SOT Spotlight: Q&A with Claire Hamaji

Posted on Behalf of  Claire M. Hamaji

What is the title of your presentation?

A Risk Assessment of Inorganic Mercury Renal Toxicity from Application of Skin Lightening Products from Multiple Countries.

What was the scope of your research?

After some initial research into skin whitening products, we realized that there are numerous case reports in the scientific literature documenting renal abnormalities among users of these products. We found that inorganic mercury is often added as an active ingredient to skin whitening products since it inhibits tyrosinase, an enzyme involved in melanin production. As such, through this analysis we sought to:

  • Characterize the distribution of mercury concentrations in a survey of over-the-counter skin whitening products from around the world;
  • Compare the concentrations of mercury between skin whitening products from different countries;
  • Conduct a probabilistic risk assessment to evaluate whether dermal exposure to inorganic mercury through the regular use of skin whitening products presents a human health risk, specifically to the kidneys.

What did you find?

Products from Thailand, China, and the Dominican Republic contained some of the highest mercury concentrations. Approximately 46% of products surveyed contained mercury above 1 ppm, the FDA’s limit for mercury in cosmetics. We found that mercury was not detected in approximately 26% of products surveyed.

One of the primary conclusions of our analysis is that many over-the-counter skin whitening products from around the world contain concentrations of mercury that exceed FDA’s limit for U.S. cosmetics, often by multiple orders of magnitude.

Further, approximately 80% of margins of safety (MOS) in our model were calculated as less than 1.0, indicating that the estimated daily dose of mercury exceeded the RfD for inorganic mercury for 80% of the exposure scenarios in our model simulations. Our model results indicate that risk of renal damage among users of skin-whitening products may be possible under certain exposure scenarios.

What are the next steps/what other research is needed?

Our next steps will be to refine our analysis by generating MOS for different categories of products within our dataset, such as leave-on versus rinse-off products, and products from different countries. We will also expand our search for any additional studies of mercury concentrations in skin whitening products that we can use to supplement our dataset and analysis.