Preexisting disease

The effects attributed to air pollutants range from mild eye irritation to mortality. In most cases, the effect is to aggravate preexisting diseases or to degrade the health status, making persons more susceptible to infection or development of a chronic respiratory disease. Some of the effects associated with specific pollutants are listed in Table 7-2. Further information is available in the U.S. Environmental Protection Agency criteria documents summarized in Chapter 22. 

Detection of preexisting diseases or medical conditions that place employees performing certain tasks at increased risk... 

A biomarker of susceptibility is an indicator of an inherent or acquired limitation of an organism s ability to respond to the challenge of exposure to a specific xenobiotic substance. It can be an intrinsic genetic or other characteristic or a preexisting disease that results in an increase in absorbed dose, a decrease in the biologically effective dose, or a target tissue response. If biomarkers of susceptibility exist, they are discussed in Section 3.10 Populations That Are Unusually Susceptible. 

Unusually susceptible populations are those groups of individuals who respond more quickly or at lower exposure levels than the general population to the toxic effects of methyl parathion. These responses may be genetic in origin or may be due to differences in development or life style factors such as nutrition or behavior, or due to preexisting disease states. 

Preexisting disease, such as renal or hepatic disease, can especially influence the metabolism and excretion of certain drugs. In clinical trials, and in electronic longitudinal medical records, it is important to have sufficient variability in disease states and concomitant diseases among subjects in both the... 

The usual adult oral dose of cyclosporine ranges from 4 to 18 mg/kg per day in two divided doses.11 Appropriate selection of the starting dose usually depends on the organ type, the patient s preexisting disease states, and other concomitant immunosuppressive agents used. Cyclosporine microemulsion is available as 25 and 100 mg individually blister-packed capsules and... 

One model of an ionic mechanism of action of Li+ in affective disorders has been proposed, in which the receptors for Li+ are ion channels and cation coenzyme receptor sites, and in which the presence of intracellular Li+ in excitable cells results in the displacement of exogenous Na+ and/or other intracellular cations [13]. It has been suggested that this could lead to a decrease in the release of neurotransmitters alternatively it may be that this intracellular Li+ is altering a preexisting, disease-related electrolyte imbalance [14]. A number of observations of such imbalances in affective disorders have been made depression is associated with elevated levels of intracellular Na+ [15] retention of Li+ is observed in manic-depressive patients prior to an episode of mania [ 16] and Na+/K+ activity is defective during both mania and depression [17]. 

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