Salinas Valley, CAA new studysuggests that prenatal exposure to chemicals in personal care products may speed puberty in girls,according to Berkeley News.

The study, known as the Center for the Health Assessment of Mothers and Children of Salinas (CHAMCOS) study, was primarily intended to examine the impact of pesticide exposure on childhood development. Researchers used the opportunity to examine the effects of other chemicals, though—specifically, phthalates, parabens, and phenols.

The team of researchers recruited pregnant women living in the farm-working, primarily Latino communities of Salinas Valley between 1999 and 2000. They measured the concentrations of phthalates, parabens, and phenols in urine samples taken from mothers twice during pregnancy, and from the children once they hit the age of 9. They followed the growth of the 159 boys and 179 girls up to the age of 13, tracking the timing of developmental milestones marking different stages of puberty.

More than 90% of urine samples from mothers and children showed detectable concentrations of diethyl phthalates and parabens. Triclosan was present in approximately 70% of samples.

The researchers found that every time the concentrations of diethyl phthalate and triclosan doubled in the mother’s urine, the timing of developmental milestones in girls shifted approximately one month earlier. Girls who had higher concentrations of parabens in their urine at age 9 also experienced puberty at younger ages, although in that case, it was unclear if the chemicals were causing the shift, or if girls who reached puberty earlier were more likely to start using personal care products at younger ages, according to Kim Harley, an associate adjunct professor in the School of Public Health, who spoke with Berkeley News on this topic.

These trends were not observed in boys.

Diethyl phthalate is often used as a stabilizer in fragrances and cosmetics. Triclosan is used in some toothpastes as an antimicrobial agent; it used to be in hand soap, until 2017, when the FDA banned it because it was shown to be ineffective. Parabens are used as preservatives in cosmetics.

These three chemicals, according to Berkeley News, have been shown to alter reproductive development in rats.

The study notes that these chemicals are quickly metabolized, and that one to two urinary measurements per developmental point may not accurately reflect usual exposure.