The route of exposure of toxicant is determined by its nature. Human beings can be exposed to gases and vaporous toxic substances by inhalation whereas for liquid can be exposed through skin absorption or injection. In toxicology, “exposure” refers to the concentrations or amount of a substance presented to individuals or amount of toxicant found in specific volumes of air or water, or in soil.
Four Major routes of exposure of toxic substances
1.Inhalation – Chemicals or any toxicant in the form of vapors, gases, mists, or particulates, is majorly exposed through inhalation. Once inhaled, chemicals are either exhaled or deposited in the respiratory tract. If deposited, damage can occur through direct contact with tissue or the toxicant may get diffused into the blood. Upon contact with tissue in the upper respiratory tract or lungs, chemicals may cause health issues ranging from simple irritation to severe other problems. Substances absorbed into the blood are circulated and distributed to organs (TRANSLOCATION) that have an affinity for that toxicant.
Example – Hydrogen cyanide
The following factors affect inhalation of toxic substances:
- Concentration of toxic substance in the air,
- Solubility of substance in the blood and tissue,
- Respiration rate,
- Length and frequency of exposure,
- Size of toxic particle
- Condition of respiratory tract
2. Skin or eye Absorption: Toxicants can be adsorbed through Skin and can bring mild to severe effects on human system. Many toxic substances can cross the skin barrier and get directly absorbed into the blood system. Once absorbed, they may produce damage to internal organs. The eyes on the other hands bring serious damage even after a short exposure. It can bring serious eye problem or it may be transported to other body parts. The primary point of contact
for toxic substances is the cornea. Damage to the eye or body is brought mainly by acidic and basic compounds in exposure through eye absorption.
Example – Organophosphate insecticides
Factors affecting Skin absorption of toxic substances include
- 1.The condition of the skin – Damage to protective layer i.e. skin such as cut, wounds or abrasion may lead to the absorption of some toxic chemicals. if a toxic substance penetrates the skin and goes deep into the dermis, they can readily enter the blood stream and may also go to other parts of the body.
- The nature of the toxicant – Inorganic substances are not easily absorbed through intact, healthy skin (such as lead and mercury). Organic toxicants that dissolve in water also do not penetrate the skin as skin is impermeable to water. Organic solvents, such as paint thinner or gasoline, are easily absorbed through skin.
3. Ingestion: The digestive tract consists of the mouth, the esophagus (food canal), stomach, and intestine (large and small). Chemicals that are deliberately or inadvertently put into the mouth and are swallowed do not generally harm the gastrointestinal tract itself unless they are corrosive.
Chemicals that are insoluble in the fluids of the gastrointestinal tract are generally excreted. But that are soluble are absorbed through the lining of the gastrointestinal tract. They are then transported by the blood to internal organs where they can cause damage.
Example – Pesticides , Strychnine
4. Injection: Toxic Substances can enter the body if the skin is penetrated or punctured with the help of injections. Effects can varied depending on the nature of toxicant and lethality of the substance.
Injection can be administered by following ways
- Intravenous injections (into a vein)
- Intramuscular injections (into the muscle)
- Intra peritoneal injections (into the abdominal cavity)
- Intradermal injections (into the skin)
- Subcutaneous injections (under the skin)
Example – Mercury poisoning
In our next post , we will be covering TYPES OF EXPOSURE OF TOXICANTS. Keep Visiting the Website. Ans like I always say, have a doubt, Shoot it at Us and we will KILL it for forever 🙂