Global Beauty Hazard: Assessing Mercury in Skin-Lightening Products

Women seated at a bus stop in Thailand in front of a billboard for skin lightening products

studies they reviewed. Mercury content varied widely, with many products containing hundreds or thousands of micrograms per gram; one cream had a concentration of 314,387 lg=g.
The researchers organized peer-reviewed studies into four topic groups: a) mercury levels in skin-lightening products, b) skin-lightening product usage, c) health impacts related to such products, and d) biomarkers of mercury exposure. "Societal perception of beauty continues to perpetuate the notion that lighter skin is more desirable," the authors wrote, calling the market for skin-lightening products "one of the world's fastestgrowing beauty industries." 3 Niladri Basu, the review's senior author and a professor of environmental health sciences at McGill University in Montreal, has been studying mercury exposures for years, but this focus on skin-lightening products is new. "I can tell you how much mining and fossil fuel combustion contribute to mercury pollution," he says. But scientists do not know the extent to which cosmetic products contribute to the global mercury burden. "It's going to be significant because there are tens, if not hundreds, of millions of people who use these products," says Basu.
People around the world seek products that promise to lighten skin, which sometimes contain mercury. Besides health reasons such as pigmentary disorders, such products are sought in response to media images (such as this billboard at a bus stop in Thailand) associating beauty with lighter skin, and the pressure of colorism, which refers to discrimination against those within one's same ethnic or racial group who have darker skin. 9 Image: ©iStock.com/ oneclearvision.

Science Selection
The review describes baseline conditions and provides data that Basu expects will be helpful to scientists, regulators, and policy makers. For example, five studies measured urinary mercury in populations in Hong Kong and the western United States. Across these studies, urinary mercury concentrations ranged between 0 and 770 lg=L, with roughly two-thirds of all the study participants' levels exceeding 20 lg=L (identified as a reference value by all studies reviewed, the authors noted). 3 By comparison, when Basu and colleagues assessed global mercury exposure from all sources, not just skin lighteners, urinary levels were generally below 3 lg=L. 8 Mercury concentrations in tested products varied across geographic regions, the authors found, with the highest median concentrations measured in products purchased from countries in the Eastern Mediterranean, Southeast Asian, and Western Pacific regions.
The high variability of mercury concentrations in skinlightening products caught the attention of Kyla Taylor, a health scientist in the Division of Translational Toxicology at the National Institute of Environmental Health Sciences. "These products are popular in many different countries and are widely available for purchase on the Internet," says Taylor, who was not involved in the new work. She adds that the paper may understate the problem. Because most studies analyzed the use of skinlighting products purchased in stores, Taylor explains, this review likely missed the growing number of products advertised on social media and sold online. 7 The authors recognized other gaps, including the need for more studies from Europe, Southeast Asia, and Latin America, where people are known to use skin lighteners. 2 In addition, some of the biomarker studies did not differentiate between mercury from skin lighteners and exposures from other sources, such as seafood consumption and amalgam dental fillings.
After combing through more than 2,300 peer-reviewed scientific papers, only 41 papers from 22 countries met the authors' criteria for inclusion: that they be original articles published in or after 2000 and that their data about human use could be extracted and used in the analysis. Basu was surprised to find so few highquality, well-designed studies. "This topic has largely not been investigated that well," he says. "The data that are published are not the strongest, unfortunately," he explained, citing shortcomings such as small sample sizes, not controlling for other mercury exposures, and too little information on the amount of product applied and duration of use. Basu calls for more resources to be dedicated to the work. His team's next steps will be to fill in some of the data gaps, he says, noting that the foundational work done in this assessment is "the tip of the iceberg."