We can’t afford to delay getting to grips with chemical pollution

IN 1855, Michael Faraday wrote a letter to the UK parliament alerting MPs to the state of the river Thames, which was used both as a sewer and a source of drinking water. He had conducted an experiment in which he sank pieces of paper to see at what point they disappeared from view in the turbid water. Barely any depth at all, he found, concluding that the river had become a cesspool. “If we neglect this subject, we cannot expect to do so with impunity,” he warned.

Parliament neglected the matter, and was punished. In 1858, the Great Stink …