The following figure describes the effect of an acute dose compared to exposure to several smaller doses. The body may be unable to remove the toxic chemical, for example cadmium, which therefore accumulates in the body. When the body has a limited capacity to remove the toxic chemical, the accumulation is slower but with repeated exposure it can reach a level causing health problems. There are two main ways in which chemicals may exert their effects. Local effects occur at the area of the body which has been in contact with the chemical.
Examples are injuries from acids or lung injuries from inhaled reactive gases.
Systemic effects occur after the chemical has been absorbed and distributed from the entry point to other parts of the body. Most substances produce systemic effects, but some substances may cause both types of effects. An example is tetraethyl lead, which is a gasoline additive and produces skin effects at the contact site. It is absorbed and transported into the body causing typical effects on the central nervous system and on other organs. The degree of the toxic effect is not the same in all organs.