Chemicals that interfere with the transfer of oxygen to the tissues are called asphyxiants. The exposed individual literally suffocates because the bloodstream cannot supply enough oxygen for life.

There are two main classes of asphyxiants—simple and chemical. Simple asphyxiants displace oxygen in the air, thereby leaving less or none for breathing.

Chemical asphyxiants cause the same effect by interfe ring with the body’s ability to take up, transport, or use oxygen. Simple asphyxiants are a major hazard in confined spaces, where breathable air can be displaced by gas from sewa g e, for instance.

When the normal oxygen level of 21% drops to 16%, breathing and other problems begin, such as lightheadedness, buzzing in the ears, and rapid heartbeat. Simple asphyxiants in construction include argon, propane, and methane.

These chemicals usually have no other toxic properties asphyxiant. It combines with the oxygen-carrying compound in the blood and reduces its ability to pick up “new” oxygen.

Hydrogen sulphide, on the other hand, interferes with the chemical pathways which transfer the oxygen, while hydrogen cyanide paralyzes the respiratory centre of the brain.

Absorption through the skin is another common form of entry for toxic substances (e.g., organic solvents). The skin is the largest organ of the body and has the largest surface area that can come into contact with harmful substances.

Some chemicals can penetrate through the skin, reach the bloodstream, and get to other parts of the body where they can cause harm. Toluene and Cellosolve are examples of chemicals which are absorbed through the skin. Mineral spirits and other solvents used in the manufacturing of paint can easily penetrate the skin.

The skin protects the internal organs of the body from the outside environment. Its outer layer is composed of hardened, dead cells which make the skin resistant to daily wear and tear. Sweat glands cool the body when the environment is hot.

Sebaceous glands produce oils which repel water. A network of small blood vessels, or capillaries, plays a key role in controlling body temperature. These capillaries open when it is hot, radiating heat outward into the air, and constrict when it is cold, conserving heat in the body.

The skin also has a protective layer of oils and proteins which helps to prevent injury or penetration by harmful substances.

A substance may be absorbed and travel to another part of the body, or it may cause damage at the point of entry (the skin), and start the disease process. Such substances are usually identified in an MSDS with a notation “skin” along with their exposure limits, indicating that the exposure can occur through the skin, mucous membranes, or eyes, or may damage the skin itself.

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