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Last week, about 140 countries signed the United Nations’ Minamata Convention, a global treaty that includes a ban on mercury for cosmetics and soaps.

However, Scientific American reports that mascara and other eye makeup is exempt because, as the treaty states: “no effective safe substitute alternatives are available” and “the intention is not to cover cosmetics, soaps or creams with trace contaminants.”

Small amounts of mercury are used in mascara as a preservative and to prevent bacterial growth that could cause infections in the eye. The Food and Drug Administration allows mercury in cosmetics, as long as the concentration remains below 65 parts per million. But some consumer advocates are not reassured by that policy. Stacy Malkan, co-founder of the advocacy group Campaign for Safe Cosmetics, told Scientific American that there is no justification that “a known neurotoxin should be allowed in any of these products,” since there are alternatives that she said many U.S. companies are already using.

The goal of banning mercury in cosmetics was to prevent its use in skin lightening creams that often rely on high levels of the metal. Mercury can be absorbed through the skin and has been linked to kidney damage, as well as developmental abnormalities in developing fetuses.

[Scientific American]