Relationship between emergency room visits for respiratory disease and atmospheric pollution in Ciudad Juarez, Chihuahua.

Objective. To assess the relationship of less than or equal to 10 mu m part icles (PM10) and atmospheric ozone concentrations, with the daily number of emergency visits due to asthma and acute respiratory diseases, among child ren aged under 15, living in Ciudad Juarez, Chihuahua, Mexico. Material and methods. Between 1998 and 1999, an ecologic study was conducted. Atmospher ic data were obtained from the Environmental Protection Agency (EPA), from eight monitoring stations located in Ciudad Juarez, Chihuahua, and El Paso, Texas. From July 1997 to December 1998, data from emergency room visits fo r respiratory illness were abstracted from existing medical records of two Mexican Institute of Social Security (IMSS) hospitals in Ciudad Juarez. Dia gnoses were classified into two groups: a) asthma, and b) upper respiratory infections (URI), according to the International Classification of Disease s (ICD-9 and/or IDC-IO). Statistical analysis was carried out using the Poi sson regression time series method. Results. During the study period, the m ean 24-hour PM10 level was 34.46 mu g/m(3) (SD=17.99) and the mean ozone le vel was 51.60 ppb (SD=20.70). The model shows that an increase of 20 mu g/m (3) in the mean 24-hour exposure to PM10 was related to an increase of 4.97 % (95% CI 0.97-9.13) in emergency visits for asthma, with a 5-day lag, as w ell as to an increase of 9% (95% CI 1.8-16.8) when a cumulative 5-day expos ure was considered. URI increased 2.95% as a cause of emergency room visits , for each 20 mu g/m(3) increase in the mean 24-hour exposure to PM10. The impact of PM10 on emergency visits for asthma was greater on days with ozon e ambient levels exceeded 49 ppb (median value). Conclusions. A positive as sociation was Found between environmental PM10 and ozone concentrations and the daily number of emergency room visits due to asthma and acute respirat ory diseases, even with levels lower than the Mexican standard levels. Also , a synergic effect between PM10 and O-3 was found.