Document rBMDjOw15YyMm3YN55Nx9zR7r

FILE NAME: Asbestos Textile Product Use (ATPU) DATE: 1971 DOC#: ATPU006 DOCUMENT DESCRIPTION: Journal, Letter to the Editor - Letter from K.P.S. Lumley RE "Asbestos Dust Levels Inside Firefighting Helmets with Chrysotile Asbestos Covers" 'SSSSBjlSSBSmSmm Ann. Occup. Hyg. Vo!. 14. pp. 285-286. Pergamon Press 1971. Printed in Great Britain LETTER TO THE EDITOR Asbestos dust levels inside firefighting helmets with chrysotiie asbestos covers Sir, Attention has been drawn by Bamber and Butterworth (1970) to a possible asbestos hazard caused by wearing asbestos protective clothing. Naval firefighting teams wear firefighting helmets which have chrysotiie asbestos covers. Since the helmet completely encloses the head and shoulders it seemed possible that the wearer might be exposed to harmful levels of asbestos dust. Tests were therefore made to assess the dust levels which are likely to arise in the breathing zones of the wearers of these helmets. Three helmets were tested. The first was a new helmet with an unlined chrysotiie asbestos cover, the surface of which seemed to contain loose fibres. The second helmet was identical to the first except that it had been laundered several times and its appearance suggested that most of the loose fibres had been removed by washing. The third helmet was covered with asbestos cloth aluminised on its inner and outer surfaces, and it appeared least likely to liberate asbestos dust. A subject protected by an approved dust filter respirator wore each helmet for twenty-five min. Dust samples were collected inside each helmet in the breathing zone of the wearer. The samples were collected on millipore membrane filters, 37 mm dia. and pore size 0.8 urn, using a long running Casella Type C personal sampler at 3 1/min. The method of preparing and counting the samples was that described by Holmes (1965) using a light microscope under phase contrast conditions at X400 magnification. The dust levels recorded for each helmet are shown in the Table. The figures Type of helmet New helmet with unlined asbestos cloth cover Old helmet with unlined asbestos cloth cover Helmet with aluminised asbestos cover Dust'concentration (fibres/cms) 2-30 Sampling period (min) 22-4 1-38 20-6 0 20-5 suggest that asbestos dust levels encountered by the wearers of helmets with unlined asbestos covers are likely to be close to the tentative threshold level of 2 fibres,enr' for chrysotiie adopted by HM F actory Inspectorate (1969). This value is based 285 earSJ*i 286 Letter to the Editor M l. O CCU P. / on the concept that there is probably a 1 per cent risk of developing asbestosis with 100 fibre yr/cms of asbestos exposure. The time weighted average concentrations of asbestos dust associated with wearing firefighting helmets will be lower than those found in these tests because the helmets are not worn continuously. The risk from asbestos dust is very small and is far outweighed by the protection against fire pro vided by the helmets. The use of aluminised asbestos cloth covered firefighting helmets is to be recommended because no airborne asbestos associated with this type of helmet was detected in these tests. I am grateful to Mr. D . Sweet for carrying ouf the dust sampling and to the Medical D irector General (Naval) for permission to publish this letter. The RAt Medical Research Unit No. 1 East Avenue HM Dockyard (South) Devonport PL\ 4RU K. P. S. Lumley Protectio about the and advi< the Unite communi REFERENCES Bamber, H. A. and Butterworth, R. (1970) Ann. occup. Hyg. 13, 77. D epartment of E mployment and P roductivity, HM F actory Inspectorate (1969) Technical provides Service, j place of a r D ata Note 13 Standards fo r Asbestos Dust Concentration fo r Use With the Asbestos Regulations radiologi< 33 1969, HMSO London. These dir H olmes, S. (1965) Ann. N Y Acad. Sei. 132, 288. TheC and the 1 Sir Char! Professoi McLean Director and Mr. er - Mr. L. C Headqua Glasgow. Protectio Centres t Furth Protectio Assistant Radiolog EXPOS In 1960 microwa Relating mendatic human b