Which term describes the interaction where the combined effect equals the sum of the individual effects?

Which term describes the interaction where the combined effect equals the sum of the individual effects?

• A. Antagonistic
• B. Synergistic
• C. Additive
• D. Independent

Answer: (C)

Additive interactions occur when the combined effect equals the sum of the individual effects. This happens when two hazards contribute to the outcome in ways that simply add up, often because they act on the same toxicity pathway or behave in a dose-additive manner. For example, if one chemical produces a response of two units and another produces three units, their joint effect is about five units. A synergistic interaction would push the total above five, while an antagonistic interaction would push it below five. Independent describes a situation where mechanisms don’t interact in a way that allows straightforward dose addition, so the total isn’t guaranteed to be the simple sum.

Additive interactions occur when the combined effect equals the sum of the individual effects. This happens when two hazards contribute to the outcome in ways that simply add up, often because they act on the same toxicity pathway or behave in a dose-additive manner. For example, if one chemical produces a response of two units and another produces three units, their joint effect is about five units. A synergistic interaction would push the total above five, while an antagonistic interaction would push it below five. Independent describes a situation where mechanisms don’t interact in a way that allows straightforward dose addition, so the total isn’t guaranteed to be the simple sum.