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Mr. Kevin T. Haroff Page 7 0 0 In addition to the concern for free crystalline silica, is the concern regarding amorphous silica. in 1987, the IARC, in its "monograph" for silica, stated that "since amorphous silica is less fibrogenic than crystalline silica, silicosis has rarely been observed after exposure to pure amorphous silica" (p93) . IARC concluded that there was inadequate evidence for the carcinogenicity of amorphous silica to humans or experimental animals (p109) . It did state, however, that experimental evidence indicate that, ". . .amorphous silica can be fibrogenic, but is less so than pure crystalline samples" (p85) . There is evidence that in experimental systems, amorphous silica elicits in vitro cytotoxic responses (Davies, 1981) , in vivo immune responses (Burrell, 1981) , inflammatory responses (Hemenway, et al. , 1986) , and nodular fibrosis, along with significant alterations in respiratory function (troth, et al. , 1981) . Recent evidence suggests that man-made mineral fibers made of amorphous silica such as glass wool and mineral wool are associated with increased risk of mortality from lung cancer and chronic pulmonary disease [Enterline and Marsh (1982) , Saracci and Simonato (1982) , Weil, et al. , (1983) , . NIOSH, in reports dated December 1986 (Report Number 92.5.5) and December 1988 (Interim Report No. 1; HETA 88-119) , evaluated potential health affects from the breathing of sugar cane smoke containing amorphous silica particles. In Report Number 92.5.5, NIOSH stated that ". . .although the health effects of inhaling amorphous silica fibers are unknown. . . , the similarity of these fibers with other fibers which are known to cause serious health effects is reason for concern." (p.9) Although not enough scientific research has been conducted to conclusively establish amorphous silica as a causative agent for silicosis or pneumoconiosis, the questions and suspicions revolving around amorphous silica warrant a conservative approach by the Department regarding this waste or any waste containing amorphous silica. Based on data provided in Wadham's March 9, 1990 report by ENSR, the concentration of respirable amorphous silica in the ash is 0.393 percent (from analytical reports by RJ Lee) . The information obtained from both AIHL and Wadham shows that particles of respirable size do exist in the Wadham ash. Although the proportion of particles less than five µm in the samples appears to be relatively small (less than one percent by weight) , other information provided by Wadham raises concern. In the November 22, 1989 application, on page 5 of the Appendix, the following was stated: "It should be noted that the sieve test involves a certain amount of mechanical shaking that can break up the test material into finer particles, thus tending to