MORE than one million people in the Chinese city of Handan awoke last week to the alarming news that an essential source of their drinking water, the Zhouzhang River, had been dangerously contaminated by a 39-ton chemical spill in the nearby city of Changzhi. What made the news even more shocking was that the leak, from a factory pipe, had started at least five days earlier but had been kept secret by government officials, who allowed millions of their neighbors to keep drinking.

The people of Handan reacted to these disclosures the same way almost anyone else would. First, they panicked, mobbing stores for bottled water. Then, they were furious, demanding to know why no one had told them they were drinking water laced with a probable carcinogen. If history is any guide, they will never get a satisfactory answer.

For me, reading about Handan prompted a sick feeling of déjà vu. For the last five years I have been writing a history of the chemical industry’s egregious 60-year involvement in the New Jersey shore town of Toms River, which gained unwanted notoriety in the late 1990s thanks to a remarkably well-documented cluster of childhood cancer cases and a long history of often hidden industrial pollution.

When news of the cancer cluster leaked in 1996, there was the predictable townwide panic, including a run on bottled water supplies. After a wrenching five-year investigation, state and federal health officials concluded that the sick children were more likely to have lived in parts of town where exposure to industrial chemicals — via drinking water and polluted air — were highest.