Widespread environmental pollutants may retard puberty, suggests a new study of adolescents.
Since the 1970s, research has shown that these polychlorinated aromatic hydrocarbons can disrupt hormonal pathways in animals and people, thereby damaging sperm production and increasing the incidence of certain cancers (SN: 11/4/00, p. 303). The chemicals–which have been used in industry and are released from burning plastics–include dioxins, polychlorinated biphenyls (PCBs), and furans.
Now, a study from the University of Lueven in Belgium has examined the effects of these chemicals on sexual development of adolescents in two heavily polluted suburbs of Antwerp. The neighborhoods are home to an industrial smelter, a crematorium, several trash-incinerating plants, and other industries, and their freeways carry 80,000 vehicles a day.
The researchers recruited 200 17-year-olds of both sexes. Half were lifelong residents of the two polluted suburbs, and the others lived in a rural Belgian town 15 to 25 kilometers away from the nearest industrial sources of pollution. The groups had similar numbers of boys and girls of about the same social class.
The scientists tested the youngsters’ blood for chemical markers of PCBs and dioxin. The team found that blood concentrations of the markers were significantly higher in the adolescents from the suburbs than in their rural counterparts. The researchers also found that the suburban teens were, on average, at earlier stages of puberty than the rural youngsters were.
The stage of pubertal development was related to blood-marker concentrations. For example, a doubling of the dioxinlike compound in her blood gives a girl 2.3 times the likelihood of having immature breasts, says lead author Elly Den Hond. The findings will be detailed in an upcoming Environmental Health Perspectives.
“We didn’t expect such a strong correlation, since exposure levels [in even the two suburbs] are relatively low,” says Den Hond. She stresses that although sexual development appears slightly delayed in the polluted area, all youths in the study are within the normal range of maturation stages for their age.
The results are provocative, comments Richard M. Sharpe of the Centre for Reproductive Biology in Edinburgh. However, he cautions, there may be another explanation for them. For instance, the adrenal gland, which produces sex hormones, also mediates stress responses. Differences in stress between the groups could affect sexual development, he says.
The Belgian study may be the first showing polychlorinated aromatic hydrocarbons delaying puberty, says Marcia Herman-Giddens of the University of North Carolina at Chapel Hill. Her research has shown that the onset of puberty in girls often begins earlier today than it did 30 years ago. “For all we know, the [pollution-exposed] girls could begin development earlier and reach maturity later,” she adds, noting that the study didn’t consider onset of puberty in the young people.
“Much of the damage [from the chemicals] is at the fetal stage . . . and only the most minute amounts are required,” says Herman-Giddens. Some of the developmental delays noted in Den Hond’s study may result from fetal exposure to pollutants.
“There is a lot of evidence [for fetal effects],” says Herman-Giddens, “and this paper adds to it.” The chemicals should be regulated more tightly than they currently are, she concludes.