Premature Puberty

Is Early Sexual Development the Price of Pollution?
Blackshear Illustration

Ten-year-old Christina Carter (not her real name) hides in her room when she wants to play Barbies. Although she has the mind of a 10-year-old, Christina has the body of a sexually mature woman. She started developing breasts and pubic hair at the age of eight, and just began menstruating. She is five feet, nine inches tall, and wears a ladies’ size 10 shoe. People expect her maturity to match her appearance-not her real age.

“She should be playing with dolls because she is only 10,” says Christina’s mother, Natalie. “But she is embarrassed because people think she is much older. Christina is so confused because she doesn’t fit in with other children, and she doesn’t fit in with adults, either.”

A Widespread Problem

Christina has a condition known as early puberty, and she isn’t alone. A recent nationwide study published in Pediatrics raises concerns that incidences of early puberty and other forms of early sexual development may be increasing in the U.S. Nearly half of all black girls and 15 percent of white girls, the study says, are beginning to develop sexually at the age of eight. For some, the trend starts even earlier, and is known as precocious puberty: Three percent of black girls, and one percent of white girls, show signs of sexual development as early as the age of three.

“When I was in clinical practice examining children, colleagues and I noticed that an unusually large number of girls already were developing sexual characteristics,” says one of the authors of the early puberty study, Dr. Marcia E. Herman-Giddens of the University of North Carolina at Chapel Hill School of Public Health.

Sexual development in children six years and younger should be evaluated by a physician. In some cases, early sexual development can be caused by a tumor or other pathological conditions. Natalie said when she took Christina to the doctor, he told her not to worry, that early sexual development is common. “But this hasn’t always been,” Natalie says. “I believe it has something to do with the foods we’re eating, along with their additives, hormones, preservatives and pesticides.”

Natalie believes that Christina’s condition is due to the exposure, in the womb and after birth, to growth hormones and pesticide residues in meat and other foods. She also believes these factors caused her son to be born with only one testicle.

The Pediatrics report also contradicts standard pediatric textbooks and earlier U.S. studies about the average age that girls begin to mature. The study found that, on average, black girls begin the process between eight and nine years, and white girls by age 10. Black girls are, the study says, entering puberty approximately one to one and a half years earlier than white girls and beginning menstruation approximately eight and a half months earlier.

“We have no explanation for this,” says Dr. Herman-Giddens. “Neither can we explain the earlier development among black girls in general. This study strongly suggest that earlier puberty is a real phenomenon, and that this has important clinical, educational and social implications.”

So far, there’s no indication that boys are being similarly affected, though Dr. Herman-Giddens says, “The same chemicals could affect boys differently and even cause a delay in puberty. That’s one reason it needs to be looked at.”

The study’s shocking results are no surprise to Charlotte Brody, organizing director of the Virginia-based Citizen’s Clearinghouse on Hazardous Wastes. “We’ve seen this problem before the study came out,” she says. “It’s another warning that we are messing with the fundamentals of life, and the weight of evidence points to endocrine disruptors.” As a result, she says, “I go out of my way to get hormone-free milk.”

Possible Causes

The researchers say that hair products containing estrogen or placenta could be one of the culprits. Endocrine-disrupting chemicals are also suspected. The list of potential triggers includes insecticides, growth hormones in meat and milk, estrogen-like substances in dental sealants used on children, and the plastic wrap used on sandwiches for kids’ lunches. The existence of common estrogen-like compounds in the environment can’t explain all of the sexual precociousness, though: The early development of sexual hair, for instance, is under the influence of male hormones.

Dr. Theo Colborn, co-author of the influential Our Stolen Future, says that laboratory studies in female rats and mice have shown that prenatal exposure to endocrine-disrupting chemicals can cause early puberty and hermaphroditism.

“That would certainly indicate that a pregnant woman should be very careful about what she is exposed to,” said Colborn, who is also director of the Wildlife and Contaminants Program at the World Wildlife Fund. “As the list of endocrine-disrupting chemicals grows, we realize that we are exposed to chemicals day-in and day-out that interfere with hormonal messengers that control development. Those are the kinds of chemicals anyone should be alerted to avoid, but especially prior to and during pregnancy.”

Colborn says that being cautious about diet is the safest way to address the issue of preventing early sexual development and such adult illnesses as breast cancer, which is believed to be related to estrogenic chemical exposure. Colborn recommends organically-grown foods and a low-fat diet. “The ultimate problem here is exposure through chemicals,” she says.

Something Fishy

It has been shown that endocrine-disrupting chemicals are at fault in early or precocious sexual maturity in fish. “Some studies, including one in the Great Lakes, show that fish exposed to contaminants become precocious. In fact, some salmon stocks have a very high prevalence of precocious males [up to 80 percent],” says Steven L. Goodbred, one of the authors of a U.S. Geological Survey (USGS) study that found such disruption in stream and river fish across the U.S.

Goodbred says the endocrine systems of animals are remarkably similar to humans. “So I suspect that, with a lot of these endocrine-disrupting contaminants, you can infer effects from one species to another within the animal community,” he says. “Most evidence supports the idea that if a chemical is estrogenic in one species, it will be in others, too.”

On average, black girls begin puberty between eight and nine years, and white girls by age 10.

The USGS data is the most extensive investigation yet of endocrine disruption in fish, and Dr. Gordon Eaton, USGS director, says its dramatic findings are “both a cause for concern and a call for further investigation.” More than 600 common carp were collected and analyzed from 25 streams in 13 states and the District of Columbia. Results of the study indicate significant differences in sex hormones and vitellogenin, an estrogen-controlled protein necessary for egg development in fish and birds.

Goodbred says that natural variability undoubtedly played a role, but that “certain contaminants”-pesticides in water, phenol compounds in streambed sediments and organochlorine compounds in biological tissue-are also implicated. “It may not be significant if fish hormones are a little different,” he says, “but it is important how those hormones affect reproduction. Particularly for endangered species, we need to find out how biologically significant these changes are.”

Fish are not people, and the Pediatrics study will have to be backed up by considerably more research before public concern rises and governmental action occurs. But it is increasingly evident that endocrine disruption is occurring, and that it is causing big changes in how children develop.

BECKY GILLETTE is a freelance writer based in Ocean Springs, Mississippi.