OZONE LEVEL POSES RISK TO WOMEN BABIES BORN UNDERWEIGHT.

Byline: Staff and Wire Services

SANTA CLARITA - Women exposed to high levels of ozone are at risk of giving birth to babies who are significantly underweight, researchers at the USC Keck School of Medicine said Monday.

The news is especially significant in Santa Clarita, one of the worst spots in the nation for ozone, an invisible pollutant that gets trapped by the surrounding mountains and cooks in the summer heat.

High levels of ozone can put babies at risk for intrauterine growth retardation, the researchers said. These babies are typically born in the 15th percentile for their expected size.

``These findings add further evidence that our ozone standards are not protecting the most vulnerable members of the population,'' said Frank D. Gilliland, the study's senior author.

From Jan. 1 to Aug. 10, the Santa Clarita Valley recorded 42 days of ozone levels that exceeded federal standards, compared with 36 in the same period last year. In 2003, 48 days exceeding standards were tallied in that time.

Researchers found that an increase of 12 parts per billion in ozone levels can result in a tenth-of-a-pound drop in birth weight.

Women in their second and third trimesters are more susceptible to air pollution. Every 17 parts per billion increase in daily ozone levels during a woman's third trimester increases the risk of intrauterine growth retardation by 20 percent.

Ground level ozone is created through tailpipe exhaust, gasoline vapors, industrial emissions and chemical solvents.

The gas reduces hemoglobin's ability to carry oxygen to parts of the body, thus affecting a fetus.

``Fetal growth and birth weight are strongly linked to morbidity and mortality during childhood and adulthood, so it's clear that air quality is important to everyone's healthy development,'' Gilliland said.

Researchers studied the gestational age, birth weight and birth place of 3,901 children born in California between 1975 and 1987. The children were all a part of the Children's Health Study, which monitors levels of major pollutants in Southern California communities.