Association of air pollution with daily GP consultations for asthma and other lower respiratory conditions in London.
BACKGROUND
Very few published studies have looked at the effects of air pollution on health in the primary care setting. As part of a large study to examine the association between air pollution and a number of health outcomes, the relationship between daily GP consultations for asthma and other lower respiratory diseases (LRD) and air pollution in London was investigated.


METHODS
Time-series analysis of daily numbers of GP consultations controlling for time trends, seasonal factors, day of week cycles, influenza, weather, pollen levels, and serial correlation was performed. Consultation data were available from between 268 718 and 295 740 registered patients from 45-47 London practices contributing to the General Practice Research Database during 1992-4.


RESULTS
Positive associations, weakly significant and consistent across lags, were observed between asthma consultations and nitrogen dioxide (NO2) and carbon monoxide (CO) in children and particulate matter of less than 10 microm in diameter (PM10) in adults, and between other LRD consultations and sulphur dioxide (SO2) in children. A consistently negative association with ozone in children was observed in both disease categories. The effect estimates of most pollutants were much larger when analysed separately by season, particularly in the children: percentage change in asthma consultations during the warm season (April-September) for a 10-90th percentile increase in 24 hour NO2 lagged by one day = 13.2% (95% CI 5.6 to 21.3), with CO = 11.4% (95% CI 3.3 to 20.0), and with SO2 = 9.0% (95% CI 2.2 to 16.2). In adults the only association consistent over different lag periods was with PM10 = 9.2% (3.7 to 15.1). The associations of pollution and consultations for LRD were increased mainly in the winter months: percentage change in consultations by children in winter with NO2 = 7.2% (95% CI 2.8 to 11.6), CO = 6.2% (95% CI 2.3 to 10.2), and SO2 = 5.8% (95% CI 1.6 to 10.2).


CONCLUSIONS
There are associations between air pollution and daily consultations for asthma and other lower respiratory disease in London. The most significant associations were observed in children and the most important pollutants were NO2, CO, and SO2. In adults the only consistent association was with PM10.
Hajat
S
S
Department of Primary Care and Population Sciences, Royal Free and University College Medical School, University College London, London NW3 2PF, UK.
Haines
A
A
Goubet
S A
SA
Atkinson
R W
RW
Anderson
H R
HR
D000293:Adolescent; D000328:Adult; D000368:Aged; D000397:Air Pollution / Q000009:adverse effects*; D001249:Asthma / Q000628:therapy; D002248:Carbon Monoxide; D002648:Child; D002675:Child, Preschool; D016208:Databases, Factual; D005194:Family Practice / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D008131:London / Q000453:epidemiology; D008171:Lung Diseases / Q000628:therapy*; D008875:Middle Aged; D015233:Models, Statistical; D009585:Nitrogen Dioxide; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data*; D012621:Seasons; D013458:Sulfur Dioxide
D013458:Sulfur Dioxide; D002248:Carbon Monoxide; D009585:Nitrogen Dioxide