News stories frequently cover controversies concerning the safety of food or drinking water. Is it safe to eat irradiated beef? How about fruits or vegetables containing traces of pesticide residues? Should fluoride be added to drinking water? Is diet soda safe to drink, or will it cause cancer? These questions relate to chemical risk, the chance that you will experience health problems as a result of exposure to a particular chemical.
For any particular chemical, risk assessment can be summarized with the equation:
Exposure is an estimate of how much of the chemical a person is likely to eat, drink, or absorb from water, air, or other sources. Toxicity indicates what health problems are associated with various doses or concentrations. It is estimated using two sources of information: 1) any available data on effects on humans, and 2) bioassay experiments.
The EI website provides instructions for carrying out bioassay experiments using lettuce seeds, Daphnia, and duckweed. These experiments are designed for evaluating the toxicity of chemicals to plants and animals in the environment. In order to use bioassays to predict toxicity to humans, you would need to use organisms such as laboratory rats or mice that are known to provide a better model of human response to toxic chemicals.
For more information on student bioassay experiments, read about Assessing Toxic Risk.