Which statement best characterizes a dose-response curve and the difference between threshold and non-threshold models?

Which statement best characterizes a dose-response curve and the difference between threshold and non-threshold models?

• A. It graphs exposure time versus response; threshold models show immediate effect, non-threshold models show delayed effect.
• B. It graphs effect versus dose; threshold models show no effect below a threshold, non-threshold models imply risk even at very low doses.
• C. It lists jobs and hazards; threshold models are for acute effects, non-threshold for chronic.
• D. It compares two chemicals; threshold models assume additivity, non-threshold assume synergy.

Answer: (B)

The key idea is how a dose-response curve represents the relationship between dose and effect and the distinction between threshold and non-threshold models. A dose-response curve plots the magnitude of an effect (response) against the dose of a substance. In a threshold model, there is a dose below which no adverse effect occurs, so the curve remains at zero response up to that point. In a non-threshold model, any nonzero dose carries some risk, so the curve shows some response even at very low doses and rises as the dose increases. This distinction matters for risk assessment because it influences whether a safe exposure level can be defined. The statement correctly captures both the graphing of effect versus dose and the difference between threshold (no effect below a threshold) and non-threshold (risk at very low doses) models. The other options misstate what is graphed (dose vs exposure time) or mischaracterize the concepts (such as linking threshold to immediate versus delayed effects, or using hazard listings, or tying them to additivity or synergy).

The key idea is how a dose-response curve represents the relationship between dose and effect and the distinction between threshold and non-threshold models. A dose-response curve plots the magnitude of an effect (response) against the dose of a substance. In a threshold model, there is a dose below which no adverse effect occurs, so the curve remains at zero response up to that point. In a non-threshold model, any nonzero dose carries some risk, so the curve shows some response even at very low doses and rises as the dose increases. This distinction matters for risk assessment because it influences whether a safe exposure level can be defined.

The statement correctly captures both the graphing of effect versus dose and the difference between threshold (no effect below a threshold) and non-threshold (risk at very low doses) models. The other options misstate what is graphed (dose vs exposure time) or mischaracterize the concepts (such as linking threshold to immediate versus delayed effects, or using hazard listings, or tying them to additivity or synergy).