All natural sources of drinking water contain low levels of contaminants from geological sources. For example, arsenic is often present in parts per million. The presence of arsenic in drinking water has been tested repeatedly in mice and found to have no effect on their health even at much higher levels than those that occur naturally. However, studies of people who have been drinking water containing different trace levels of arsenic all their lives reveal an increased level of bladder cancer that begins to appear after 30 years. The more arsenic in drinking water the more cancers, with no amount that can be judged to be “completely safe”.
Which of the following statements represents the best use of the science?
A. The data on humans should be ignored until experiments with mice and other animals can explain how arsenic can cause cancer.
B. Since we know of no level of arsenic in drinking water that is safe, governments should spend whatever is necessary to remove absolutely all arsenic from drinking water.
C. A cost-benefit analysis should be conducted to determine some level of arsenic in drinking water that a society will need to tolerate, recognizing that we cannot afford to eliminate every death from bladder cancer caused by arsenic in drinking water.
D. We should not try to control how much arsenic people drink in their water now, because it is certain that science will soon develop a cure for bladder cancer that costs less than treating our water to remove the arsenic.
Click on this link to access answers, including feedback for both correct and incorrect student choices.