ISLAMABAD, March 29 (Online): The prevalence of neurological and neurodevelopmental conditions has increased over the past decade.
Although some of this increase may be due to better diagnosis, experts suggest that environmental factors could play a part.
A new study has found that some common environmental chemicals damage vital brain cells called oligodendrocytes.
The researchers suggest that this damage could help explain the rise in conditions such as autism-spectrum and attention-deficit disorders, as well as multiple sclerosis.
The number of people diagnosed with neurodevelopmental conditions, such as autism-spectrumTrusted Source and attention-deficit disordersTrusted Source has increasedTrusted Source greatly over the past decade. This could be a result of greater recognition and diagnosis of the conditions, but experts suggest that environmental factors might be driving these increases.
According to a new study, some common chemicals, found in personal-care and household products, damage specialized brain cells called oligodendrocytesTrusted Source that generate the myelin sheathsTrusted Source on nerve cells. The researchers suggest that exposure to these chemicals could lead to neurodevelopmental and neurological conditions, such as autism-spectrum conditions, attention deficit disorders and multiple sclerosisTrusted Source.
The study, from Case Western Reserve University School of Medicine, assessed the effect of a wide range of chemicals on isolated oligodendrocytes, organoid systems, and developing brains of mice. They found that two groups — organophosphate flame retardantsTrusted Source and quaternary ammonium compounds (QACs) — damaged or caused the death of oligodendrocytes, but did not affect other brain cells.
The research is published in Nature Trusted SourceNeuroscienceTrusted Source.
“This is a fascinating study in which the authors have performed screening on close to 1,900 chemicals to identify classes of compounds that may regulate toxicity or developmental defects in oligodendrocytes. The screening technique the authors used is impressive, as most tools currently used only look at cytotoxic effects. As the authors have shown in this paper, non-cytotoxic chemicals can have other effects on cells, and that is important to study.”
— Dr. Souvarish Sarkar, Ph.D., assistant professor of environmental medicine and neuroscience at the University of Rochester Medical Center.
2 groups of common chemicals
Oligodendrocyte production begins during fetal development, with the majority of these cells being made during the first 2 years of life. Mature oligodendrocytes are responsible for manufacturing and maintaining the myelin sheathsTrusted Source that protect nerve cells and speed up the transmission of nerve impulses.
“Oligodendrocytes are a type of glial cells in the brain that can regulate various vital physiological functions, including myelin sheath production. Hence, studying how environmental chemicals regulate these cells is important and critical to understanding various disease etiology,” Dr. Sarkar told Medical News Today.
In this study, the researchers generated oligodendrocyte progenitor cells (OPCs) from mouse pluripotent stem cellsTrusted Source (cells that can develop into all cells in the body). They then exposed these cells to 1,823 different chemicals to assess whether these affected their ability to develop into oligodendrocytes.
More than 80% of the chemicals had no effect on oligodendrocyte development. However, 292 were cytotoxicTrusted Source — killed the oligodendrocytes — and 47 inhibited oligodendrocyte generation.
Chemicals from 2 groups had an adverse effect on oligodendrocytes. Organophosphate flame retardants, which are commonly found in electronics and furniture, inhibited the generation of oligodendrocytes from OPCs. Quaternary ammonium compounds, which are in many personal-care products and disinfectants, killed the cells.
Damage to developing cells in mice
The researchers also tested whether the chemicals had a similar effect on developing oligodendrocytes in mouse brains. They found that quaternary ammonium compounds (QACs), when given orally to mice, successfully crossed the blood-brain barrier and built up in brain tissue.
The mice lost oligodendrocyte cells in many areas of the brain, showing that these chemicals may pose a risk to the developing brain.
Following the mouse findings, they tested the organophosphate flame retardant tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) on a human cortical organoid model. The chemical reduced the numbers of mature oligodendrocytes by 70%, and the OPCs by 30%, suggesting that it was preventing the cells from maturing.
Very common household chemicals
People may come into contact with these chemicals daily, as Dr. Jagdish Khubchandani, professor of public health at New Mexico State University, who was not involved in the study, explained to MNT:
“Unfortunately, these products are widely in use (e.g. organophosphates for making of dyes, varnishes, textiles, resins, etc, and quaternary ammonium for disinfectants and personal care products). Also, they came about due to disrepute of earlier classes of chemicals and their use has increased substantially.”
“The findings of this study suggest that we did not come up with good alternatives for earlier classes of chemicals (e.g. PBDEs). While the study uses a mouse model and lab cultures, there could be profound human health implications,” he added.
The researchers then assessed the levels of organophosphates that children aged 3-11 were exposed to using datasets from the National Health and Nutrition Examination Survey (NHANES)Trusted Source of the CDC, which recorded levels of the metabolite bis (1,3-dichloro-2-propy) phosphate (BDCIPP) in their urine.
They found that children with the highest levels of BDCIPP were 2–6 times more likely to have special educational needs or motor dysfunction than those with the lowest levels.
They suggest this is strong evidence of a positive association between organophosphate flame retardant exposure and abnormal neurodevelopment.
How to avoid these chemicals
“The general rule is to reduce the consumption of these products at the household level. Specifically, pregnant women, children, and individuals with chronic diseases need protection from these chemicals. Since the COVID-19 pandemic started, the use of some of these chemicals has increased exponentially (e.g. disinfectants) and people should be mindful and use alternate practices (e.g. handwashing).”
— Dr. Jagdish Khubchandani
StudiesTrusted Source have suggested 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 excessive exposure to quaternary ammonium compounds (QACs).
Dr. Sarkar advised caution when interpreting the findings, but agreed that they might be a basis for future studies:
“Although the role of oligodendrocytes has been well-established in the development of diseases like MS and autism, we should take the findings of this study cautiously. Human beings are much more complex than cells on a plate. Also, the route of exposure is critical when we are trying to add translational relevance to basic science research.”
“The authors have also pointed to the fact that this study can be the foundation, but we need a lot more epidemiological and fundamental studies on this subject to make the claim that these compounds can directly cause some of the diseases mentioned,” he added.
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