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Global climate change and toxicology: Exacerbation of toxicity of pollutants by thermal stress
Citation:
Gordon, C., C. Aydin, AND A. Johnstone. Global climate change and toxicology: Exacerbation of toxicity of pollutants by thermal stress. Presented at Society of Toxicology Annual Meeting, March 10 - 14, 2013.
Impact/Purpose:
will be presented at the Society of Toxicology Annual Meeting, San Antonio, March 10-14, 2012
Description:
Relatively small elevations in the average global temperature can translate to greater incidences of heat alerts during the summer months, an effect that is especially prevalent in urban areas where simultaneous exposure to heat stress and excessive levels of air pollutants is common (e.g., ozone alerts). It is important to understand how heat stress will alter the health effects of toxicants. With few exceptions, the toxicity of pesticides and airborne toxicants is exacerbated when exposures occur in a warm environment. As air temperature increases, the pulmonary intake of air pollutants and absorption of pesticides applied to the skin is generally accelerated. The cellular toxicity is generally exacerbated when body temperature is elevated. This is primarily a result of a Q10 effect, meaning that the rate of a biochemical reaction doubles with a 10 °C increase in tissue temperature. The generation of reactive oxygen species is also exacerbated with warmer temperatures. Thus, in a warm environment, toxicity is potentiated by two key mechanisms; enhancement in the intake of the toxicant and increase in the cellular toxicity. In view of the impact of temperature on chemical toxicity, a thermoregulatory response to lower body temperature can be protective. Hyperthermia is most likely going to be detrimental in the recovery from toxicant exposure. Rodents and other small mammals have relatively large surface area volume ratio. Following exposure to pesticides and air pollutants, metabolism is reduced and a rapid reduction in body temperature ensues. If given the opportunity to thermoregulate behaviorally, rodents seek colder temperatures, allowing body temperature to decrease quickly. Thus, the hypothermic response is a regulated response. This is thought to be an adaptive response because the hypothermic response is protective. Large mammals, including humans, have a greater thermal inertia and are unable to mount a hypothermic response as is seen in rodents. A warmer environmental temperature will thus impede the hypothermic response to toxicant exposure in rodents and will also be stressful to large mammals that are unable to undergo a significant cooling response. In view of the potential impact of global climate change on increased incidents of heat stress in urban areas that are rife with pollution, the topic of thermoregulatory responses to environmental toxicants is timely. This is an abstract or a proposed presentation and does not necessarily reflect EPA policy. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.