The Dose Makes the Poison – or does it?

Updated: Apr 7

by Kacee Deener, Communications Director, EPA National Center for Environmental Assessment


When I was a graduate student, one of the first lectures in my toxicology class was about the history and basic principles of toxicology. We learned about Paracelsus, the 16th century physician-alchemist known as the father of toxicology, and how he coined the phrase “the dose makes the poison.” This has been a central tenant of toxicology and an important concept in human health risk assessment. The more we learn about the health effects of chemicals, however, the more we realize things may not be quite this simple.

I recently wrote about identifying the hazards of chemicals. Once we know what such hazards are, how do we know what levels of exposure will cause those health effects in humans? This is a really important question. To answer it, scientists do something called dose-response analysis, the next step in the human health risk assessment process. To do this, scientists calculate how different amounts (exposures or doses) of a chemical can impact health effects (responses) in humans.

Read more on the EPA It All Starts with Science Blog here.

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