Such testing, if done humanely can be justified for use in medical research that may be used to save lives. Doses to laboratory animals are usually large and then scaled down, assuming that small doses produce proportionally lesser effects. All uncertainties must be considered. Life histories, autopsies, and other supporting data on the sickness or death of the person may not be available. Uncertainties must be considered.
Scientific studies including test groups and control groups are more useful.
Certain contaminants have threshold limits, in which a small dose is not harmful. Once the threshold limit is reached, however, a hazard exists. These contaminants are not carcinogenic. Lethal doses of various chemical agents can be compared using the LD50. The lower the number the more virulent the chemical agent.