According to a study by UC Berkeley researchers, early menstruation in girls and early gonad development in boys may be due to exposure to certain chemicals found in commonly used personal care products and cosmetics.

Published Tuesday, the study researched how early onset puberty may be triggered by chemicals such as phthalate metabolites, methylparaben and propylparaben, and phenols. Early onset puberty has been associated with a greater risk of mental health problems, breast and ovarian cancer in girls and testicular cancer in boys, according to the study.

According to Kim Harley, the lead researcher on the study and Associate Director for Health Effects Research at the Center for Environmental Research and Children’s Health, the study was started to examine why recent decades have seen a trend in early puberty, focusing on chemical exposure during pregnancy.

Pregnant women were enrolled in the study from 1999-2000 at the Center for the Health Assessment of Mothers and Children of Salinas, and their children were assessed in how external environmental exposures affected their health and development from the womb to adolescence.

The study used urine collections to test for different levels of chemical concentrations. Pubertal timing was then assessed among children between ages nine and 13 every nine months. According to Harley, the researchers divided the urine collection samples into differing levels of chemical concentrations: low, medium, medium high and high.

According to Harley, the study found that some mothers who exhibited low levels of molecular phthalates such as diethyl phthalate — a chemical found in many scented products such as perfumes, shampoos and deodorants — gave birth to girls who experienced pubic hair development up to six months earlier. Some mothers who exhibited a phenol called triclosan — an antibacterial agent used in toothpaste — in their urine sample gave birth to girls who menstruated up to four months earlier, Harley said.

In boys, the study cited earlier gonad development associated with the chemical propylparaben.

According to the study, the data’s accuracy could have been affected by the possibility that children entering puberty earlier may use more of these chemical-containing personal products, along with other factors.

Exposure to these chemicals is widespread, according to the study, and in the United States alone, more than 96 percent of women who participated in the nationally representative National Health and Nutrition Examination Survey had detectable concentrations of these puberty-accelerating chemicals in their urine.

Campus senior Danny Chandra said he was surprised by the results of the study and said that he would avoid these products if he were a parent.

“It might be unavoidable if these are everyday products but I would do everything possible…under my control to avoid them,” Chandra said.