Abstracts: Health/biological Effects Fluoride Poisoning: a Puzzle with Hidden Pieces

s Fluoride 38(4)328–334 November 2005 Abstracts 328 328 ABSTRACTS: HEALTH/BIOLOGICAL EFFECTSS: HEALTH/BIOLOGICAL EFFECTS FLUORIDE POISONING: A PUZZLE WITH HIDDEN PIECES Prior to World War II, Kaj Roholm’s monumental 1937 study of fluorine intoxication, which centered on workers in a Danish cryolite factory, was the most reliable primary source of data on the uses and biological effects of fluorides. With the onset of WWII, production of fluorine compounds increased dramatically to meet warfare needs, especially for the Manhattan Project engaged in producing the world’s first atomic bombs. Large quantities of fluorine were required to prepare uranium hexafluoride (UF6, bp 56oC) used for separating the fissile uranium 235 isotope by multi-stage diffusion from the much more abundant non-fissile uranium 238 isotope. Wartime requirements for security kept most information about such fluoride use and its health effects secret during that period and for a long time afterwards. As a consequence, critical industry data regarding harm from chronically inhaled fluoride remained publicly unavailable for decades. However, recent access to unpublished reports reveals three examples of data mishandling that disguise the need for more stringent occupational standards for fluorine and for particulate and gaseous fluorides. These newly available reports of injury to workers handling fluoride chemicals reveal that unjustifiable reporting of lower numbers of actual injuries and disabilities in the process of publication shifted concern from respiratory to mineralized tissue damage. Selective editing and omission of data promoted bias for claiming that fluoride reduces caries without detrimental effects. A published 1949 report described two serious accidents leading to acute fluoride poisoning of Manhattan Project workers handling UF6. In 1997, the Department of Energy declassified a 1946 unpublished report about workers handling UF6 at a plant involved in the Manhattan Project. This 1946 document showed that the 1949 report was incomplete and misleading about the hazards of handling HF, UF6, and fluorine. Dental conditions of these workers who were continuously exposed to hydrofluoric acid were published in the Journal of the American Dental Association (JADA) in 1948. These employees at a chemical company worked in an atmosphere so contaminated with HF that it etched window glass and eyeglass lenses, dehydrated animate surfaces, killed microorganisms, disintegrated shoe leather, and repelled animals from the vicinity. Despite such an environment, the 1948 JADA article reported: “On the whole, employees working with the hydrofluoric acid appeared to be unusually healthy men, physically sound, and comparatively immune to colds, infections and other common illnesses.” The later declassified unpublished reports, however, gave a more balanced picture than the JADA article. Industry’s failure to publish an important industry-funded laboratory study buried knowledge of low thresholds for fluoride-induced lung disease. This study reported deleterious consequences of the breathing of calcium fluoride dust by dogs. The damage to the lungs and lymph nodes was only detected by post-mortem and microscopic examination. Data from that study are presented to clarify the doseand duration-dependent changes caused by chronic inhalation of calcium fluoride. By analysis and review of the data available from these studies, the article concludes (italics in original): “1. The occupational standard for fluorides should be reduced from 2.5 mg/m3 to 1.0 mg/m3 to fit the published and unpublished data regarding respiratory effects. . . . 2. The current threshold limit values for fluorine (1 ppm or 1.6 mg/m3) should be lowered back to the pre-1973 level (0.1 ppm) to fit the published and unpublished data. . . . 3. Respiratory disorders (e.g., potroom asthma and emphysema) and dental problems (e.g., enamel erosion, periodontal disease, and tooth loss) should be recognized as occupational risks of fluoride exposure and worthy of compensation. . . . ” Abstracts Fluoride 38(4)328–334 November 2005 Abstracts 329 329s Fluoride 38(4)328–334 November 2005 Abstracts 329 329 Author: Mullenix PJ. Correspondence: P.O. Box 753, Andover, MA 018810, USA. Email: [email protected]