Some everyday chemicals have long been suspected of harming our health. Now a study suggests that two of these groups of chemicals may be damaging certain cells in our brains. These substances are found in some disinfectants, care products and flame retardants. In experiments with cell cultures and mice, these chemicals disrupted the development of certain helper cells in the brain or killed them. However, it is still unclear whether environmental toxins pose a direct threat to our health.
There are countless chemicals and toxins in the environment that could potentially harm our brains if we absorb them into our bodies through our mouths, skin, or lungs. Researchers regularly investigate what these are and how they work in the brain using cell cultures in the laboratory. As a rule, however, they only use the nerve cells, the neurons. However, our brain also consists of other cell types that support neurons in signal processing.
How do everyday chemicals affect the white matter of the brain?
A research team led by Erin Cohn from Case Western Reserve University in Cleveland has now taken a closer look at one such cell type: the oligodendrocytes from the so-called white matter of the brain. These cells surround neurons like a protective coat and thus improve the transmission of information. Their development takes significantly longer than that of neurons and extends into adulthood. Cohn and her colleagues therefore suspected that these brain cells could be particularly vulnerable to environmental chemicals. To test this theory, the neuroscientists first tested 1,823 different chemicals on oligodendrocyte cultures from mice.
They found that 292 of the substances are lethal for this cell type. 47 more of these chemicals inhibited oligodendrocyte development. These findings were confirmed in follow-up experiments on growing mice and human brain organoid models. According to the researchers, these toxins can be assigned to two classes of chemicals: quaternary ammonium compounds and organophosphates. The former are found in some disinfectants and care products and killed brain cells in the experiments. The second type of chemical that interfered with oligodendrocyte growth is a flame retardant and is found in some upholstered furniture, building materials and electronics. The chemicals examined are found in many households, as the neuroscientists report.
Detected also in the urine of children
But how exposed are people to these potentially harmful chemicals? To find out, Cohn and her colleagues analyzed stored urine samples from a US national database collected between 2013 and 2018. This showed that a breakdown product of a flame retardant could be detected in almost all of the urine samples tested from children between the ages of three and eleven. The substance called BDCIPP was found in 1,753 of 1,763 samples. In the samples from later years, the BDCIPP concentration was also higher than in older urine samples. This suggests that children have been increasingly exposed to flame retardants in recent years, the researchers conclude.
At the same time, children with particularly high BDCIPP values were more likely to have problems with gross motor skills and needed special instruction more often, as the analysis of the health data showed. This suggests that there is a connection between environmental toxins and children’s mental development. The researchers also consider a connection with neurological diseases to be conceivable. “Loss of oligodendrocytes underlies multiple sclerosis and other neurological diseases,” says senior author Paul Tesar from Case Western Reserve University, citing previous studies. “We now show that certain chemicals in consumer products can directly damage oligodendrocytes. This represents a previously unrecognized risk factor for neurological diseases.”
However, future studies must first clarify the concentrations in which the chemicals actually occur in the brains of adults and children. This should provide information about whether and in what doses the substances cause illnesses or developmental disorders. “The question arises as to whether the plausibly proven, potentially harmful biological properties of the substances can also pose a risk to human health when realistically recorded by humans,” comments Martin Göttlicher from the Helmholtz Zentrum München, who was not involved in the study .
Source: Erin Cohn (Case Western Reserve University) et al., Nature Neuroscience, doi: 10.1038/s41593-024-01599-2