For example, animals are smaller, they have shorter lifespans and their bodies sometimes handle chemicals differently from humans. Large doses are used in the animal studies to see if there will be any effect. When guidelines or standards for human exposure to chemicals are developed, these differences and others are taken into account. Some chemicals, like acids, are nonspecific and cause damage on direct contact. Other chemicals, like gasoline, can be absorbed into the blood, and carried throughout the body.
Some chemicals affect only certain target systems or target organs.
Every organ system has different functions and physical characteristics. So the effect of chemicals on each system has to be evaluated slightly differently. First, chemical exposure can affect a man's or woman's reproductive system by making the production of normal sperm or eggs more difficult. Since chemicals can be transferred from the mother's blood to the unborn baby's blood, the fetus can be affected when the mother is exposed to certain chemicals. A pregnant woman who drinks alcohol can have a baby with fetal alcohol syndrome.