Toxicology

TOXICOLOGY

Toxicology and Toxic Responses

Toxicology

Toxicology is one of the discipline in sciences which involve in the study of the actual or potential danger presented by the harmful effects of substances such as poisons on living organisms and the ecosystems , of the relationship of such harmful effects to exposure , and of the mechanisms of action , diagnosis , prevention and treatments (Biomonitoringinfo , 2008

Toxicity of substances on the other hand simply means the degree or extent to which a particular substance can harm humans or animals . It is usually classified

based on the duration of its effects on the host hence toxicity can be acute , sub-chronic or chronic . The acute toxicity normally involve short term duration in it overall effects on patients or other animals while the sub-chronic form of toxicity is usually found to be more than a year but not having a prolong effect throughout the life time of the patient or the animal . The chronic form of toxicity usually has a prolonged effect which tends to be throughout the affected animal 's lifespan

Types of toxic responses

There are different types of toxic responses . Biological response to toxic substance varies a lot but there is usually many cause of cellular injury . The whole organism usually responds in a way to a particular toxic substance . The response can be classified into basically six classes

Direct toxic action

Biochemical lesion

Pharmacological or physiological effects

Immunotoxicity

Teratogenicity

Genetic toxicity

Carcinogenicity

The responses can also be classified as immediate response or delayed response depending on the time it takes for the development of the response . The variations in the toxicity response basically depend on the following criteria

Selective toxicity

Genetic Polymorphism

Species difference

In selective toxicity there is usually a selective effect on a type of living organism by the chemical not to all the living organism

Classification of Toxicants

There are different forms of classification of toxicant this was as follows according to the ChemSafe , physiological classification of toxic response

Irritants

Asphyxiant

Anesthetics (alcohols and halogenated

Hepatotoxic agents

Nephrotoxic agent (chloroform and mercury

Neurotoxic agent (mercury and lead

Hematopoietic toxicants (benzene and xylene

Pulmonary toxin (asbestos and silica ozone

Reproductive toxin (lead and dibromodichloropropane

Carcinogens (asbestos and Bis-chloromethyl ether

Teratogenic (lead and thalidomide (ChemSafe , 2008

Exposure and toxicity

There is greater influence of repeated exposure to a toxic agent on its toxicity on humans or animals . Increase in the frequency of exposure is directly related to the toxicity of most substances . The frequency is also time related for instance if there is an exposure of 2 consecutive exposure for a duration of 12hrs a day is quite different from three consecutive 8 hour exposure

This aspect of the relationship between exposure and toxicity should be greatly considered when planning the work scheduled for workers at risk of exposure to toxicity is quite important to prevent the life threatening effects of such chemical substances

There are different phases to exposure to toxic agent these are the acute exposure and the chronic exposure...