Document pmB0302oJJRrjJK8GK10oVZqa

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 (1968) 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 ftbrcs/cm* should not be exceeded during any period of 10 rein, i.e. we might regard 12 fibres/cm * as a ceiling 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 mot "biologically -actirej-would be -very -difftcutrwith -a -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, where 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, 1969. 23 e SCF-FA-6346