Because it is not legal or ethical to perform toxicology research on humans, scientists use animals such as fish, mice, and other organisms whose bodies respond similarly to those of humans. These are called animal models. Scientists then make predictions about how a chemical will affect humans based on results of the animal tests. Whenever possible, scientists study chemical effects on cells or tissue samples.

What does a fish experiment have to do with human health?


Most vertebrates (animals with a spinal column) are very similar in the early stages of development. In fact, it is difficult to tell the difference between embryos from a human, a fish, and a chicken. See if you can tell the difference.

Because of these similarities, scientists have discovered that chemicals that affect a vertebrate animal embryo often have similar effects on a human embryo.




Why not just measure chemical concentrations with a lab instrument?


There are many instruments available to measure chemical concentration in the environment. However, using an animal model can be more useful for several reasons.

  • More specific: You may be able to observe a change in an organism’s genetic expression caused by exposure to a very low concentration of chemical. This concentration is sometimes much lower than what can be detected with even the most sensitive analytical instrument.
  • More relevant to health: Simply knowing the concentration of a chemical does not tell you if it is harmful at that concentration. Observing a response in a test animal confirms that the chemical does or does not have a health effect at that concentration.
  • More information: Animal models can be useful when you do not know what kind of chemical you are looking for. As you learned in this experiment, specific changes in gene expression patterns can give clues about what type of chemical is present.

Who Studies Developmental Toxicology?