Which sentence is most clearly written?

The first sentence is most clearly written because it uses a semicolon correctly to connect two related independent clauses. The phrase "Living near a power station can be unhealthy" is a complete thought, and so is "it is associated with higher rates of cancer." By using the semicolon, the writer effectively indicates a close relationship between the two ideas—suggesting that the unhealthiness is directly tied to higher cancer rates.

In contrast, the second sentence mistakenly uses a comma to join two independent clauses. This creates a grammatical error known as a comma splice, which may confuse readers about the relationship between the two statements. Using a semicolon in the first sentence enhances clarity and readability, making it the better choice.