Study: Personal Care Product Chemicals May Damage Brain Cells, Cause Autism

According to a new study, chemicals found in person­al care products such as toothpaste, mouthwash, disinfectants, hand san­itizers, wipes, sprays, glues, and furniture textiles could cause damage to brain cells, and neu­rological conditions such as mul­tiple sclerosis and autism spec­trum disorders.

Results from the study were published in ‘Nature Neurosci­ence’.

Starting with 1,823 compounds of unknown toxicity found in the environment, Erin Cohn, a mo­lecular biologist at Case Western Reserve University in Ohio, and colleagues identified two classes of chemicals that either killed or halted the maturation of cells called oligodendrocytes under laboratory conditions.

Oligodendrocytes are a type of neurological support cell: They wrap around neurons to form an insulating covering that keeps brain signals scooting along at speed.

One of the two chemical class­es identified were quaternary compounds. These are used in disinfectant sprays, wipes hand sanitizers, and personal care products such as toothpaste and mouthwash to kill bacteria and viruses, and can be ingested or inhaled if misused or in poorly ventilated spaces.

The other class of compounds was organophosphates. As flame retardants, they are commonly found in textiles, glues, and household items such as fur­niture and electronics and can ‘off-gas’ into the air of rooms we commonly spend time in. Being fat-soluble, organophosphates can be absorbed through the skin and potentially make their way into the brain.

In mice experiments, pups given an oral dose of one of three quaternary compounds had detectable levels of those chemicals in their brain tissue days later, suggesting that the compounds can cross the blood-brain barrier, the protective for­tress between the bloodstream and brain cells.

The animals also had depleted numbers of oligodendrocytes in their brains after 10 daily doses of one particular quaternary compound, cetylpyridinium chlo­ride, administered in a key peri­od of brain development, starting five days after birth.

Similar effects were seen in brain organoids; clusters of hu­man stem cells grown in a dish and coaxed into behaving like developing brain tissue.

“We found that oligoden­drocytes – but not other brain cells – are surprisingly vulner­able to quaternary ammonium compounds and organophos­phate flame retardants,” said Cohn.

Experts, however, aren’t imme­diately alarmed by the results of this lab-based study, which treat­ed cells and mice with concentra­tions higher than what humans would typically be exposed to, and in ways that don’t reflect how humans would come into contact with these chemicals.

“It’s not a question of if some­thing is toxic or not but if it is tox­ic under the conditions to which we are likely to be exposed,” said environmental chemist Oliver Jones of RMIT University in Melbourne, Australia.

“In this case, the authors have exposed cells in a Petri dish to a relatively high amount of these compounds which is not the same dose route or duration of expo­sure that humans might encoun­ter normally.”

However, we know that some people, such as school and hos­pital cleaners, childcare provid­ers, and people in correctional facilities, are more exposed to quaternary compounds than oth­ers because industrial-strength disinfectants are commonly used in these settings.

What’s more, until only re­cently, research into the toxicity of quaternary compounds came from animal and cell studies.

But now studies are probing the health effects in humans, and finding that people had double the levels of quaternary com­pounds in their blood during the pandemic than before – likely be­cause of the widespread use of disinfectants.

This has led some researchers to flag these chemicals as a “class of emerging concern”, noting the challenges of fully understand­ing the human health risks of these compounds due to their vast structural diversity.

It’s similar to organophos­phate flame retardants, which have been widely detected in the environment, and human blood, urine, placenta tissue, and breast milk.

“Watch out for them to come to the attention of the Stock­holm Convention when it’s done struggling with organofluorines (PFAS)!” says environmental chemist Ian Rae, who is an advi­sor to the United Nations Envi­ronment Programme on chemi­cals in the environment and who was not involved in the current research.

In their study, Cohn and col­leagues analysed levels of one flame retardant by analysing lev­els of one flame retardant metab­olite, BDCIPP, in children’s urine samples collected in the US CDC’s National Health and Nutrition Examination Survey between 2013 and 2018.

Almost all of the 1,763 children aged three to 11 years had BD­CIPP present in their pee. Those with the highest levels were two and six times more likely than those with low exposure to ex­perience adverse neurodevelop­mental outcomes such as motor dysfunction or requirements for educational assistance.

But observational data can only point to associations, not direct causes, and large gaps re­main in our understanding of how these chemicals affect hu­mans since like this study, most of the data comes from animals and cells.

That’s reason enough to keep investigating the health effects of these compounds, especially in children, Cohn and colleagues ar­gue that: “The developing central ner­vous system is particularly sen­sitive to environmental insults, and chemical exposures can be especially harmful to children if they occur during critical periods of development.”