The food we eat, the water and beverages we drink, and the air we breathe all are made up of complex mixtures of chemicals. Many of these chemicals are beneficial to our health when we consume them in small amounts but would be harmful at larger doses. For example, vitamin D is an important part of the human diet, but it also is a highly toxic chemical. In tiny amounts it is good for you, but taking higher than the recommended doses can cause serious health problems including kidney stones, high blood pressure, deafness, and even death. Environmental toxicology is the study of the effects of chemicals on plants, animals, and the ecosystems in which they live.
Scientists use experiments called bioassays to determine the effects of chemicals on living things.