15. Early Puberty Onset for Girls May be Linked to Chemicals in the Environment and Increases in Breast Cancer

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Source: ENVIRONMENTAL HEALTH MONTHLY; Pediatrics, December 1998, Vol. 11, No. 3 Title: “Secondary Sexual Characteristics and Menses in Young Girls Seen in Office Practice: A Study from the Pediatric Research in Office Settings Network”, Editor: Stephen Lester, Authors: Marcia E. Herman-Giddens, P.A.; Eric J. Slora, Ph.D.; Richard C. Wasserman, M.D., M.P.H.; Carlos J. Bourdony, M.D.; Manju V. Bhapkar, M.S.; Gary G. Koch, Ph.D.; and Cynthia M. Hasermeier, B.S.

Faculty Evaluator: Derek Girman, Ph.D.
Student Researcher: Melissa Bonham

Endocrine disrupters may be responsible for young girls maturing faster, creating an increased risk of breast cancer. A University of North Carolina cross-sectional study, conducted on girls between the ages of 3 and 12 years, found that girls are developing pubertal characteristics at younger ages than suggested by standard pediatric textbooks. The study found that on average, African-American girls begin puberty between 8 and 9 years of age and White girls by 10 years of age, which is six months to a year sooner than previous data suggests. Although it is unclear what is causing this early onset of puberty, environmental exposures have been implicated.

The study, which ran from July 1992 through September 1993, included 17,077 girls from across the United States who were undergoing physical examinations by certified pediatricians. The study data was collected using a one-page, two-sided standardized form for each subject that elicited information on the girl’s age, height, weight, race, ethnicity, chronic illness and medication history, presence or absence of menses, and stages of development of breast, pubic hair, and auxiliary hair. The main area of interest were the proportions of girls at a given age with secondary sexual characteristics and menses and the mean ages of onset for each characteristic.

Of the girls studied, 9.6 percent were African American and the remaining 90.4 percent of girls were White. The study found that by three years of age, 3 percent of the African-American girls and 1.2 percent of the White girls showed signs of breast and/or pubic hair development. By the age of seven, these proportions increased to 27.2 percent of African-American girls and 6.7 percent of White girls showing these signs of development. By eight years old, 48.3 percent of African-American girls and 14.7 percent of White girls had begun development.

The mean age of the onset of breast development for African-American girls was 8.87 years old and for White girls was 9.96 years old. Further, the mean age of the onset of pubic hair was 8.78 years for African-American girls and 10.51 years for White girls. The study found that African-American girls entered puberty approximately 1 to 1.5 years earlier than White girls and were beginning menses approximately 8.5 months earlier. No explanation could be given for the statistical differences in the onset of puberty or subsequent menses in the two ethnic groups. The authors concluded that these girls are “….developing pubertal characteristics at younger ages than commonly used norms…” and that “the study strongly suggests that earlier puberty is a real phenomenon, and [that] this has important clinical, educational, and social implications.”

The authors specifically raised the issue of how their findings might impact the development of breast cancer. Breast cancer risks include the early onset of puberty that is brought on by the release of natural estrogens in the body. Women who go through puberty early have longer exposure to these estrogens and therefore may be at greater risk of developing breast cancer. In addition, puberty is marked by the rapid growth of breast tissue that may be especially sensitive to the effects of cancer-causing agents. This study raises some troubling questions about whether exposure to endocrine-disrupting chemicals, which mimic the female hormone estrogen, brings on early puberty.

UPDATE BY EDITOR STEVE LEST: This story is important because it raises questions about the impact of widespread exposure of the American people to low levels of chemicals that interfere with the normal functions of hormones. These endocrine-disrupting chemicals include substances, such as dioxin, PCBs, DDT, and many pesticides. Many of these chemicals are known to cause reproductive and developmental abnormalities in wildlife, and now, we are beginning to see increases in some of the same problems in people, including birth defects, breast cancer, prostate cancer, and infertility.

The onset of early puberty in girls is just one such piece of evidence. Research furthers indicates that women who report having had their first menstrual cycle at younger ages have greater lifelong risks of getting breast cancer.

As a direct result of research into the adverse effects of endocrine-disrupting chemicals in people and wildlife, the Environmental Protection Agency (EPA) proposed guidelines in December 1998 for testing more than 15,000 chemicals to determine if they interfere with endocrine function. These chemicals include many common-use substances from cosmetics to plastics to pesticides. The agency plans to use screening tests to identify around 1,000 chemicals for more in-depth testing that will be paid for by the manufacturers. In November 1998, the European Parliament voted for “gradual withdrawal” of hormone-disrupting chemicals from the European market, calling for strict labeling of products containing synthetic chemicals. “The burden should be on the manufacturers to prove that their products are safe,” said Kristen Jensen, who proposed the motion.

(Note: As a direct result of this research, the Pediatric Endocrine Society undertook a comprehensive review of this topic. The primary conclusions of this review have just been published in the Journal of Pediatrics.)

There was some coverage in the mainstream press. The Associated Press also ran the story that was picked up by a few local newspapers. Yet overall, there was not much attention given to the story beyond an initial reporting on the day of the release. I don’t recall any TV coverage. The TV news programs did not cover it; PBS did do a one-hour special on the general topic of endocrine disrupters, but they did not focus on the issue of premature puberty. Radio gave it very little attention, as did the print newsweeklies. Given that the general population is exposed to so many of these chemicals, that children are the primary target, and that the effects are so severe, though subtle, the story certainly should have gotten much wider coverage.


Generations at Risk, Ted Schettler, Gina Solomon, Maria Valenti, and Annette Huddle (Cambridge, MA: MIT Press, June 1999); Our Stolen Future, Theo Colborn, Dianne Dumanoski, and John Peterson Myers (New York: Dutton/Penguin, March 1996); Commonweal, P.O. Box 316, Bolinas, CA 94924, Tel: (415) 868-0970, E-mail:dbaltz@igc.apc.org; Center for Health, Environment and Justice, P.O. Box 6806, Falls Church, VA 22040, Tel: (703) 237-2249, E-mail: cchw@essential.org; Web site: Endocrine Disruptors Resource Center, International Agriculture and Trade Project: http://www.iatp.org/edrc.