| Mortality and Ambient Fine Particles in Southwest Mexico City, 1993-1995 Víctor H. Borja-Aburto,1,2 Margarita Castillejos,3 Diane R. Gold,4,5 Silvia Bierzwinski,3 and Dana Loomis6,7 1Centro de Investigaciones y Estudios Avanzados, Instituto Politécnico Nacional, México, DF, Mexico
2Centro Nacional de Salud Ambiental, Metepec, Mexico
3Universidad Autónoma Metropolitana-Xochimilco, México, DF, Mexico
4Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School
5Department of Environmental Health, Harvard School of Public Health, Harvard University, Boston, MA 02115 USA
6Instituto Nacional de Salud Pública, Cuernavaca, Morelos, Mexico
7University of North Carolina, Chapel Hill, NC 27599 USA Abstract
Epidemiologic studies have focused attention on the health effects of fine particulate air pollutants <2.5 µm in diameter (PM2.5) . To further characterize the potential effects of fine particles, we investigated the relationship of air pollution to mortality in Mexico City during 1993-1995. The concentration of PM2.5 was measured on a 24-hr integrated basis ; concentrations of NO2 and ozone were measured hourly and reduced to 24-hr means. Daily mortality was determined from death registration records, and Poisson regression was used to model daily death counts as a function of air pollutant levels on the same and previous days, while controlling for temperature and periodic cycles. Without taking other air pollutants into account, a 10 µg/m3 increase in the level of PM2.5 was associated with a 1.4% increase in total mortality, both on the current day and 4 days after exposure [95% confidence interval (CI) , 0.2-2.5]. An equivalent increase in PM2.5 was also associated with somewhat larger excesses of deaths among people over 65 years of age and from cardiovascular and respiratory causes, which occurred after a lag of 4 days. The mean concentration of ozone over a 2-day period was associated with a 1.8% increase in mortality from cardiovascular diseases. NO2 was not consistently related to mortality. Fine particles had an independent effect on mortality when modeled simultaneously with other pollutants, and the association of ozone with cardiovascular mortality was strengthened after adjusting for NO2 and PM2.5. These results support previous findings that urban air pollution at current levels leads to excess mortality and suggest that fine particles may play a causal role in producing that excess. Key words: air pollution, cardiovascular disease, Mexico, mortality, ozone, particles, respiratory disease. Environ Health Perspect 106:849-855 (1998) . [Online 18 November 1998] http://ehpnet1.niehs.nih.gov/docs/1998/106p849-855borja-aburto/ abstract.html Address correspondence to D. Loomis, Department of Epidemiology, CB-7400 School of Public Health, University of North Carolina, Chapel Hill, NC 27599-7400 USA. Supported by cooperative agreements CR-820076 and CR-821762 between the U.S. Environmental Protection Agency and the University of North Carolina and Harvard University Schools of Public Health, the Mexico-U.S. Commission for Educational and Cultural Exchange, the Edward and Amalie Kass Fellowship at the Harvard Medical School, and CONSERVA. We thank Douglas Dockery, Marie O'Neill, Armando Retama, Daniel Varela, and Bill McDonnell for contributions to the research and comments on the manuscript. Received 6 May 1998 ; accepted 4 August 1998.
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