Clean Air Act 1956

The one entry about air rather than water, and it earns its place on the death toll that prompted it. London's Great Smog of December 1952 killed an estimated 4,000 people across five days, with later estimates of 12,000 once the longer-term effects were counted. The Clean Air Act 1956 created smoke-free areas across London and regulated coal burning in homes and factories. Coal slowly gave way to gas, and power stations were moved out of the capital. The same logic as the sewers applies: deal with the source, not the sick.