Deck 4: Hazard, Exposure, and Risk Modeling

Question 1

What is a QSAR? How does this apply to polychlorinated dibenzodioxins and dibenzofurans?

Answer 1

It is the quantitative structure-activity relationshps and is the first tool used to assess how a new chemical may be toxic based on the structural relationships is shares with known toxicants. For chemicals with high toxicity based on their strong binding to the Ah receptor, they are assessed based on TEFs or Toxic Equivalency Factors or Total Dioxin-TEQ (how they compare to 2,3,7,8-TCDD, the compound with the greatest affinity for this receptor and cause cell proliferation/cancer).

Question 2

What is a hazard in risk assessment terms?

Answer 2

Hazard is the toxicology profile developed through log concentration or dosage vs. probit morbidity or mortality plots. This is used to extrapolate to human exposures via uncertainty factors based on the route used to test an animal, the animal model, and the chronicity of exposure.

Question 3

What is a LOEL, LOEC, NOEL and NOEC and how are they determined?

Answer 3

The NOEL and NOEC are the dose/dosage and concentration, respectively, where the toxicity is no different from controls. The LOEL and LOEC are the dose/dosage and concentration, respectively that are just significantly different from controls. These values are important to protect humans and endangered species.

Question 4

How is exposure determined? What is its usefulness?

Question 5

Why is toxicokinetics and toxicodynamics the best but a very expensive approach to modeling a hazard and its risk?

Question 6

What is the AUC?

Question 7

What is a TWA?

Question 8

What is a RgD?

Question 9

How is carcinogenicity taken into account in risk analyses?