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William S. Linn,^1,2 Yaga Szlachcic,^1,3 Henry Gong, Jr.,^1,2,3 Patrick L. Kinney,⁴ and Kiros T. Berhane²

¹Rancho Los Amigos National Rehabilitation Center, Downey, California, USA
²Department of Preventive Medicine, ³Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
⁴Division of Environmental Sciences, Joseph A. Mailman School of Public Health, Columbia University, New York, New York, USA

Abstract

We used daily time-series analysis to evaluate associations between ambient carbon monoxide, nitrogen dioxide, particulate matter 10 µm in aerodynamic diameter (PM₁₀) , or ozone concentrations, and hospital admissions for cardiopulmonary illnesses in metropolitan Los Angeles during 1992-1995. We performed Poisson regressions for the entire patient population and for subgroups defined by season, region, or personal characteristics, allowing for effects of temporal variation, weather, and autocorrelation. CO showed the most consistently significant (p < 0.05) relationships to cardiovascular admissions. A wintertime 25th-75th percentile increase in CO (1.1-2.2 ppm) predicted an increase of 4% in cardiovascular admissions. NO₂, and, to a lesser extent, PM₁₀ tracked CO and showed similar associations with cardiovascular disease, but O₃ was negatively or nonsignificantly associated. No significant demographic differences were found, although increased cardiovascular effects were suggested in diabetics, in whites and blacks (relative to Hispanics and Asians) , and in persons older than 65 years of age. Pulmonary disease admissions associated more with NO₂ and PM₁₀ than with CO. Pulmonary effects were generally smaller than cardiovascular effects and were more sensitive to the choice of model. We conclude that in Los Angeles, atmospheric stagnation with high primary (CO/NO₂/PM₁₀) pollution, most common in autumn/winter, increases the risk of hospitalization for cardiopulmonary illness. Summer photochemical pollution (high O₃) apparently presents less risk. Key words: air pollutants, carbon monoxide, epidemiology, Los Angeles, morbidity, nitrogen dioxide, ozone, particulate matter. Environ Health Perspect 108:427-434 (2000) . [Online 27 March 2000]

http://ehpnet1.niehs.nih.gov/docs/2000/108p427-434linn/ abstract.html

Address correspondence to W.S. Linn, 51 Medical Science Building, Rancho Los Amigos National Rehabilitation Center, 7601 Imperial Highway, Downey, CA 90242 USA. Telephone: (562) 401-7561. Fax: (562) 803-6883. E-mail: linn@hsc.usc.edu

We thank the following for donating data and for help and advice: G. Cox, J. White, H. Lomas, B-M. Kim, M. Zeldin, S. Prasad, and F. Lurmann. We thank J. Solomon for programming and data quality assurance ; C. Linn for consultation on hospital admission data interpretation ; S. Terrell for computer artwork ; and K. Clark, V. Valdez, and M. Avila for administrative assistance. We thank M.P. Jones, M. Lipsett, and J. Schwartz for advice on data handling and statistical analysis.

Major support for this project was provided by the American Heart Association, Western States Affiliate (grant 1134-GI1) . The Southern California Environmental Health Sciences Center, funded by the National Institute of Environmental Health Sciences (grant 5P30 ES07048-03) , provided additional support.

Received 13 July 1999 ; accepted 1 December 1999.