Right-to-know policies and related market-oriented occupational health policies require an institutionalized means through which workers can interpret and act on information about quality differences among jobs. In principle, labor unions could play this role. However, union coverage has been declining since the 1950s, and the decline has accelerated in recent years. This paper documents the growth in occupational health and safety activities in unionized workplaces from 1957 to 1987 and the decline in union representation in hazardous workplaces from 1971 to 1986. It also analyzes the relationship between right-to-know and right-to-refuse-hazardous-work guarantees under industrial relations and occupational health law.