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Health effects of hazardous substances
This section will help you understand some of the common terms used in material safety data sheets to describe health effects of hazardous substances. For a more extensive list of technical terms, see the glossary.
Acute effects
Acute effects show up after a single, brief exposure to a material. These symptoms include rashes or skin irritation, headache, nausea, or burns. Acute effects are often reversible when the exposure stops.
Chronic effects
Repeated or prolonged exposures to hazardous materials can result in chronic effects. They may take weeks, months, or even years to show up. The effects depend on the amount and frequency of exposure. Examples of chronic effects are liver and kidney disease, nerve and brain disorders, and reproductive damage. Often chronic effects cannot be reversed even if the exposure is stopped.
Some chemicals have both acute and chronic effects. One such chemical is a solvent called trichloroethylene (TCE). Its acute effects can include drowsiness, nausea, dizziness, and blistering of the skin while chronic effects may include liver damage and cancer.
Local effects
When a toxic substance causes damage at the point of original contact it has a local effect. Some examples of local effects:
- Skin exposure: symptoms include skin dryness, blistering, redness, rashes, and itching.
- Eye exposure: the most common symptoms of eye exposure are burning, itching, and watering of the eyes.
- Respiratory tract exposure: symptoms may include headache, nose and throat irritation, dizziness, and disorientation.
Systemic effects
Some toxic substances can pass through the point of original contact and affect the organs of the
body, such as the liver, heart, nervous system, and muscles. Harm to organs “system-wide” beyond
the original point of contact is called a systemic effect.
- Liver and kidneys. Chemicals can damage our liver and kidneys. The liver detoxifies or modifies many chemicals so they are no longer harmful. Our kidneys filter impurities from the blood for elimination from the body. These organs may be damaged while performing these functions.
- Central nervous system. The central nervous system consists of the brain and spinal cord connected to thousands of nerves throughout the body. When we inhale chemicals such as carbon dioxide or solvents, brain function can be impaired, by a lack of oxygen. We may become dizzy or drowsy, or even unconscious. Some chemicals impair nerve function by blocking nerve impulses. Some examples of chemicals that can cause nerve dysfunction are pesticides, mercury, and lead. Your symptoms may show up as a loss of reflexes, loss of feeling, tremors, or even paralysis. These effects may be temporary or permanent.
- Carcinogens and reproductive effects. A carcinogen can cause
cancer. There are 14 known human carcinogens and more than one thousand substances that we suspect
to cause cancer. We must label
known or suspected carcinogens in the workplace.
A mutagen affects the genetic material in human cells and causes changes or mutations. There are two kinds of hazards associated with mutagens.
- Reproductive damage can affect both men and women by damaging or killing egg and sperm cells, which may prevent conception. If conception does occur, a miscarriage or a fetus with genetic defects may result. Many mutagens have also been found to be carcinogens.
- A reproductive toxin affects
the reproductive process. It may cause menstrual problems in women, which inhibit conception.
In
men it may cause lowered sperm count or sperm motility.
In either
sex, it may cause decreased sex drive.
A teratogen affects the developing fetus. The fetus may be exposed to the substance through the mother’s blood stream. Even though the mother may suffer no ill effects from exposure to the teratogen, the fetus may be more sensitive. It is especially important that pregnant women are aware of the hazardous materials to which they are exposed.
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