Document 15N3yxkdaR81L0KG0BEqvovBa

03/10/2005 The Measurement of the Exposure of Workers to Respirable Crystalline Silica (RCS) Peter Stacey Health and Safety Laboratory Sheffield S3 7HQ HEA^^^tfEIY LABORATORY Topics National and international pressure to reduce the occupational exposure limits for Respirable Crystalline Silica (RCS) The work of the organisation for standardisation working group ISO/TC146/SC2/WG 7 -Air quality/workplace air/silica HEA^^^tfEIY LABORATORY Occupational Exposure to Respirable Crystalline Silica Crystalline silica is abundant and used in a wide range of materials Workers working with silica containing materials represent the largest potentially exposed groups - 1.7 million workers in the USA - 100,000 workers in the UK HEALTH & SAFETY LABORATORY Silica Exposure HEALTH & SAFETY LABORATORY Selection of current occupational exposure standards mg.m-3 County Germany Austria Netherlands Australia France Belgium Italy Ireland Quartz 0.15 0.15 0.075 0.1 0.1 0.1 0.05 0.05 Cristobalite 0.15 0.15 0.075 0.05 0.05 0.05 0.05 0.05 HEALTH ASAFETY LABORATORY 1 03/10/2005 Legislative Position in UK Control of Substances Hazardous to Health Regulations (COSHH) Workplace Exposure Limit (WEL) 0.3 mg.m-3 (8 hours TWA) HSE are considering reducing to 0.1 or 0.05 mg.m-3 Medical surveillance recommended at 0.075 mg/m3 HEALTH & SAFETY LABORATORY Percentage After 1 m u_ o i. Risk of Silicosis 25 o^ 20 152 0.04 0.08 0.12 0.16 0.2 0.24 0.28 xposure to Air Concentration of RCS for 15 Years -3 mg.m HEALTH A SAFETY LABORATORY Goals Elimination of silicosis - Despite improvements a persistent levels remains In Europe - it is proposed that to eliminate silicosis the occupational exposure standard should be below 0.05 mg.irr3 HEALTH a WOT LABORATORY Silica Analysis Methods . Gravimetric analysis for respirable dust X-ray diffraction - Direct on-filter analysis - Redeposition onto silver filters Infrared - Direct on-filter analysis - Redeposition onto filter - KBr Pellet HEALTH A SAFETY LABORATORY Infrared spectra A = Amorphous C = Cristobalite K = Kaolin (clay) Q = Quartz Source: Madsen, et.al. Appl Occ. Environ. Hyg. 10(12): _____________________ 991-1002 (1995)________ ____________________iMaumn Methods in SA NIOSH 7602 - Infrared KBr disc (6 laboratories) NIOSH 7500 - X-ray diffraction - deposition (1 laboratory) MDHS 101 - X-ray diffraction and infrared - Direct on air sample filter analysis (1 laboratory) HEALTH A SAFETY LABORATORY 2 03/10/2005 Limits of detection for XRD Source NIOSH 7500 NIOSH 7602 MDHS 101 Method Limit Re-deposition Re-deposition 5 pg 5 pg Direct analysis 3-6 pg HEALTH & SAFETY LABORATORY Quality of Measurement Primary instrument to ensure compliance with the law To enforce the law the precision of measurement must be sufficiently reliable - To reduce the incidence of dispute -To avoid incorrect interpretation HEALTH & SAFETY LABORATORY Standards for Analytical Performance EN482 - Uncertainty of occupational hygiene measurements including bias and sampling Within 30 % (0.5 - 2 the exposure limit) NIOSH - Accuracy including sampling Within 25 % HEALTH & SAFETY LABORATORY Precision between laboratories in WASP Mass Measured On-Filter . Exposure Limit mg/m3 0.3 8- hour sample Mg 316 4 - hour sample ________ MS 156 ' 0.1 106 53 . , 0.05 53 26 0.025 26 13 WASP Analytical Range 60 - 460 pg HEALTH & AFETY Predicted Between Laboratory Precision 3 03/10/2005 The Challenge Some laboratories are not likely to achieve the requirements of EN482 - especially if interferences are present To measure samples of 4 hours duration or less from an air concentration of 0.05 mg.irr3 HEALTH X SAFER' LABORATORY ISO Working Group TC146/SC2/WG7 Silica Guidance to ensure the quality of respirable crystalline silica measurements - Targeted at analyst . Underdevelopment . . Guidance for the selection of methods ' ' . - Targeted at end those that commission work ' - May include advice about the interpretation of results ..... Not yet proposed as a new work item . HEALTH & SAFETY LABORATORY Ensuring quality Comparing the crystalline content and particle size distribution of the calibration standard against a certified material Encouraging the measurement of a significant number of calibration standards Applying recovery and quality control checks and correcting for differences with the expected result Applying instrumental checks for drift, peak and resolution. Interpretation HEALTH & SAFETY LABORATORY Proficiency testing Analysis at low levels involves interpretation - Interferences .' . - Peak shape - Movement of peak position ' . This adds to the differences of results between . laboratories . Some countries may demand participation in PT schemes and/or accreditation - 'The asbestos precedent'-why not for other disabling lung diseases? HEALTH & SAFETY LABORATORY Conclusion Precision of measurement is not sufficient to reliably measure at 0.05 mg.irr3 A multi disciplined approach is needed to help eliminate silicosis HEA^^^tfETY LABORATORY 4 Want to help improve silica measurement ? Contact your standards organisation and encourage their participation in our ISO working group - TC146/SC2/WG7 - Air Quality\Workplace Air\Silica HEALTH & SAFETY LABORATORY 03/10/2005 5