Document 2NvLpqNXm2gX0w7K0wrzrQL1b

( ncrocnod to peso 200 nuK.h. Since the matorial do rocelved contained many long fibers, it was ground In a otool ball mill to roduoe prac oally all the particles to 3 aicrona or loan In. size. Yihen uood alone In tho standard duatlng machi.no, this finely-ground asbostos tended to paok in the hoppor and It became nooesoary to mix ouo volume of the un- ground materiel with throo volumoa of the ground to gonerato a aatia- faotory dust cloud. It is portinont to mention horo that tho addition of tho amall quantity of unground asbestos was unfortunato bccauao it con fused tho Interpretation of results. The composition of tho short-fiber aobostoa as receivod & by tho choraioal and petrographic analyses given In tables 2 and 3. Sam ples taken before and after grinding yielded about the name vuluca on analysis. Indicating thut there hub no contamination from tho mill or nont, tho llght-flold oounto for atmoaphorio aarcples colloctad inside the animal aagos vlth the inpinger apparatus ranging from 03 million to 182 million. Tho average of counts was 130 million for tho first year of tho experiment, 134 million for tho aocond year and 140 million for the third year. Slzo-frc.quoncy moaouremento of air-floated dust from lncldo tho oagoa at a magnification of 1300X revealed a groat preponderance of fino partlolos, nearly 20 por cont of tho particlos aoen bolng amallor than 3 It v-'j:: ostlnatod that approximately-1 per cent microns. :Apcprn3:Axaafcelyx;x:prrxxunrfc of tho dunt was in tho fonn of fibers greator than 10 microns in longth. Four opeolon of animala - gulnoa pigs, white rats, oato and rabbits were used in this experiment. The roaulta of the dust oxpooure, aunsnar-- ited in table 6, arc pronontod in greater detail bolow. -1G-