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Household chemicals may increase the risk of autism and multiple sclerosis

 
, medical expert
Last reviewed: 07.06.2024
 
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04 April 2024, 12:00

The number of people diagnosed with neurodevelopmental disorders such as autism and attention deficit disorder has increased significantly over the past decade. This may be the result of increased recognition and diagnosis of the disorders, but experts suggest that environmental factors may be responsible for this increase.

Some common chemicals found in personal care products and household items damage specialized brain cells called oligodendrocytes, which form myelin sheaths on nerve cells, according to a new study. Researchers suggest that exposure to these chemicals can lead to neurodevelopmental disorders and neurological diseases such as autism spectrum conditions, attention deficit disorder and multiple sclerosis.

A study at Case Western Reserve University School of Medicine evaluated the effects of a wide range of chemicals on isolated oligodendrocytes, organoid systems, and the developing mouse brain. They found that two groups, organophosphorus flame retardants and quaternary ammonium compounds (QACs), damaged or caused oligodendrocyte death but had no effect on other cells brain.

"This is a study in which the authors screened about 1,900 chemicals to identify classes of compounds that have toxicity and cause defects in oligodendrocyte development. The screening methodology used by the authors is impressive because most tools currently in use only study cytotoxic effects. As the authors have shown in this paper, non-cytotoxic chemicals can have other effects on cells and this is important to study." - Dr. Suvarish Sarkar, PhD, assistant professor in the Department of Environmental Medicine and Neurobiology at the University of Rochester Medical Center.

How do chemicals affect oligodendrocytes?

Oligodendrocyte production begins during fetal development, with the majority of these cells forming during the first 2 years of life. Mature oligodendrocytes are responsible for the production and maintenance of myelin sheaths, which protect nerve cells and speed up the transmission of nerve impulses.

"Oligodendrocytes are a type of glial cells in the brain that can regulate a variety of vital physiological functions, including myelin sheath production. Hence, studying how environmental chemicals regulate these cells is important and critical to understanding the etiology of various diseases," said Dr. Sarkar.

In this study, scientists created oligodendrocyte precursor cells (OPCs) from mouse pluripotent stem cells (cells that can develop into all cells in the body). They then exposed these cells to 1,823 different chemicals to assess whether they affected their ability to develop into oligodendrocytes.

More than 80% of the chemicals had no effect on oligodendrocyte development. However, 292 of them were cytotoxic - killing oligodendrocytes - and 47 inhibited oligodendrocyte formation.

Group 2 chemicals had unfavorable effects on oligodendrocytes. Organophosphorus flame retardants, which are commonly found in electronics and furniture, inhibit oligodendrocyte formation from OPC. Quaternary ammonium compounds, which are found in many personal care products and disinfectants, kill cells.

Damage to developing cells in mice

The researchers also tested whether the chemicals have a similar effect on the development of oligodendrocytes in the brains of mice. They found that quaternary ammonium compounds (QAC) successfully crossed the blood-brain barrier and accumulated in brain tissue when administered orally to mice.

The mice lost oligodendrocyte cells in many areas of the brain, showing that these chemicals may pose a risk to the developing brain.

Following their results in mice, they tested the organophosphate flame retardant tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) in a human cortical organoid model. The chemical reduced the number of mature oligodendrocytes by 70% and OPC by 30%, suggesting that it inhibits cell maturation.

Very popular household chemicals

People can come into contact with these chemicals on a daily basis, as explained by Dr. Jagdish Khubchandani, a professor of public health at the University of New Mexico who was not involved in the study:

"Unfortunately, these products are widely used (e.g., organophosphates for dyes, varnishes, textiles, resins, etc., and quaternary ammonium for disinfectants and personal care products). They have also become popular because of the poor reputation of earlier classes of chemicals, and their use has increased substantially."

"The results of this study show that we have not come up with good alternatives to earlier classes of chemicals (such as PBDEs). Although the study uses mouse models and laboratory cultures, it could have serious implications for human health," he added.

The researchers then estimated the levels of organophosphate to which children aged 3 to 11 years were exposed using the National Health and Nutrition Examination Survey (NHANES) datasets, a reliable source from the Centers for Disease Control and Prevention (CDC) that recorded levels of the metabolite bis (1,3-dichloro-2-propyl)phosphate (BDCIPP) in urine.

They found that children with the highest levels of BDCIPP were 2-6 times more likely to have motor dysfunction than those with the lowest levels.

They suggest that this is strong evidence for a positive association between exposure to organophosphorus flame retardants and abnormal development of the nervous system.

How do you avoid these chemicals?

"The general rule of thumb is to reduce consumption of these products at the household level. In particular, protection from these chemicals is necessary for pregnant women, children, and people with chronic illnesses. Since the COVID-19 pandemic began, the use of some of these chemicals (e.g., disinfectants) has increased exponentially, and people should be careful to use alternative methods (e.g., hand washing)," - said Dr. Jagdish Khubchandani

Studies have shown, that alternative disinfectants such as caprylic acid, citric acid, lactic acid and other active ingredients such as hydrogen peroxide and alcohol should be used where possible to avoid overexposure to quaternary ammonium compounds (QACs).

The study is published in the journal Nature Trusted SourceNeuroscienceTrusted Source

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