Mr. Mazzocchi was an activist in the labor and occupational safety and health movements for all of his adult life. He played a pioneering role in establishing occupational health as an issue for labor unions and in promoting legislation to protect workers from job hazards. He helped to initiate the national movement to set up local Committees for Occupational Safety and Health. There are now more than 20 across the country.

For much of his career, Mr. Mazzocchi was active in the Oil, Chemical and Atomic Workers Union (OCAW), serving as a local union president, legislative director, health and safety director, vice president and secretary-treasurer.

His work on behalf of workplace safety and health began when he went to work in a chemical plant in 1950. As he recently told an interviewer, "Worker safety at that time was only understood in terms of physical trauma: getting hit with something, falling from something or getting your hand stuck in something. Chemical hazards weren't part of our consciousness."

By the mid-1960s, Mr. Mazzocchi and others in what was then the Gas, Coke and Chemical Workers began to push for a federal worker safety law. Beginning in 1967, he organized a coast-to-coast series of workers' conferences on hazardous job conditions. He then helped to bring workers to Washington to testify and to lobby, paving the way for passage of the Occupational Safety and Health Act in 1970.

Safety and health activists say Mr. Mazzocchi was not only the intellectual father of the "right to know" and "right to act" movements, he coined the phrases that identify them. His position, which is now partly codified in federal regulations and many local laws, was that workers and anyone else who might be exposed to a chemical have the right to know what the hazard is and how to protect themselves from it. People exposed should also have a right to act to prevent exposure or eliminate the hazard completely.