Two Studies Focus On Asthma And Exposure To Pollutants
University of Southern California researchers found that young children who live near a major road are significantly more likely to have asthma than children who live only blocks away. In a separate study of children with asthma, researchers at the Cincinnati Children's Hospital Medical Center concluded that exposure to environmental tobacco smoke, even at low levels, is associated with behavioral problems in children and preteens.
University of Southern California Study
The study, announced on May 1, found that children living within 75 meters (about 82 yards) of a major road had a 50 percent greater risk of having had asthma symptoms in the past year than were children who lived more than 300 meters (about 328 yards) away. Higher traffic volumes on the different roads also were related to increased rates of asthma.
"These findings are consistent with an emerging body of evidence that local traffic around homes and schools may be causing an increase in asthma," said lead author Rob McConnell, MD, professor of preventive medicine at the Keck School of Medicine of the University of Southern California. "This is a potentially important public health problem because many children live near major roads."
More than 5,000 children ages 5 to 7 were involved in the study which was an expansion of the Children's Health Study, currently underway in 13 southern California communities. The researchers determined how far each participating child lived from a major road -- a freeway, large highway or a feeder road to a highway.
"These results suggest that living in residential areas with high traffic-related pollution significantly increases the risk of childhood asthma," said David A. Schwartz, MD, director of the National Institute of Environmental Health Sciences (NIEHS), the primary agency that funded the study. "Children with no parental history of asthma who had long-term exposure or early-life exposure to these pollutants were among the most susceptible."
Children who lived at the same residence since age 2 had slightly higher rates of asthma than those who had moved to the residence later. "That is what you would expect if the asthma was being caused by traffic," McConnell said. Risk for wheeze also decreased the further away a home was from a major road, dropping to background rates at roughly 150 meters (not quite two blocks).
Study sites included the cities of Alpine, Anaheim, Glendora, Lake Arrowhead, Lake Elsinore, Long Beach, Mira Loma, Riverside, San Bernardino, San Dimas, Santa Barbara, Santa Maria and Upland. McConnell noted that air pollution regulations typically focus on regional air pollutants rather than localized exposures within communities, such as living near a busy road, that may also be a problem.
"We've taken some tentative steps to address that, for example with a law that a new school can't be built within 500 feet of a freeway. But we have to also consider whether building parks, play areas, or homes right next to a major road is a wise land use decision in terms of health," McConnell said.
McConnell and his colleagues plan to follow up with a subgroup of the children to measure pollutants in their homes and also to look at characteristics that may make children more susceptible (or that may be protective), such as genetic characteristics.
Rob McConnell: http://www.usc.edu/schools/medicine/util/directories/faculty/profile.php?PersonIs_ID=760
Keck School of Medicine: http://www.usc.edu/schools/medicine/ksom.html
Cincinnati Children's Hospital Medical Center Study
Kimberly Yolton, PhD, a researcher at the Children's Environmental Health Center at Cincinnati Children's and the study's main author, examined 225 children and pre-teens (5 to 11 years old) exposed to at least five cigarettes a day. On average, the children were exposed to approximately 14 cigarettes a day. The children were enrolled in an asthma intervention study. Yolton included additional measures to assess child behaviors.
To measure exposure to environmental tobacco smoke, Yolton measured levels of cotinine in the children's blood. Cotinine is a substance produced when nicotine is broken down by the body and can be measured in blood, urine, saliva and hair. It is considered the best available marker of environmental tobacco smoke exposure, the researcher said.
Yolton found a relationship between cotinine levels and increases in "acting out"; increases in holding things in, often manifested by anxiety and depression; increases in behavior problems as rated by parents, and behavior and school problems as rated by teachers; and, decreases in the ability to adapt to behavior problems.
"The greater the exposure to tobacco smoke, the greater the problems these children had," Yolton said. "Behavior problems in children have increased from 7 to 18 percent over the last 20 years for reasons that are poorly understood. Exposure to environmental tobacco smoke is increasingly recognized as a risk factor for child behavior problems."
In the United States, about 25 percent of children are exposed to environmental tobacco smoke in their own homes, yet more than 50 percent of children have detectable levels of cotinine in their blood, according to Yolton.
Previous studies have found link between tobacco smoke and birth weight, number of infections and other health problems, including asthma exacerbations. In a 2002 study, Yolton found that exposure to environmental tobacco smoke, even at extremely low levels, is associated with decreases in certain cognitive skills, including reading, math, and logic and reasoning, in children and adolescents.
The findings of the latest study were presented on April 30, at the annual meeting of the Pediatric Academic Societies in San Francisco.
Kimberly Yolton: http://www.cincinnatichildrens.org/svc/find-professional/y/kimberly-yolton.htm
Cincinnati Children's Hospital Medical Center: http://www.cincinnatichildrens.org
This article originally appeared in the 05/01/2006 issue of Environmental Protection.