Banned chemicals -- present in amounts higher than levels found in recent years in US adults -- are turning up in the blood of young girls being studied in California and Ohio.
Researchers from Kaiser Permanente Northern California, UCSF and the California Department of Public Health (CDPH) led the study to measure blood levels of the chemicals. They assessed levels of PCBs, DDT and related pesticides, and flame retardants in nearly 600 girls, ages six to eight. These chemicals can act like hormones. Scientists and public health experts want to know how they might affect children as they develop through adolescence and into adulthood.
The main difference found between girls in Ohio and California was that the California girls had higher levels of all three classes of chemicals in their blood, on average.
The potentially hormonally active fire retardants measured in the study are called polybrominated diphenyl ethers (PBDEs). They have been banned in Europe, but they are still used in products sold in the United States to help meet fire safety standards. Products containing PBDEs include foam upholstery, textiles and home furnishings.
In the United States, PCBs were used in transformers and industrial applications until 1979, when their use was banned. DDT and related pesticides also are banned but persistent. In addition, these pesticides are still used on crops in Mexico.
The study identified additional differences in average blood levels of chemicals among the girls. Black girls had significantly higher levels of PBDEs in their blood in comparison to white girls. In general, levels of PCBs and pesticides were significantly lower among girls born to less educated mothers. Mexican-American girls had the highest levels of pesticides in their blood. Chemical levels also tended to be lower in girls who were obese.
The research report is in press and already available online in the scientific journal Environmental Research. The findings are among the first to be reported from a long-term, multi-site collaboration called the Breast Cancer and the Environment Research Centers
(BCERCs). The project is funded primarily by the National Cancer Institute and the National Institute of Environmental Health Sciences.
The main exposures to these chemicals occur in utero or through breast feeding, according to the study authors, but additional exposures occur during childhood.
"This study demonstrates that measurable levels of chemicals that might interfere with normal hormonal pathways are present in the blood of girls during the time of breast development," says Robert Hiatt, MD, PhD
, director for population sciences for the UCSF Helen Diller Family Comprehensive Cancer Center and lead scientist for the Bay Area BCERC.
"The next step is to determine if we can detect any evidence that these chemicals have effects on pubertal development at the levels we have detected them."'Cause for Concern'
According to study leader Lawrence Kushi, ScD, associate director for epidemiology at Kaiser Permanente Northern California, these findings indicate that exposures to these chemicals are widespread. "Although we don't know what the health implications of these exposures are, the fact that they are found in almost all of our study population suggests some cause for concern," Kushi says.
Childhood and especially adolescence are thought to represent a window of time when girls might be especially vulnerable to environmental exposures that can influence breast cancer risk in later years. This idea stems from lab studies of animals and population studies of women who had received radiation treatment when they were girls. Reproductive factors -- including early age of first menstruation, late age of menopause and delayed childbearing -- already are known to increase a woman's risk for breast cancer.
Read more at Jeffrey Norris, UCSF Science Cafe