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Tox practice questions

36 questions from the hazwoper 40-hour practice test.

Tox practice test

10 questions, graded as you go, with the reason for every answer. No sign-up.

What this covers

Sample questions

Which of these is the best example of a chronic health effect?

  1. Lung scarring that appears after years of breathing low levels of dust
  2. Dizziness within minutes of opening a drum of solvent in a closed room
  3. A skin burn right after concentrated acid splashes on a bare forearm
  4. Coughing and tearing as a cloud of chlorine gas drifts over a worker
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A. Lung scarring that appears after years of breathing low levels of dust

Chronic effects develop slowly from repeated or long-term exposure and may not appear for years. The other three happen within minutes of a single exposure, which makes them acute effects.

Reference: 29 CFR 1910.1200 Appendix A; basic toxicology

What does the term LD50 mean?

  1. The air level that kills half of a test animal population
  2. The dose that causes no effect in half of the test animals
  3. The dose that kills half of a test animal population
  4. The lowest dose known to have killed a human being
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C. The dose that kills half of a test animal population

LD50 is the lethal dose for 50 percent of the test animals, usually given in milligrams per kilogram of body weight. The airborne version is LC50, the lethal concentration, which is the easy one to mix it up with.

Reference: 29 CFR 1910.1200 Appendix A, A.1 (acute toxicity)

Chemical A has an oral LD50 of 5 mg/kg and Chemical B has an oral LD50 of 500 mg/kg. What does this tell you?

  1. Chemical A is more acutely toxic, because less of it is needed to kill
  2. Chemical B is more acutely toxic, because its LD50 number is higher
  3. The chemicals are equally toxic, because both doses kill half the animals
  4. Chemical A is more likely to cause cancer, because LD50 measures chronic harm
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A. Chemical A is more acutely toxic, because less of it is needed to kill

The lower the LD50, the smaller the dose needed to kill, so the more toxic the substance. Reading a bigger number as more dangerous is the common mistake. LD50 measures acute lethality and says nothing about cancer.

Reference: 29 CFR 1910.1200 Appendix A, A.1 (acute toxicity)

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