A 47-year-old woman in Sacramento, California, has been left severely impaired—unable to talk or care for herself and requiring a feeding tube—after using tainted face cream that contained highly toxic methylmercury.

Her poisoning, first reported in local media in September, is now the subject of a detailed case report published today in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report (MMWR).

In it, health officials describe the progression of the woman’s symptoms, which began in July with weakness in her upper extremities and abnormal, painful sensations (dysesthesia). Over the next two weeks, she developed slurred speech, blurry vision, and unsteadiness while walking. She was then admitted to the hospital where her condition went downhill quickly, resulting in a state of agitated delirium.

Blood and urine screens in the hospital detected mercury. But the levels were so high, they exceeded what the screens could quantify. At that point, the state’s health department and poison control center got involved. The poison control center recommended that she start a treatment of oral dimercaptosuccinic acid, a metal chelator. This binds to and removes heavy metals from the body, and it has been used to treat heavy metal poisoning since the 1950s.

The health department, meanwhile, tracked the source of the poison to a skin-lightening cream she obtained from Mexico. The woman’s family told health investigators she had used such face creams twice a day, every day for the past seven years.

Further testing determined that she had 2,620 micrograms of mercury per liter of blood. According to the New York State Department of Health, usual amounts of mercury in blood—typically from dietary sources—are up to about 5 micrograms/liter.

Poisonous products

Adulterated skin-lightening creams are well-known to contain forms of mercury. But until now, they’ve typically been found to contain only inorganic mercury salts. According to the World Health Organization, mercury salts can inhibit the formation of melanin, resulting in a lighter skin tone. Inorganic mercury in creams and soap most often causes kidney damage, but it can also cause psychosis and nerve damage, WHO reports.

In the woman’s case, health officials found the organic mercury compound methylmercury in her skin cream, which is more dangerous. While inorganic mercury has been found in creams at concentrations up to 200,000 parts-per-million, the woman’s face cream contained methylmercury at just 12,000ppm.

The relatively lower concentration “underscores the far higher toxicity of organic mercury compounds,” the health officials write in the MMWR report. They go on to note that the woman’s progression is pretty typical of such poisonings. “Central nervous system toxicity, the hallmark of organic mercury, typically manifests after weeks to months of exposure, progresses rapidly after onset, worsens despite cessation of further exposure, persists even with chelation (although mercury excretion might increase), and leaves profound residual impairment,” the officials write.

The woman’s son told a local news outlet that his mother knew that the cream was adulterated somehow, but she used it anyway because it worked better than other creams.

The authors of the MMWR report note that this is the first time that methylmercury has shown up in skin-lightening creams. It’s still unclear why it was added and where it came from. The state’s public health department is testing additional creams and is warning consumers about the potential threat.

Beyond the skin cream, the most common source of methylmercury exposure is from eating fish, which essentially accumulate it from polluted food. Pregnant women are advised to restrict the types and amounts of fish they eat because methylmercury can cause brain damage in a developing fetus.

MMWR, 2019. DOI: 10.15585/mmwr.mm6850a4 (About DOIs).