How important is it to wear a seat belt while riding in a car, or to wear a helmet while motorcycling, bicycling, or skiing? These questions relate to risk, the chance that harm will occur under a certain set of conditions. We all make many decisions based on our ideas about risk.

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.

Chemical Risk
If you want to assess the risk to human health from exposure to a chemical, you will need to ask two questions:

  1. What health problems could this chemical cause?
  2. How likely are these health problems to occur?

For any particular chemical, risk assessment can be summarized with the equation:

Chemical Risk = Toxicity   X   Exposure

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.

Risk Links

How Safe Am I? Helping Communities Evaluate Chemical Risks
Risk Assessment: What's It All About?
Risk Assessment Student Issues
Chemical Risks in Foods
Risk in the News
Reporting on Risk Assessment
Institute for Environmental Toxicology


Copyright 2009 Environmental Inquiry, Cornell University and Penn State University