Teratology and reproduction studies assess a chemical's potential to cause birth defects. Mutagenicity studies assess a chemical's tendency to cause adverse changes in the genetic makeup of an organism. An LD-50 rating is calculated for the dose at which one half of the test animals can be expected to die following the ingestion of the test substance. HPB has no requirement for LD-50 test data obtained by using the classic, statistically precise test. The test is also not used by Environment Canada as a basis for regulatory decision-making.
Tests requiring far fewer animals are preferred.
In this test, animals are given a single dose or, if necessary, a few equally spaced doses of the chemical within a 24-hour period. The dose given relates to body weight. Although the results of the limit test may not be as precise, this form of testing is usually a sufficient replacement for the classic LD-50. Because of the risk of accidental overexposure or poisoning, toxicologists need to know how a substance works in the body. Careful observation of the animals and analysis of body chemistry provide this essential information.