Personal care products such as shampoos, hair sprays, makeup and deodorant often contain endocrine-disrupting chemicals (EDCs), such as phenols, parabens and phthalates. Endocrine disruptors can increase the risk of infertility and interfere with fetal development.

Because women tend to use more of these products, they are at particular risk, especially teenagers. “Teen girls may be at serious risk since it’s a time of rapid reproductive development, and research has suggested that they use more personal care products per day that the average adult woman,” Kim Harley, lead author of the Hermosa study, said in a statement.

“Seeing the drop in chemical levels after just three days [of using safer products] shows that simple actions can be taken, such as choosing products with fewer chemicals, and make a difference.”

Working with researchers from from the University of California at Berkeley, local high school students helped to design and carry out the study to encourage the teens to learn about the science behind endocrine disruptors' effects on the body and how to protect their own health and the health of their communities.

Just a three-day break from products with phenols, parabens and phthalates significantly reduced levels of these chemicals in the girls' bodies, the study found. “After learning of the results, the girls took it upon themselves to educate friends and community members, and presented their cause to legislatures in Sacramento,” said Kimberly Parra, the community principal investigator.

Harley, the associate director of the UC Berkeley Center for Environmental Research and Children’s Health, and her colleagues enrolled 100 girls between the ages of 14 and 18 years old in their study. Study participants used products free of triclosan, phthalates, parabens and benzophenone-3 (BP-3) for three days instead of their usual personal care products.

The girls received deodorant, small containers of shampoo, conditioner, body wash and body lotion. They were also given a bar of hand soap for home and a small container of liquid hand soap for their purse. The girls were also allowed to choose four EDC-free items from among the following: liquid or powder foundation, mascara, eyeliner, lip gloss/lipstick/lip balm and sunscreen.

Urine samples before and after the switch were used to measure the presence of endocrine-disrupting compounds in the girls' bodies. Levels of metabolites of diethyl phthalate, commonly used in fragrances, decreased by 27 percent after the 3-day period. Levels of methyl and propyl parabens, used as makeup preservatives, dropped 44 and 45 percent respectively. Levels of both triclosan, found in antibacterial soaps and some brands of toothpaste, and benzophenone-3 (BP-3), found in some sunscreens under the name oxybenzone, decreased by 36 percent.

One of the study goals was to make people aware of the chemicals in the products they use. “Seeing the drop in chemical levels after just three days shows that simple actions can be taken, such as choosing products with fewer chemicals, and make a difference,” said Maritza Cardenas, one of the teens who was a study co-author and is now an undergraduate at UC Berkeley studying molecular and cell biology.

The study is published in Environmental Health Perspectives.