About Exposure

Exposure is contact. No matter how dangerous a substance or activity, without exposure, it cannot harm you.

Amount of Exposure

The dose is the amount of a substance that enters or contacts a person. The greater the dose, the more likely that health effects could occur. Large amounts of even a relatively harmless substance can be toxic. For example, two aspirin can help to relieve a headache, but taking an entire bottle of aspirin can cause stomach pain, nausea, vomiting, headache, convulsions, or death.

Routes of Exposure

The routes of exposure are how substances can get into the body.

  • Inhalation. Breathing in gases, vapors, dusts or mists can irritate the nose, air passages and lungs. By breathing, substances can enter the airways or be absorbed through the lungs into the bloodstream. The blood can then carry these substances to the rest of the body.
  • Direct contact. Touching or direct contact with substances by the skin or eyes can allow some substances to enter the bloodstream. Broken, cut or cracked skin make it even easier for susbtances to get in the body.
  • Ingestion. Chemicals that get in our food, on our utensils, or hands can be swallowed. Children are at greater risk than adults because they often put their fingers or other objects in their mouths. Substances can be absorbed into the blood and then transported to the rest of the body.

Length of Exposure

The amount of time someone is exposed to a substance can also affect health.

Acute exposure is short-term contact with a substance. It could last a few seconds or hours. For example, it might take a few minutes to clean windows with ammonia, use nail polish remover, or spray a can of paint. The fumes someone might inhale during these activities are examples of acute exposures.

Chronic exposure is continuous or repeated contact with a substance over months or years, such as using a chemical every day on the job or at home. Over time, some chemicals such as PCBs and lead, can build up in the body. Chemicals in household furniture, carpeting, or cleaners can also be sources of chronic exposure.


All people are not equally sensitive to chemicals, and are not affected by them in the same way.

  • People's bodies absorb and break down certain chemicals differently due to genetic differences.
  • People may be allergic to a chemical after being exposed. Then they may react to very low levels of the chemical and have different or more serious health effects than people who are not allergic exposed to the same amount. For example, people who are allergic to bee venom have a more serious reaction to a bee sting than people who are not allergic.
  • Factors such as age, illness, diet, alcohol use, pregnancy, and drug use can also affect a person's sensitivity to a chemical. Young children are often more sensitive to chemicals for a number of reasons. Their bodies are still developing and they cannot get rid of some chemicals as well as adults. Also, children absorb greater amounts of some chemicals (such as lead) into their blood than adults.

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