ABSTRACT
Environmental physiology is broadly defined as the study of the physiological mechanisms that allow animals to cope with and adapt to changes in temperature, humidity, atmospheric pressure, and other natural factors of their physical environment (Folk, 1974). The physiological response to a toxicant is determined by three factors (Casarett and Doull, 1975): the nature of the poison or toxic agent, the exposure situation, and the subject. Moreover, the factors that influence the subject are subdivided into internal (i.e., factors inherent in the subject such as species, nutritional status, age, etc.) and external to the subject (i.e., environmental factors). Toxicologists rarely study how the external environmental factors modulate the physiological response to toxic agents. Likewise, only a handful of environmental physiologists have an interest in toxicology. In this chapter, I have attempted to meld the fields of environmental physiology and toxicology to assess the impact of environmental stress on the thermoregulatory response to chemical toxicants.
It is evident throughout this book that there has been an interest in assessing how environmental factors influence toxicity. Temperature is probably the most frequently studied of all environmental variables. There is a remarkable amount of research beginning in the early 20th century that showed how ambient and body temperature could modulate the toxicity of a variety of toxicological and phar macological agents (see Chapter 4). Dr. Anna Baetjer was one of the first to make notable contributions in the fields of environmental physiology and toxicology. Using anti-ChE insecticides with a specific mode of action that affects the neural control of body temperature (see Chapter 3), she was the first to develop a comprehensive picture of how environmental heat and cold stress interact with the physiological responses to a toxicant (Baetjer and Smith, 1956). Her work showed a direct relation between the toxicity of an organophosphate insecticide (parathion) and changes in body and ambient temperature (see Chapter 4 for further discussion of her work).
