We examined the role that ambient air pollution plays in exacerbating cardiac disease by relating daily fluctuations in admissions to 134 hospitals for congestive heart failure in the elderly to daily variations in ambient concentrations of carbon monoxide, nitrogen dioxide, sulfur dioxide, ozone, and the coefficient of haze in Canada's 10 largest cities for the 11-year period 1981-1991 inclusive. We adjusted the hospitalization time series for seasonal, subseasonal, and weekly cycles and for hospital usage patterns. The logarithm of the daily high-hour ambient carbon monoxide concentration recorded on the day of admission displayed the strongest and most consistent association with hospitalization rates among the pollutants, after stratifying the time series by month of year and adjusting simultaneously for temperature, dew point, and the other ambient air pollutants. The relative risk for a change from 1 ppm to 3 ppm, the 25th and 75th percentiles of the exposure distribution, was 1.065 (95% confidence interval = 1.028-1.104). The regression coefficients of the other air pollutants were much more sensitive to simultaneous adjustment for either multiple pollutant or weather model specifications.
The effects of tropospheric ozone on lung function and respiratory symptoms have been well documented at relatively high concentrations. However, previous investigations have failed to establish a clear association between tropospheric ozone and respiratory diseases severe enough to require hospitalization after controlling for climate, and with gaseous and particulate air pollution at the lower concentrations typically observed in Canada today. To determine if low levels of tropospheric ozone contribute to hospitalization for respiratory disease, air pollution data were compared to hospital admissions for 16 cities across Canada representing 12.6 million people. During the 3927-day period from April 1, 1981, to December 31, 1991, there were 720,519 admissions for which the principle diagnosis was a respiratory disease. After controlling for sulfur dioxide, nitrogen dioxide, carbon monoxide, soiling index, and dew point temperature, the daily high hour concentration of ozone recorded 1 day previous to the date of admission was positively associated with respiratory admissions in the April to December period but not in the winter months. The relative risk for a 30 ppb increase in ozone varied from 1.043 (P
The association of daily cardiac and respiratory admissions to 168 acute care hospitals in Ontario, Canada, with daily levels of particulate sulfates was examined over the 6-year period 1983-1988. Sulfate levels were recorded at nine monitoring stations in regions of southern and central Ontario spanned by three monitoring networks. A 13-micrograms/m3 increase in sulfates recorded on the day prior to admission (the 95th percentile) was associated with a 3.7% (p
A case-control study of lung cancer in relation to exposure to radon in homes in Winnipeg, Manitoba, Canada, was conducted during 1983-1990. In total, 738 individuals with histologically confirmed incident cases of lung cancer were interviewed, along with 738 controls matched on age (+/- 5 years) and sex. Radon dosimeters were placed in all residences in which the study subjects had reported living within the Winnipeg metropolitan area for at least 1 year. Radon dosimetry was done by means of integrated alpha-track measurements over a 1-year period. In the homes monitored, the average level of radon-222 was about 120 becquerels (Bq)/m3 in the bedroom area and 200 Bq/m3 in the basement. After adjusting for cigarette smoking and education, no increase in the relative risk for any of the histologic types of lung cancer observed among the cases was detected in relation to cumulative exposure to radon.
Comment In: Am J Epidemiol. 1995 Nov 15;142(10):1121-27485057
Comment In: Am J Epidemiol. 1995 Oct 15;142(8):884-67572965
Comment In: Am J Epidemiol. 1994 Aug 15;140(4):323-328059767
Comment In: Am J Epidemiol. 1994 Aug 15;140(4):333-98059768
Assess associations between short-term exposure to gaseous pollutants and asthma hospitalisation among boys and girls 6 to12 years of age.
A bi-directional case-crossover analysis was used. Conditional logistic regression models were fitted to the data for boys and girls separately. Exposures averaged over periods ranging from one to seven days were used to assess the effects of gaseous pollutants on asthma hospitalisation. Estimated relative risks for asthma hospitalisation were calculated for an incremental exposure corresponding to the interquartile range in pollutant levels, adjusted for daily weather conditions and concomitant exposure to particulate matter.
Toronto, Ontario, Canada.
A total of 7319 asthma hospitalisations for children 6 to 12 years of age (4629 for boys and 2690 for girls) in Toronto between 1981 and 1993.
A significant acute effect of carbon monoxide on asthma hospitalisation was found in boys, and sulphur dioxide showed significant effects of prolonged exposure in girls. Nitrogen dioxide was positively associated with asthma admissions in both sexes. The lag time for certain gaseous pollutant effects seemed to be shorter in boys (around two to three days for carbon monoxide and nitrogen dioxide), as compared with girls (about six to seven days for sulphur dioxide and nitrogen dioxide). The effects of gaseous pollutants on asthma hospitalisation remained after adjustment of particulate matter. The data showed no association between ozone and asthma hospitalisation in children.
The study showed positive relations between gaseous pollutants (carbon monoxide, sulphur dioxide, and nitrogen dioxide) at comparatively low levels and asthma hospitalisation in children, using bi-directional case-crossover analyses. Though, the effects of certain specific gaseous pollutants were found to vary in boys and girls.
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To investigate the acute respiratory health effects of ambient air pollution, the number of emergency of urgent daily respiratory admissions to 168 acute care hospitals in Ontario were related to estimates of exposure to ozone and sulfates in the vicinity of each hospital. Ozone levels were obtained from 22 monitoring stations maintained by the Ontario Ministry of the Environment for the period January 1, 1983 to December 31, 1988. Daily levels of sulfates were recorded at nine monitoring stations representing three different networks operated by the Ontario Ministry of the Environment and Environment Canada. Positive and statistically significant associations were found between hospital admissions and both ozone and sulfates recorded on the day of admission and up to 3 days prior to the date of admission. Five percent of daily respiratory admissions in the months of May to August were associated with ozone, with sulfates accounting for an additional 1% of these admissions. Ozone was a stronger predictor of admissions than sulfates. Positive and statistically significant (P
The association between daily fluctuations in ambient particulate matter and daily variations in nonaccidental mortality have been extensively investigated. Although it is now widely recognized that such an association exists, the form of the concentration-response model is still in question. Linear, no threshold and linear threshold models have been most commonly examined. In this paper we considered methods to detect and estimate threshold concentrations using time series data of daily mortality rates and air pollution concentrations. Because exposure is measured with error, we also considered the influence of measurement error in distinguishing between these two completing model specifications. The methods were illustrated on a 15-year daily time series of nonaccidental mortality and particulate air pollution data in Toronto, Canada. Nonparametric smoothed representations of the association between mortality and air pollution were adequate to graphically distinguish between these two forms. Weighted nonlinear regression methods for relative risk models were adequate to give nearly unbiased estimates of threshold concentrations even under conditions of extreme exposure measurement error. The uncertainty in the threshold estimates increased with the degree of exposure error. Regression models incorporating threshold concentrations could be clearly distinguished from linear relative risk models in the presence of exposure measurement error. The assumption of a linear model given that a threshold model was the correct form usually resulted in overestimates in the number of averted premature deaths, except for low threshold concentrations and large measurement error.