Babies in the womb are more susceptible than their mothers to DNA damage from air pollution, despite the added protection that the placenta is thought to provide in filtering out toxins.
In a study of newborns and their mothers in New York City , scientists found that developing babies had accumulated a relatively high number of genetic mutations, and they linked the mutations to emissions from vehicles and other sources of urban pollution.
The newborns also had more toxins in their bodies from secondhand smoke than their mothers, who were all nonsmokers. The study appears in Environmental Health Perspectives .
The findings “highlight the need to protect pregnant women and especially their children as a sensitive subset of the population,” the researchers conclude.
For years, scientists have suspected that a developing fetus may be more susceptible to environmental toxins than an adult. But the new research is among a handful of large studies that have analyzed the genetic effects of this exposure.
It is not known what the health effects of this DNA damage, if any, are for newborns. Exposure to these types of pollutants and tobacco smoke has been linked to increased risk for cancer in adults.
“This finding raises concern about fetal susceptibility and underscores the importance of reducing air pollution,” says Frederica Perera, who led the study at the Columbia Center for Children's Environmental Health in New York City .
The study included 265 pairs of nonsmoking African-American and Latina mothers and newborns in New York City . The researchers collected cord blood samples from the babies at the time of delivery and blood samples from the mothers a day after giving birth.
Mothers and newborns had the same level of DNA damage from air pollutants, but the researchers estimate that the fetus is exposed to a ten-fold lower dose of pollutants than the mother because the placenta serves as a filter.
Thus, fetuses appear to be particularly susceptible to environmental toxins and may not be able to clear them from their bodies or repair damaged DNA. The finding that newborns had higher levels of cotinine, a byproduct of nicotine, in their blood than did their mothers reinforces the concern that babies are more affected by secondhand smoke.
The scientists were able to measure the level of DNA damage from air pollutants in mothers and newborns by analyzing stretches of mutated DNA, called biomarkers, that have been associated with exposure to diesel emissions and other air pollutants.
“In the old days, we used to have to be satisfied with studies that showed there was, say, a lot of diesel exhaust in an area where kids had asthma,” says Ellen Crain, a pediatrician who specializes in asthma at Albert Einstein College of Medicine in New York City.
“Now, with biomarkers we can say with confidence that an infant or person has been exposed to a particular carcinogen,” she says.
In a previous study of Caucasian women and their newborns in Krakow , Poland , Perera and her colleagues found similar prenatal susceptibility to air pollution. Because New York City has much lower levels of pollution than Krakow , they wanted to see if the same damage occurred.
The latest study is part of a larger, ongoing project at Columbia Center for Children's Environmental Health to monitor the health risks for urban mothers and their newborns. The project includes more than 700 women in the city.
The researchers will continue to monitor the children's development through second grade to see whether they experience health problems such as asthma, cancer, and learning disabilities. Perera points out that the findings do not mean that any individual infant is at an increased risk of cancer or other diseases.
The study was funded by the U.S. National Institute of Environmental Health Sciences, which is part of the National Institutes of Health, and the U.S. Environmental Protection Agency.
This article was published by Environmental Health Perspectives , copyright 2004.