During the 1960s, several highly visible environmental health issues converged, simultaneously creating greater awareness in the general public of their surroundings and heightening their concern over exposure to the ever-increasing number of man-made chemicals released into the environment. The breadth and intensity of this concern was exemplified by the establishment of an international ‘‘Earth Day’’ in 1970. Shortly thereafter, two other events, the ‘‘War on Cancer’’ initiated in 1971 and the discovery of human toxicity associated with the Love Canal chemical waste site in 1977, contributed to the growing interest in the effects of environmental chemicals on genes and chromosomes.