Climate toxicology: The impact on human health

Eduardo A. González, B.S. and Pamela J. Lein, Ph.D., University of California, Davis discuss how global climate change is increasing toxicological impacts on human health

The global climate is changing at an unprecedented pace, driven largely by increased carbon dioxide emissions that are steadily warming the Earth. Worldwide warming trends are contributing to melting of the polar ice caps, rising sea levels, worsening global air pollution, deteriorating watershed conditions, drought, and increased frequency and severity of extreme weather events. As documented in the 2018 World Health Organization (WHO) COP24 Special Report entitled “Health & Climate Change”, these destabilising climate changes are already exerting significant negative impacts on human health.

Direct effects of climate change on human health include the physiological effects of extreme heat (heatstroke and increased incidence of heart attacks, stroke and respiratory distress), as well injuries and death caused by extreme weather events, such as drought, floods, heatwaves, storms and wildfires. Climate change also affects human health indirectly, largely via ecological changes that compromise food and water security, promote the spread of infectious disease, and/or force the displacement of populations. Emerging scientific evidence suggests that global climate change also impacts human health by increasing human exposure to toxic chemicals and/or increasing chemical toxicity.

A number of persistent organic pollutants have historically been sequestered in polar regions due to the phenomenon of global distillation. Temperature and wind patterns carry volatile chemicals towards the poles, depositing them in frozen water and soils for decades.

However, melting of the polar ice caps is releasing these pollutants back into the environment. Multiple studies have documented increasing levels of bisphenol A, polychlorinated biphenyls, and DDT, being released from polar regions. Increasing temperatures allow these chemicals to more readily transition into the gaseous phase, which facilitates their global redistribution.

Current climate prediction models estimate significantly altered patterns of precipitation, and significantly increased incidence of extreme weather events. Increased rainfall will increase chemical deposition into soils and runoff into water sources. Increased nutrient runoff due to flooding or increased irrigation in areas of drought coupled with warming of surface waters will increase the…

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