Assessing chemical exposures key to understanding neuro diseases and disorders

CHICAGO — Environmental chemical exposure is a risk factor for neurodegenerative diseases and neurodevelopmental disorders, an expert at the 2022 American Neurological Association annual meeting said.

“There are over 80,000 chemicals in existence, of which over 41,000 are currently active,” Deborah A. Cory-Slechta, PhD, of the department of environmental medicine at the University of Rochester Medical Center, said during a presentation. “Given the large number of chemicals in commerce and their varying potential to influence human health, why is it they are largely ignored as risk factors?”

One major reason, Cory-Slechta noted, is that most diseases and disorders arise because of factors present before birth — genetics, parental lifestyles, prenatal issues and the external environment. After birth, she said, the same factors are present along with the cumulative effects of diet, exercise, stress, lifestyle choices, behavior, socioeconomic status and aging.

Chemical exposures are but one of many external factors, she added, but despite high profile cases of such exposures, they do not appear to cause alarm. Plus, effect sizes from these exposures to the general population tend to be small.

According to Cory-Slechta, lead that seeps into bones has a half-life of decades, and for pregnant or postpartum persons, the element can migrate back into the bloodstream, where the fetus or infant can be exposed.

However, ultrafine particles from environmental pollutants can reach the brain through inhalation and bypass the blood-brain barrier where they cannot be detected with serum markers, she stated. Once there, these pollutants can affect the prefrontal cortex, olfactory regions, the vagal nerve and brainstem.

Ultimately, according to Cory-Slechta, clinicians need to fully understand the complexities of chemical exposures to get to the root of neurodevelopmental disorders and neurodegenerative diseases. That includes examining traffic-generated air pollution as a primary source; chemical reactions from air pollutants and weather as secondary sources; natural sources, such as volcanic eruptions; and stationary sources, such as power plants.

In addition, everyday exposures to airborne toxins, organic carbon compounds and various metals through contact with household items need to be considered, she said.

“From a risk management point of view, one could also examine the economic costs of addressing these chemicals in a cost-benefit analysis,” Cory-Slechta said.