Conference Publication Details
Mandatory Fields
Healy, C., Coggins, A.M., Van Tongeren, M., Mac Calman, L., McGowan, P.
x2012 7th International Conference on the Science of Exposure Assessment
Study of respirable crystalline silica exposures among stone workers involved in restoration work
2012
July
Unpublished
1
()
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Exposure assessment
Determinants of respirable crystalline silica (RCS) exposures among stoneworkers involved in stone restoration work. Catherine B. Healy1, Marie A. Coggins1, Martie Van Tongeren2, Laura MacCalman2, Ken Moore3 1School of Physics, National University of Ireland, Galway, Galway, Ireland, 2Institute of Occupational Medicine, UK, 3 Office of Public Works, Jonathan Swift Street, Trim, Co Meath, Ireland. † Background † Crystalline silica occurs as a significant component of many traditional materials used in restoration stonework such as sandstone and other commonly used building materials. When these materials are processed through activities such as grinding and cutting, particulates containing varying quantities of RCS are released into the occupational environment. Exposure to dust containing RCS can result in the development of silicosis, an irreversible debilitating lung disease and may also lead to the development of lung cancer. The aim of this research is to i) quantify the respirable crystalline silica exposure of a group of stoneworkers involved in the restoration and maintenance of heritage properties in Ireland and ii) to identify the main determinants of exposure among this occupational group. These results will facilitate the development of technical interventions in areas of high exposure risk within this occupational group. † Methods An exposure assessment has been carried out over a 3 year period amongst a group of stonemasons and stone cutters involved in the restoration and maintenance of heritage properties. Personal air samples (n=113) with corresponding contextual information in various stone restoration jobs were collected. Similar exposure groups (SEGs) were formed based on tasks and materials used. Descriptive statistics were generated for the SEGs. Exposure data were analysed using multiple linear regression analysis to identify significant determinants of exposure and to investigate their contribution to the individualís mean exposure. Mixed effects models were used to identify determinants of exposure and to evaluate the between- and within-worker variability in exposure among stoneworkers and variability associated with depots. Results Currently, 113 personal exposure samples have been collected. The RCS exposure measurements ranged from 0.02 mg/m3- 2.98 mg/m3 (8hr-TWA). In many cases worker exposure to RCS exceeded the occupational exposure limit value (OELV) of 0.1mg/m3 (8hr- TWA). Multiple linear regression identified a significant relationship between RCS (8hr- TWA) exposure and different materials, tasks and level of enclosure (P <0.001). Task contributed the most to individual mean RCS exposure (R2 = 43.2, P <.001) where exposure was higher for the tasks of shaping and dry cutting. Task was followed by material (R2 = 36.8, P <0.001) where RCS was higher for tasks involving sandstone. The 95% Upper Confidence Limit of the arithmetic mean (UCL1,95% ) exposure for both tasks of cutting and shaping of sandstone was found to be 1.24 mg/m3 which is above the occupational exposure limit value of 0.1mg/m3 and is deemed unacceptable. In combination, task, material and level of enclosure together accounted for 72% of the variation in RCS exposure. Results from the mixed effects models also revealed that task and material are strong predictors of RCS exposure within this occupational group. The results indicate that the tasks of dry cutting and shaping sandstone are predictors of increased exposure to RCS dust. Task such as wet cutting and repointing and working with materials such as limestone, lime mortar and granite were associated with decreased exposure to RCS dust. The between depot and between worker within depot variance components were reduced by 64% from 1.096 in the random effects model to 0.39 in the mixed effects model and 86% from 1.125 in the random effects model to 0.15 in the mixed effects model respectively when task and material were taken into account. These results suggest that the differences in mean exposures between depots are more prominent than differences in mean exposures between workers within depots Tools and materials which create excessive exposure to RCS dust have been targeted for control and a technical intervention has commenced in order to reduce exposure to as low as practically possible.† Post intervention exposure data and results from the mixed effects models will be presented. † Conclusions Initial analysis of the exposure data collected to date shows that workers can be regularly over exposed to RCS dust when working with sandstone, as compared to the OELV. Results show that task and material are strong predictors of RCS exposure within the occupational group restoration stoneworkers. † † †
Commissioners for Public Works
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