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12 November 2019 - Medscape - Environmental Contamination Linked to Neurologic Disorders

Daniel M. Keller, PhD

pollution

Airborne chemical contamination is a major environmental risk factor worldwide and contributes significantly to many diseases, including neurologic diseases.

FAB RESEARCH COMMENT:

This was a XXIV World Congress of Neurology presentation. For further articles on the effects of pollutants on brain health, see here.

Airborne chemical contamination is a major environmental risk factor worldwide and contributes significantly to many diseases, including neurologic diseases.

A XXIV World Congress of Neurology (WCN) session on the environment and neurology explored the link between environmental contamination and neurologic disorders.

Environmental pollution is considered the third greatest contributor to disability-adjusted life years (DALYs) due to stroke, as supported by observations of seasonal, diurnal, and geographic variations in stroke incidence. Strokes track very closely with and soon after increases in conjunction with levels of carbon monoxide, sulfur dioxide, nitrogen dioxide, and fine particulate matter (≤2.5 μm).

The World Health Organization (WHO) has estimated that 90% of the world's population breathes air that exceeds WHO contamination limits. The Global Burden of Diseases study 2015 estimated that 898,100 cerebrovascular disease deaths and 19.2 million DALYs were attributable to ambient particulate matter air pollution.

Air pollution accounts for nearly 30% of global stroke burden, with the greatest effects in low- and middle-income countries. In these countries, much of the pollution is within households as a result of incomplete combustion of fuels for cooking and heating.

Long-term exposure to airborne contaminants results in accelerated carotid atherosclerosis, damage to vascular endothelium, increased sympathetic nervous system activity, vasoconstriction, increased blood pressure, and thrombosis. Acute exposures affect cerebrovascular hemodynamics and vascular resistance, with reduced blood flow and atrial arrhythmia. Not only are these exposures important risk factors for neurodegenerative diseases, but they also play a role in neurodevelopmental disorders.

Even solid particles in the environment can affect the nervous system. It has been documented that solid plastic nanoparticles work their way up the food chain; they are ingested by algae, which are eaten by daphnia, then spread to fish, disrupting the function of ecosystems all along the way. Eventually these particles end up at the top of the food chain, including humans. They are small enough to cross the blood-brain barrier.

Contaminant concentration occurs up the food chain. The now banned insecticide DDT (dichlorodiphenyltrichloroethane) could be found in water at 3 parts/trillion in past years. It spread from zooplankton to small fish to larger fish and ended up in the tissue of fish-eating birds at 25 parts/million ― a more than 8 million–fold increase. DDT and other endocrine disrupting chemicals  affected birds in various physical and behavioral ways, culminating in reduced reproductive success.