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Infant Pesticide Exposure Linked to Early Asthma
(Beyond Pesticides, May 29, 2003)
Exposure to cockroaches, weed killers, insecticides, fuel oil, soot, exhaust and farm crops, dust and animals beginning in the first year of life are linked to early asthma, according to a study presented at the American Thoracic Society on May 21, 2003. Frank D. Gilliland, M.D., Ph.D., professor of preventive medicine at the Keck School of Medicine at University of Southern California (USC), and his colleagues found that herbicide exposure before one year of age increases the risk of asthma by more than four and a half times and that other types of pesticide exposure before one year of age increases the risk by nearly two and a half times.

"The first year of life seems uniquely important in terms of susceptibility to environmental triggers of asthma," Gilliland says.

Researchers looked at 338 children who were diagnosed with asthma by a physician before they turned 5 years old. They then matched those children to 570 asthma-free children of the same age who lived in the same communities. They also matched them according to whether the children had been exposed to maternal smoking while still in the womb. They found that the risk of developing asthma before age 5 rises significantly with the following exposures (figures given in odds ratios):

Types of exposures and the resulting increases in risk of asthma.
Cockroaches in home before age 1; Over two times (2.03)
Around herbicides before age 1; Over four-and-a-half times (4.59)
Around pesticides before age 1; Nearly two-and-a-half times (2.40)
Farm crops, dust or animals before age 1; Nearly two times (1.81)
Daycare attendance before 4 months of age; Nearly two-and-a-half times (2.34)
Wood or oil smoke, soot or exhaust anytime between birth and age 5; More than 50 percent (1.57)

The study was not designed to find out specifically why risk increased. In general, Gilliland noted: "The first year of life is a critical time period of lung development-both for immunity and airway structure. Others have shown that certain early life exposures are important for asthma development."

The research team found that the more siblings a child had at birth, the lower the child's risk of early asthma. But they found nothing to indicate that other early childhood experiences such as exclusive breast-feeding or exposure to cats, dogs or other pets protect against early asthma.

More research is needed to determine what levels of exposure may be important and whether reducing exposures reduces asthma risk.

The research team conducted the case-control study within a subset of children participating in the ongoing USC-led Children's Health Study. According to the Keck School website, the Children's Health Study is an epidemiologic investigation to identify chronic effects of ambient pollutants in Southern California by performing cross-sectional and longitudinal studies in school children in several communities with varying exposures to ozone, particulates, and acid vapors. Researchers with the Children's Health Study have monitored levels of major pollutants in a dozen Southern California communities since 1993, while following the respiratory health of more than 3,000 students.

Asthma is the most common chronic disease of childhood, affecting about one in 14 children in the United States, according to the National Heart, Lung and Blood Institute, or NHLBI, one of the groups sponsoring the research. The California Air Resources Board, National Institute of Environmental Health Sciences and Environmental Protection Agency also sponsored the study.

Gilliland presented the findings at the 99th Annual International Conference of the American Thoracic Society on May 21, 2003 in Seattle, Washington (F.D. Gilliland, M.T. Salam, Y. Li and B.M. Langholz, "Early Life Risk Factors for Asthma: Findings from the Children's Health Study," ATS 2003-International Conference of the American Thoracic Society, Mini-symposium D011, 9:15 a.m. May 21, 2003). For more information contact Jon Weiner, USC Health Sciences Public Relations, DEI 2510, 1450 San Pablo Street, Los Angeles, Calif. 90089-9221, 323-442-2830.