Rise in soil fluorides from man-made sources has peaked concern about harm to human health. Fluoride in the earth's crust from natural volcanic or oceanic emissions and rock or mineral erosion created soil concentrations that increased with depth. In contrast, anthropogenic fluoride caused soil levels that decreased with depth and distance from industry. Starting in the 1700's, fluoride-containing minerals were used as flux in smelting operations, to aid aluminum production and supply calcium and phosphorus. By the 1940's, man-made fluorides related to pesticides, refrigerants, aerosols, lubricants, plastics, medicines and bomb-grade uranium plus aluminum and fertilizers. As man-made fluoride sources increased, so did worry over health effects. Agricultural studies found that farm animals were hurt by high fluoride levels in feed rations, and in 1943-44, medical and dental associations warned that fluorides were "protoplasmic poisons," enzyme inhibitors, goitrogenic and disturbed bone and tooth development. Yet, the late 1940's in the United States saw concern for fluoride poisoning virtually disappear. Fluoridation of drinking water began, as did the Manhattan Project, a highly classified military program that later produced the first atomic bomb. Manhattan Project workers handled fluorides daily, but death and injury details were kept secret for national security reasons. Data pertinent to setting occupational standards and settling injury claims were hidden. Fear of legal challenges prompted fluoride industries to continue laboratory research into the 1960's, but important results were still not published. Recently, Manhattan Project reports and unpublished industry data were unveiled, and current cases of occupational injury from fluorides are being documented. Laboratory studies have demonstrated that fluoride interferes with cell receptor function, explaining its potential toxic mechanisms. As the "rare" label on chronic fluoride poisoning disintegrates in the United States, the game of deflecting blame must be replaced with a more reasonable approach to controlling the mounting fluoride problem.