Friday, August 31, 2012

Early Puberty? A New Study Finds that Girls Exposed to Household Chemical Menstruate Earlier

By Lindsey Konkel
 of Environmental Health News
Fri, Aug 31, 2012 at 10:03 AM

Girls exposed to high levels of a common household chemical had their first period seven months earlier than girls with lower exposures, according to new research by federal scientists. “This study adds to the growing body of scientific research that exposure to environmental chemicals may be associated with early puberty,” said Danielle Buttke, a reproductive physiologist at the US Centers for Disease Control and Prevention who was the study’s lead author.

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Age of menarche — when a girl has her first period — has fallen over the past century, from an average of 16-17 years to 12-13 years. Experts are not sure why, but they suspect that better nutrition and rising obesity rates play a major role. Some evidence also points to chemicals in consumer products that can mimic estrogen, a hormone that is critical to the timing of puberty.

The CDC study is the first to link the chemical dichlorobenzene and the age of girls’ first period. Dichlorobenzene, a solvent, is used in some mothballs and solid blocks of toilet bowl deodorizers and air fresheners. Nearly all people tested by the CDC in the 1990s had its residue in their bodies, and breathing indoor air is the primary exposure.

Buttke said the role that environmental factors may play in the timing of puberty is not easy to tease out but it’s a serious public health issue that warrants further study. Early menarche raises the risk of developing breast cancer and other diseases in adulthood.

Whether there are health effects from exposure to dichlorobenzene is largely unknown. It is classified as a possible human carcinogen and previous studies have linked prenatal exposure to low birth weight in boys. Because it appears to alter hormones in lab animals, the US Environmental Protection Agency has named it a priority for screening for hormonal effects.

The new research included 440 girls aged 12 to 16 who participated in the CDC’s National Health and Nutrition Examination Survey. For those with the highest levels of dichlorobenzene metabolites in their urine, the average age of first menstruation was 11.8 years, while for girls with the lowest levels it was 12.4 years, or more than seven months later, according to the study published online in Environmental Health Perspectives on August 14.

The CDC scientists found no significant association between age of first period and levels of other potential endocrine-disrupting chemicals found in consumer products, including bisphenol A (BPA), phthalates, and parabens.

Blacks and Hispanics had higher levels of the dichlorobenzene residue than white girls. But the scientists adjusted their data on menstruation to include racial factors, which can play a role in the timing of puberty. Previous studies found that heavier girls as well as blacks and Hispanics tend to have their first period at an earlier age.

Buttke and other scientists said it’s impossible to say from this study alone whether exposure to the chemical actually causes girls to menstruate earlier. One major weakness is that the researchers measured the chemical in the girls’ urine when they were 12 to 16 years old, after most had already started menstruating. As a result, they do not know what the girls were exposed to before their periods started, which most likely would be the critical time. “Future studies should look at exposure in the years leading up to menarche as well as exposures in utero,” Buttke said.

Dichlorobenzene is short-lived inside the body. It breaks down quickly and is removed from the body through urine within hours of exposure. “While it’s entirely possible that chemicals with endocrine-disrupting properties can influence timing of puberty, it’s unclear whether chemical exposures during certain periods of child development can have a bigger impact than at other times,” said Mary Wolff, director of the Center for Children’s Environmental Health and Disease Prevention Research at Mount Sinai Hospital in New York. She was not involved in the current study.

It also is possible that women who experience early puberty have some difference in the way their body metabolizes the dichlorobenzene, leading to higher levels in urine. “Perhaps the chemical has nothing to do with when they started menstruating and is simply a marker of some physiological difference,” said Dr. Richard Stahlhut, an environmental health researcher and preventive medicine specialist at the University of Rochester Medical Center.

Nationwide tests found dichlorobenzene residue in 98 percent of people tested in the early 1990s. It can pass to a fetus in the womb, and it also has been widely found in breast milk. Because of its cancer risk and its widespread discovery in sewage, California in 2006 banned dichlorobenzene, also known as PDCB, in toilet and urinal deodorizers and solid room fresheners. That regulation aimed to reduce indoor air levels in California by 60 percent, according to a report by the California Air Resources Board.
“It is clear from the data presented that PDCB in toilet/urinal blocks, and solid air fresheners, along with mothballs are a major source of human exposure,” the California report said.

Representatives of the Chlorobenzene Producers Association, which represents manufacturers of dichlorobenzene, were not available for comment on the new CDC study.

Earlier research has linked premature puberty to other contaminants. Adolescent girls with high levels of brominated flame retardants had their first periods earlier than other girls in a 2011 study. Also, girls prenatally exposed to other, now-banned flame retardants called PBBs began to menstruate at a younger age, according to one study of Michigan women who in 1973, while pregnant, ate food contaminated with the chemicals. In-the-womb exposure to the banned insecticide DDT was associated with early menarche in a study of mothers and daughters in the Great Lakes region in the 1970s and 1980s.

While the new study found no link between BPA or phthalates and early menarche, some previous studies suggest that these chemicals, used in many consumer products, may play a role in lowering the age of puberty in humans and animals.

This report was originally published by Environmental Health News.

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