How climate change can alter the toxicity of chemicals

Article: Noyes P. D., McElwee M. K., Miller H. D., Clark B. W., Van Tiem L. A., Walcott K. C., Erwin K. N. and Levin E. D. (2009). The toxicology of climate change: Environmental contaminants in a warming world. Environment International, 35(6), 971–986. doi: 10.1016/j.envint.2009.02.006


We know climate change may affect our health in a multitude of ways, mainly by increasing rates of many diseases and temperature-related deaths. But have you ever wondered how climate change might affect humans via changes to harmful chemicals?

This article looks at how climate change alters temperature and moisture, and how this can change the presence, movement, and toxicity of chemicals in the environment. Altering the temperature or moisture can create or hasten the formation of certain chemicals, as well as, change how chemicals move through the environment. In turn, this can impact our health and that of other organisms on our planet.

Change in temperature

By 2100, climate change is expected to increase Earth’s temperature by approximately 1.8 to 4ºC (3.2 to 7.2ºF). Most of the warming will happen at and near the North Pole (Figure 1a). A warmer climate will produce more ozone gas and other toxic chemicals. We typically consider ozone to be good, because it protects us from the sun’s harmful ultraviolet (UV) rays. But if the ozone is at the earth’s surface, it can be inhaled, damaging our lungs.

Increased temperature can vaporize some chemicals, releasing them from soil or water. It can also cause chemicals to dissolve in drinking water. Melting ice and snow can also release stored chemicals. All of these activities will increase the number of chemicals we are exposed to.

High temperatures can also break down chemicals, and may affect the activity of microorganisms that attack chemicals. Depending on the chemical, these processes can either make a chemical more or less harmful.

Change in moisture

Climate change is expected to increase moisture levels in North and South America, northern Europe, and northern and central Asia. These regions will experience more rainfall, flooding and storms. Moisture levels are expected to decrease in southern Africa, central America and the Mediterranean (Figure 1b), potentially causing substantial droughts.

On a global scale, the ozone layer can be destroyed by high moisture and high temperature. Low moisture conditions will produce toxic air particles, while high moisture will cause chemicals in the air to drop to the ground via rain (i.e., acid rain) or snow.

Also, more chemicals can dissolve in water bodies if moisture levels increase and, correspondingly, more will bind tightly to soil and persist longer if moisture decreases. High moisture levels will also hasten the breakdown of chemicals.

Figure 1: Earth’s average predicted temperature (a) and moisture levels (b) for 2081-2100, relative to 1986-2005. Source: Intergovernmental Panel on Climate Change’s 2014 synthesis report.
Problems for humans

Humans will have more breathing and heart problems as higher temperatures produce ozone and other toxic particles. As moisture levels are likely to vary between regions, some populations may be exposed to more chemicals, leading to more allergies and toxic exposures. And since toxic chemicals can suppress the immune (i.e., microbial defense) system, we may fall sick more easily and more often. The elderly, children, those with existing health problems, and the poor (due to limited resources and insufficient medical care) are most likely to be affected.

Problems for wildlife

Scientists expect hotter weather to increase the amount of chemicals organisms take in, store, break down, and eliminate. As many wild species cannot regulate their own body temperature, they will experience higher physical stress from climate change. This will make them more vulnerable to toxic chemicals, which may in turn prevent them from adjusting to altered climate conditions. As with humans, their immune system may weaken and they may get sick more easily and more often.

Climate change will cause sea levels to rise, which may contaminate freshwater rivers and lakes with salt. Salt prevents chemicals from dissolving effectively in water. As a result, chemicals are free to enter organisms’ bodies in higher concentrations. Species with low population numbers or those that can survive only under certain conditions are more likely to be affected. Also, if a species at the bottom of the food chain is killed or contaminated due to chemicals, species relying on them for food will also be affected.


While many more studies need to be done before we can confidently make a conclusion, it seems likely that climate change will increase human and wildlife exposure to harmful chemicals. Furthermore, the combined stress of dealing with a changing climate and a harmful chemical may make living organisms more vulnerable to the chemical’s effects.

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Niranjana Krishnan

Niranjana Krishnan

I am a Ph.D. student in Environmental Toxicology at Iowa State University. I am studying the risks of insecticide exposure on monarch butterflies. Some of my favorite hobbies include reading, running, yoga and traveling.

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