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Full Version: Factors Governing the Expression of a Toxicant
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A study on toxicants and factor influencing the toxicity:

Any substance that is known to cause deleterious effect on a biological system upon interacting with the system is called as toxicant and the ability of the substance to bring about such change is described as Toxicity. A substance classified as a toxicant requires a medium or host to exhibit its toxicity and it is not as simple as that for the substance to bring about immediate effect. The expression of toxicity by a toxicant is governed by various factors like nature of the toxicant, the mode of exposure and the biologic system (individual coming in contact with the toxicant).

The chemical and physical nature of a toxicant, presence of any adulterant, stability of the toxicant when stored and in the biological system and the elements used for proper delivery of the toxicant are the factors influencing toxicity classified under the nature of the toxicant. In case of any impurities present along with the toxicant, the chances are that the impurity may itself be more toxic than the toxicant or the impurity may alter the toxicity of the toxicant. Same is the case with the additional compounds used in the formulation of a toxic agent. Also the media used to either dissolve the toxicant or suspend the toxicant for the better mobility influences toxicity which draws a closer observation while selecting the media.

The dose of the toxic agent, the concentration and the quantity of the toxicant, the route and site of administration, the rate of absorption, time of exposure and the frequency and length of exposure are all the exposure related factors governing the toxicity of the toxic agent.

Next factor influencing the toxicity is the biological system. Biological system refers to the animal or the individual who is coming in contact with the toxicant. The internal environment of the individual and the external environment which acts as the habitat for the individual have influence over the toxic agent entering the individual. The internal environment includes the type of species, genetic profile, immunologic profile, the dietary factors, age and gender and health and the existing disease if any. The ill effect produced by a toxin may not be same for all the species. A substance more toxic in one species may be less toxic or may not be toxic in the other.

The genetic profile influencing toxicity is explained by difference in response shown by the rabbits to the drug atropine. Few rabbits were found to have developed effects of the drug whereas few others showed resistance to the drug and the reason for the resistance was explained by the detection of the enzyme atropine esterase in the blood. This experiment validates the role of genetic profile in determining the toxicity. An altered toxic response to the same toxicant by an individual who developed sensitized reactions in response to the same toxicant earlier explains the role of immune system in influencing toxicity. As diet has direct influence over the health, metabolic process, biological function of the body ultimately it also has influence over the toxicity of the toxicant. Effect of toxicants in starved animals, toxicity of the substance in partially fed animals, expression of toxicity by the toxicant in response to altered diets are the various researches conducted on animals to understand the complete relationship between the diet of the animal and its effects on the toxicity of the test element. Though it is a very complex criteria to derive the relationship between different diets and different toxicants, it is understood that toxicity is influenced by diet.

Many experiments have been conducted to validate the effect of sex and hormones on the toxicity. One such experiment is that chloroform was found to be lethal for male mice of specific strain whereas the female mice of the same strain were found to be unaffected. Introducing estrogens to the male mice and introducing androgens to female mice before exposure to chloroform showed altered effects like male mice was protected to an extent and the female mice was found to be susceptible to the effects of chloroform.

Temperature, pressure and radiation are the factors related to external environment influencing the toxicity. Temperature is directly proportional to the toxicity and inversely proportional to the period to develop response. Next the change in pressure builds a stress in the body which may have effect on the toxicity. So it is advisable to consider pressure as a factor while studying the toxicity of an element. The known effects of radiation on the biologic system make it another factor influencing the toxicity.

The effect of one toxicant varies over the other under the above discussed influential parameters making it really a complex matter of subject to understand while studying toxicants.