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Bioassays: Background Information
A bioassay involves use of a biological organism to test for chemical toxicity. Perhaps the oldest and most commonly known example is the canary in the coal mine. Traditionally, coal miners have taken caged canaries down into the mines to help ensure a safe air supply.  Canaries are more sensitive than humans to methane, an odorless gas released during the mining process, so they were used to provide an advanced warning of when methane was building up to dangerous levels in the mines. If the canary died, it meant the miners should leave the mine as quickly as possible.

Another sort of bioassay is used to test the effects of compounds being considered for use in drugs or skin care products. Before a chemical compound receives FDA approval as an ingredient in products for human use, it must be thoroughly tested on laboratory animals.

For environmental testing, bioassays provide an integrated picture of overall toxicity of an effluent or a sample of water, sediment, or soil from a contaminated site. Fathead minnows, various aquatic invertebrates, earthworms, protozoans, and seeds all are used for bioassays of aquatic samples (see Keddy et al., 1995, for an extensive review). The idea behind these bioassays is that the test organism will react in a predictable way to various types of environmental contaminants. Several studies have compared the sensitivies of various types of seeds to common pollutants (for example, Wang and Williams, 1988; Wang, 1987; Wang, 1986).

The following are a few examples of ways in which lettuce seed bioassays have been used by scientists for environmental testing purposes:

  • to map areas for clean-up of Superfund sites (Thomas et al., 1986)
  • to screen industrial effluents (Wang and Williams, 1988)
  • to test the effectiveness of clean-up of lead-contaminated soil (Chang et al., 1997)
  • to design clean-up strategies at a site contaminated by treatment of lumber with creosote and other compounds (Athey et al., 1989)

Read more about lettuce seed, Daphnia, or duckweed bioassays.


Athey, L.A., J.M. Thomas, W.E. Miller, and J.Q. Word. 1989. Evaluation of bioassays for designing sediment cleanup strategies at a wood treatment site. Environmental Toxicology and Chemistry, 8: 223-230.

Bowers, N., J.R. Pratt, D. Beeson, and M. Lewis. 1997. Comparative evaluation of soil toxicity using lettuce seeds and soil ciliates. Environmental Toxicology and Chemistry, 16: 207-213.

Chang, L.W., J.R. Meier, and M.K. Smith. 1997. Application of plant and earthworm bioassays to evaluate remediation of a lead-contaminated soil. Arch. Environ. Contam. Toxicol., 32: 166-171.

Keddy, C.J., J.C. Greene, and M.A. Bonnell. 1995. Review of whole-organism bioassays: soil, freshwater sediment, and freshwater assessment in Canada. Ecotoxicology and Environmental Safety, 30: 221-251.

Thomas, J.M., J.R. Skalski, J.F. Cline, M.C. McShane, & J.C. Simpson. 1986. Characterization of chemical waste site contamination and determination of its extent using bioassays. Environmental Toxicology and Chemistry, 5: 487-501.

Wang, W. 1987. Root elongation method for toxicity testing of organic and inganic pollutants. Environmental Toxicology and Chemistry, 6: 409-414.

Wang, W. 1986. Comparative toxicology of phenolic compounds using root elongation method. Environmental Toxicology and Chemistry, 5: 891-896.

Wang, W., and J.M. Williams. 1988. Screening and biomonitoring of industrial effluents using phytotoxicity tests. Environmental Toxicology and Chemistry, 7: 645-652.


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