USA–– Pregnant women exposed to wildfire smoke during Southern Californias epic 2003 fire season had babies with lower birth weights, UC Berkeley researchers have found.
The scientists examined birth records in areas affected by smoke from seven fires including the Old Fire that burned across the mountains and into the city of San Bernardino that altogether consumed 750,000 acres. The results of the study were published online Wednesday, Sept. 5, in the journal Environmental Health Perspectives.
The differences in the newborns weights were small, slightly less than 10 grams for those exposed during the second trimester of the pregnancy, but the finding was significant, said Rachel Morello-Frosch, one of the authors and an associate professors at Berkeleys School of Public Health.
The study shows that climate change can affect health, she said, pointing out that wildfires are expected to become more frequent as the planet warms.
Smoke from such fires also could make a bad situation worse. The Inland region does not meet clean air standards for soot and other fine-particle pollution that has been linked in other research to low birth weights.
Still, the effect from fires alone is slight, Morello-Frosch said. By comparison, women who smoke cigarettes have babies whose weight is reduced by as much as 150 grams.
Morello-Frosch cautioned that she and her colleagues did not determine why the women living in smoke-exposed areas had smaller babies. Toxic substances in the smoke could have compromised cellular function, or the fires could have put the women under stress, resulting in earlier deliveries.
It is worth doing more research to look at both, Morello-Frosch said in a telephone interview.
Dr. Richard Chinnock, head of the Pediatrics Department at Loma Linda University Medical Center, said 10 grams is so slight that no one would notice a difference in the delivery room.
Still, the research helps in understanding childrens health, he said. Smoke exposure could be one insult that adds to another insult for a cumulative effect.
Urban air pollution also effects birth weight.
In 2005, researchers with the U.S. Environmental Protection Agency and the Centers for Disease Control and Prevention found that women living in areas with high levels of fine-particle pollution had babies that weighed, on average, 33 grams 1.2 ounces less than babies born to women in communities with clean air.
Inland Southern California has unhealthful levels of fine-particle pollution, although the levels are dropping.
Low birth weight is associated with a higher risk of a baby not surviving its first year. It also is linked with a higher risk of chronic health problems later in life, including obesity and heart disease.
The Berkeley researchers looked at birth records of 886,030 babies, including 138,444 whose mothers lived in smoke-exposed areas during the 2003 fires. The women exposed to the smoke had babies whose birth weights were measurably lower, although the differences varied according to the stage of pregnancy. Fetuses exposed during the third trimester were 7.0 grams smaller. For the second trimester, the difference was 9.7 grams, and, for the first trimester, 3.3 grams.
The Old Fire started on Oct. 25, 2003, in Waterman Canyon north of San Bernardino. In nine days, it destroyed 91,281acres and 940 homes and claimed six lives.