Inhalation - local effect - lung
systemic effect- blood, target organ

Ingestion - local effect - GI tract
systemic effect - blood, target organ

Absorption - local effect - skin
systemic effect - blood, target organ

Eye - local effect - eye
systemic effect - blood, target organ

Acute effect - Effects that are usually of short duration. (minutes, hours, days) An adverse effect on a human or animal body resulting from a single exposure with symptoms developing almost immediately or shortly after exposure occurs.

Chronic effects - Effects that occur after a longer period of time (months, years) An adverse effect on a human or animal body resulting from repeated low level exposure, with symptoms that develop slowly over a long period of time or that recur frequently.

There are several types of effects which hazardous substances may have on the body. A single agent may have more than one type of effect at the same time. Additionally, when more than one chemical is present the effect can be compounded and in some cases synergistic (multiplied by working together). AS A WORKER, BE ESPECIALLY CAUTIOUS IF YOU ARE BEING EXPOSED TO A MULTITUDE OF CHEMICALS. YOU ARE THE BEST PROTECTOR OF YOUR HEALTH. IF YOU FEEL ILL, REPORT IT TO YOUR EMPLOYER.

TO FIND OUT A CHEMICAL'S PHYSICAL AND HEALTH HAZARDS, LOOK UP THE CHEMICAL ALPHABETICALLY IN THE National Institute for Occupational Safety and Health (NIOSH)'s "Pocket Guide to Chemical Hazards."


A SIMPLE ASPHYXIANT does not allow oxygen to be transferred to the cells. Examples are: Carbon dioxide, hydrogen, methane, and nitrogen.

A CHEMICAL ASPHYXIANT prevents the uptake of oxygen by the cells. Examples are: Carbon Monoxide - prevents oxygen transport by combining with hemoglobin developing carboxy hemoglobin. Hydrogen Sulfide - at high enough concentrations, it paralyzes the respiratory center of the brain.


An irritant is a material that causes inflammation to a part of the body.

RESPIRATORY IRRITANTS cause injury to the nose, mouth, throat and lungs. Materials that are very water soluble affect mainly the nose and throat. Less water soluble materials act deeper in the lungs.

SKIN (DERMAL) IRRITANTS may cause contact dermatitis (irritated rash), and erythema. Examples are organic solvents.

Very corrosive agents can cause skin ulcers and destroy tissue.


Some individuals become sensitized to certain chemicals, such that repeated exposures cause a more pronounced response with subsequent exposures or a more pronounced response can develop with subsequent exposures that are lower in concentrations. Allergic responses generally affect the skin and respiratory tract. Examples include: isocyanates and formaldehydes.


BLOOD SYSTEM TOXINS - These agents damage blood components or depress blood cell formation. Examples include benzene, methylene chloride, and arsine.

NEUROTOXINS (Central Nervous System) - These compounds damage the nerve cells (neurons) or inhibit their function by acting on a part of the nerve cell. Typical symptoms include dullness, muscle tremor, restlessness, convulsions, loss of memory, and loss of muscle coordination.

LIVER (HEPATO-) TOXINS - These compounds can cause liver damage. Examples include alcohols and some solvents.

KIDNEY (NEPHRO-) TOXINS - These agents damage the kidney, causing swelling and increased serum (blood) proteins in the urine.


CARCINOGENS - Carcinogens cause cancer. Cancer is the development of malignant growths or neoplasms at any site in the body. The development of cancer may be delayed for 20-30 years. Examples include vinyl chloride, asbestos, ethylene dibromide, and acrylonitrile.

TERATOGENS - Teratogens are agents that cause physical defects in the developing embryo or fetus. In the 1960's methyl mercury was the first industrial chemical shown to be a teratogen. Examples include thalidomide, anesthetic gases, and ionizing radiation.

MUTAGENS - Mutagens are agents which cause a change (mutation) in the genes by altering the DNA. Mutation of the reproductive cells may cause birth defects. Mutation of other cells may cause cancer or a teratogenic response to the exposed person or her child. Examples include ethylene oxide, benzene, hydrazine, and ionizing radiation.

TUMORIGENIC - The chemicals can cause a non-cancer tumor. However, theses tumors can become cancerous.

OXYGEN DEPLETION - Normal oxygen levels on the planet occur at 20.9 percent of total atmospheric gases. We can live and normally function with a minimum oxygen percential of 19.5. While life can be sustained at lower oxygen levels, function greatly deteriorates and can lead to death. The following chart shows effects of oxygen depletion:
Percent of
Oxygen in Air
20. 9 Normal
less than 19.5 Respiration volume increases, muscular coordination diminishes, attention and clear-thinking requires more effort.
12 to 19.5 Shortness of breath, headache, dizziness, quickned pulse, efforts fatique quickly, muscular coordination for skilled movements lost.
10 to 12 Nausea and vomiting exertion impossible, paralysis of motion
6 to 10 Collapse and unconsciousness occurs
6 or below Death in 6 to 8 minutes

While there are no adverse health effects from oxygen levels greater than the normal background levels of 20.9%, oxygen levels that exceed 25% present a serious fire danger. Given an ignition source in an atmosphere in excess of 25% oxygen, everything that is fuel will ignite and burn, including the human body, even dust. Oxygen-rich work environments present an extreme danger to workers who can ignite in the event of a spark of some kind. When in a confined space, the safe level of oxygen is less than 23.5% but more than 19.5%. Oxygen meters exist that can read the level of oxygen in the atmosphere and some have alarms that alert to unsafe levels.


Toxicology is based on the dose-response relationship. This relates the amount of a substance (the dose) given to a test animal to the effect shown by the animal (the response).

The simplest study relates the percentage of test animals which die (mortality) to the dose given. The dose is usually expressed in mg/kg (for ingestion or inoculation), in mg/m3 (for skin exposure), or in parts-per-million (ppm). The response is expressed in percent of animals which have died.

The LD50 is the lethal dose of a substance that caused the death of 50% of a group of experimental animals. The important thing for hazard awareness is that the smaller an LD50 is, the more toxic the chemical is likely to be. The LD10 is level of chemical dosage or exposure that killed the first laboratory or experimental animal. The LD10 information can be of use to workers who have allergy troubles, or who may have been sensitized to chemicals by exposure.