Soot particles from the exhaust of diesel trucks constitute a major contributor to the alarmingly high rates of asthma symptoms among school-aged children in the South Bronx, according to the results of a five-year study by researchers at New York University’s School of Medicine and Robert F. Wagner Graduate School of Public Service.
Over the course of the study, asthma symptoms, particularly wheezing, doubled among elementary school children on high traffic days, as large numbers attend schools in close proximity to busy truck routes because of past land-use decisions.
The South Bronx has among the highest incidences of asthma hospital admissions in New York City, and a recent city survey of asthma in the South Bronx’s Hunts Point district found an asthma prevalence rate in elementary school of 21% to 23%. The South Bronx is surrounded by several major highways, including Interstates 95, 87, 278 and 895. At Hunts Point Market alone, some 12,000 trucks roll in and out daily.
As part of the investigation, the NYU team dispatched a mobile van lab to assess ground-level pollution levels, and they conducted a “Backpack Study” to monitor carbon concentrations taken from air samples collected by commuting students. The findings have shown that high concentrations of air pollution worsen asthma problems among elementary school children in the South Bronx.
The schools in the study were: PS 154, MS 302, CS 152 and MS 201. Ten elementary school children with asthma from each of the four schools were followed for a month. Data on respiratory symptoms, lung function, activity patterns, as well as personal air pollution exposures were collected at the same time.
According to the study, among all of the children the daily average exposure to particulate matter smaller than 2.5 microns (PM2.5) ranged from 20 to 50 micrograms per cubic meter. In addition, the Environmental Protection Agency’s proposed daily limit of 35 micrograms per cubic meter was exceeded on about one-third of the study days. Only about 10% of the total mass of tiny particles was diesel soot, but it was this portion that was most closely related to children’s adverse health effects.
Particles smaller than 2.5 microns have been mostly closely linked to lung and heart disease. The EPA has regulated PM2.5 since 1997, limiting each person’s average exposure per year to no more than 15 micrograms per cubic meter.
Other studies have shown that people who live near highways have a higher incidence of asthma. But researchers had not measured levels of traffic air pollutants to which individuals were being exposed.
We went in and actually measured personal exposures to traffic pollution, which had not been done before. Our results confirm that diesel soot particles in air pollution are causing exacerbations of asthma in children.—George Thurston, Sc.D., Associate Professor of Environmental Medicine at NYU School of Medicine
The major type of air pollutant that was associated with symptoms of asthma was elemental carbon. This type of carbon, called black soot, is found in diesel exhaust and is a component of particulate matter in pollution that is smaller than 2.5 microns. This type of carbon has been cited as a causal agent in asthma in a number of other controlled-exposure studies in the laboratory.