Carcinogenesis studies of crocidolite @entity1355 were conducted with male and female F344/ @entity35 . This form of @entity1355 was administered at a concentration of 1% in pelleted diet for the lifetime of the @entity35 , starting with the dams of the study animals. The studies were started in January 1978 and ended in December 1980. Group sizes were 118 for male and female controls and 250 for male and female crocidolite @entity1355 -exposed @entity35 . The offspring from mothers exposed to crocidolite @entity1355 and the controls were similar in size at birth but were slightly smaller at weaning and remained so throughout their life. Feed consumption and survival were comparable in the exposed and control groups. No overt @entity137 was observed in the crocidolite @entity1355 -exposed animals. There was an elevated (P<0.05) incidence of thyroid gland C-cell @entity652 (control, 4/117, 3%, vs. exposed, 23/250, 9%) and of @entity259 (12/117, 10%, vs. 46/250, 18%) in crocidolite @entity1355 -exposed female @entity35 relative to concurrent controls. Because these control incidences were low relative to control incidences observed in other contemporary studies at this laboratory (21% for @entity259 ), this slight increase was not regarded as being biologically important. The data, documents, and pathology materials from the lifetime studies of @entity17110 @entity1355 have been audited. The audit findings show that the conduct of these studies is documented adequately and support the data and results presented in this Technical Report. Conclusions: Under the conditions of these feed studies, crocidolite @entity1355 was not overtly toxic and did not cause a carcinogenic response when ingested at a concentration of 1% in the diet by male and female F344/ @entity35 for their lifetime. Levels of Evidence of Carcinogenicity: Male @entity35 : Negative Female @entity35 : Negative

NTP Toxicology and Carcinogenesis Studies of @entity17110 (CAS No. 12001-28-4) In F344/ XXXX (Feed Studies).

@entity137 :: ('MESH:D064420', 'Disease') :: ['toxicity'] @entity17110 :: ('MESH:D017638', 'Chemical') :: ['crocidolite'] @entity35 :: ('10116', 'Species') :: ['N rats', 'Rats', 'rats'] @entity652 :: ('MESH:D000236', 'Disease') :: ['adenomas'] @entity259 :: ('MESH:D013964', 'Disease') :: ['thyroid gland C-cell carcinomas', 'thyroid gland C-cell tumors'] @entity1355 :: ('MESH:D001195', 'Disease') :: ['asbestos']
@entity35 :: (10116,Species) :: ['N Rats']
