Document b50oRVBkG0y5Zz2656DpKxaa3

Dr. 3, Holmes Health Hasarda associated with the "Limpet1 Asbestos-Cement Spray Proeesa Three reports hara now baan issued to data on this subject. Tha following la a briaf resume of tha aontraata of eaeh:- 1 J. . Robarta Limited "Limpet" Aabaatoa Cement Sprar Haohlna J.S.Evans 17.3.50. Mr. Evenk work was carried out in Oatober, 19A9 uaing a Thermal Precipitator or unknown Bake, atrapped in aooa oaaea, to tV* chart of tha spray-operator. Sampling waa carried out (36 ^inuta taat run a) In a aaall room, tha asbestos-assent being auppliad in a continuous Banner. Tha author comparea tha resulta with those obtained in tha Spinning Hoorn at J .If.Roberts in 1938 and refers to. a Report on a Conference between Employers and Inspectors , concerning Methods of suppressing Dust in Tactile Factories published in 1931 This apparently suggests a "dust datum" IstsI as that given by "conditions arising from flyer spinning carried on without exhaust under good general conditions". From his results, Mr. Brans concludes that after pre-damping of the spray material in the opening machine, the exposure to asbestos fibre is approximately "that of a good flyer spinning room" and for material pre-damped in a drum the exposure (concentration) is less than "that in a flyer spinning room". ' 2. Turner Brothers Asbestos Co. Ltd. "An investigation of tha Health Hasard associated with the "Limpet" asbestos-cement process" W.S.ffrixht 17.10.40. This report details preliminary work carried out by Phvsics Research Department at J.W.Roberts Ltd. (in the Spray booth) and two work sites (including S.S. Empress of Canada). The sampling instrument employed for this investigation was the Casella Thermal Precipitator, the suitability of which was queried for use in rapidly changing atmospheres. High dust con centrations were reoorded at Horwioh and at one of the working sites. In most instances, the effect of "damping" was disappointing. 3. Turner Brothers Asbestos Co. Ltd."An assessment of the concen tration of airborne dust resulting from the application of "Limpet" Aabcatoa-^emcnt Sorar. R,Sykes 12.7.61. This report gives an account of preliminary work oarried out continued: -.v -2- In the Spmy booth at Horwioh using tha "Long Running Thermal Precipitator" as a ssapling unit. Ilia rasuits, particularly using "undamped" aatarial ara rathar variable, but tha advantageous effect of daaplng is clearly indiaatad. Tha rasuits ara conpars4 with thosa obtainad froa normal asbsstos taxtila manufacturing processes, tha lattar baing appreciably lowar, in aagnituda, than thosa rasulting froa tha "daapad" spray proasss. in apparent "shift" in sisa distributions is indioatad by tha additional use of "Calgon" to tha danping madiua. Discussion of the aboTa Tha evidence, to date, is somewhat eonflieting. Reports Rif. ` 4 3 abore agree on tha affect of "daaping" but disagree oi. the assassaant of tha overall dust level. Ur. Evans claims ha was readily able to differentiate botwaan asbestos and oeaant particles a problem not overcome by Kr. Wright whose report tabulates "overall counts" (i.a. asbestos * cement particles). Incidentally Ur. Evans quotas madiua sisas of cement partiolas that ara significantly lower than a recent evaluation carried out by our department. Ur. Wright's results led him to doubt tha suitability of the Casella Thermal Precipitator, but it is interesting to note the different sise distribution, after damping, of the blue fibre. This tendency has been "echoed" in the tests carried out with the Long Running Thermal Precipitator. (Ref. 3) The varikbllity experienced in most of the tests oonduoted to date, is perhaps not so surprising when one considers the large number of faotors influencing the process of assessment. The following is not intended to be oomplete, but relevant "variables" can include (a) The nature of the Asbestos-Cement Spray material. (b) The nature of the surfaee to be coated. (e) Type of spray equipment in use and operating conditions. (d) Damping techniques (if any) adopted. (e) Uanipulatlon and orientation of equipment. (f) Site environment, (Humidity). (g) Type and working donditions of dust-sampling equipment; position of same relative to the working tree. continued: I* *w I 3- In tha writara opinion, raprodusibla and sora conelualra rajulti can only ba axpaolad by tha oontrol ud attainment of knowledge of the influence of tha above fastora. It ia with great interact, tharafora, that on* haara of tha propoaed oonatruotion of a teat tunnel'- In order to carry out sore raaliatic ipii.,0. iu addition to thia, I oomidar periodic. riaita to Spraying aitaa with auitable duat aaapliag equipment would probably prorida data of conaiderable ralua. Ia v