Should you worry about the chemicals in your makeup, lotion, shaving cream, soap and shampoo? The answer is a clear maybe.

Why maybe? That’s because some critics suspect that chemicals such as phthalates and parabens can interfere with the body’s hormones, most notably reproductive hormones such as estrogen and testosterone. The possible health risks could include chronic diseases, cancers and a host of developmental disorders and fertility problems.

Manufacturers use phthalates to help dissolve other ingredients into a consistent solution, to make nail polishes less brittle and to keep hair spray from making hair too stiff. Parabens in personal care products act as preservatives and antimicrobials. The chemicals are not regulated in consumer products, in large part because the Food and Drug Administration says there’s no evidence that current exposures are a health hazard.

Indeed, the science of endocrine-disrupting chemicals is fraught with uncertainty. Sometimes exposure — how much and for how long — is under question; sometimes the health effects in humans are not clear for compounds that have been studied in animals and cell culture.

Here’s what’s certain: Phthalates and parabens are not inert substances: They have biological activity. In animal studies, for instance, some phthalates act to counter male hormones and disrupt development of male sex organs. Both phthalates and parabens act on estrogen pathways, which in humans have been associated with such varied effects as decreased sperm count, endometriosis and insulin resistance.

Also, there’s no question that most Americans are regularly exposed to these chemicals. Large-scale monitoring studies show that phthalates, parabens and the chemicals created by their metabolism are present in the urine of nearly everyone tested, according to the Centers for Disease Control and Prevention.

Here’s what’s not certain: the level of chemical exposure that might pose a risk to human health and whether even the highest exposures measured in people are a problem.

Scientists continue to study the effects of these endocrine disruptors and have investigated possible links to miscarriage, premature birth, birth defects, deficient sperm, obesity, metabolic disease, bone density and breast cancer. But how much exposure might lead to these health risks simply isn’t known, and scientists cannot ethically conduct tests to directly show such effects.

“We just don’t do these experiments in people,” says Julia Brody, executive director of the Silent Spring Institute, a nonprofit research organization in Newton, Mass. “Therefore, we have to consider animal and cell-culture evidence.”

That leaves a lot of room for doubt. How much exposure is bad for you? Which chemicals — if you could avoid them — would be best to avoid?

Here’s another thing that’s not certain: which chemicals are in any particular personal care product. Yes, there are ingredients labels, but they’re not very helpful in avoiding phthalates and parabens. That’s because both terms encompass a class of chemicals containing many different compounds. Even to label-reading consumers, some compounds may not be recognizable as a phthalates or parabens.

That makes it difficult to determine potential health risks in the makeup, shaving cream and sunscreen that you buy. If a product’s label says phthalate-free or paraben-free, that provides clarity. Otherwise, there’s no way to be sure, says John Meeker, an associate professor of environmental health sciences at the University of Michigan. “It could be in there under vague names like ‘fragrances.’ ”

“Fragrance can include dozens, hundreds of chemicals,” Brody says. “Avoiding fragrance is one way you can reduce your exposure.”

Several studies have shown that the more toiletries people use, the more phthalates and parabens end up in their bodies. For instance, a recent study asked 177 pregnant women which personal-care products they used and analyzed their urine for evidence of phthalates and parabens. The number of products a woman used correlated with the amount of chemicals found in her urine. Of all the products used, lotions, cosmetics, hair gels and perfumes were the biggest contributors.

A similar study of 337 postpartum women found nearly three times the amount of one particular phthalate in the women who used perfume. Hair spray, nail polish and deodorant use were also identified as contributors.

Brody and her colleagues tested 213 commercial products for the presence of 66 chemical compounds. Parabens were detected in some products that did not list them on their labels. Indeed, the highest level of a compound called methyl paraben was found in “alternative” sunscreens marketed as “green” products.

And three phthalate compounds were found only in “green” products whose labels did not list those chemicals, which the study authors suggest were used as substitute for better-known phthalates.

So, to avoid these chemicals altogether, what should you do? Meeker says that, if given the option, he’ll choose a phthalate-free or paraben-free product. Brody advises using fragrance-free products. “That gets rid of a whole class of chemicals,” she says.

The Silent Spring Institute has a list of buying tips on its Web site. To review the list, go to www.silentspring.org/

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