Explanation:

- The phrase “something made impure by exposure to polluting substances” refers to an item, surface, or environment having pollutants added to it, resulting in impurity or defilement.

- Contagious refers to a disease or something that can be transmitted from one person to another. It’s about spreading infectious agents.

- Contractual means related to a contract or agreement, not relevant to impurity or pollution.

- Contented describes a state of satisfaction or happiness, unrelated to the concept of impurity.

- Contaminated specifically means made impure by exposure to pollutants, aligning precisely with the provided definition.

The correct option for the provided description is:

- Option 4: Contaminated