Experiments with rats show early exposure causes genetic changes in breast cells
THURSDAY, Dec. 6 (HealthDay News) -- A chemical found in many plastic products used in households caused accelerated breast development and genetic changes in newborn female lab rats, a condition that might predispose the animals to breast cancer later in life, a new study says.
Butyl benzyl phthalate (BBP) is commonly used to soften polymers and plastics. It's found in everything from plastic pipes, vinyl floor tiles and carpet backing to lipstick. BBP has also been found to be an endocrine disruptor, which mimics the effect of hormones. Endocrine disruptors are known to damage wildlife and have also been implicated in reduced sperm counts and neurological problems in humans, the researchers said.
"Our study is the first one demonstrating that exposure to this compound (BBP) soon after birth results in alterations in the expression of genes present in the mammary gland," said lead researcher Dr. Jose Russo, a breast cancer expert at the Fox Chase Cancer Center, in Philadelphia.
The findings are important, Russo said, because the researchers are studying the lifetime effect of BBP on the mammary gland, long before it starts developing under the influence of the hormones of puberty, and the potential implications on humans.
Because of lasting genetic changes in the breast, exposure to BBP could increase the risk for developing breast cancer later in life, Russo said.
"To prevent breast cancer in adulthood, it is necessary to protect both the newborn child and the mother from exposure to this compound that has an estrogenic effect and could act as an endocrine disruptor," he added.
For the study, Russo's team fed lactating rats BBP, which their offspring absorbed through breast milk. The rat pups received levels of the chemical equivalent to the U.S. Environmental Protection Agency's safe dose limit for humans, according to the report in the Dec. 5 online issue of BMC Genomics.
The researchers found that BBP affected characteristics of the female offspring of the rats, such as more rapid breast development and changes in the genetic profile of the mammary glands. While these effects wore off after exposure to BBP was stopped, the changes caused by the chemical might have an effect later in life, the researchers said.
"Our original observations are that the genomic changes induced by BBP occur very early in life, and they could result in significant modifications in the risk of the mammary gland to develop cancer later on in life," Russo said.
Russo said he and his colleagues are currently evaluating how changes in gene expression caused by BBP respond to cancer-causing chemicals given to adult rats.
"We are also studying the effects of exposure to BBP before birth. In addition, we are following a cohort of girls entering puberty for determining the tempo of breast development and their first menstrual period and associating these events with exposure to environmental agents such as BBP," Russo said.
One expert said scientists are only beginning to learn how many genes are affected by exposure to chemicals early in life.
"The early exposure to BBP altered breast development and may therefore alter the susceptibility to breast cancer," said Dr. Ted Schettler, science director at the Science and Environmental Health Network, in Ames, Iowa.
Schettler thinks people need to be aware of the possible effects of chemicals on genes during early life, and how these changes can influence susceptibility to disease in adulthood.
"People are finally getting the idea that early life events can matter later in life," Schettler said. "When people see that commonly encountered environmental agents like BBP can cause genetic changes, it's of public health interest."
However, Dr. Jonathan Borak, a clinical professor of environmental medicine at Yale University School of Public Health, said there's no evidence that exposure to BBP increases the risk of breast cancer.
"To date, studies have failed to find an association between BBP and breast cancer," Borak said. "This study doesn't add specific information on breast cancer and environmental interactions."
Efforts to reach the American Chemistry Council, a chemical industry group, for comment on the study were unsuccessful.
In October, California adopted a law that will ban trace amounts of BBP in toys and baby products such as teething rings, according to published reports.
And in March, a study published in the journal Environmental Health Perspectives suggested that exposure to phthalates could be fueling the obesity epidemic by contributing to abdominal obesity and insulin resistance in men.
For more on breast cancer, visit the American Cancer Society.
SOURCES: Jose Russo, M.D., Medical Science Division, Fox Chase Cancer Center, Philadelphia; Ted Schettler, M.D., M.P.H., science director, Science and Environmental Health Network, Ames, Iowa; Jonathan Borak, M.D., clinical professor, environmental medicine, Yale University School of Public Health, New Haven, Conn.; Dec. 5, 2007, BMC Genomics
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