Which statement best describes a threshold dose-response model? 

A)  It implies there is a dose below which no detectable harmful effects occur. 
B)  It implies that each dose of ionizing radiation or toxic chemical carries a risk of causing harm. 
C)  It is useful for assessing chronic toxicity. 
D)  It errs on the side of safety.

A threshold dose-response model suggests that there is a certain minimum level of exposure below which no noticeable harm or effect occurs. This means that a certain threshold must be met before any negative impacts are seen.

Answer: B
The linear dose-response model suggests that the risk of damage from a substance or radiation exposure is directly proportional to the dose received. As a result, each dose of ionizing radiation or toxic chemical carries a risk of causing harm.

Answer: C
Threshold dose-response models are best suited for assessing chronic toxicity. Chronic toxicity is characterized by negative effects that occur over a long-term period with low-dose or repeated exposure. As a result, the threshold limit for harmful effects may be lower than for acute toxicity.

Answer: D
Threshold dose-response models tend to err on the side of safety. This means that the threshold limit for harmful effects is set lower than the actual limit, ensuring that individuals are not exposed to potentially hazardous substances or radiation.