Girls exposed to chemicals commonly found in toothpaste, makeup, soap and other personal care products before birth may hit puberty earlier, according to a new longitudinal study led by researchers at the University of California, Berkeley. These girls hit puberty earlier than their peers who aren’t exposed to these chemicals in the womb, a U.S. study suggests.
Researchers studied 388 children in California who were taking part in a long-term study. Pregnant women were enrolled to the study between 1999 and 2000.
Many chemicals have been linked to early puberty in animal studies including phthalates, which are often found in scented products like perfumes, soaps and shampoos; parabens, which are used as preservatives in cosmetics; and phenols, which include triclosan, researchers note in Human Reproduction.
While this is thought to interfere with sex hormones and puberty timing, few studies have explored this connection in human children.
For the current study, researchers followed 338 children from birth through adolescence. They tested mothers’ urine during pregnancy and interviewed them about potential chemical exposures, then tested kids’ urine for chemical exposure at 9 years old and examined children for signs of puberty development every nine months between ages 9 and 13 years.
Over 90 per cent of kids’ urine samples showed concentrations of all the potentially hormone-altering chemicals, except for triclosan, which was found in 73 per cent of pregnant mothers’ urine samples and 69 per cent of their kids’ urine samples.
For every doubling in concentration of a phthalate indicator in mothers’ urine, their daughters developed pubic hair an average of 1.3 months earlier, the study found. And with every doubling of mothers’ urine concentrations of triclosan, girls started menstruating one month earlier.
Boys’ puberty timing didn’t appear to be influenced by prenatal exposure to these chemicals.
“There has been considerable concern about why girls are entering puberty earlier and hormone disrupting chemicals like the ones in personal care products that we studied have been suggested as one possible reason,” said lead study author Kim Harley, associate director of the Center for Environmental Research and Children’s Health at the University of California, Berkeley.
Half of the girls in the study started growing pubic hair when they were at least 9.2 years old and then began menstruating when they were 10.3 years old, the study found.
Phthalates, parabens and triclosan are not banned for use in personal care products, and there isn’t solid evidence yet that they cause health effects in humans, Harley said.
But the current results add to increasing evidence from lab studies that suggests these chemicals can disrupt or interfere with natural hormones in the body like estrogen, Harley added.
“The fact that we find associations with earlier puberty in girls is additionally concerning,” Harley said. “The good news is, that if women want to reduce their exposure to these chemicals, there are steps they can take.”
Triclosan is no longer allowed in antibacterial soap in the U.S., but it is still in toothpaste, Harley said. Consumers should make sure it’s not a listed ingredient on any toothpaste they buy, she advised.
Parabens are also on the ingredients list, often as methyl paraben, or propyl paraben, and consumers should avoid these products, too, Harley said.
Diethyl phthalate is harder to avoid, however, because it isn’t listed on labels and is often used in fragrances, Harley said.
The study wasn’t designed to prove whether or how prenatal exposure to these chemicals might have caused early puberty. And one limitation of the study is that researchers lacked data to know if girls going through puberty might be more likely to use these personal care products, and be directly exposed that way, the study authors note.
“The effects of these chemicals are very complex,” said Dr. Luz Claudio of the Icahn School of Medicine at Mount Sinai in New York City.
“Their effects on the hormonal system is different with different chemicals, they have different potencies, their effects can be modulated by other factors such as genetic predisposition, and importantly, their effects can be different depending on the timing of the exposure,” Claudio, who wasn’t involved in the study.
He added, “With that said, this and other studies, together with the laboratory experimental evidence point to potential effects on children.”