Neurological diseases like multiple sclerosis, muscular dystrophy and Parkinson's affect millions of people. Some cases can be linked to genetic predisposition, but many others cannot, raising the prospect that unknown factors such as chemical exposure contribute to the development of these diseases.

Two classes of common household chemicals deplete cells in the brain linked to conditions like multiple sclerosis.

A recent set of findings by researchers from Case Western Reserve University and the U.S. Environmental Protection Agency suggests exposure to two chemicals plays a role.

The research identified two classes of common household chemicals that specifically deplete cells in the brain that produce myelin, the protective insulation around nerve cells. The loss of these cells, called oligodendrocytes, has been linked to conditions such as multiple sclerosis.

“Understanding human exposure to these chemicals may help explain a missing link in how some neurological diseases arise,” Erin Cohn, lead author and a graduate student at Case Western, said in a statement.

After screening more than 1,800 chemicals using methods they developed involving mouse and human stem cells, the researchers found that:

  • Flame retardants containing organophosphates common in furniture and electronics prevented oligodendrocyte maturation.
  • Personal care products and disinfectants containing quaternary ammonium compounds resulted in the apoptosis, or cell death, of oligodendrocytes.

Both of these compounds prevented oligodendrocyte development in mice after birth as well as in a 3-dimensional model of prenatal development in the human brain.

Exposure during childhood to the most common organophosphate flame retardant identified by the initial screen, tris (1,3-dichloro-2-propyl) phosphate (TDCIPP), had a negative effect on neurodevelopment.

Data from the National Health and Nutrition Examination Survey showed that BDCIPP, a metabolite of TDCIPP, was present in 99 percent of urine samples from a population of children between the ages of three and 11 years old.

BDCIPP levels were significantly higher in children than adults, suggesting that children may experience higher internal doses of phosphates when exposed to flame retardants. When they compared BDCIPP levels across different years of the ongoing survey, the researchers saw that childhood exposure to organophosphate flame retardants may be increasing overall.

Children with the highest levels of BDCIPP in their urine were more likely to report gross motor dysfunction, or the inability to control whole-body movements such as walking or running, than those with the lowest BDCIPP levels. They were also more likely to require special education.

Children may experience higher internal doses of phosphates when exposed to flame retardants.

Needed in the future, the researchers say, are more work to examine the effects of these chemicals on brain health more closely and studies tracking chemical levels in the brains of children and adults to determine the length and amount of chemical exposure required to cause disease or make it worse.

“Our findings suggest that more comprehensive scrutiny of the impacts of these common household chemicals on brain health is necessary,” said the principal investigator, Paul Tesar, the Dr. Donald and Ruth Weber Goodman Professor of Innovative Therapeutics and director of the Institute for Glial Sciences at Case Western. “We hope our work will contribute to informed decisions regarding regulatory measures or behavioral interventions to minimize chemical exposure and protect human health.”

The study is published in Nature Neuroscience.