Pregnant women living near freeways face greater miscarriage risk
Tuesday, December 8, 2009
Pregnant African-American women who live near freeways are far more likely to have miscarriages than women who don’t regularly breathe exhaust fumes, California environmental health scientists have found.
The California Office of Environmental Health Hazard Assessment reports that African-Americans were about three times more likely to miscarry if they lived within a half-block of a freeway or busy boulevard than if they resided near lighter traffic.
The researchers also found that women who don’t smoke but regularly inhale traffic exhaust increased their odds of miscarriage by about 50 percent, a study of nearly 5,000 pregnant women in California shows.
Dr. Joan Denton, director of the Office of Environmental Health Hazard Assessment, which led the research, said in a statement:
“This study adds weight to the growing body of evidence that constant, heavy exposure to traffic exhaust significantly increases the risk of reproductive harm.”
Several studies have shown links between exposure to air pollution or traffic and low birth weight, premature birth and birth defects. The new research is the first published study of the effect of residential traffic exposure on the risk of miscarriage, said Dr. Shelley Green, who led the study and specializes in the health effects of air pollution.
The paper was published in the scientific journal Environmental Health Perspectives. Co-authors of the paper included researchers from OEHHA, the California Department of Public Health and the University of Rochester School of Medicine and Dentistry. Here is a link to the full report.
Green analyzed data from telephone interviews that Kaiser Permanente conducted in 1990-1991 when pregnant women called to schedule their first prenatal appointment at clinics in the East Bay and in the counties of Santa Clara and San Bernardino. The survey of residential, medical and pregnancy history was limited to volunteers who were no more than 12 weeks pregnant.
About 9 percent of the almost 5,000 women in the study had miscarried, which is within the normal range. Researchers examined the miscarriages in relation to traffic exhaust, using residential proximity to busy roads as a proxy for exposure to vehicle pollution. The roads carried average traffic of at least 15,200 vehicles per day.
Pregnant women who lived within 55 yards of busy roads showed a higher rate of miscarriage compared with women who lived further away from roads with heavy traffic. The scientists found statistically significant associations between miscarriage and proximity to traffic for African-Americans and women who did not smoke while pregnant. While the association with high traffic was more evident for the nonsmokers, their neighbors who smoked had a 10 percent higher risk of miscarriage.
“Because smokers already are exposed through their tobacco smoke to many of the same chemicals found in vehicle exhaust, the effect of traffic may be masked by the smoking effect.”
The environmental health office, which is part of the California Environmental Protection Agency, narrowly escaped losing its funding in the most recent budget negotiation. The office gained attention earlier this year for listing marjuana smoke as toxic. It also has been involved in studying bisphenol-A, widely used in plastics and thought by some to be a reproductive toxin.