Exposure physiology

The interindividual variability reflects differences in the extent of exposure, in toxicokinetics as well as in toxicodynamics. The variability due to factors which influence the extent of exposure (physiological differences in the intake, e.g., inhalation rates) can be considered by means of suitable parameters for the internal exposure (absorbed dose, area under the curve AUC, plasma concentration) if sufficient information is available. With respect to toxicokinetic factors, interindi-vidual differences in the metabolism of chemicals are generally considered as the most significant explanatory factor. Hardly any knowledge is available with respect to the factors that influence toxicodynamics. In the following, a brief overview of the factors playing a role for the toxicokinetic and toxicodynamic differences is presented. 

However, in no case have such studies informed us of the chemical bases for the toxic reactions. Examinations of lesions in the field can lead to the identification of newly polluted areas and new pollutants. Experiments in the greenhouse and laboratory can determine the dose response in terms of pollutant concentration and duration of exposure. Physiological studies of intact plants can correlate metabolic changes with the development of toxic symptoms. If we are to understand fully the effects of air pollutants on plants, however, it is essential that we elucidate the biochemical mechanisms of their action. 

All toxic effects of chemical, biological, radiological, nuclear, and explosive agents (CBRNE) are dose dependent. The dose for respiratory exposure is the concentration of the agent multiplied by time of exposure. Physiological factors, such as rate and depth of respiration during the exposure period, will also determine the final pathophysiological outcome of the patient. 

Workers should be made aware of specific problems related to cold exposure physiological and psychological reactions, health risks and controls, and sufficient and appropriate protective clothing. Special precautions need to be taken for older workers or workers with circulatory problems. 

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