The Health Effects Institute also commissioned an original nationwide study of the short-term effects of air pollution on human health in the 90 largest American cities. A team of investigators led by Dr. Jonathan Samet and Dr. Scott Zeger of the Johns Hopkins University School of Hygiene and Public Health examined short-term increases in mortality rates caused by short-term elevations in particulate air pollution. Harvard School of Public Health researchers Dr. Douglas Dockery and Dr. Joel Schwartz studied effects on hospitalization in a subset of these cities. NMMAPS developed a new standardized methodology for examining pollution effects across many cities. Investigators developed state-of-the-art statistical techniques to examine the effects of multiple pollutants and the extent of life-shortening.

Some critics have argued that short-term increases in the death rate are unimportant because the individuals affected are very frail and near death, even in the absence of air pollution. NMMAPS dispels this “harvesting” notion. NMMAPS investigators report that life is not shortened by a matter of days, but that life shortening is on the order of months or more.

Critics have also argued that other pollutants may be responsible for observed health effects. NMMAPS found strong evidence linking daily increases in particulate pollution to increases in death, in the twenty largest U.S. cities. The association between particulate matter and mortality persisted even when other pollutants were included in the analysis.

In addition, NMMAPS found stable and robust associations between particulate pollution and increased hospital admissions for cardiovascular disease, pneumonia, and chronic obstructive pulmonary disease.

In an abstract prepared for the HEI Annual Conference, investigators concluded “these complementary analyses of mortality and morbidity provide new and strong evidence linking particulate air pollution at current levels to adverse health effects.”