Physically precocious young girls often must endure stares and nasty catcalls. The problem of early development is particularly prevalent in Puerto Rico, and researchers there have found a possible culprit.
For more than 2 decades, their island has hosted an inexplicable epidemic of premature breast development, or thelarche. The incidence there—at least 7 or 8 per 1,000 girls—is the highest known. Most of the affected girls begin developing breasts between the ages of 6 and 24 months, notes Carlos J. Bourdony, a pediatric endocrinologist at San Juan City Hospital.
In the September Environmental Health Perspectives, he and his colleagues at the University of Puerto Rico, San Juan report data linking this condition with phthalates, a family of ubiquitous pollutants. The chemicals are used in the manufacture of many products, among them, plastics, lubricants, and solvents.
These are the same compounds that a panel commissioned by the National Toxicology Program (NTP) recently concluded may harm reproductive development in boys (SN: 9/2/00, p. 152: https://www.sciencenews.org/20000902/bob1.asp).
The San Juan researchers had thought that the thelarche might trace to pesticides that mimic estrogen, a hormone that spurs breast development. However, when they compared the blood of 41 girls with premature thelarche with that of 35 who are developing normally, “we did not find pesticides or their metabolites at higher levels,” notes University of Puerto Rico chemist Osvaldo Rosario.
“What we did see more of in girls with premature breast development,” he says, “were phthalates,” chemicals that can mimic or alter activity of sex hormones in animals. Within the premature thelarche group, 24 girls (68 percent) had detectable phthalates in their blood, compared with just 6 (17 percent) of the girls developing normally.
The most dramatic difference showed up in the blood concentrations of di-2-ethylhexyl phthalate (DEHP), the most widely used phthalate. In the five normal girls whose blood contained DEHP, its concentration averaged 70 parts per billion; among the girls with premature breast development and detectable DEHP, the concentration averaged 450 ppb.
Such data fall far short of proving that phthalates play a role in thelarche, observes Shanna H. Swan of the University of Missouri in Columbia. Still, she says, the study “is definitely important” and offers the strongest potential explanation yet for Puerto Rico’s early-thelarche rate.
Marcia E. Herman-Giddens of the University of North Carolina School of Public Health in Chapel Hill suggests that the phthalate connection may also help explain a disturbing trend that she and her colleagues reported 3 years ago. They found that the age at which U.S. girls enter puberty has been falling (SN: 5/3/97, p. 272). Herman-Giddens suspects that several factors—such as genetics and obesity—conspire with pollutants to hasten puberty.
If phthalates play a role, diet may be a major source. A recent study led by Jens H. Petersen of the Institute of Food Research and Nutrition in Seborg, Denmark, found phthalates in baby food and formulas. Fetal exposure to phthalates is also possible.
In fact, women of childbearing age had significantly higher phthalate exposures than any other group in a recent survey, according to John W. Brock of the Centers for Disease Control and Prevention in Atlanta. He recently measured phthalate breakdown products in the urine of 289 U.S. men and women. Surprisingly, among the women, the biggest contributor—di-ethyl phthalate (DEP)—is a solvent in colognes. Commercial production of DEP is far less than that of the phthalate plasticizers. Brock’s findings will appear in the October Environmental Health Perspectives.
The good news, says toxicologist Paul M.D. Foster of the Chemical Industry Institute of Technology in Research Triangle Park, N.C., is that extensive tests show that DEP “doesn’t have reproductive effects.” Unfortunately, his data on developing male rodents show considerable reproductive toxicity for another pollutant that Brock detected in the young women: di-butyl phthalate (DBP). This phthalate appears in fingernail polish, dyes, and plastics such as those in some food wraps.
When the NTP panel reviewed phthalates’ reproductive effects, Foster notes, it assumed that women would be exposed to less than one-tenth the concentration of DBP that Brock’s team measured in the urine of his female participants. In light of the new data, Foster says, “I hope NTP reevaluates [DBP’s] risk.”