Avobenzone

The days are long, school is out, and the kids are outside. With sunscreen-slathering season here, it's a good idea to learn more about those cosmetic concoctions and their potential health hazards. Choosing a sunscreen--or choosing to avoid sunscreen and cover up instead--depends on your particular health priorities.

Skin Cancer: Sunscreens protect skin from carcinogenic ultraviolet rays. If your goal is to stave off skin cancer, the most common cancer in the US, apply sunscreen on exposed skin at least 20 minutes before going out in the sun, and reapply--even waterproof formulas--after swimming, perspiring, or toweling off. Choose a sunscreen that protects against both UV-A and UV-B rays (look for "broad spectrum protection" on the label), shake the bottle before use, and don't skimp. But sunscreen is not a surefire cancer buster: an independent, nonfederal expert panel concluded last year that sunscreen "should not be counted on to provide UV protection by itself" (American Journal of Preventive Medicine, December 2004). Indeed, some have speculated that sunscreen might be responsible for the rise in the rate of skin cancer. This may be due to the tendency of sunscreen wearers to increase their time spent in the sun, or the fact that they don't apply sunscreen generously enough.

Allergenic Ingredients: PABA, a formerly ubiquitous sunscreen ingredient, causes red, itchy skin in up to 40 percent of all users. Benzophenone and avobenzone (aka Parsol 1789) also may irritate skin. As with all cosmetic products, synthetic fragrances, which are unregulated and unlabeled, may aggravate allergies or asthma. Bright white zinc oxide, found in surf shops, does not irritate skin and is a very effective sunblock.

Hormone Disruption: Benzophenone, octyl-methoxycinnamate (aka octinoxate), and homosalate interfere with the endocrine systems of laboratory rats. It is unclear whether they have an effect on human hormones. In one study, daily application of the first two ingredients for one week caused no changes in the hormone levels of 32 adults (children may respond differently). The parabens (butyl, ethyl, methyl, and propyl), preservatives widely used in cosmetic products, may also mimic estrogen. Again, zinc oxide is not known to have any effect on the endocrine system.

Carcinogenic Ingredients: Diethanolamine (DEA) and related ingredients (e.g., triethanolamine, or TEA) may form carcinogenic nitrosamines if the formula contains nitrites as a preservative or contaminant. Some studies have indicated that padimate-O, avobenzone, and titanium dioxide cause DNA damage that might in turn lead to cancer. However, these studies were not done on living animals.

Seek Shade: If you choose to apply sunscreen less often or not at all, practice sun avoidance: wear a wide-brimmed hat and tightly woven clothes, and seek shade, especially during the peak sunlight hours of 10 a.m. to 4 p.m.

Beneficial Rays: Very limited exposure to UV light is wholesome, enabling the body to synthesize vitamin D, which is essential for healthy bones. A total of 30 minutes of sunscreen-free direct sunlight each week will keep your baby's vitamin D supply strong.

See Claire Gutierrez and Sunscreen Product Report, "Best Sun Protection Tips: Why Sunscreen Alone Is Not Enough," www. thegreenguide.com

MOLLY RAUCH is science editor of The Green Guide (www.thegreenguide.com).

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