Case-crossover analysis of air pollution and cardiorespiratory hospitalizations: Using routinely collected health and environmental data for tracking

Background: From the early 1900s until its closure in February 1998, the LTV Steel coke oven in Pittsburgh (Hazelwood), Pennsylvania was a key source of air pollution. A case-crossover study was performed to assess the associations between daily air pollution and cardiorespiratory (ICD-9: 390-519) hospitalizations before and after plant closure and to evaluate how closure influenced these associations.

Methods: Air pollution data, climatic data and cardiorespiratory hospitalizations among Hazelwood-area residents 65 years and older were obtained for the period of 1996 through 2000. Data were analyzed using a case-crossover design and conditional logistical regression. Two distinct referent sampling approaches were compared.

Results: Significant associations were observed between the fourth quartile in PM10 and cardiorespiratory hospitalizations (OR: 1.12; 95%CI: 1.02-1.23) as well as cardiovascular hospitalizations only (ICD-9: 390-459) (OR: 1.13; 95%CI: 1.01-1.26) before the plant closure. After closure of the plant, PM10 was not significantly associated with cardiorespiratory or cardiovascular disease hospitalizations. Moreover, the referent sampling approaches did not greatly alter the estimations in the case-crossover analysis.

Conclusion: Existing secondary data is an economical source to assess the impact of point source polluters on the environmental landscape. The findings suggest that closure of the LTV coke plant was associated with a reduction risk of the cardiovascular hospitalizations.

Keywords: case-crossover analysis; cardiorespiratory; air pollution

Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, Pennsylvania 15261, USA.