The Harvard Epidemiologic Studies of the Health Risks of Air Pollution in Children

Abstract

The public and scientific debate over acidic air pollution has focused on the ecological effects of the removal of acid from the atmosphere as acid rain. Far less concern has been shown for the direct human health effects either acute or chronic, due to acid aerosols, that is liquid droplets of acid suspended in the air. Several epidemiologic studies at the Harvard School of Public Health are attempting to quantify the risks of acid aerosol pollution on the respiratory health of school children. These studies have been designed based on the results of a large, longitudinal study of the effects of sulfur oxides and particles on respiratory health of children living in six U.S. communities. This study has shown that respiratory illness and symptom are reported two to three times as frequently in the most polluted communities in the United States, compared to clean communities. An exposure-response association has been observed across the six cities which appears to be strongest with annual mean aerosol acidity concentrations. No permanent change in pulmonary function has been observed associated with these long term exposures, but reversible declines in lung function have been observed following episodes of high particulate and sulfur pollution. These findings have led to a new study of the respiratory health effects of acid aerosols on children in twenty-four small communities in the United States and Canada. Communities are selected based on expected annual mean concentrations of acid aerosols, acid gases, and photochemical oxidants. Sixteen communities have been studied to date in this five year study. Preliminary analyses of the has been consistent with the Six Cities study findings, that is suggesting increased respiratory symptom reporting in communities with high acid aerosol concentrations. A study of the acute changes in lung function following exposure to episodes of high acid aerosol concentrations was undertaken this summer in Uniontown, PA, the community with the highest observed acid aerosol concentrations. A cohort of children with reported chronic respiratory symptoms were asked to perform a peak expiratory flow measurement each day upon rising in the morning and before going to bed. These measurements are being correlated with concurrent measurements of aerosol acidity and ozone concentrations. These studies will provide important new information on the acute and chronic health effects of these currently unregulated pollutants.