The relative potential of a substance or combination of different substances in causing injury or harm to living organisms is called toxicity.
If chemical substances are responsible for toxicity then it is called chemical toxicity and the chemical substances are known as chemical toxicants, or toxins.
Most chemical substances are poisons or toxins and it is the right dose which differentiates a poison and a remedy. The dose is expressed as milligram of chemical ingested per kilogram of body weight.
One measure of toxicity of something is the amount needed (dose) to cause some acute response, such as injury of organ, coma or even death. However, not every member of an exposed population will react the same way to a toxin and the response depends on condition of health, age, food habits, etc.
Toxicity can be both acute and chronic. Acute toxicity refers to effects that are caused within a short period of time, after a single exposure to the chemical and chronic toxicity refers to effects that take place after prolonged exposure.
The transmission or flow of toxic substances or toxins, through the body of living organisms follows a definite path and is known as ‘pharmacokinetics’.
There are four steps in pharmacokinetics such as:
All these steps occur simultaneously.
The absorption of toxins can be through ingestion with food or drink, through inhalation or by dermal (skin) contact or other exterior surfaces such as eyes.
Once in the body, it can be absorbed by the blood and distributed to various organs and systems. The toxicant or toxin may then be stored (e.g., DDT in fat) or may be eliminated from the body by excretion or by biotransformation.