Urinary concentrations and determinants of glyphosate and glufosinate in pregnant Canadian participants in the MIREC study

BACKGROUND

Glyphosate is the most widely applied herbicide in agriculture. Glufosinate is a broad spectrum herbicide used to manage glyphosate-resistant weeds. Despite the widespread use of these herbicides, biomonitoring data - which inform risk assessment and management - are sparse.

OBJECTIVES

To identify determinants of urinary concentrations of these herbicides and their metabolites in pregnancy.

METHODS

We measured urinary concentrations of glyphosate, glufosinate, and their primary metabolites aminomethylphosphonic acid (AMPA) and 3-methylphosphinicopropionic acid (3-MPPA) in a single spot urine specimen collected during the first trimester of pregnancy from the Maternal-Infant Research on Environmental Chemicals (MIREC) study. MIREC recruited about 2000 pregnant women from 10 Canadian cities between 2008 and 2011. We used UItra-Performance Liquid Chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) with sensitive limits of detection to quantify analyte concentrations. We examined urinary concentrations according to maternal sociodemographics, sample collection characteristics, reported pesticide use, and consumption of fruits, vegetables, legumes, and grain products. We used ANOVA models with specific gravity-standardized chemical concentrations as the dependent variable to determine associations with maternal and sample determinants.

RESULTS

Among women with biobanked urine samples (n = 1829-1854), 74% and 72% had detectable concentrations of glyphosate and AMPA, respectively. In contrast, one and six percent of women had detectable concentrations of glufosinate and 3-MPPA, respectively. The specific gravity-standardized geometric mean (95% CI) concentrations of glyphosate and AMPA were 0.112 (0.099-0.127) μg/L and 0.159 (0.147-0.172) μg/L, respectively. We observed a dose-response relationship between consumption of whole grain bread and higher urinary glyphosate concentrations. Season of urine collection and self-reported pesticide use were not associated with increased concentrations of any analyte.

CONCLUSIONS

We detected glyphosate and AMPA in the majority of pregnant women from this predominantly urban Canadian cohort. Diet was a probable route of exposure.

Prevalence of handheld laser device use, exposure and associated injury

BACKGROUND

This study assessed the use of and exposure to handheld laser devices by Canadians and the potential associated health risks.

DATA AND METHODS

The 2019 Canadian Community Health Survey collected data from 12,397 Canadians on the prevalence of handheld laser exposure or use, and associated eye or skin injuries.

RESULTS

In 2019, an estimated 12.4% (95% CI: 11.4% to 13.4%) of Canadians reported using a handheld laser device or being exposed to its beam in the previous year, and those between the ages of 12 and 17 represented 30.5% (95% CI: 26.6% to 34.4%) of users. The highest laser device use or exposure was among those with a university education (13.8%; 95% CI: 11.8% to 15.8%), and a significant trend was found over income categories (p < 0.0001). The highest prevalence of exposure or use involved laser pointers (69.4%; 95% CI: 65.4% to 73.4%), followed by laser toys (38.5%; 95% CI: 34.6% to 42.5%), laser torches (8.2%; 95% CI: 6.1% to 10.4%) and-lastly-search-and-rescue lasers (0.8%E; 95% CI: 0.3% to 1.2%). Overall, 0.7%E (95% CI: 0.2% to 1.2%) of Canadians reported discomfort or injury in the past 12 months. One-quarter (27.9%; 95% CI: 23.8% to 31.9%) of users had a laser beam intentionally directed toward their eyes or skin. Most users did not buy the device (56.3%; 95% CI: 52.1% to 60.5%), while 40.5% (95% CI: 36.2% to 44.7%) purchased it at a Canadian retail store or online (3.8%E; 95% CI: 2.6% to 5.0%).

DISCUSSION

The prevalence of handheld laser device use and beam exposure was 12.4% (95% CI: 11.4% to 13.4%), representing approximately 3.9 million Canadians. While the number of reported injuries was low, ongoing surveillance helps assess the effectiveness of current risk management approaches for laser products.

Prevalence of tanning equipment use among Canadians

The objective of this study was to collect prevalence estimates of indoor tanning usage and associated injuries in Canada. The rapid response component of the 2019 Canadian Community Health Survey collected data on the use of tanning equipment in the previous 12 months, including reasons for use, frequency/duration of use, precautions taken and adverse reactions or injuries. The 2019 research findings were as follows, an estimated 3.0% (95% CI: 2.5-3.4%) of Canadians reported that they had used indoor tanning equipment in the past year. Among users, 71.1% (95% CI: 63.9-78.3%) were female and females aged 18-34 were significantly more prevalent users compared to females aged 45 or older. The prevalence of indoor tanning was higher among people without a university degree; however, there were no differences in prevalence by household income or region. Most users indicated they used indoor tanning equipment within a tanning salon (75.3%: 95% CI: 69.1-81.6%) and the most common reason for usage was to develop a "protective" base tan (72.1%: 95% CI: 65.2-78.9%). Over one third (39.2%: 95% CI: 31.1-47.2%) of all users reported 10 or more sessions in the past year. The prevalence of indoor UV tanning usage is declining in Canada. Similar to results in 2014, the majority of users continue to be female, with a large number in the 18 to 34 age group.

Evaluation of daily time spent in transportation and traffic-influenced microenvironments by urban Canadians

Exposure to traffic and traffic-related air pollution is associated with a wide array of health effects. Time spent in a vehicle, in active transportation, along roadsides, and in close proximity to traffic can substantially contribute to daily exposure to air pollutants. For this study, we evaluated daily time spent in transportation and traffic-influenced microenvironments by urban Canadians using the Canadian Human Activity Pattern Survey (CHAPS) 2 results. Approximately 4-7% of daily time was spent in on- or near-road locations, mainly associated with being in a vehicle and smaller contributions from active transportation. Indoor microenvironments can be impacted by traffic emissions, especially when located near major roadways. Over 60% of the target population reported living within one block of a roadway with moderate to heavy traffic, which was variable with income level and city, and confirmed based on elevated NO₂ exposure estimated using land use regression. Furthermore, over 55% of the target population ≤ 18 years reported attending a school or daycare in close proximity to moderate to heavy traffic, and little variation was observed based on income or city. The results underline the importance of traffic emissions as a major source of exposure in Canadian urban centers, given the time spent in traffic-influenced microenvironments.

Urban-rural differences in daily time-activity patterns, occupational activity and housing characteristics

BACKGROUND

There is evidence that rural residents experience a health disadvantage compared to urban residents, associated with a greater prevalence of health risk factors and socioeconomic differences. We examined differences between urban and rural Canadians using data from the Canadian Human Activity Pattern Survey (CHAPS) 2.

METHODS

Data were collected from 1460 respondents in two rural areas (Haldimand-Norfolk, Ontario and Annapolis Valley-Kings County, Nova Scotia) and 3551 respondents in five urban areas (Vancouver, Edmonton, Toronto, Montreal, and Halifax) using a 24-h recall diary and supplementary questionnaires administered using computer-assisted telephone interviews. We evaluated differences in time-activity patterns, occupational activity, and housing characteristics between rural and urban populations using multivariable linear and logistic regression models adjusted for design as well as demographic and socioeconomic covariates. Taylor linearization method and design-adjusted Wald tests were used to test statistical significance.

RESULTS

After adjustment for demographic and socioeconomic covariates, rural children, adults and seniors spent on average 0.7 (p < 0.05), 1.2 (p < 0.001), and 0.9 (p < 0.001) more hours outdoors per day respectively than urban counterparts. 23.1% (95% CI: 19.0-27.2%) of urban and 37.8% (95% CI: 31.2-44.4%) of rural employed populations reported working outdoors and the distributions of job skill level and industry differed significantly (p < 0.001) between urban and rural residents. In particular, 11.4% of rural residents vs. 4.9% of urban residents were employed in unskilled jobs, and 11.5% of rural residents vs. <0.5% of urban residents were employ in primary industry. Rural residents were also more likely than urban residents to report spending time near gas or diesel powered equipment other than vehicles (16.9% vs. 5.2%, p < 0.001), more likely to report wood as a heating fuel (9.8% vs. <0.1%; p < 0.001 for difference in distribution of heating fuels), less likely to have an air conditioner (43.0% vs. 57.2%, p < 0.001), and more likely to smoke (29.1% vs. 19.0 %, p < 0.001). Private wells were the main water source in rural areas (68.6%) in contrast to public water systems (97.6%) in urban areas (p < 0.001). Despite these differences, no differences in self-reported health status were observed between urban and rural residents.

CONCLUSIONS

We identified a number of differences between urban and rural residents, which provide evidence pertinent to the urban-rural health disparity.

Indirect adjustment for multiple missing variables applicable to environmental epidemiology

OBJECTIVES

Develop statistical methods for survival models to indirectly adjust hazard ratios of environmental exposures for missing risk factors.

METHODS

A partitioned regression approach for linear models is applied to time to event survival analyses of cohort study data. Information on the correlation between observed and missing risk factors is obtained from ancillary data sources such as national health surveys. The relationship between the missing risk factors and survival is obtained from previously published studies. We first evaluated the methodology using simulations, by considering the Weibull survival distribution for a proportional hazards regression model with varied baseline functions, correlations between an adjusted variable and an adjustment variable as well as selected censoring rates. Then we illustrate the method in a large, representative Canadian cohort of the association between concentrations of ambient fine particulate matter and mortality from ischemic heart disease.

RESULTS

Indirect adjustment for cigarette smoking habits and obesity increased the fine particulate matter-ischemic heart disease association by 3%-123%, depending on the number of variables considered in the adjustment model due to the negative correlation between these two risk factors and ambient air pollution concentrations in Canada. The simulations suggested that the method yielded small relative bias (<40%) for most cohort designs encountered in environmental epidemiology.

CONCLUSIONS

This method can accommodate adjustment for multiple missing risk factors simultaneously while accounting for the associations between observed and missing risk factors and between missing risk factors and health endpoints.

Effects of age, season, gender and urban-rural status on time-activity: CanadianHuman Activity Pattern Survey 2 (CHAPS 2)

Estimation of population exposure is a main component of human health risk assessment for environmental contaminants. Population-level exposure assessments require time-activity pattern distributions in relation to microenvironments where people spend their time. Societal trends may have influenced time-activity patterns since previous Canadian data were collected 15 years ago. The Canadian Human Activity Pattern Survey 2 (CHAPS 2) was a national survey conducted in 2010–2011 to collect time-activity information from Canadians of all ages. Five urban and two rural locations were sampled using telephone surveys. Infants and children, key groups in risk assessment activities, were over-sampled. Survey participants (n = 5,011) provided time-activity information in 24-hour recall diaries and responded to supplemental questionnaires concerning potential exposures to specific pollutants, dwelling characteristics, and socio-economic factors. Results indicated that a majority of the time was spent indoors (88.9%), most of which was indoors at home, with limited time spent outdoors (5.8%) or in a vehicle (5.3%). Season, age, gender and rurality were significant predictors of time activity patterns. Compared to earlier data, adults reported spending more time indoors at home and adolescents reported spending less time outdoors, which could be indicative of broader societal trends. These findings have potentially important implications for assessment of exposure and risk. The CHAPS 2 data also provide much larger sample sizes to allow for improved precision and are more representative of infants, children and rural residents.

Long-term fine particulate matter exposure and mortality from diabetes in Canada

OBJECTIVE

Recent studies suggest that chronic exposure to air pollution can promote the development of diabetes. However, whether this relationship actually translates into an increased risk of mortality attributable to diabetes is uncertain.

RESEARCH DESIGN AND METHODS

We evaluated the association between long-term exposure to ambient fine particulate matter (PM2.5) and diabetes-related mortality in a prospective cohort analysis of 2.1 million adults from the 1991 Canadian census mortality follow-up study. Mortality information, including ∼5,200 deaths coded as diabetes being the underlying cause, was ascertained by linkage to the Canadian Mortality Database from 1991 to 2001. Subject-level estimates of long-term exposure to PM2.5 were derived from satellite observations. The hazard ratios (HRs) for diabetes-related mortality were related to PM2.5 and adjusted for individual-level and contextual variables using Cox proportional hazards survival models.

RESULTS

Mean PM2.5 exposure levels for the entire population were low (8.7 µg/m3; SD, 3.9 µg/m3; interquartile range, 6.2 µg/m3). In fully adjusted models, a 10-µg/m3 elevation in PM2.5 exposure was associated with an increase in risk for diabetes-related mortality (HR, 1.49; 95% CI, 1.37-1.62). The monotonic change in risk to the population persisted to PM2.5 concentration<5 µg/m3.

CONCLUSIONS

Long-term exposure to PM2.5, even at low levels, is related to an increased risk of mortality attributable to diabetes. These findings have considerable public health importance given the billions of people exposed to air pollution and the worldwide growing epidemic of diabetes.

Risk of nonaccidental and cardiovascular mortality in relation to long-term exposure to low concentrations of fine particulate matter: a Canadian national-level cohort study

BACKGROUND

Few cohort studies have evaluated the risk of mortality associated with long-term exposure to fine particulate matter [≤ 2.5 μm in aerodynamic diameter (PM(2.5))]. This is the first national-level cohort study to investigate these risks in Canada.

OBJECTIVE

We investigated the association between long-term exposure to ambient PM(2.5) and cardiovascular mortality in nonimmigrant Canadian adults.

METHODS

We assigned estimates of exposure to ambient PM(2.5) derived from satellite observations to a cohort of 2.1 million Canadian adults who in 1991 were among the 20% of the population mandated to provide detailed census data. We identified deaths occurring between 1991 and 2001 through record linkage. We calculated hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for available individual-level and contextual covariates using both standard Cox proportional survival models and nested, spatial random-effects survival models.

RESULTS

Using standard Cox models, we calculated HRs of 1.15 (95% CI: 1.13, 1.16) from nonaccidental causes and 1.31 (95% CI: 1.27, 1.35) from ischemic heart disease for each 10-μg/m(3) increase in concentrations of PM(2.5). Using spatial random-effects models controlling for the same variables, we calculated HRs of 1.10 (95% CI: 1.05, 1.15) and 1.30 (95% CI: 1.18, 1.43), respectively. We found similar associations between nonaccidental mortality and PM2.5 based on satellite-derived estimates and ground-based measurements in a subanalysis of subjects in 11 cities.

CONCLUSIONS

In this large national cohort of nonimmigrant Canadians, mortality was associated with long-term exposure to PM(2.5). Associations were observed with exposures to PM(2.5) at concentrations that were predominantly lower (mean, 8.7 μg/m(3); interquartile range, 6.2 μg/m(3)) than those reported previously.

A temporal, multicity model to estimate the effects of short-term exposure to ambient air pollution on health

BACKGROUND

Countries worldwide are expending significant resources to improve air quality partly to improve the health of their citizens. Are these societal expenditures improving public health?

OBJECTIVES

We consider these issues by tracking the risk of death associated with outdoor air pollution over both space and time in Canadian cities.

MATERIALS AND METHODS

We propose two multi-year estimators that use current plus several previous years of data to estimate current year risk. The estimators are derived from sequential time series analyses using moving time windows. To evaluate the statistical properties of the proposed methods, a simulation study with three scenarios of changing risk was conducted based on 12 Canadian cities from 1981 to 2000. Then an optimal estimator was applied to 24 of Canada's largest cities over the 17-year period from 1984 to 2000.

RESULTS

The annual average daily concentrations of ozone appeared to be increasing over the time period, whereas those of nitrogen dioxide were decreasing. However, the proposed method returns different time trends in public health risks. Evidence for some monotonic increasing trends in the annual risks is weak for O(3) (p = 0.3870) but somewhat stronger for NO(2) (p = 0.1082). In particular, an increasing time trend becomes apparent when excluding year 1998, which reveals lower risk than proximal years, even though concentrations of NO(2) were decreasing. The simulation results validate our two proposed methods, producing estimates close to the preassigned values.

CONCLUSIONS

Despite decreasing ambient concentrations, public health risks related to NO(2) appear to be increasing. Further investigations are necessary to understand why the concentrations and adverse effects of NO(2) show opposite time trends.

A new multipollutant, no-threshold air quality health index based on short-term associations observed in daily time-series analyses

Air quality indices currently in use have been criticized because they do not capture additive effects of multiple pollutants, or reflect the apparent no-threshold concentration-response relationship between air pollution and health. We propose a new air quality health index (AQHI), constructed as the sum of excess mortality risk associated with individual pollutants from a time-series analysis of air pollution and mortality in Canadian cities, adjusted to a 0-10 scale, and calculated hourly on the basis of trailing 3-hr average pollutant concentrations. Extensive sensitivity analyses were conducted using alternative combinations of pollutants from single and multipollutant models. All formulations considered produced frequency distributions of the daily maximum AQHI that were right-skewed, with modal values of 3 or 4, and less than 10% of values at 7 or above on the 10-point scale. In the absence of a gold standard and given the uncertainty in how to best reflect the mix of pollutants, we recommend a formulation based on associations of nitrogen dioxide, ozone, and particulate matter of median aerodynamic diameter less than 2.5 microm with mortality from single-pollutant models. Further sensitivity analyses revealed good agreement of this formulation with others based on alternative sources of coefficients drawn from published studies of mortality and morbidity. These analyses provide evidence that the AQHI represents a valid approach to formulating an index with the objective of allowing people to judge the relative probability of experiencing adverse health effects from day to day. Together with health messages and a graphic display, the AQHI scale appears promising as an air quality risk communication tool.

Open-chain analysis of single stance

In this study we present a model by which the kinematics of single stance standing can be formulated and solved from forceplate measurements. A three-segment model with four rotation coordinates, two at the ankle and two at the hip, was developed as an open chain of linkages, with the trunk treated as the end-effector. Using the Denavit-Hartenberg notation, the trajectory of the center of mass (CoM) was evaluated by an iteration procedure, combining angular momentum principles with direct integration of the equations of motion. Kinematics and torques in the joints were thereafter solved. Single stance standing experiments were made on six healthy subjects and forceplate measurements served as input data for the model. The results show that the typical CoM excursion is within 2-3 cm roughly one order of magnitude higher than in double stance standing. Average oscillations of the joint angles ranged from 0.79 to 4.57 deg, with the higher values taking place in the hip sagittal rotation. The highest torques were coronal, at the hip, amounting to an average of 141 Nm. It was also found that when moving from ankle to hip the sequence of torque and angular displacement is inverted, indicating that the power delivered to the muscles at the distal/proximal joint is taken back by the muscles acting about the upper/lower joint. This provides evidence for the central strategy of the body to keep the CoM in a stable position.