David M. Stieb

Modelling psychosocial effects of exposure to solid waste facilities

A parallel case study design was used to investigate psychosocial effects in populations exposed to solid waste facilities. Psychosocial effects were defined as a complex of distress, dysfunction and disability, manifested in a range of psychological, social and behavioural outcomes, as a consequence of actual or perceived environmental contamination. This paper presents the results of logistic regression analyses designed to identify determinants of psychosocial effects of exposure. The data come from an epidemiologic survey of residents (N = 696) living within a prescribed radius from each of three solid waste facilities in southern Ontario. The analytical model has three main components: external variables (e.g. individual and exposure-related variables); mediating variables (e.g. social network membership and involvement, general health status measures); and outcome variables (e.g. concern, effects and actions). Results for a series of site specific analyses show that outcome measures can be successfully explained by a combination of external and mediating factors. In general, variables from each of the three main components enter the concern-related models while the action models are clearly dominated by social network variables. Analyses using data from all three sites indicate the explanatory power of site-related characteristics. However, given the number and diversity of variables in the models, there is no support for a simple cause and effect relationship. The implication is that strategies aimed to address and alleviate psychosocial effects need to be specific to the characteristics of the populations in particular settings.

Air pollution, aeroallergens and cardiorespiratory emergency department visits in Saint John, Canada.

Existing studies of the association between air pollution, aeroallergens and emergency department (ED) visits have generally examined the effects of a few pollutants or aeroallergens on individual conditions such as asthma or chronic obstructive pulmonary disease. In this study, we considered a wide variety of respiratory and cardiac conditions and an extensive set of pollutants and aeroallergens, and utilized prospectively collected information on possible effect modifiers which would not normally be available from purely administrative data. The association between air pollution, aeroallergens and cardiorespiratory ED visits (n=19,821) was examined for the period 1992 to 1996 using generalized additive models. ED visit, air pollution and aeroallergen time series were prefiltered using LOESS smoothers to minimize temporal confounding, and a parsimonious model was constructed to control for confounding by weather and day of week. Multipollutant and multi-aeroallergen models were constructed using stepwise procedures and sensitivity analyses were conducted by season, diagnosis, and selected individual characteristics or effect modifiers. In single-pollutant models, positive effects of all pollutants but NO2 and COH were observed on asthma visits, and positive effects on all respiratory diagnosis groups were observed for O3, SO2, PM10, PM2.5, and SO42−. Among cardiac conditions, only dysrhythmia visits were positively associated with all measures of particulate matter. In the final year-round multipollutant models, a 20.9% increase in cardiac ED visits was attributed to the combination of O3 (16.0%, 95% CI 2.8–30.9) and SO2 (4.9%, 95%CI 1.7–8.2) at the mean concentration of each pollutant. In the final multipollutant model for respiratory visits, O3 accounted for 3.9% of visits (95% CI 0.8–7.2), and SO2 for 3.7% (95% CI 1.5–6.0), whereas a weak, negative association was observed with NO2. In multi-aeroallergen models of warm season asthma ED visits, Ascomycetes, Alternaria and small round fungal spores accounted for 4.5% (95% CI 1.8–7.4), 4.7% (95% CI 1.0–8.6) and 3.0% (95% CI 0.8–5.1), respectively, of visits at their mean concentrations, and these effects were not sensitive to adjustment for air pollution effects. In conclusion, we observed a significant influence of the air pollution mix on cardiac and respiratory ED visits. Although in single-pollutant models, positive associations were noted between ED visits and some measures of particulate matter, in multipollutant models, pollutant gases, particularly ozone, exhibited more consistent effects. Aeroallergens were also significantly associated with warm season asthma ED visits.

Effects of Age, Season, Gender and Urban-Rural Status on Time-Activity: Canadian Human 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.

A Review of Time-Series Studies Used to Evaluate the Short-Term Effects of Air Pollution on Human Health

We review the methodology used in the analysis of time-series studies of ambient air pollution. Our focus is on mortality studies, in which daily counts of death are correlated with changes in air pollution. We first illustrate the methods by showing data from the 1950s, during which the effects of air pollution were much more pronounced, and then describe current methods that were developed to identify associations when the signal-to-noise ratio is much lower. We describe basic data sources, details of statistical methods, and current state of the art, especially as it refers to problems found recently with the fitting algorithm used in the generalized additive models. A summary of the findings from mortality studies is presented and the pre-eminent issues regarding methods, interpretation, and identification of susceptible populations are discussed. We conclude by describing possible biological mechanisms and suggesting other designs that will aid in the interpretation of data from studies of acute health effects.

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 O3 (p = 0.3870) but somewhat stronger for NO2 (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 NO2 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 NO2 appear to be increasing. Further investigations are necessary to understand why the concentrations and adverse effects of NO2 show opposite time trends.

Asthma and Allergic Disease Prevalence in a Diverse Sample of Toronto School Children: Results from the Toronto Child Health Evaluation Questionnaire (T-CHEQ) Study

BACKGROUND Asthma is the most common chronic disease in children. OBJECTIVES To describe the prevalence of asthma and allergic disease in a multiethnic, population-based sample of Toronto (Ontario) school children attending grades 1 and 2. METHODS In 2006, the Toronto Child Health Evaluation Questionnaire (T-CHEQ) used the International Study of Asthma and Allergies in Childhood survey methodology to administer questionnaires to 23,379 Toronto school children attending grades 1 and 2. Modifications were made to the methodology to conform with current privacy legislation and capture the ethnic diversity of the population. Lifetime asthma, wheeze, hay fever and eczema prevalence were defined by parental report. Asthma was considered to be current if the child also reported wheeze or asthma medication use in the previous 12 months. RESULTS A total of 5619 children from 283 randomly sampled public schools participated. Children were five to nine years of age, with a mean age of 6.7 years. The overall prevalence of lifetime asthma was 16.1%, while only 11.3% had current asthma. The reported prevalence of lifetime wheeze was 29.2%, while 14.2% reported wheeze in the past 12 months. Sociodemographic and major health determinant characteristics of the T-CHEQ population were similar to 2001 census data, suggesting a diverse sample that was representative of the urban childhood population. CONCLUSIONS Asthma continues to be a highly prevalent chronic disease in Canadian children. A large proportion of children with reported lifetime asthma, who were five to nine years of age, did not report current asthma symptomatology or medication use.

The Air Quality Health Index as a predictor of emergency department visits for ischemic stroke in Edmonton, Canada

The Air Quality Health Index (AQHI) is an aggregate measure of outdoor air quality. We investigated associations between the AQHI and emergency department (ED) visits for acute ischemic stroke to validate the AQHI as a predictor of risk of morbidity from stroke. ED visits in Edmonton, Canada between 1998 and 2002 were linked to hourly AQHI values and concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), ozone, particulate matter with aerodynamic diameter less than 2.5 and 10 μm, and sulfur dioxide. A time-stratified case-crossover analysis was employed, and measures of association were adjusted for temperature and relative humidity. The AQHI, NO2 and CO were positively associated with the number of ED visits for ischemic stroke during April–September, and associations were strongest for persons 75 years of age and older. In this age range, the odds ratios (95% confidence intervals) for an interquartile range increase of AQHI in 1–24 h, 25–48 h, and 1–72 h lag periods were 1.23 (1.08–1.40), 1.15 (1.01–1.31), and 1.30 (1.10–1.54), respectively. Significant positive associations were also observed for NO2 and CO. Our finding that ED visits for stroke were significantly associated with the AQHI suggests that the AQHI may be a valid communication tool for air pollution morbidity effects related to stroke.

Health Effects of Air Pollution in Canada: Expert Panel Findings for The Canadian Smog Advisory Program

OBJECTIVE: To review the evidence on health effects of air pollution for the Canadian Smog Advisory Program.

Assessment of long-term exposure to air pollution in a longitudinal national health survey

Self-reported data on the municipality of residence were used to assess long-term exposure to outdoor air pollution from 1980 to 2002 in the longitudinal Canadian National Population Health Survey. Exposure to carbon monoxide, nitrogen dioxide, ozone, sulfur dioxide, and particulate matter was determined using data obtained from fixed-site air pollution monitors operated principally in urban areas. Four different methods of attributing pollution exposure were used based on residence in (1) 1980, (2) 1994, (3) 1980 and 1994, and (4) at all locations between 1980 and 2002. Between 1,693 and 4,274 of 10,515 members of the cohort could be assigned exposures to individual pollutants using these methods. On average, subjects spent 71.4% of the 1980–2002 period in the census subdivision where they lived in 1980. A single exposure measure in 1980 or 1994 or a mean of the two measures was highly correlated (r>0.7, P<0.0001) with a measure which accounted for all moves between 1980 and 2002. Although our ability to characterize long-term exposure was constrained by a lack of data from fixed-site monitors, the low frequency of moves meant that measures based on a single year generally provided a good approximation of long-term exposure at the census subdivision level.