Document Exvj80k5Y5kjdpdvxJmNeNQax

ffm Hft> Vol. U. iv- 2^)4. hrpn ftc0 It70. P*<au4 w Gttil louia vanuary 1770 TECHNICAL IMPLEMENTATION . ` OF THE NEW ASBESTOS REGULATIONS* S. Luxon H.M. Factory Inspectorate, Department of Employment and Productivity, Chepstow Place, Westbourne Grove, London WJ. The new Asbestos Regulations were signed by the First Secretary of State on May 13 1969, and will therefore come into operation on May 14 1970. They are based on the concept that asbestos dust must be so controlled as to be at a level which will not be liable to cause injury to health. . For the purposes of our discussion today, I believe we should take this to be a level of 2 fibres/cm* and 0'1 mg`m* for chrysotile asbestos. A fibre is taken as being 5 |i or over in length with an aspect ratio of at least 3:1. This is of course the standard proposed by the British Occupational Hygiene Society (196S) and is based on time* weighed averse: concentrations. There is a practical limit on th: time over which samples can be taken if the exercise is not to become unnecessarily cumbersome and expensive. On this basis, a sample of 4 hr duration seems a reasonable compromise. If we accept this, as a practical sampling time then the overall standard becomes 2 fibres/cm* over this four hour sampling period. We cannot, however, afford to ignore entirely peak concentrations which will occur during this period, and it seems reasonable to expect that a concentration of say 12 fibrcs/cm* should not be exceeded during any period of 10 rein, i.e. we might regard 12 fibres/cm* as a ceiiing value. It must be remembered that we arc using the fibre count not bs an absolute measure of concentration but rather as a conveniently measurable parameter to indicate the total asbestos in the air. The work leading to the formulation of the BOHS Standard referred to above related to conditions in the textile industry and not enough informa tion is yet available on the relationship between mass of asbestos and fibre counts in other industries. To further complicate the problem, it is not known what fibre sizes are biologically active and, even if this were known, appropriate elutriation (i.e. the -rejection of'material not "biologically -actinej-would "be -very difficuh'wrth n 'fibrous material such as asbestos. We, ourselves, are making both fibre counts and total mass determinations by X-ray diffraction analysis in industries, such as the motor industry, whbre degradation of the fibres may occur, resulting in a substantial change in size distribution. Hickisii and Knight (1969) have described conditions during the servicing of braking systems. The figures they have quoted are, to a large extent, reassuring in 'This paper was originally presented at a Conference on Exposure to Asbestos during Brake and CHrtch Maintenance, held at Brentwood, Essex. March, I960. , e. 23 . SCF-FA-6346 :< that they indicate that the levels likely to be found in many sections of the industry engaged in this work arc below the level of 2 fibres/cm', which is considered, in the light of past knowledge, a safe one for chrysolite asbestos. Their highest figures for the time-weighted average concentration over 4 hr, however, dearly show that over a period of 10 min we may have concentrations exceeding substantially the level of 12 fibres which are quoted above. .* 1 was interested to hear of the increasing tendency to carry out brake overitauls on a production line basis. This, dearly, must increase the exposure of particular in dividual workers, making the development of adequate precautionary measures even more important and, in this connection, I hope the devices which will be described later to-day can be improved and developed to the point where they become univer sally acceptable to the operator. Certainly we should not be blowing out brake dust, even if it contains only a few per cent of asbestos. In regard to this latter statement, perhaps i should say that work at our Industrial Hygiene laboratory confirms the .figures indicated in the previous paper. We have found that samples of dust from brake drums, when subjected to X-ray diffraction analysis, contained between 1 per cent and 3 per cent of chrysotile asbestos although the original lining material contained more than 40 per cent asbestos. There seems little doubt that this is due to the considerable thermal degradation which occurs consequent bn the high temperatures generated by friction at the interface between tlte lining and tbe drum. -' REFERENCES . Asbestos Refutations (19691 Statutory Instrument 1969 No. 690. ' Committee on Hygiene Standards. British Occupational Hygiene Society (1968) Hyjitne Standards for Chrysotile Asbestos Dust, Perjamon Press. Oxford. Hickbh. D. E. and Knight. K_ L. (1969) Ann. Oeatp. Hyf., 13,17. PO. 1ha,\ The short then T. event loss ii Hi the rt frictio Th pregn: which, The m spherit resulte drying abrasic As degrad In otht Art that te: neither condttii 1940's i asbesto; because proved Thb Clutch h-