Chemicals & Human Health

Toxicology Problem Set

Problem 6: Measuring dose

For help to answer the question:

Which will NOT help you determine the dose of a hazardous gas received by a person?
A. their respiration rate
B. their length of exposure to the gas
C. the source of the gas
D. their frequency of exposure to the gas
E. the concentration of the gas
F. the gas's chemical and biological properties


When a person is exposed to a hazard, such as a toxic gas, there are several things that determine the amount that actually enters the body. One way to determine a person's dose is to do a blood test to measure the amount of chemical in their body. For many chemicals, there is no easy way to measure them in the blood. Scientists must measure other factors to estimate does. Some measurements that can be used are:

respiration rate - A hazardous gas usually enters a person's body through inhalation into their lungs. If they are breathing quickly, they will breathe in more of the gas than if they are breathing slowly. So their dose is higher if they are breathing heavily.

hazard concentration - A higher concentration of a hazardous gas means a higher dose because there is more of the hazard to breath in.

frequency of exposure - A person exposed only once is likely to have a smaller dose than a person exposed many times.

length of exposure - A person exposed for a short time will have a lower dose than a person exposed for a long length of time.

properties of the toxin - Some gases are not easily absorbed by the human body and exposure does not lead to as high a dose as exposure to a gas that is easily absorbed.

Knowing the source of a hazard will help the scientists to reduce exposure in the future, but will not help to determine how much a person has in their body.

Toxicology Problem Set Chemicals & Human Health

The Southwest Environmental Health Sciences Center
The Biology Project
The University of Arizona
Tuesday, September 16, 1997
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