Exposure of expectant mothers to urban air pollution may alter the structure of babies' chromosomes while in the womb

A new study of 60 newborns in New York City reveals that exposure of expectant mothers to combustion-related urban air pollution may alter the structure of babies' chromosomes while in the womb. While previous experiments have linked such genetic alterations to an increased risk of leukemia and other cancers, much larger studies would be required to determine the precise increase in risk as these children reach adulthood.

The air pollutants considered in this study include emissions from cars, trucks, bus engines, residential heating, power generation and tobacco smoking. These pollutants can cross the placenta and reach the fetus.

The study was funded by the National Institute of Environmental Health Sciences, the U.S. Environmental Protection Agency, and other private foundations. The research was conducted by scientists from the Columbia University Center for Children's Environmental Health. Study results will be published in the February issue of Cancer Epidemiology Biomarkers and Prevention, and are available online at http://cebp.aacrjournals.org.

"This is the first study to show that environmental exposures to specific combustion pollutants during pregnancy can result in chromosomal abnormalities in fetal tissues," said Kenneth Olden, Ph.D., the director of NIEHS. "These findings may lead to new approaches for the prevention of certain cancers."

Researchers monitored exposure to airborne pollutants, known as polycyclic aromatic hydrocarbons (PAHs), among non-smoking African-American and Dominican mothers residing in three low-income neighborhoods of New York City -- Harlem, Washington Heights and the South Bronx.

"Although the study was conducted in Manhattan neighborhoods, exhaust pollutants are prevalent in all urban areas, and therefore the study results are relevant to populations in other urban areas," said Dr. Frederica P. Perera, director of the Columbia Center for Children's Environmental Health and senior author of the study.

Exposure to combustion pollutants was assessed through personal questionnaires and portable air monitors worn by the mothers during the third trimester of their pregnancies. Researchers then calculated the concentration of air pollution to which each pregnant woman and her baby were exposed. Study participants exposed to air pollution levels below the average were designated as having "low exposure," while those exposed to pollution levels above the average were designated as having "high exposure."

"We observed 4.7 chromosome abnormalities per thousand white blood cells in newborns from mothers in the low exposure group, and 7.2 abnormalities per thousand white blood cells in newborns from the high exposure mothers," said Perera. "In particular, stable alterations were increased, which are of greatest concern for potential risk of cancer, since cells with this type of abnormality can persist in the body for long periods of time."

Chromosomal abnormalities were measured in umbilical cord blood by a "chromosome painting" technique called fluorescence in situ hybridization, one that enabled researchers to observe the structural changes within the chromosome. Chromosomes are the threadlike packages in the nucleus of the cell that contain the cell's genetic information.

"This evidence that air pollutants can alter chromosomes in utero is troubling since other studies have validated this type of genetic alteration as a biomarker of cancer risk," said Perera. "While we can't estimate the precise increase in cancer risk, these findings underscore the need for policymakers at the federal, state, and local levels to take appropriate steps to protect children from these avoidable exposures."

Previous studies conducted by Perera and colleagues showed that combustion-related air pollutants significantly reduce fetal growth, which may affect cognitive development during childhood.

The study is part of a broader, multi-year research project, "The Mothers & Children Study in New York City," started in 1998, which examines the health effects of exposure of pregnant women and babies to air pollutants from vehicle exhaust, the commercial burning of fuels, and tobacco smoking, as well as from residential use of pesticides and allergens.