Science News - August 4, 2004

Fetuses very susceptible to combustion pollutants

Despite research on rats that shows the placenta can block certain combustion-related pollutants, researchers have found that a marker of secondhand cigarette smoke accumulates at greater levels in the plasma of fetuses than that in mothers. They also discovered that cancer-causing benzo[a]pyrene (BP) has more harmful effects on fetal than on maternal DNA. This study bolstered previous findings in Poland, where women were exposed to secondhand smoke and levels of BP that were 30 times higher.

Corresponding author Frederica P. Perera, director of the Columbia Center of Children’s Environmental Health at Columbia University, says the results are a concern, because exposure to BP has been linked to DNA damage and increased risk of cancer.

“This study demonstrates that the fetus is more susceptible to DNA damage from combustion-related pollutants than previously thought,” says Perera.

Researchers from the Columbia Center and the Center for Disease Control and Prevention tracked 265 nonsmoking mothers and their newborns in New York City. The mothers are exposed to significant air pollution in their neighborhood, where the average ambient BP concentration was less than 0.5 nanograms per cubic meter of air. Perera says higher levels can be found in California and many European cities. This study was published in the July issue of Environmental Health Perspectives (Environ. Health Perspect. 2004, 12, 1133–1136).

The researchers found that 45% of newborns had detectable BP-DNA adducts, as did 41% of mothers. The levels of adduct formation were similar in mother and child: 0.24 adducts per 100 milllion nucleotides in mothers and 0.22 adducts per 100 million nucleotides in newborns.

Cotinine, a metabolite of nicotine, was detected in the serum of 47% of newborns and 44% of mothers. The levels were also quite similar, at 1.7 nanograms per milliliter (ng/mL) in newborns versus 1.28 ng/mL in mothers. The higher levels of cotinine in newborns indicate that the effects of environmental tobacco smoke are only slowly cleared from the fetuses’ blood.

Previous research on the same cohort of New Yorkers found that elevated levels of BP-DNA adducts in combination with secondhand smoke correlated with poor birth outcomes, including smaller head circumference and lower birth weight.

“We know that there is a lot of smoking in these neighborhoods, but you would think that with nonsmoking mothers that these babies would be protected,” says Ellen F. Crain, professor of pediatrics at the Albert Einstein College of Medicine. “What I find interesting about this study is that we’re finally starting to look for a mechanism for some of the outcomes we find clinically.” —PAUL D. THACKER