Book excerpt: Hazards of the Job explores the roots of modern environmentalism in the early-twentieth-century United States. It was in the workplace of this era, argues Christopher Sellers, that our contemporary understanding of environmental health dangers first took shape. At the crossroads where medicine and science met business, labor, and the state, industrial hygiene became a crucible for molding midcentury notions of corporate interest and professional disinterest as well as environmental concepts of the 'normal' and the 'natural.' The evolution of industrial hygiene illuminates how powerfully battles over knowledge and objectivity could reverberate in American society: new ways of establishing cause and effect begat new predicaments in medicine, law, economics, politics, and ethics, even as they enhanced the potential for environmental control. From the 1910s through the 1930s, as Sellers shows, industrial hygiene investigators fashioned a professional culture that gained the confidence of corporations, unions, and a broader public. As the hygienists moved beyond the workplace, this microenvironment prefigured their understanding of the environment at large. Transforming themselves into linchpins of science-based production and modern consumerism, they also laid the groundwork for many controversies to come.