Contaminants that enter the organism will usually attack specific organs and may be chemically altered by the body. Contaminants in solution are more easily absorbed by the body. The toxicology of the contaminants must be studied. We judge risks to human health from data derived from animal testing and epidemiological studies. Both methods have uncertainties that cause results to be conservative.
Animal testing raises ethical issues, especially when used for testing products.
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.