WASHINGTON (REUTERS) — Everyday exposure to a chemical ingredient used to preserve many cosmetics and soften plastics like those used in baby toys may contribute to sperm damage in adult men, according to a study published Monday.

In one of the first trials asserting the effects of the chemical, phthalates, on humans, Harvard University researchers found signs of correlation between exposure to the chemical and damage to the DNA of human sperm.

The study, published in the government journal Environmental Health Perspectives, does not show whether this DNA damage could cause any reproductive harm, the researchers stressed.

Last month the U.S. Cosmetic Ingredient Review panel, an industry-sponsored watchdog, sparked fury from health and environmental lobbyists when it voted to allow the continued use of three phthalates in perfumes and beauty products, saying the chemicals were safe in their current uses.

Phthalates, used to make fragrances last longer and to soften plastics, have been linked in previous studies to birth defects in animals, although no evidence proved they are harmful to humans.

The American Chemistry Council maintains that phthalates are safe, and the U.S. government so far has declined to limit their use. But the European Union banned their use in some products, including baby toys, in 1999.

The study, conducted at a Massachusetts fertility clinic, analyzed urine and semen samples from 168 men believed to have average levels of exposure to diethyl phthalates through the use of cosmetics products and plastics.

Russ Hauser, a Harvard School of Public Health professor and a co-author of the study, said preliminary results suggested exposure to those phthalates was associated with increased DNA damage in sperm but said it was too early to tell how severe the damage was.

“What the significance of it is, we don’t know. What it predicts in terms of end points in the fetus or child is really unclear at this point,” he said in a telephone interview.

Hauser said his group planned to extend its research to include between 700 and 800 men in order to verify the findings and planned to cross-reference results with findings of other studies measuring factors like pregnancy success rates.

“This paper shows early findings in a relatively small number of men,” he said. “Our next step here really is to expand the study and repeat the analyzes.”

But a group that has been fighting the use of phthalates, Health Care Without Harm, said the study showed they were right.

“The correlation found in this study is extremely troubling and deserves urgent follow up,” the group’s Dr. Ted Schettler said in a statement.