On September 19, 2011, sixty thousand people gathered in Tokyo to protest against nuclear power and radiation pollution after reactor meltdowns at the Fukushima Daiichi Nuclear Power Plant. Their protest evoked memories of the 1960s when Japan was among the most polluted locations on the planet with hazardous levels of air, water, and ground contamination. Observers at the time described the country as a polluters' paradise and advised tourists to pack a gas mask. By the early 1970s, however, the Japanese had addressed many their thorniest pollution problems and the country possessed some of the strictest regulatory standards in theworld. In this article I analyze the activities of an influential group of natural and social scientists, the Pollution Research Committee, which spearheaded the struggle against pollution. I make two claims. First, on the positive side, the committee played a decisive role in Japan's pollution turnaround through its field research, pollution victim advocacy, and extensive international activities. But, second, the reactive victim-centered environmental agenda of the committee and other contemporary groups never developed into a preventive movement capable of identifying and scrutinizing potential forms of pollution such as radiation. The result was a nuclear blind spot in Japanese environmental activism only made visible with the Fukushima disaster of 2011.