Exposure to Respirable Crystalline Silica in the GB Brick Manufacturing and Stone Working Industries.

The aim of this work was to benchmark respirable crystalline silica (RCS) exposures in brick manufacturing and stone working sectors in Great Britain. This will contribute to a larger programme of work, which will be used to better understand the role of health surveillance in preventing the development of further cases of silicosis and chronic obstructive pulmonary disease. This work was undertaken by means of site visits to measure RCS and respirable dust exposures and assess exposure controls. In addition, historic exposure reports from the sites were collated to allow assessment of exposure trends. The survey, which was conducted in 20 sites (10 from each sector), found that in both sectors over 20% of the measured exposures exceeded the UK RCS 8-hour time-weighted averaged workplace exposure limit (WEL) of 0.1 mg/m3. In the stone sector over 40% of the 8 h time-weighted average RCS exposures were above the RCS WEL compared to 20% in the brick manufacturing sector. In the stone sector, 61% of RCS exposures where water suppression was present exceeded the RCS WEL. This indicates that a variety of exposure controls will be required to control RCS exposures, including respiratory protective equipment (RPE). The use of RPE in situations where RCS exposure exceeded the RCS WEL was more prevalent in stone working than in the brick sector. There were differences associated with RPE and the use of other exposure controls in both sectors. The contextual information in historic consultant's exposure reports was generally limited, with exposure controls either not mentioned or not fully described. This affects the usefulness of exposure monitoring to dutyholders. This work will provide information on exposures allowing construction of lifetime exposure estimates for use in analysis of the health effects data. A second survey to the sites is planned to determine how exposures have altered.

Exposure to Diisocyanates and Their Corresponding Diamines in Seven Different Workplaces.

Biological monitoring to assess exposure to diisocyanates in the workplace is becoming increasingly widespread due to its relative ease of use and ability to look at all exposure routes. Currently, biological monitoring measures the corresponding isocyanate-derived diamine in urine, after hydrolysis. Because of this, any exposure to the diamines themselves released during the industrial process could confound the assessment of diisocyanate exposure. This paper reports an initial assessment of the extent of diamine formation and exposure during different processes involving diisocyanates including casting, grouting, core making, spray painting, foam blowing, and floor screeding. Air monitoring and glove analysis were conducted for both the relevant diisocyanate (measured as total NCO) and its corresponding diamine; urine samples were analysed (after hydrolysis) for the isocyanate-derived diamine. Processes that generated aerosols (as demonstrated by impinger analysis) such as spray painting and foam blowing were associated with the detection of diamines. Those processes that did not generate aerosols (casting, grouting, core making, and screeding) had no diamines detected, either in air or on gloves. In spray-painting tasks, diamines were a minor component (<15%) of the ambient concentration whereas in the foam blowing processes, where water is added to the process, diamine generation is more marked (up to eight times the airborne NCO concentration). Some non-aerosol processes gave rise to substantial diamine levels in urine (in exceedance of international guidance values, >5 µmol mol-1 creatinine) despite airborne levels being well within occupational exposure limits (20 µg m-3 total NCO in Great Britain); measurement data and statistical modelling indicated that skin absorption was the most likely exposure route. Foam blowing exposures were more complex, but urinary levels were greater than those expected from diisocyanate inhalation alone (measured as total NCO). This study provides evidence that biological monitoring for diisocyanates based on measuring the corresponding diamine in urine is valid, although any co-exposure to diamines themselves should be considered when interpreting results. It also demonstrates the potential for substantial skin absorption of diisocyanates in certain processes such as floor screeding and foam production.

Dehydroabietic acid as a biomarker for exposure to colophony.

BACKGROUND: Colophony (rosin) is a natural product derived from the resin of coniferous trees with many industrial applications including soldering fluxes. Exposure to colophony fume through soldering is one of the leading causes of occupational asthma in the UK. AIMS: To assess occupational exposure to colophony from solder fume at selected workplaces in the UK and to investigate the use of dehydroabietic acid (DHA) as a biomarker of exposure. METHODS: Six companies in the UK electronics industry were visited and occupational hygiene assessments of extent and control of exposure to rosin-based solder flux fume were undertaken. Urine samples were analysed for one of the main constituents of rosin, DHA. RESULTS: There was a positive linear relationship between airborne exposure to solder fume and urinary DHA level. The levels of urinary DHA measured in UK workers were significantly lower than those previously measured in African workers because of the use of appropriate exposure control measures, for example, local exhaust ventilation with fixed ducting and flexible hose, tip extraction, etc. It is suggested that good occupational hygiene practice would result in urinary DHA levels of <3 micromol/mol creatinine in a post-shift urine sample. CONCLUSIONS: Urinary DHA is a valid biomarker of exposure to colophony in solder fume. Further work on the excretion kinetics of urinary DHA, the possibility of skin absorption and further occupational hygiene surveys would be beneficial.