Unexplored Links: Climate Change and Environmental Contaminants

By Roberta Attanasio, IEAM Blog Editor

Climate change is here and now, and the rate of change is also speeding up, as demonstrated by a . The most dramatic effects are clearly visible all around us—shifting precipitation patterns, sea level rise, ocean acidification, shrinking Arctic sea ice, melting of the Greenland and Antarctica ice sheets, and amplified occurrence of wildfires, floods, heat waves, and droughts. Climate change is also a “”—the environmental fallout it causes can exacerbate political instability in the world’s most dangerous regions and increase the chances of armed conflict. In addition to these conspicuously damaging effects, there are some others that are causing alarm, although not discussed as often and not as clearly discernible at this time: climate change may alter the release, dispersal, and toxic effect of chemicals in the environment, potentially resulting in dangerous levels of human exposure and deleterious consequences for ecosystems.

One “climate hypothesis” provides an example of how climate change interacts with environmental pollutants. Formulated to explain , the reasoning goes, “As the earth warms, the high-pressure system of cold air known as the Siberian High that influences many places, including China, weakens. That means there is less wind to blow away the smog and stagnant air where pollutants accumulate and interact. That leads to increased haze, cutting sunlight’s access to the ground, leaving it cooler. The effect reduces the heat that produces convectional rainfall that could clear the air.” Such interactions have been defined “not so much a vicious circle as a vicious pretzel, or even knot.”

So why use a “hypothesis” as an example of the effects that climate change could have on the environmental impacts of toxic chemicals? Simply said, not enough is known about these effects. Despite significant concerns raised in the past few years, research in the area is lacking.

Back in 2010, Rick Wenning (Editor-in-Chief, Integrated Environmental Assessment and Management) and his collaborators issued a “.” Together, they challenged environmental chemists, toxicologists, and risk assessors belonging to the Society of Environmental Toxicology and Chemistry () to work together to understand how global climate change influences the mechanisms and ramifications of contaminants on humans and the environment.

However, despite the initial call, not much progress has been made. A follow-up article published at the end of 2014, “”, reveals that there continues to be a lack of studies seeking to understand the interactions between climate change, contaminants, and environmental risk. The article highlights five points of consensus that represent a call to arms for research to advance our understanding of environmental chemistry and toxicology in the context of global climate change.

Lead author Wayne Landis at Western Washington University explained in a recent interview released to the IEAM blog that global climate change and human actions interact to control the fate and distribution of chemicals in the environment—the recognition of such an interaction is at the basis of the first point of consensus. What about the other four points?

Landis goes on to explain that climate change affects the toxicity of chemicals, and that the toxicity of chemicals affects the ability of organisms to adapt to climate change (point 2). In addition, the rate of effects on ecosystems is variable—some populations are more vulnerable, whereas others may show little immediate change (point 3). The fourth point of consensus states that it is necessary to incorporate the effects of climate change on human health and in ecological risk assessments, in order to correctly predict the risks posed by chemicals and other stressors. Finally, the fifth point of consensus recognizes that the reference state, or baseline, for estimating injury to natural resources will be shifting as a consequence of climate change.

The five points of consensus clearly highlight the complexity of the interactions between climate change and environmental pollutants—complexity that was first delineated years ago. Indeed, released by the Intergovernmental Forum on Chemical Safety states: “The physical changes in temperature, wind, and rainfall caused by climate change will affect the distribution and breakdown of chemicals in complex ways. The effect on human exposure will vary widely according to the properties of specific chemicals and chemical combinations, soil and water conditions, wind patterns, topography, land use, level of development, and human population characteristics.”

So, why is it taking so long for researchers to fully realize that toxic effects are influenced by climate change, and that climate change is critical to the future of toxicology? A lack of interdisciplinary collaboration may be to blame. According to Landis: “Climate change research has been dominated by climatologists, as it should have been. Ecologists often have little background on the effects of manufactured chemicals. Toxicologists work at the molecular to ecological scales, and have little interaction with climate scientists. Without interaction, cross-fertilization among different disciplines cannot occur.”

Although the multiplicity of factors that play a role in the interaction between climate change and environmental pollutants, and the cross-fertilization of disciplines required to understand these interactions may represent a challenge for the development of viable research plans, the 5 points of consensus provide a framework for action. As Landis points out, the merging of climate change and toxicology requires a paradigm shift. All together, scientists need to recognize that chemical contamination is widespread, and that climate is a toxicological driver. The call to arms cannot be left unanswered.