Urban asthma.
OBJECTIVE
To review the possible reasons why the prevalence and morbidity of asthma are greater in those living in an urban setting.


RESULTS
Urban asthma is associated with exposure to air pollution, urban allergens, and violence. Outdoor air pollution is a particular problem in urban areas and affects children more than adults. Asthma has been shown to be exacerbated by ozone, respirable particulates, and nitrogen dioxide. Exposure to high point sources of pollutants such as heavy traffic is of particular concern. Urban allergens include cockroach, mouse, and rat. Cockroach exposure increases the risk of asthma exacerbations and may increase the risk of developing asthma. Although mouse allergen is also found in suburban homes, the concentration is a log-fold higher in inner-city homes at levels known to elicit symptoms in workers in animal facilities. Rat allergen is found in a third of inner-city homes and is associated with asthma morbidity. A recent interventional study showed that comprehensive environmental control of cockroach allergen reduced asthma morbidity. Finally, stress elicits asthma symptoms and exposure to violence is associated with greater asthma morbidity.


CONCLUSIONS
The increase in prevalence and morbidity of asthma associated with urban living is associated with at least three plausible causative factors each of which is amenable to intervention, raising the issue of environmental justice issues: controlling air pollution in general and exposure to point sources in particular; reducing cockroach, mice, and rat infestations; and preventing violence.
Byrd
Robert S
RS
University of California at Davis Medical Center, Sacramento, California 95817, USA. robert.byrd@ucdmc.ucdavis.edu
Joad
Jesse P
JP
D000397:Air Pollution; D000485:Allergens; D001249:Asthma / Q000453:epidemiology / Q000209:etiology*; D004781:Environmental Exposure; D006801:Humans; D009017:Morbidity; D015995:Prevalence; D012307:Risk Factors; D014504:Urban Health; D014505:Urban Population
D000485:Allergens