Toxicity factors influencing

Once a chemical enters the body of animal or human, it undergoes metabolic reaction. A host of factors modulate the reaction rate and the induction of toxicological effects. These factors have been termed intrinsic factors and include animal species, gender, age, nutritional status, pregnancy, other health status, and circadian rhythms. In addition, there are certain extrinsic factors (e.g., physicochemical properties of chemicals, solvent or vehicle, route of exposure, temperature, and humidity) during exposure to chemicals that also influence the effect of a test chemical. We shall discuss these factors in greater detail. 

Species and Strains Many studies have shown that phase I and phase II activities in different animal species differ significantly and influence the detoxification of chemicals. For example, the basal values of hepatic microsomal systems differ to a large extent between species of rodents.46,47 There are wide variations among animals species such as birds, albino rat, Swiss mouse, guinea pigs, New 

TABLE 2-4 Acute Toxicity of Chemicals in Different Species of Birds 

Animal Gender Role of gender and metabolism of xenobiotics has been studied in a variety of experimental animals, particularly rats. The toxicological effects of many chemicals have shown differences between male and female animals. A classic example is the acute toxicity data of different pesticides between male and female rats. This difference was found both when animals were exposed by ingestion or dermal absorption. The ratio between male and female in oral LD50 values for of chemicals (e.g., pesticides) ranges from 0.21 to 4.62, which 

TABLE 2-5 Acute Oral Toxicity of Chemicals in Male and Female Rats 

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This entry presents a discussion of the principles of respiratory toxicology including (1) an historical perspective, (2) approaches used to evaluate respiratory responses to inhaled chemicals, (3) classification of airborne chemicals, (4) concepts of dose-time relationships, (5) factors influencing toxicity of airborne substances, (6) the basic biology of the respiratory system with emphasis on those structures and functions that are involved in toxicological responses, (7) biomarkers of pulmonary effects, (8) toxicological response associated with inhaled chemicals, and (9) assessing the human risk of airborne chemicals. 

The reason for conducting the study, which is often related to the potential end use of the anti-ChE (e.g., for pesticides, a determination of all potential occupational hazards, factors influencing toxicity, safe working conditions, protective and precautionary measures, and therapeutic measures for chemical warfare purposes, an a.ssessment of the lethal potential of the anti-ChE and thus its threat capability and, secondary to this, considerations of protective and antidotal measures). 

Several factors influence toxic effects, one of which is the concentration of a material (see Eigure 8.5). Concentrations may be expressed in terms of percentage or parts per million or billion per milligram or kilogram the higher the concentration, the more serious the effect. Eigure 8.6 illustrates some parts-per-million approximations. Some materials can also have an anesthetic effect. This may range from loss... 

Factors influencing toxicity. There are a number of important factors which influence and to a degree determine the impact that exposure to a solvent will have on the human body. These factors are the extent to which the solvent is... 

In addition to the electrochemical character and the solubility of a metal ion and its compounds, there are many factors influencing toxicity [66,70] ... 

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