Correspondence

Fine Particulate Air Pollution and Mortality in 20 U.S. Cities

N Engl J Med 2001; 344:1253-1254April 19, 2001

Article

To the Editor:

Samet et al. (Dec. 14 issue)1 provide compelling, additional evidence of the link between outdoor air pollution — respirable particulate matter less than 10 μm in aerodynamic diameter (PM₁₀), in particular — and mortality. One perplexing finding, however, is the observed associations between outdoor ozone levels and mortality. These were marginally significant and positive during the summer but significant and negative during the winter. The authors suggest that the associations in the summer may reflect the higher levels of ozone during these months, but they fail to address the significance of the negative associations in the winter.

In a recent study, we showed that outdoor ozone levels are not associated with actual exposures to ozone but are strongly associated with exposures to fine particulate matter (PM_2.5), a correlated component of PM₁₀ that has been widely implicated in epidemiologic studies as the size fraction responsible for adverse effects on health.2 During the summer, we found that outdoor ozone levels were significantly and positively correlated with both outdoor levels of and personal exposures to PM_2.5. During the winter, outdoor ozone levels were also strongly associated with outdoor levels of and personal exposures to PM_2.5, but in a negative direction. These results suggest that the results with respect to ozone and mortality reported by Samet et al. are attributable to the fact that ambient ozone is a surrogate for PM_2.5 and that the observed associations between ozone levels and mortality, both positive and negative, reflect the effect of exposures to PM_2.5.

Jeremy A. Sarnat, S.M.
Joel Schwartz, Ph.D.
Helen H. Suh, S.D.
Harvard School of Public Health, Boston, MA 02115

2 References

1. 1

   Samet JM, Dominici F, Curriero FC, Coursac I, Zeger SL. Fine particulate air pollution and mortality in 20 U.S. cities, 1987-1994. N Engl J Med 2000;343:1742-1749
   Full Text | Web of Science | Medline

2. 2

   Schwartz J, Neas LM. Fine particles are more strongly associated than coarse particles with acute respiratory health effects in schoolchildren. Epidemiology 2000;11:6-10
   CrossRef | Web of Science | Medline

Author/Editor Response

The authors reply:

To the Editor: Sarnat and colleagues speculate about our finding of a negative association between ozone levels and mortality during the coldest months. We note that in the seasonal analyses, we considered ozone levels alone and did not control for levels of PM₁₀ particulate matter. We did perform analyses for the full year that simultaneously included both ozone and PM₁₀; these analyses showed that the estimate of the effect of ozone was not changed by inclusion of PM₁₀ in the statistical model. Similar analyses were not carried out for the coldest months alone because of the limited data available for this three-month interval. As we expand our data base, we will be able to test the hypothesis offered by Sarnat and colleagues.

Jonathan M. Samet, M.D.
Francesca Dominici, Ph.D.
Scott L. Zeger, Ph.D.
Johns Hopkins University, Baltimore, MD 21205-2179

Citing Articles (7)

Citing Articles

1. 1

   Lijuan Wen, Jiming Jin, Michael D. Wojcik. (2011) High-resolution simulations of particulate matter emitted by different agriculture tillage under different weather conditions in California, USA. Environmental Earth Sciences 64:4, 1021-1029
   CrossRef

2. 2

   Wilson WS Tam, Tze Wai Wong, Andromeda HS Wong, David SC Hui. (2011) Effect of dust storm events on daily emergency admissions for respiratory diseases. Respirologyno-no
   CrossRef

3. 3

   Kyoungwoo Kim, Eun-Young Park, Kwan-Hee Lee, Jung-Duck Park, Yong-Dae Kim, Yun-Chul Hong. (2009) Differential oxidative stress response in young children and the elderly following exposure to PM2.5. Environmental Health and Preventive Medicine 14:1, 60-66
   CrossRef

4. 4

   Marlene Cortez-Lugo, Hortensia Moreno-Macias, Fernando Holguin-Molina, Judith C Chow, John G Watson, Victor Gutiérrez-Avedoy, Francisco Mandujano, Mauricio Hernández-Ávila, Isabelle Romieu. (2008) Relationship between indoor, outdoor, and personal fine particle concentrations for individuals with COPD and predictors of indoor-outdoor ratio in Mexico city. Journal of Exposure Science and Environmental Epidemiology 18:1, 109-115
   CrossRef

5. 5

   J. Topinka, O. Sevastyanova, B. Binkova, I. Chvatalova, A. Milcova, Z. Lnenickova, Z. Novakova, I. Solansky, R.J. Sram. (2007) Biomarkers of air pollution exposure—A study of policemen in Prague. Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 624:1-2, 9-17
   CrossRef

6. 6

   Marc Riedl, David Diaz-Sanchez. (2005) Biology of diesel exhaust effects on respiratory function. Journal of Allergy and Clinical Immunology 115:2, 221-228
   CrossRef

7. 7

   Jeffrey Sullivan, Lianne Sheppard, Astrid Schreuder, Naomi Ishikawa, David Siscovick, Joel Kaufman. (2005) Relation Between Short-Term Fine-Particulate Matter Exposure and Onset of Myocardial Infarction. Epidemiology 16:1, 41-48
   CrossRef