How Toxic is Trichloroethylene?
The trichloroethylene case asks how much scientific certainty is needed before engineers, regulators, or public officials should act to protect people from possible harm. Trichloroethylene is a clear, nonflammable solvent that was widely used for industrial purposes for much of the twentieth century. In the 1990s, researchers found that it caused cancer in mice, but experts disagreed about whether the evidence was strong enough to classify it as a human carcinogen. Some organizations concluded that trichloroethylene could reasonably be anticipated to cause cancer in humans, while others took the stronger position that it was a known carcinogen. The main question of this case is whether regulators must know that a product is dangerous before restricting it, or whether reasonable suspicion is enough when the possible harm is serious. This case highlights the difficulty of making ethical decisions under uncertainty, especially when waiting for definitive proof may expose workers, consumers, or communities to avoidable risk.