Two types of chemical compounds found in household products harm the development of oligodendrocytes, a type of cell essential for brain maturation and function. Epidemiological data confirm that children exposed to higher levels of these compounds have a higher risk of having motor dysfunctions or special educational needs.
Pollutants harmful to oligodendrocytes are so-called quaternary compounds (found in disinfectant and personal hygiene products) and organophosphates (used as flame retardants in furniture, electronic products and construction materials), according to research by the Case Western Reserve University in Cleveland (USA).
Researchers have focused on oligodendrocytes because until now “their vulnerability to the vast majority of chemical compounds present in the environment has not been studied,” the researchers write in Nature Neuroscience, where they present their results today. These cells generate brain myelin, a compound that covers the axons of neurons and is necessary for them to communicate with each other.
The research is part of an attempt to understand why neurodevelopmental disorders, such as autism spectrum disorder (ASD) or attention deficit hyperactivity disorder (ADHD), are on the rise in the US and other countries. “Genetic factors are not sufficient to explain this increase,” the researchers point out.
To identify environmental factors that may affect neurodevelopment, researchers have evaluated 1,823 chemical compounds considered environmental contaminants. They have analyzed its effects in cell cultures of oligodendrocytes that were in the process of formation. The vast majority of contaminants have been found to be harmless to oligodendrocytes. But 239 compounds (13% of the total) inhibit the formation or development of cells.
The most toxic are quaternary compounds and organophosphates. From there, researchers have exposed mice that were in developmental stages to these compounds. They have proven that pollutants cross the blood-brain barrier, access the brain and, once there, affect the development of the cortex, cerebellum, corpus callosum and hippocampus.
They have confirmed these detrimental effects in developing human brain organoids.
Finally, they have carried out an epidemiological study of the exposure of the US children's population to these contaminants based on data from the National Health and Nutrition Survey. They have discovered that 99.4% of boys and girls between 3 and 11 years old have a detectable organophosphate metabolite in their urine.
Organophosphates “are used as additives in construction materials, electronic devices and furniture, but are not chemically integrated into the product; Therefore, they can be released into the environment and cause human exposure through inhalation, skin absorption or hand-mouth contact,” Paul Tesar, director of the research, informs La Vanguardia.
Children with a higher level of exposure to organophosphates have been found to be twice as likely to have special educational needs than those with a lower level of exposure. For motor dysfunctions, the risk is six times higher. These values have been calculated by comparing the 25% of children with the highest levels of the metabolite and the 25% of children with the lowest levels.
Both disorders depend on the correct development of oligodendrocytes, since myelination of the brain influences memory, learning and motor functions.
The development of oligodendrocytes “initiates during fetal development and intensifies in the first two years of life,” the researchers write in Nature Neuroscience. “Once mature, oligodendrocytes myelinate neurons, a process that has its maximum in childhood but continues until adolescence and adulthood. "Therefore, oligodendrocytes are not only vulnerable during fetal development, but for a long period after birth."
There is still no epidemiological data on the exposure of the child population to quaternary compounds, reports the director of the research, who believes that “these data will be essential to establish direct connections between exposure to quaternary compounds and health problems.”
Within the broad group of quaternary compounds, as with organophosphates, not all have proven to be equally toxic in experiments with oligodendrocytes.
With the results obtained so far, “we do not recommend that these chemical compounds be completely eliminated from our environment since many of them fulfill important functions,” states Paul Tesar. “Before recommending behavioral changes to citizens, studies designed to investigate whether specific levels of exposure can initiate or exacerbate diseases are necessary.”
