Question

when scientists think a chemical might be risky, what rule says we need to check if its safe before we use it more?
precautionary principle
eutrophic principle

Explanation:

The Precautionary Principle states that if an action or policy has a suspected risk of causing harm to the public or the environment, in the absence of scientific consensus that the action or policy is not harmful, the burden of proof that it is not harmful falls on those taking the action. In the context of a chemical that might be risky, this principle would require checking its safety before increased use. The Eutrophic Principle is not relevant here; eutrophication refers to the enrichment of water bodies with nutrients, leading to excessive plant growth.

Answer:

Precautionary Principle