Air pollution, pollens, and daily admissions for asthma in London 1987-92

Abstract

Background-A study was undertaken to investigate the relationship between daily hospital admissions for asthma and air pollution in London in 1987-92 and the possible confounding and modifying effects of airborne pollen. Methods-For all ages together and the age groups 0-14, 15-64 and 65+ years, Poisson regression was used to estimate the relative risk of daily asthma admissions associated with changes in ozone, sulphur dioxide, nitrogen dioxide and particles (black smoke), controlling for time trends, seasonal factors, calendar eVects, influenza epidemics, temperature, humidity, and autocorrelation. Independent eVects of individual pollutants and interactions with aeroallergens were explored using two pollutant models and models including pollen counts (grass, oak and birch). Results-In all-year analyses ozone was significantly associated with admissions in the 15-64 age group (10 ppb eight hour ozone, 3.93% increase), nitrogen dioxide in the 0-14 and 65+ age groups (10 ppb 24 hour nitrogen dioxide, 1.25% and 2.96%, respectively), sulphur dioxide in the 0-14 age group (10 µg/m 3 24 hour sulphur dioxide, 1.64%), and black smoke in the 65+ age group (10 µg/m 3 black smoke, 5.60%). Significant seasonal differences were observed for ozone in the 0-14 and 15-64 age groups, and in the 0-14 age group there were negative associations with ozone in the cool season. In general, cumulative lags of up to three days tended to show stronger and more significant eVects than single day lags. In twopollutant models these associations were most robust for ozone and least for nitrogen dioxide. There was no evidence that the associations with air pollutants were due to confounding by any of the pollens, and little evidence of an interaction between pollens and pollution except for synergism of sulphur dioxide and grass pollen in children (p<0.01). Conclusions-Ozone, sulphur dioxide, nitrogen dioxide, and particles were all found to have significant associations with daily hospital admissions for asthma, but there was a lack of consistency across the age groups in the specific pollutant. These associations were not explained by confounding by airborne pollens nor was there convincing evidence that the eVects of air pollutants and airborne pollens interact in causing hospital admissions for asthma. (Thorax 1998;53:842-848)

A tale of two cities: effects of air pollution on hospital admissions in Hong Kong and London compared.

“…It could be postulated that the Hong Kong population would be more resistant to O 3 because the diet is higher in antioxidants and because air conditioning is used in most closed spaces, but our data suggest that both populations are equally susceptible. It is relevant to note that O 3 also shows associations with respiratory admissions in a range of European cities, with little heterogeneity (33,38). In both London and Hong Kong, the association with O 3 was very robust to the inclusion of other pollutants in the model.…”

Association of asthma symptoms with peak particulate air pollution and effect modification by anti-inflammatory medication use.

“…Our previous asthma panel studies did not find confounding of air pollutant associations by outdoor pollen or fungi (1,7,8). Several time-series investigations have found associations between asthma hospital admissions and both outdoor air pollutants (particles, NO 2 , or O 3 ) and pollen or fungi, but none has found any confounding between aeroallergens and these pollutants (54,60,61). In two studies, there was evidence that SO 2 , NO 2 , and O 3 enhanced the effect of grass pollen on asthma admissions (54,60), although there was a negative interaction between O 3 and tree pollen in one of these studies (54).…”

“…Several time-series investigations have found associations between asthma hospital admissions and both outdoor air pollutants (particles, NO 2 , or O 3 ) and pollen or fungi, but none has found any confounding between aeroallergens and these pollutants (54,60,61). In two studies, there was evidence that SO 2 , NO 2 , and O 3 enhanced the effect of grass pollen on asthma admissions (54,60), although there was a negative interaction between O 3 and tree pollen in one of these studies (54). The general inconsistency between epidemiologic and experimental data on the enhancement of allergen-induced respiratory responses by air pollutants may be explained by a lack of temporally resolved data to account for hourly exposures and a lack of spatially resolved data to account for personal exposures to pollutants and aeroallergens.…”

Pollen Loads and Allergic Rhinitis in Darwin, Australia: A Potential Health Outcome of the Grass-Fire Cycle

“…As there is uncertainty regarding the shape of the concentrationresponse functions and the possibility of threshold levels of aeroallergens and allergic disease outcomes (Anderson et al, 1998;Stieb et al, 2000;Dales et al, 2004), we used a two-stage approach to our analysis. First, we used generalized additive models (GAM) with penalized cubic regression splines to assess the shape of the concentrationresponse curves at each lag (Wood, 2004).…”