collocation of instruments at the National Air Pollution Surveillance site operated by Environment Canada and at the Michigan Department of Environmental Quality site in Allen Park, Detroit, MI. During field sampling, duplicate and blank samples were also completed and these data are reported. In total, 50 adults and 51 asthmatic children were recruited to participate, resulting in 922 participant days of data. When comparing the methods used in the study with standard reference methods, field blanks were low and bias was acceptable, with most methods being within 20% of reference methods. Duplicates were typically within less than 10% of each other, indicating that study results can be used with confidence. This paper covers study design, recruitment, methodology, time activity diary, surveys, and quality assurance and control results for the different methods used. [Box: see text].

Windsor, Ontario Exposure Assessment Study: Design and Methods Validation of Personal, Indoor, and Outdoor Air Pollution Monitoring

The Windsor, Ontario Exposure Assessment Study evaluated the contribution of ambient air pollutants to personal and indoor exposures of adults and asthmatic children living in Windsor, Ontario, Canada. In addition, the role of personal, indoor, and outdoor air pollution exposures upon asthmatic children's respiratory health was assessed. Several active and passive sampling methods were applied, or adapted, for personal, indoor, and outdoor residential monitoring of nitrogen dioxide, volatile organic compounds, particulate matter (PM; PM ≤2.5 μm [PM_2.5] and ≤ 10 μm [PM₁₀] in aerodynamic diameter), elemental carbon, ultrafine particles, ozone, air exchange rates, allergens in settled dust, and particulate-associated metals. Participants completed five consecutive days of monitoring during the winter and summer of 2005 and 2006. During 2006, in addition to undertaking the air pollution measurements, asthmatic children completed respiratory health measurements (including peak flow meter tests and exhaled breath condensate) and tracked respiratory symptoms in a diary. Extensive quality assurance and quality control steps were implemented, including the collocation of instruments at the National Air Pollution Surveillance site operated by Environment Canada and at the Michigan Department of Environmental Quality site in Allen Park, Detroit, MI. During field sampling, duplicate and blank samples were also completed and these data are reported. In total, 50 adults and 51 asthmatic children were recruited to participate, resulting in 922 participant days of data. When comparing the methods used in the study with standard reference methods, field blanks were low and bias was acceptable, with most methods being within 20% of reference methods. Duplicates were typically within less than 10% of each other, indicating that study results can be used with confidence. This paper covers study design, recruitment, methodology, time activity diary, surveys, and quality assurance and control results for the different methods used. [Box: see text].

Particulate air pollution, metabolic syndrome, and heart rate variability: the multi-ethnic study of atherosclerosis (MESA)

BACKGROUND

Cardiac autonomic dysfunction has been suggested as a possible biologic pathway for the association between fine particulate matter ≤ 2.5 µm in diameter (PM2.5) and cardiovascular disease (CVD). We examined the associations of PM2.5 with heart rate variability, a marker of autonomic function, and whether metabolic syndrome (MetS) modified these associations.

METHODS

We used data from the Multi-Ethnic Study of Atherosclerosis to measure the standard deviation of normal-to-normal intervals (SDNN) and the root mean square of successive differences (rMSSD) of 5,465 participants 45-84 years old who were free of CVD at the baseline examination (2000-2002). Data from the U.S. regulatory monitor network were used to estimate ambient PM2.5 concentrations at the participants' residences. MetS was defined as having three or more of the following criteria: abdominal obesity, hypertriglyceridemia, low high-density lipoprotein cholesterol, high blood pressure, and high fasting glucose.

RESULTS

After controlling for confounders, we found that an interquartile range (IQR) increase in 2-day average PM2.5 (10.2 µg/m3) was associated with a 2.1% decrease in rMSSD [95% confidence interval (CI), -4.2 to 0.0] and nonsignificantly associated with a 1.8% decrease in SDNN (95% CI, -3.7 to 0.1). Associations were stronger among individuals with MetS than among those without MetS: an IQR elevation in 2-day PM2.5 was associated with a 6.2% decrease in rMSSD (95% CI, -9.4 to -2.9) among participants with MetS, whereas almost no change was found among participants without MetS (p-interaction = 0.005). Similar effect modification was observed in SDNN (p-interaction = 0.011).

CONCLUSION

These findings suggest that autonomic dysfunction may be a mechanism through which PM exposure affects cardiovascular risk, especially among persons with MetS.

Associations of PM10 with sleep and sleep-disordered breathing in adults from seven U.S. urban areas

RATIONALE

Sleep-disordered breathing (SDB), the recurrent episodic disruption of normal breathing during sleep, affects as much as 17% of U.S. adults, and may be more prevalent in poor urban environments. SDB and air pollution have been linked to increased cardiovascular diseases and mortality, but the association between pollution and SDB is poorly understood.

OBJECTIVES

We used data from the Sleep Heart Health Study (SHHS), a U.S. multicenter cohort study assessing cardiovascular and other consequences of SDB, to examine whether particulate air matter less than 10 μm in aerodynamic diameter (PM(10)) was associated with SDB among persons 39 years of age and older.

METHODS

Using baseline data from SHHS urban sites, outcomes included the following: the respiratory disturbance index (RDI); percentage of sleep time at less than 90% O(2) saturation; and sleep efficiency, measured by overnight in-home polysomnography. We applied a fixed-effect model containing a city effect, controlling for potential predictors. In all models we included both the 365-day moving averages of PM(10) and temperature (long-term effects) and the differences between the daily measures of these two predictors and their 365-day average (short-term effects).

MEASUREMENTS AND MAIN RESULTS

In summer, increases in RDI or percentage of sleep time at less than 90% O(2) saturation, and decreases in sleep efficiency, were all associated with increases in short-term variation in PM(10). Over all seasons, we found that increased RDI was associated with an 11.5% (95% confidence interval: 1.96, 22.01) increase per interquartile range increase (25.5°F) in temperature.

CONCLUSIONS

Reduction in air pollution exposure may decrease the severity of SDB and nocturnal hypoxemia and may improve cardiac risk.

Surveillance of the short-term impact of fine particle air pollution on cardiovascular disease hospitalizations in New York State

BACKGROUND

Studies have shown that the effects of particulate matter on health vary based on factors including the vulnerability of the population, health care practices, exposure factors, and the pollutant mix.

METHODS

We used time-stratified case-crossover to estimate differences in the short-term impacts of PM2.5 on cardiovascular disease hospital admissions in New York State by geographic area, year, age, gender, co-morbid conditions, and area poverty rates.

RESULTS

PM2.5 had a stronger impact on heart failure than other cardiovascular diagnoses, with 3.1% of heart failure admissions attributable to short-term PM2.5 exposure over background levels of 5 ug/m3. Older adults were significantly more susceptible to heart failure after short-term ambient PM2.5 exposure than younger adults.

CONCLUSION

The short-term impact of PM2.5 on cardiovascular disease admissions, and modifications of that impact, are small and difficult to measure with precision. Multi-state collaborations will be necessary to attain more precision to describe spatiotemporal differences in health impacts.

Modification of the interleukin-6 response to air pollution by interleukin-6 and fibrinogen polymorphisms

BACKGROUND

Evidence suggests that cardiovascular effects of air pollution are mediated by inflammation and that air pollution can induce genetic expression of the interleukin-6 gene (IL6).

OBJECTIVES

We investigated whether IL6 and fibrinogen gene variants can affect plasma IL-6 responses to air pollution in patients with cardiovascular disease.

METHODS

We repeatedly determined plasma IL-6 in 955 myocardial infarction survivors from six European cities (n = 5,539). We conducted city-specific analyses using additive mixed models adjusting for patient characteristics, time trend, and weather to assess the impact of air pollutants on plasma IL-6. We pooled city-specific estimates using meta-analysis methodology. We selected three IL6 single-nucleotide polymorphisms (SNPs) and one SNP each from the fibrinogen alpha-chain gene (FGA) and beta-chain gene (FGB) for gene-environment analyses.

RESULTS

We found the most consistent modifications for variants in IL6 rs2069832 and FBG rs1800790 after exposure to carbon monoxide (CO; 24-hr average; p-values for interaction, 0.034 and 0.019, respectively). Nitrogen dioxide effects were consistently modified, but p-values for interaction were larger (0.09 and 0.19, respectively). The strongest effects were seen 6-11 hr after exposure, when, for example, the overall effect of a 2.2% increase in IL-6 per 0.64 mg/m(3) CO was modified to a 10% (95% confidence interval, 4.6-16%) increase in IL-6 (p-value for interaction = 0.002) for minor homozygotes of FGB rs1800790.

CONCLUSIONS

The effect of gaseous traffic-related air pollution on inflammation may be stronger in genetic subpopulations with ischemic heart disease. This information could offer an opportunity to identify postinfarction patients who would benefit more than others from a cleaner environment and antiinflammatory treatment.

Exposure to environmental carbon monoxide may have a greater negative effect on cardiac autonomic function in people with metabolic syndrome

Carbon monoxide (CO) has been recognized as a risk factor for adverse cardiovascular outcomes. We investigated the effects of CO on cardiac autonomic function by measuring the heart rate variability (HRV) in patients with and without metabolic syndrome (MetS). We also explored the relationship between CO exposure and specific components of MetS. Data were obtained from air pollution measurements and from health examinations on a total of 986 subjects, from a Korean community. Measurements of the 5-min HRV and examinations for MetS were conducted, and a linear regression model with a time lag was evaluated for any association. The group with MetS showed a significant reduction in the standard deviation of the normal-to-normal intervals (SDNN) and in the high frequency domain of HRV. After adjusting for age, sex, smoking status, day of the week effect, month effect, temperature, and relative humidity, these declines were significantly associated with exposure to CO for 25 to 48 h prior to the HRV measurement. Evidence for effect-modification by two specific MetS components, fasting blood glucose and triglycerides, was also observed in relation to CO exposure. These results suggest that CO exposure may trigger changes in cardiac autonomic function, and that subjects at high risk for heart disease may be more susceptible to CO effects.

Panel discussion review: session two--interpretation of observed associations between multiple ambient air pollutants and health effects in epidemiologic analyses

Air pollution epidemiologic research has often utilized ambient air concentrations measured from centrally located monitors as a surrogate measure of exposure to these pollutants. Associations between these ambient concentrations and health outcomes such as lung function, hospital admissions, and mortality have been examined in short- and long-term cohort studies as well as in time-series and case-crossover studies. The issues related to interpreting the observed associations of ambient air pollutants with health outcomes were discussed at the US EPA sponsored workshop on December 13 and 14, 2006 in Chapel Hill, North Carolina, USA. The second session of this workshop focused on the following topics: (1) statistical methodology and study designs that may improve understanding of multipollutant health effects; (2) ambient concentrations as surrogate measures of pollutant mixtures; and (3) source-focused epidemiologic research. New methodology and approaches to better distinguish the effects of individual pollutants include multicity hierarchical modeling and the use of case-crossover analysis to control for copollutants. An alternative approach is to examine the mixture as a whole using principal component analysis. Another important consideration is to what extent the observed health associations are attributable to individual pollutants, which are often from common sources and are correlated, versus the pollutant mixtures that the pollutants are representing. For example, several ambient air concentrations, such as particulate matter mass, nitrogen dioxide, and carbon monoxide, may be serving as surrogate measures of motor vehicle exhaust. Source apportionment analysis is one method that may allow further advancement in understanding the source components that contribute to multipollutant health effects.