OEHHA Study Shows Possible Link Between Traffic Pollution, Children’s Respiratory Symptoms

FOR IMMEDIATE RELEASE:
No. 04- 09

CONTACT: Allan Hirsch
(916) 324-0955

Even in an area with good regional air quality, air pollution from nearby traffic may pose a health risk, according to a recently completed study by scientists from Cal/EPA’s Office of Environmental Health Hazard Assessment (OEHHA) that shows a possible link between air pollution from nearby traffic and respiratory symptoms in children.

The study, which involved air monitoring and a health survey of about 1,100 students at 10 Alameda County elementary schools located various distances from major roads, found moderately higher rates of asthma and bronchitis symptoms (such as wheezing and excessive phlegm) in children residing and attending school in neighborhoods with higher levels of traffic- related air pollution.  Scientists from OEHHA and the Lawrence Berkeley National Laboratory collaborated on the study, which was published in the September 1, 2004 issue of the American Journal of Respiratory and Critical Care Medicine.

In addition, a recent companion study by scientists at OEHHA and the state Department of Health Services found that about 150,000 California students (about 2.5 percent of students statewide) may be attending schools located   close to roads with very high traffic levels (more than 50,000 vehicles/day). That study was published in Environmental Health Perspectives in January 2004.

“Our studies underline the importance of California’s continuing efforts to reduce motor vehicle emissions,” OEHHA Director Dr. Joan E. Denton said. “There is a growing body of evidence that children exposed to high levels of traffic pollution may be more susceptible to asthma and bronchitis symptoms.”

In the respiratory health study, which took place during the 2000-01 school year, Berkeley Lab scientists measured concentrations of several traffic-related pollutants (including particulate matter  – or soot - and nitrogen oxides) outside 10 schools in an area between Oakland and Hayward.  OEHHA scientists used questionnaires, completed by participating students’ parents, to collect health and demographic information on nearly 1,100 third, fourth and fifth graders at the schools. The school locations were assumed to be representative of the children’s overall exposure to traffic pollutants, as most of the students live in neighborhoods close to their schools.

Although a number of studies (primarily in Europe) have reported links between residential proximity to busy roads and respiratory health effects, few have actually measured pollutant concentrations in areas near busy roads. In fact, OEHHA’s study was the first in the United States to evaluate the relationship between measured levels of traffic-related pollutants and respiratory symptoms.

The study found that the prevalence of asthma and bronchitis symptoms were about 7 percent higher in children in neighborhoods with higher levels of traffic pollutants compared with other children in the study. The study was not designed to determine whether traffic pollution causes new cases of asthma, but instead whether traffic pollution is associated with the likelihood of symptoms in children with existing asthma.

“It was important to perform this kind of study in California, because we have a different mix of motor vehicles and different land use patterns than in Europe. We could not assume that the European study results automatically apply to California and other states,” said Dr. Bart Ostro, an OEHHA scientist and one of the study’s co-authors.

“The Bay Area was a good location for the study because it has relatively good regional air quality,” Ostro said. “That makes it easier to evaluate the specific effects of air pollution from nearby traffic.”

In the companion study, OEHHA and DHS researchers used databases from the Department of Education (CDE) and the Department of Transportation  to evaluate the proximity of almost 7,500 California public schools to freeways and busy roads. In light of previous studies that have found traffic pollution levels to be higher within 500 feet downwind of major roads, the study estimated the number of schools within 500 feet downwind of roads with traffic volumes exceeding 25,000 vehicles per day and 50,000 vehicles per day.

The study found that about 2.3% of public schools (about 170 schools) enrolling about 150,000 students are located within 150 meters (500 feet) of roads exceeding 50,000 vehicles per day. An additional 7 % of public schools (about 530 schools) enrolling about 570,000 students are located within 500 feet of roads with 25,000 to 50,000 vehicles per day.

Furthermore, using school demographic data and 2000 census data, state scientists found that schools located closer to high-traffic roads had higher percentages of African-American and Hispanic students compared to the schools having no busy roads nearby.  The schools located near high-traffic roads also had higher percentages of socioeconomically disadvantaged students (such as those receiving free/reduced price school meals or who are English language learners).