Spatial analysis of exposure to traffic-related air pollution at birth and childhood atopic asthma in Toronto, Ontario.

Findings from the Toronto Child Health Evaluation Questionnaire (TCHEQ) study indicate that early childhood exposure to traffic-related air pollution (TRAP) is related to the onset of atopic childhood asthma. To test this hypothesis further, we investigated whether spatial patterns in the birth neighbourhood of TCHEQ subjects with atopic asthma (136 of 909 schoolchildren in grades 1-2) could be explained by TRAP and other risk factors. If a causal relationship exists between early childhood residential exposure to TRAP and the development of atopic asthma, we hypothesise that (1) clusters of current asthma should exist around the place of residence at birth, and (2) accounting for residential concentrations of TRAP at birth should explain some of the autocorrelation. Several high asthma clusters were observed. Adjusting for TRAP completely explained one cluster; elsewhere, clusters were only partially explained by TRAP. Findings suggest that exposure during early childhood to TRAP in Toronto is an important contributor to the development of the atopic asthma phenotype and reveal the likely importance of other risk factors not measured in the fixed effects of the model.

Is outdoor air pollution associated with physician visits for allergic rhinitis among the elderly in Toronto, Canada?

BACKGROUND: While a number of studies suggest that air pollution is associated with allergic rhinitis in children, findings among adults have been equivocal. The aim of this study was to examine the relationship between outdoor air pollution and physician visits for allergic rhinitis among individuals>or=65 years of age in Toronto, Canada. METHODS: Physician visits were identified by using data from the Ontario provincial health insurance plan that is made available to all residents. Our analyses are based on 52,691 physician visits for allergic rhinitis among individuals>or=65 years of age in the Toronto metropolitan area between 1995 and 2000. Generalized linear models were used to regress daily counts of physician visits against daily measures of gaseous and particulate components of air pollution after controlling for seasonality, potential confounders (temperature, relative humidity, aeroallergens), overdispersion and serial correlation. RESULTS: A large number of comparisons were undertaken, with most showing no statistically significant associations between daily levels of air pollution and the number of physician visits for rhinitis. In contrast, an interquartile increase in the 10-day average of ragweed particles increased the mean number of daily rhinitis consultations by 6.4% (95% CI=0.7-12.4%). CONCLUSIONS: Our findings suggest that outdoor air pollution is a poor predictor of physician visits for allergic rhinitis among the elderly.

Weather and emergency room visits for migraine headaches in Ottawa, Canada.

BACKGROUND: Self-reported surveys have indicated that weather can trigger migraine headaches. However, to date, we know of no previous study that has examined the relationship between weather and emergency room (ER) visits for this condition. OBJECTIVE: To examine associations between ER visits for migraines and selected meteorological conditions within the 24 hours preceding the visit. DESIGN AND METHODS: A case-crossover design was used to study 4039 visits for migraines (ICD-9: 346) that occurred at an Ottawa hospital between 1993 and 2000. Meteorological conditions were defined using hourly readings from a fixed-site monitoring station. Conditional logistic regression was used to compare the occurrence of meteorological conditions during the 24 hours leading up to the time of the visit to control periods occurring 1 week before and after. RESULTS: Precipitation-related weather events (fog, snow, rain, thunder) were not associated with migraine visits. Similarly, no associations were observed with changes in atmospheric pressure, wind speed, and relative humidity during the 24 hours preceding presentation. No statistically significant differences in the frequency distribution of clusters defined by relative humidity, atmospheric pressure, and temperature were found between case and control intervals. Conversely, a mean wind speed in excess of 19 km per hour was associated with a reduction in ER visits 8 to 12 hours later. CONCLUSIONS: Our findings provide little support for the hypothesis that ER visits for migraines are related to weather conditions occurring within the 24 hours preceding presentation. These results should be interpreted cautiously as some comparisons are based on a small number of cases, and ER visits for migraine may represent a highly selective group of patients who suffer from this condition.

Association between ozone and hospitalization for acute respiratory diseases in children less than 2 years of age.

To clarify the health effects of ozone exposure in young children, the authors studied the association between air pollution and hospital admissions for acute respiratory problems in children less than 2 years of age during the 15-year period from 1980 to 1994 in Toronto, Canada. The daily time series of admissions was adjusted for the influences of day of the week, season, and weather. A 35% (95% confidence interval: 19%, 52%) increase in the daily hospitalization rate for respiratory problems was associated with a 5-day moving average of the daily 1-hour maximum ozone concentration of 45 parts per billion, the May-August average value. The ozone effect persisted after adjustment for other ambient air pollutants or weather variables. Ozone was not associated with hospital admissions during the September-April period. Ambient ozone levels in the summertime should be considered a risk factor for respiratory problems in children less than 2 years of age.

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 SO4(2-). 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.

The costs of cardiorespiratory disease episodes in a study of emergency department use.

OBJECTIVE: The average per person direct cost of illness of cardiorespiratory disease episodes was estimated based on a prospective study of emergency department visits. METHODS: Economic modelling of health care costs using prospectively collected resource utilization data (9/1/94 to 8/31/95) from hospital emergency department visitors assigned a diagnosis of asthma, chronic obstructive pulmonary disease (COPD), respiratory infections or cardiac conditions. RESULTS: The total direct costs (1997 CDN$) [95% C.I.] per patient were $1,043.55 [$922.65, $1,164.47] for asthma, $1,690.11 [$1,276.92, $2,103.30] for COPD, $676.50 [$574.46, $778.54] for respiratory infections, and $3,318.74 [$2,937.72, $3,699.76] for cardiac conditions. CONCLUSIONS: This study showed that on average, patients diagnosed with a cardiac condition had the highest total direct cost. Hospitalization cost was the largest component of costs for all diagnoses except asthma, for which medications were the single largest component of direct costs.

Beyond administrative data: characterizing cardiorespiratory disease episodes among patients visiting the emergency department.

We attempted to address deficiencies in administrative health service data during a study of cardiorespiratory emergency department visits. From 1994-1996, we obtained data on 9,264 visits and conducted 1,772 follow-up interviews. The median interval between symptoms and visit ranged from 0.8 days (95% CI 0-1.7) for cardiac conditions to 4.0 days for chronic obstructive pulmonary disease (COPD) (95% CI 2.7-5.3) and respiratory infections (95% CI 3.5-4.5). Infection was the most common trigger of respiratory visits. Although most had improved at follow-up, symptoms persisted following the visit for a mean of 4.5 days (95% CI 3.8-5.4) for cardiac conditions to 8.4 days (95% CI 7.2-9.5) for COPD. Among adults aged < 70, the mean number of reduced activity days per episode ranged from 4.7 (95% CI 3.9-5.4) for asthma to 6.6 (95% CI 5.9-7.4) for respiratory infections. Our data assist in interpreting epidemiological studies based on administrative data, and illustrate the broad impacts of cardiorespiratory disease episodes.

Effects of particulate and gaseous air pollution on cardiorespiratory hospitalizations.

We obtained data on daily numbers of admissions to hospital in Toronto, Canada, from 1980 to 1994 for respiratory, cardiac, cerebral vascular, and peripheral vascular diseases. We then linked the data to daily measures of particulate mass less than 10 microns in aerodynamic diameter (PM10), particulate mass less than 2.5 microns in aerodynamic diameter (PM2.5), and particulate mass between 2.5 and 10 microns in aerodynamic diameter (PM10-2.5), ozone, carbon monoxide, nitrogen dioxide, and sulfur dioxide. Air pollution was only associated weakly with hospitalization for cerebral vascular and peripheral vascular diseases. We controlled for temporal trends and climatic factors, and we found that increases of 10 microg/m3 in PM10, PM2.5, and PM10-2.5 were associated with 1.9%, 3.3%, and 2.9% respective increase in respiratory and cardiac hospital admissions. We further controlled for gaseous pollutants, and the percentages were reduced to 0.50%, 0.75%, and 0.77%, respectively. Of the 7.72 excess daily hospital admissions in Toronto attributable to the atmospheric pollution mix, 11.8% resulted from PM2.5, 8.2% to PM10-2.5, 17% to carbon monoxide, 40.4% to nitrogen dioxide, 2.8% to sulfur dioxide, and 19.8% to ozone.

Assessing diagnostic classification in an emergency department: implications for daily time series studies of air pollution.

Seven independent assessments of diagnosis were obtained for 92 records of nontrauma emergency department visits in Saint John, New Brunswick, Canada, in 1994. The hospital database was 1.18 times as likely (p < 0.05) as six external physician raters to classify visits as cardiorespiratory, which was consistent for high- and low-pollution days. Kappa was 0.70 (95 percent confidence interval (CI) 0.68-0.73). Kappajs were: asthma, 0.69 (95% CI 0.64-0.73); chronic obstructive pulmonary disease, 0.78 (95% CI 0.74-0.83); respiratory infections, 0.53 (95% CI 0.49-0.57); cardiac, 0.84 (95% CI 0.79-0.88); and other, 0.66 (95% CI 0.62-0.71). Substantial or better interobserver agreement was seen, respiratory infections notwithstanding, and there was no evidence of diagnostic bias in relation to daily air pollution level.

The association between ambient carbon monoxide levels and daily mortality in Toronto, Canada.

The role of ambient levels of carbon monoxide (CO) in the exacerbation of heart problems in individuals with both cardiac and other diseases was examined by comparing daily variations in CO levels and daily fluctuations in nonaccidental mortality in metropolitan Toronto for the 15-year period 1980-1994. After adjusting the mortality time series for day-of-the-week effects, nonparametic smoothed functions of day of study and weather variables, statistically significant positive associations were observed between daily fluctuations in mortality and ambient levels of carbon monoxide, nitrogen dioxide, sulfur dioxide, coefficient of haze, total suspended particulate matter, sulfates, and estimated PM2.5 and PM10. However, the effects of this complex mixture of air pollutants could be almost completely explained by the levels of CO and total suspended particulates (TSP). Of the 40 daily nonaccidental deaths in metropolitan Toronto, 4.7% (95% confidence interval of 3.4%-6.1%) could be attributable to CO while TSP contributed an additional 1.0% (95% confidence interval of 0.2-1.9%), based on changes in CO and TSP equivalent to their average concentrations. Statistically significant positive associations were observed between CO and mortality in all seasons, age, and disease groupings examined. Carbon monoxide should be considered as a potential public health risk to urban populations at current ambient exposure levels.

Eliciting stated health preferences: an application to willingness to pay for longevity.

The economic analysis of many health policies requires evaluation of the benefits of programs that may prolong human lives. This article contributes to the development of credible values for longevity, demonstrating the feasibility of applying stated-preference market-research techniques to a new area of preference revelation and framing the problem as extending longevity under realistic health states associated with advanced age. Respondents to the authors' stated-preference survey clearly indicated that quality of life affects the value of quantity of life. The results demonstrate the sensitivity of life-extension values to specific health and activity-limitation conditions. The article also discusses problems that remain to be solved before valid and reliable longevity values can be obtained.

Association between ozone and asthma emergency department visits in Saint John, New Brunswick, Canada.

This study examines the relationship of asthma emergency department (ED) visits to daily concentrations of ozone and other air pollutants in Saint John, New Brunswick, Canada. Data on ED visits with a presenting complaint of asthma (n = 1987) were abstracted for the period 1984-1992 (May-September). Air pollution variables included ozone, sulfur dioxide, nitrogen dioxide, sulfate, and total suspended particulate (TSP); weather variables included temperature, humidex, dewpoint, and relative humidity. Daily ED visit frequencies were filtered to remove day of the week and long wave trends, and filtered values were regressed on air pollution and weather variables for the same day and the 3 previous days. The mean daily 1-hr maximum ozone concentration during the study period was 41.6 ppb. A positive, statistically significant (p < 0.05) association was observed between ozone and asthma ED visits 2 days later, and the strength of the association was greater in nonlinear models. The frequency of asthma ED visits was 33% higher (95% CI, 10-56%) when the daily 1-hr maximum ozone concentration exceeded 75 ppb (the 95th percentile). The ozone effect was not significantly influenced by the addition of weather or other pollutant variables into the model or by the exclusion of repeat ED visits. However, given the limited number of sampling days for sulfate and TSP, a particulate effect could not be ruled out. We detected a significant association between ozone and asthma ED visits, despite the vast majority of sampling days being below current U.S. and Canadian standards.

Do smog advisories work? Results of an evaluation of the Canadian Smog Advisory Program.

OBJECTIVE: To determine the effectiveness of the Canadian Smog Advisory Program. METHODS: Telephone interviews covering perceptions, knowledge, recall of and response to advisories, and general views on their usefulness and effectiveness were conducted with 1,474 randomly selected individuals in four geographic areas. Multiple logistic regression was used to model advisory recall as a function of explanatory variables. RESULTS: Recall of advisories was higher (72%; 95% CI 68-77%) when measured immediately following an advisory in southern New Brunswick. Recall was lower when measured at the end of the smog "season", and varied significantly between Toronto (46%; 42-51%), Haldimand-Norfolk (18%; 14-24%) and Vancouver (61%; 56-65%). Education and geographic area (urban versus rural) were the strongest explanatory variables in two final multiple logistic regression models. A minority of those who recalled an advisory reported taking action. CONCLUSIONS: Smog advisories were partially successful in generating awareness, but only marginally effective in promoting action.

Health and development in the Hudson Bay/James Bay region.

This paper reviews the literature on the health status of native people in the Hudson Bay/James Bay region of Canada, and explores the role of development in explaining discrepancies between observed and expected demographic and health trends. Relevant scientific literature was identified using computerised searches of bibliographic databases, as well as manual searches of selected journals and contact with experts. Although there was evidence that native people in Hudson Bay/James Bay have experienced significant improvements in health status, overall health status remains much worse than that of other Canadians. In many native communities, the prevalence and incidence of formerly infrequent chronic diseases have now surpassed those observed in non-native populations, and injuries, poisonings and violence are at epidemic levels. While these trends may be attributable to a variety of factors, environmental contamination and accompanying social, economic and cultural changes appear to play an important role.

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.

Fatal occupational accidents in Ontario, 1986-1989.

We examined 470 fatal occupational accidents in Ontario, 1986-1989, that met eligibility criteria. Homicides and most accidents on public roads were excluded. Information was obtained from coroners' files and records of the provincial Ministry of Labour. Levels of alcohol likely to produce impairment were found in six subjects (2% of the two-thirds of fatalities tested). Cannabis was detected in 3.9% of cases (17% of those tested), but other illegal drugs were not found. Recommendations of coroner's juries showed that organizational factors were considered relevant on many occasions, although language and literacy were rarely mentioned. The incidence rate rose steadily with age. Other data items were examined, although, because of missing information and/or lack of denominator data for many of them, the conclusions that can be drawn are limited. Among these tentative findings was that more fatal accidents occurred in the first half of the shift than in the second half.

Effectiveness of Haemophilus influenzae type b vaccines.

PURPOSE: To determine the clinical effectiveness of Haemophilus influenzae type b (Hib) vaccines. STUDY IDENTIFICATION AND SELECTION: Computerized searches of MEDLINE, EMBASE and SCISEARCH databases were performed, and the reference list of each retrieved article was reviewed. Two prospective clinical trials of Hib polyribosyl ribitol phosphate conjugated with diphtheria toxoid (PRP-D) were identified. In addition, one cohort study of the PRP-D vaccine, two trials of the PRP vaccine, five case-control studies of the PRP vaccine and 10 randomized controlled trials of the immunogenicity of the PRP-D vaccine were identified. DATA EXTRACTION: Study quality was assessed and descriptive information concerning the study populations, the interventions and the outcome measurements was extracted. RESULTS: The difference in the effectiveness of the PRP-D vaccine between the prospective trials, in which a three-dose schedule had been used beginning at 2 to 3 months of age, was clinically important (37% v. 83%) but not statistically significant. The PRP vaccine, which induces lower antibody responses than the PRP-D vaccine does, was clinically effective only in a subgroup of one prospective trial; 90% effectiveness was reported among children 18 to 60 months of age. CONCLUSIONS: Hib vaccine appears to be less effective in high-risk populations. None the less, because of the large variation in baseline risk, the number of children who would have to be vaccinated to prevent one case of invasive Hib disease is substantially less for high-risk than for low-risk populations. The vaccination of children at high risk, such as native children, with the PRP-D vaccine using a four-dose schedule (at 2, 4, 6 and 14 months of age) seems warranted. The currently available evidence does not strongly support a policy of universal vaccination with either a one-dose or a four-dose schedule.