1. ^aDivision of Health Assessment and Consultation, Agency for Toxic Substances and Disease Registry, Public Health Service, Atlanta, GA, USA
2. ^bDepartment of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, NC, USA
3. ^cDivision of Health Studies, Agency for Toxic Substances and Disease Registry, Public Health Service, Atlanta, GA, USA
4. ^dDepartment of Epidemiology, School of Public Health, University of North Carolina, Chapel Hill, NC, USA
5. ^eDepartment of Biostatistics, School of Public Health, University of North Carolina, Chapel Hill, NC, USA
6. ^fNelson Institute for Environmental Studies, University of Wisconsin, Madison, WI, USA

Correspondence: Dr GV Ulirsch, Division of Health Assessment and Consultation, Agency for Toxic Substances and Disease Registry, 1825 Century Center Blvd., Atlanta, GA 30345 USA. Tel.: +1 404 498 0460; Fax: +1 404 498 0135; E-mail: gulirsch@cdc.gov.

Received 22 August 2006; Accepted 14 November 2006; Published online 14 February 2007.

Abstract

Few, if any, published time series studies have evaluated the effects of particulate matter air exposures by combining hospital admissions with medical visit data for smaller populations. We investigated the relationship between daily particulate matter (<10 m in aerometric diameter or PM₁₀) exposures with admissions and medical visits (emergency room, urgent care, and family practice) for respiratory and cardiovascular disease in Pocatello and Chubbuck, Idaho (population about 60,000), from November 1994 through March 2000. Within generalized linear models, time, weather, influenza, and day-of-week effects were controlled. In single-pollutant models, respiratory disease admissions and visits increased (7.1–15.4% per 50 g/m³ PM₁₀) for each age group analyzed, with the highest increases in two groups, children and especially the elderly. Statistical analyses suggest that the results probably did not occur by chance. Sensitivity analyses did not provide strong evidence that the respiratory disease effect estimates were sensitive to reasonable changes in the final degrees of freedom choice for time and weather effects. No strong evidence of confounding by NO₂ and SO₂ was found from results of multi-pollutant models. Ozone and carbon monoxide data were not available to include multi-pollutant models, but evidence suggests that they were not a problem. Unexpectedly, evidence of an association between PM₁₀ with cardiovascular disease was not found, possibly due to the lifestyles of the mostly Mormon study population. Successful time series analyses can be performed on smaller populations if diverse, centralized databases are available. Hospitals that offer urgent or other primary care services may be a rich source of data for researchers. Using data that potentially represented a wide-range of disease severity, the findings provide evidence that evaluating only hospital admissions or emergency room visit effects may underestimate the overall morbidity due to acute particulate matter exposures. Further work is planned to test this conclusion.