Sub-module 6B, page 1
Toxicity Assessment
In your tour through Tox Tutor you learned about the science of toxicology. Science in concerned with elucidating the laws of nature. Why do things happen? In this sub-module we will learn something about the application of the science of toxicology. Specifically how do we express a risk due to a particular exposure. Here we are no longer concerned with the science, but rather the results. The history of engineering and technology has many stories of inventors who did not understand the science of their inventions or used incorrect science, but the result worked. The opposite also happens, the science is well understood, but he invention fails for some other reason, typically human problems or economics.
If the goal of the technology we are applying is to protect people from adverse heath effects, we apply the technology, and no adverse effects follow, we term the application a success. If adverse health effects are observed, we have failed. Using those definitions, science does not matter. If our goal is to protect people from cancer due to benzene in their water supply and we charcoal filer their water and later observe that their cancer rate is the same as communities that do not have benzene in their drinking water, we have succeed. It does not matter if the benzene was really capable of causing cancer, or even if there really was any benzene in the water to start with, the charcoal filters have succeeded.
If the goal of an environmental law is to protect persons, and we protect them, it does not matter is they were actually (scientifically) threaten or not, the law has succeeded.
In this sub-module we make a distinction between the toxic effect cancer and every other toxic effect. That is, divide the world of contaminants into carcinogens and non-carcinogen. For the many chemicals that are both, we will separate the risk of cancer from the risk of the non-cancer harm, nerve damage for example. Typically the hazard identification at the beginning of the risk assessment has provided that information. Also, your SCEM and exposure analysis will provide you some information about the level and likely length of the exposure. What you want next are Toxicity Values that relate dose to response.
We will learn about the toxicity values for non-cancer effects, cancer effects. NEXT