Kyshtym disaster

Tens of thousands of people were involved in eliminating the effects of the explosion.

An excerpt from the article 42 facts about Kyshtym disaster

Up to 10,000 people worked daily in the vicinity of the epicenter in three shifts. They were constantly exposed to absorbing a potentially lethal dose of radiation, but this did not prompt any precautions.

A "daily radiation standard" was set that a worker could take, but this was not verified in any way - working hours were extended, and many workers were not tested.