Respirable Crystalline Silica Exposure Research Articles

A temporal evaluation of respirable crystalline silica exposure for construction tasks.

Personal air monitoring using a TSI SidePak AM520 personal aerosol monitor was performed on a northern Colorado construction site during five tasks from the OSHA Table 1: Specified Exposure Control Methods When Working With Materials Containing Crystalline Silica to estimate silica dust concentrations in real time. Photometric measurements were modified using a gravimetric correction factor and a % respirable crystalline silica adjustment. Each task was sampled once; sample time ranged from 14 min to 40 min, with a mean sample time of 27 min. The mean silica dust concentration estimates (μg/m3) (standard deviation [SD]) for the five tasks computed from the TSI SidePak AM520 respirable dust measurements were core drilling 12 μg/m3 [2.46], grinding 918 μg/m3 [1134.08], cutting with a walk-behind saw 36 μg/m3 [79.67], jackhammering 27 μg/m3 [23.24], and dowel drilling 66 μg/m3 [77.65]. Silica exposure estimates from real-time monitoring can be used to identify exposures that may be related to inadequate controls or worker behaviors that contribute to peak exposures. Respirable crystalline silica exposure estimates presented here are likely not generalizable to other construction sites or tasks.

Personal respirable dust and respirable crystalline silica exposure in two shafts and a concentrator of a Zambian copper mine.

Since the 1920s, Zambia's mining sector has experienced growth, which has increased the number of mine workers employed in the industry. Consequently, the potential for occupational exposure and prevalence of occupational diseases have also increased. Unfortunately, Zambia does not currently have legislative guidelines for workplace air monitoring and compliance. This study's objectives were to evaluate copper miners' personal exposure to respirable dust and respirable crystalline silica (RCS) and to assess workplace compliance using the European Standard for workplace air monitoring and measurement (EN689:2018). This cross-sectional study collected 100 personal respirable dust exposure samples at a Zambian copper mine in 2023. These samples were weighed using NIOSH method 0600 and analyzed for crystalline silica using Fourier transform infrared spectroscopy (KBr pellet) (NIOSH method 7602). Additionally, 253 respirable dust exposure measurements collected at the mine between 2017 and 2022 were included for comparison. The median respirable dust exposure for the 2023 exposure measurements was 0.200 mg/m3 (95th percentile 2.871 mg/m3) compared to 0.400 mg/m3 (95th percentile 3.050 mg/m3) for the historic data. The median RCS exposure was 0.012 mg/m3 (95th percentile 0.163 mg/m3). Using EN689:2018, it was found that from 15 work areas, only six work areas complied with the standard for respirable dust exposure and only seven work areas complied with the standard for RCS exposure. At the mining site, several work areas had substantial exposure to respirable dust and RCS. Therefore, management needs to prioritize these areas when implementing control measures to reduce dust exposure. For the Zambia mining industry to manage exposure to respirable dust and RCS, it is necessary to implement standardized monitoring strategies. This study has demonstrated that EN689:2018 can be used successfully to determine compliance among Zambian mining work areas.

An assessment of worker exposure to respirable dust and crystalline silica in workshops fabricating engineered stone.

There is a significant silicosis risk for workers fabricating engineered stone (ES) products containing crystalline silica. The aims of this study by SafeWork NSW were to: (i) assess current worker exposure to respirable dust (RD) and respirable crystalline silica (RCS) following a 5-y awareness and compliance program of inspections in ES workshops and (ii) to identify improvements in work practices from the available evidence base to further reduce exposures. One hundred and twenty-three personal full shift samples taken on as many workers and 34 static samples across 27 workshops fabricating ES were included in the final assessment. The exposure assessment was conducted using Casella Higgins-Dewell cyclones (Casella TSI) placed in the breathing zone of workers attached to SKC Air Check XR 5000 or SKC Chek TOUCH sampling pumps. Sample filters were sent to an ISO (2017) 17025:2017 accredited laboratory for gravimetric analysis for RD and X-Ray Diffraction (XRD) analysis to determine the amount of deposited RCS i.e. alpha-quartz and cristobalite. All workshops used wet methods of fabrication. The geometric mean (GM) of the pooled result for respirable dust (RD) was 0.09 mg/m3 TWA-8 h and 0.034 mg/m3 TWA-8 h for RCS. The highest exposed workers with a GM RCS of 0.062 mg/m3 TWA-8 h were those using pneumatic hand tools for cutting or grinding combined with polishing tasks. Workers operating semiautomated routers and edge polishers had the lowest GM RCS exposures of 0.022 mg/m3 TWA-8 h and 0.018 mg/m3 TWA-8 h respectively. Although ES workers remain exposed to RCS above the workplace exposure limit (WEL) of 0.05 mg/m 3 TWA-8 h, these results point to a very substantial reduction in exposures compared to poorly controlled dry methods of fabrication. Therefore, the wearing of respiratory protection by workers remains necessary until further control measures are more widely adopted across the entire industry e.g. reduction in the crystalline silica content of ES.

EP01.01-21 Respirable Crystalline Silica Exposure and Lung Cancer Risk: A Review of Cut-off Points

EP01.01-21 Respirable Crystalline Silica Exposure and Lung Cancer Risk: A Review of Cut-off Points

Concentrations of respirable crystalline silica and radon among tanzanite mining communities in Mererani, Tanzania.

Globally, the number of small-scale miners (SSM) is estimated to be more than 25 million, but it supports the livelihoods of around 100 million individuals. In Tanzania, the number of SSM has increased from an estimated 150,000 in 1987 to ~1.5 million in 2017. The miners are at a high risk of occupational-related health challenges. The study aimed to assess the concentrations of respirable crystalline silica (RCS) and radon among the tanzanite mining communities in Simanjiro District, Tanzania. We carried out a cross-sectional study involving the Mererani mines in Tanzania. These are underground mines comprised of informally employed miners, i.e. SSM. Concentrations of RCS and radon gas were measured in 44 study units, i.e. 22 mining pits and within 22 houses in the general community, e.g. shops in the peri-mining community. A total of 132 respirable personal dust exposure samples (PDS), 3 from each of the study units were taken, but only 66 PDS from the mining pits were analysed, as this was the main interest of this study. Radon concentration was measured by continuous monitoring throughout the working shift (and overnight for residences) using AlphaGuard monitor. The medians and comparison to the reference values, OSHA USA PEL and WHO/IARC references, were done for RCS and radon, respectively, using SPSS Ver. 27.0.0). The median time-weighted average (TWA) concentration of the RCS in the mining pits was 1.23 mg/m3. Of all 66 personal dust samples from the mining pits, 65 (98.5%) had concentrations of RCS above the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) of 0.05 mg/m3. Mining pits had a median radon concentration of 169.50 bq/m3, which is above the World Health Organization (WHO)/International Commission on Radiation Protection (ICRP) recommended reference of 100.00 bq/m3 but not above the upper reference of 300.00 bq/m3, while the community buildings had a median radon concentration of 88.00 bq/m3. Overall, 9 (20.5%) and 17 (38.6%) radon measurements were above 300.00 bq/m3 and between 100.00 and 300.00 bq/m3 references, respectively. Specifically, in the mining pits, 9 (40.9%) test results were above 300.00 bq/m3, while none of the test results in the community was above 300.00 bq/m3. The tanzanite SSM in Mererani we highly exposed to RCS, which increases the risk of pulmonary diseases, including silicosis, tuberculosis, and pulmonary malignancies. Immediate action by OSHA Tanzania should be enforcement of wearing respirators by all miners throughout the working hours. Health education programmes to the SSM must be strengthened and OSHA Tanzania should adopt the 0.05 mg/m3 PEL, and enforce other occupational health and safety measures, including regular use of dust suppression mechanisms (water spray and wet drilling) and monitoring of RCS exposures among SSM. Monitoring of radon exposure both in the mining pits and community buildings should be conducted, and mitigation measures should be implemented in areas that exceed the reference level of 100.00 bq/m3.

Silicosis, tuberculosis and silica exposure among artisanal and small-scale miners: A systematic review and modelling paper.

An estimated 44 million artisanal and small-scale miners (ASM), largely based in developing economies, face significant occupational risks for respiratory diseases which have not been reviewed. We therefore aimed to review studies that describe silicosis and tuberculosis prevalence and respirable crystalline silica (RCS) exposures among ASM and use background evidence to better understand the relationship between exposures and disease outcomes. We searched PubMed, Web of Science, Scopus and Embase for studies published before the 24th March 2023. Our primary outcome of interest was silicosis or tuberculosis among ASM. Secondary outcomes included measurements of respirable dust or silica, spirometry and prevalence of respiratory symptoms. A systematic review and narrative synthesis was performed and risk of bias assessed using the Joanna Briggs Prevalence Critical Appraisal Tool. Logistic and Poisson regression models with predefined parameters were used to estimate silicosis prevalence and tuberculosis incidence at different distributions of cumulative silica exposure. We identified 18 eligible studies that included 29,562 miners from 13 distinct populations in 10 countries. Silicosis prevalence ranged from 11 to 37%, despite four of five studies reporting an average median duration of mining of <6 years. Tuberculosis prevalence was high; microbiologically confirmed disease ranged from 1.8 to 6.1% and clinical disease 3.0 to 17%. Average RCS intensity was very high (range 0.19-89.5 mg/m3) and respiratory symptoms were common. Our modelling demonstrated decreases in cumulative RCS are associated with reductions in silicosis and tuberculosis, with greater reductions at higher mean exposures. Despite potential selection and measurement bias, prevalence of silicosis and tuberculosis were high in the studies identified in this review. Our modelling demonstrated the greatest respiratory health benefits of reducing RCS are in those with highest exposures. ASM face a high occupational respiratory disease burden which can be reduced by low-cost and effective reductions in RCS.

Determinants of respirable crystalline silica exposure in construction in western Canada.

Task-based respirable crystalline silica (RCS) exposure monitoring data was collected from construction work sites across 3 Canadian provinces: Alberta, British Columbia (BC), and Manitoba. In total 373 RCS samples were obtained from 70 worksites across 44 companies. Sampling was conducted between May 2015 and August 2020. The overall geometric mean (GM) RCS exposure was 0.045 mg/m3 (geometric standard deviation, GSD = 6.8). Alberta had the highest average exposure and the highest variability with GM of 0.060 mg/m3 (GSD = 9.3), the GM in BC was 0.044 (GSD = 4.3), and in Manitoba the GM was 0.033 (GSD = 7.0). A multivariable model was built using forward stepwise linear regression modeling. Province, task type, work environment (indoor vs. outdoor), construction material, sampling duration, and engineering control use were all statistically significant predictors of exposure level in partial F-tests (P < 0.05). Overall, the model explained 42% of the RCS concentration variability. Task type contributed most to the model's explanatory power. The task type with highest average exposure levels was demolition (GM 0.30 mg/m3, GSD 0.49). Breaking (GM 0.16 mg/m3, GSD 8.4) and grinding (GM 0.081 m/m3, GSD 7.4) also had high-exposure levels. Working outdoors was associated with exposure levels 39% lower than indoors. Exposure control measures such as local exhaust ventilation and wetting were also associated with lower exposure levels. Among construction materials, Cement, sand, and stone were associated with higher RCS exposure levels relative to the reference material, concrete. The results of this study indicate that workers in western Canada remain exposed to RCS at levels that exceed the health-based American Congress for Governmental Industrial Hygienists Threshold Limit Value of 0.025 mg/m3. Although there were some differences in exposure levels between the provinces, the determinants of exposure were similar in all 3. The overall GM RCS exposure was 0.045 mg/m3 (geometric standard deviation, GSD = 6.8). Alberta had the highest average exposure and the highest variability with GM of 0.060 mg/m3 (GSD = 9.3), the GM in BC was 0.044 (GSD = 4.3), and in Manitoba the GM was 0.033 (GSD = 7.0).

Evaluation of workplace exposure to respirable crystalline silica in road construction industries in Alberta.

Occupational exposure to respirable crystalline silica (RCS) is common for several occupations in construction, not only because of its presence in many handling materials but also in processes such as grinding and sawing. This study investigated workplace exposure to RCS as quartz in industries and occupations within road construction in Alberta through the RCS monitoring database provided by the Alberta Roadbuilders and Heavy Construction Association (ARHCA) between 2007 and 2016. Descriptive statistics were calculated for exposure-related variables, and mixed model analysis was performed to determine factors affecting the exposure levels. Results showed that the highest exposed workers were in the sand and gravel industry (GM = 45μg/m3). For worker occupations, geometric means ranged from 78μg/m3 for crusher operators to 10μg/m3 for concrete truck operators. The maximum exposure severity was 33.3 times the occupational exposure limit (OEL) for the sand and gravel and 31 times the OEL for tower operators. The results also showed the effect of seasonal variability on RCS exposure levels. The heterogeneous exposure results indicated significant room for improvement and that controls should focus more on the activity performed than the occupation to lower exposure to RCS levels in industries.

Proppant powder – the protection and the pain – lurking hazards of silicosis

Resources Safety and Health Queensland (RSHQ) is the independent regulator for safety and health in Queensland’s resources sector. The Petroleum and Gas Inspectorate (the Inspectorate) administers safety and health regulation for the petroleum and gas industry. RSHQ uses a risk-based and data-driven approach to pursue its vision of zero serious harm for resource sector workers. In Queensland, on average, there are 200 fraccing operations conducted annually on oil and gas wells. For each fraccing operation, up to 450 tonnes of proppant may be used with an estimated 16 340–23 800 tonnes pumped annually. The majority of proppant used in Queensland is refined sand and is a potential source of exposure to respirable crystalline silica (RCS) during these operations. In 2020 safe exposure levels for RCS was halved from 0.1 to 0.05 mg/m3. Exposure to levels above this threshold may increase the risk of adverse health outcomes, such as respiratory diseases including silicosis, chronic obstructive pulmonary disease and lung cancer. These diseases are progressive, and typically can take at least 10 years of prolonged exposure to develop symptoms. All silica dust-related diseases are preventable through using effective controls. This paper outlines a study on RCS exposure levels in hydraulic fracturing operations in Queensland. The objective of the study was to understand the adequacy of the current controls in place to protect workers against exposure to RCS following the reduction of the safe exposure levels.

15 Biomonitoring for Respirable Crystalline Silica: Determination of Si-Containing Particles in Exhaled Breath Condensate Using Single Particle Inductively Coupled Mass Spectrometry

Abstract Biological monitoring is a useful way of determining overall exposures to chemical substances; however, in the case of respirable crystalline silica (RCS), this has not been possible in conventional biological matrices. Previous research at HSE has shown that it was possible to detect silicon-containing particles in exhaled breath condensate (EBC) samples using single particle inductively coupled mass spectrometry (spICPMS) in a small number of quarry workers, and at that time the method had a particle size detection limit of around 300 nm. In more recent work presented here we will describe the advances in the methodology and the results from exhaled breath condensate samples collected from a range of UK workers with potential RCS exposures. Control samples were also collected for comparison. Static air/bulk samples were also collected to allow the size distribution and concentration of RCS to be determined in each workplace. The analytical advances include moving to using an ICP tandem MS for better specificity with an improved sample introduction system. This has increased the size range detection of silicon-containing particles, allowing measurements in the size range of 100-2000 nm, in a one minute acquisition. We have also standardised the EBC sampling by collecting the same volume of exhaled air (50L) from each volunteer. This improved methodology offers a viable biomonitoring method for a range of workplaces and has the potential to inform information about the efficacy of respiratory protective equipment and control measures in the workplace, complementing occupational hygiene.

Exposure to Particulate Matter and Respirable Crystalline Silica in Tunnel Construction Workers Using Tunnel Boring Machines.

This study aimed to assess the exposure to a selection of aerosols and gases in the work environment for workers performing tunnel construction using tunnel boring machines (TBMs), to identify determinants of exposure based on the information available and to calculate robust estimates of exposure using a statistical model. The focus was particulate matter (PM) and respirable crystalline silica (RCS). In addition, concentrations of nitrogen dioxide (NO2), elemental carbon (EC), and oil mist were assessed. Personal sampling was conducted from February 2017 to February 2019. PM in the thoracic and the respirable aerosol fractions was collected, and RCS was determined in the respirable aerosol fraction. Context information was collected on questionnaires. Because the workers could participate in the sampling more than once and multiple measurements were performed on the same date a mixed model was used in the analysis. Concentrations of PM and RCS are presented as estimated and measured geometric means (GMest and GMmea) and estimated arithmetic mean (AMest) in addition to the median. Measured concentrations of NO2, EC, and oil mist are presented as geometric means. A total of 290 and 289 personal samples of PM in the thoracic and respirable aerosol fractions were available for analysis, respectively. Work title/work location, type of work (production, maintenance, or a combination of the two), and date of sampling were identified as determinants of exposure. Workers in the front of the TBMs had the highest exposure to PM and RCS. The GMest of RCS exposure varied from 35 to 413 μg m-3 depending on the work title. The geometric standard deviations for measured RCS concentrations by work title ranged from 1.6 to 3.5. A total of 16 samples of NO2 and EC and 12 samples of oil mist were collected. Maximum values of NO2 and EC were 54 µg m-3 and 23 µg m-3, respectively. The maximum measured value of oil mist was 0.08 mg m-3. All TBM workers were exposed to PM and RCS. Exposure to RCS may be substantial, and workers in front of the TBM were exposed to the highest concentrations of both PM and RCS. A day-to-day variation was found, probably caused by differences in drilling activities. Preventive measures are warranted to keep the exposure to PM and consequently the exposure to RCS as low as possible to protect the health of workers in tunnel construction.

Occupational exposure to respirable crystalline silica among US metal and nonmetal miners, 2000-2019.

In metal and nonmetal (M/NM) mines in the United States, respirable crystalline silica (RCS) exposures are a recognized health hazard and a leading indicator of respiratory disease. This study describes hazardous exposures that exceed occupational exposure limits and examines patterns of hazardous RCS exposure over time among M/NM miners to better inform the need for interventions. Data for this study were obtained from the Mine Safety and Health Administration (MSHA) Open Government Initiative Portal for the years 2000-2019, examining respirable dust samples with MSHA-measured quartz concentration >1%. Descriptive statistics for RCS were analyzed for M/NM miners by year, mine type, sector, commodity, occupation, and location in a mine. This study found the overall geometric mean (GM) for personal exposures to RCS was 28.9 μg/m3 (geometric standard deviation: 2.5). Exposures varied significantly by year, mine type, sector, commodity, occupation, and location in a mine. Overall, the percentages of exposures above the MSHA permissible exposure limit (PEL for respirable dust with >1% quartz, approximately 100 μg/m3 RCS) and the National Institute for Occupational Safety and Health RCS recommended exposure limit (REL, 50 μg/m3 ) were 11.8% and 27.3%, respectively. GM exposures to RCS in 2018 (45.9 μg/m3 ) and 2019 (52.9 μg/m3 ) were significantly higher than the GM for all years prior. The overall 95th percentile of RCS exposures from 2000 to 2019 was 148.9 μg/m3 , suggesting a substantial risk of hazardous exposures above the PEL and REL during the entire period analyzed. The prevalence of high exposures to RCS among M/NM miners continues in the past 20 years and may be increasing in certain settings and occupations. Further research and intervention of the highest exposures are needed to minimize the risks of acquiring silica-induced respiratory diseases.

Silicosis after short-term exposure.

Silicosis develops after inhalation of dust containing respirable crystalline silica (RCS) and is recognized as an occupational disease. Workers also develop accelerated and acute silicosis after shorter exposure to respirable silica dust at high concentrations. The objective of this study is to investigate and identify the occupational groups at the highest risk of silicosis due to short-term RCS exposure. All confirmed cases of silicosis reported to the Central Register of Occupational Diseases in Poland between 2000 and 2019 were included. Data analysis covered: gender, age at the time of occupational disease diagnosis, exposure duration to RCS and sector of the national economy. A total of 2066 confirmed cases of silicosis were analysed. Thirty-two cases occurred after RCS exposure shorter than 5 years. Median age was 50. Seventy-five per cent (n = 24) of these cases were diagnosed in industrial processing workers who were mainly employed in manufacturing of non-metallic mineral products (44%, n = 14) and metal production (19%, n = 6). 16% (n = 5) of cases were associated with employment in mining and quarrying, 6% (n = 2) in conservation of monuments and 3% (n = 1) in construction. The findings identify occupational groups at risk of silicosis due to short-term silica exposure. Medical professionals should be aware of early silicosis symptoms, and occupational health professionals and employers should improve protective and preventive measures in silica related industries.

Mortality among mine and mill workers exposed to respirable crystalline silica.

BackgroundMillions of workers are potentially exposed to respirable crystalline silica (RCS) which has been associated with several diseases. We updated the mortality experience of a cohort of 2,650 mine and mill workers at four manufacturing facilities to assess cause-specific mortality risks associated with estimated cumulative RCS exposure.MethodsStudy eligibility was defined as any employee who had ≥1 year of service by 2000, with work history experience available from 1945 through 2004. Vital status and cause of death were ascertained from 1945 through 2015. RCS exposure was estimated across plant-, department-, job-, and time-dependent categories using historic industrial hygiene sampling data and professional judgment. Associations between cumulative RCS (mg/m3-years) and cause-specific mortality were examined using Cox proportional hazard regression models.ResultsIn the exposure-response analysis defined on quartiles of cumulative RCS exposure, no increasing trend (ptrend = 0.37) in lung cancer mortality (n = 116 deaths) was observed (Hazard ratio (HR) = 1.00 (referent), 1.20, 1.85, 0.92). Mortality risk for non-malignant respiratory disease was increased across quartiles (HR = 1.00, 1.35, 1.89, 1.70; ptrend = 0.15), based on 83 deaths. Non-malignant renal disease mortality was increased across quartiles (HR = 1.00, 6.64, 3.79, 3.29; ptrend = 0.11), based on 26 deaths.ConclusionsAfter nearly seven decades of follow-up, the exposure-response analyses showed no evidence of a positive trend for lung cancer, and limited evidence of a trend for non-malignant respiratory disease, and non-malignant renal disease mortality as a result of cumulative RCS exposure in this occupational cohort.

Characterization of the Emissions and Crystalline Silica Content of Airborne Dust Generated from Grinding Natural and Engineered Stones.

In this study, we systematically characterized the airborne dust generated from grinding engineered and natural stone products using a laboratory testing system designed and operated to collect representative respirable dust samples. Four stone samples tested included two engineered stones consisting of crystalline silica in a polyester resin matrix (formulations differed with Stones A having up to 90wt% crystalline silica and Stone B up to 50wt% crystalline silica), an engineered stone consisting of recycled glass in a cement matrix (Stone C), and a granite. Aerosol samples were collected by respirable dust samplers, total dust samplers, and a Micro-Orifice Uniform Deposit Impactor. Aerosol samples were analyzed by gravimetric analysis and x-ray diffraction to determine dust generation rates, crystalline silica generation rates, and crystalline silica content. Additionally, bulk dust settled on the floor of the testing system was analyzed for crystalline silica content. Real-time particle size distributions were measured using an Aerodynamic Particle Sizer. All stone types generated similar trimodal lognormal number-weighted particle size distributions during grinding with the most prominent mode at an aerodynamic diameter of about 2.0-2.3 μm, suggesting dust formation from grinding different stones is similar. Bulk dust from Stone C contained no crystalline silica. Bulk dust from Stone A, Stone B, and granite contained 60, 23, and 30wt% crystalline silica, respectively. In Stones A and B, the cristobalite form of crystalline silica was more plentiful than the quartz form. Only the quartz form was detected in granite. The bulk dust, respirable dust, and total dust for each stone had comparable amounts of crystalline silica, suggesting that crystalline silica content in the bulk dust could be representative of that in respirable dust generated during grinding. Granite generated more dust per unit volume of material removed than the engineered stones, which all had similar normalized dust generation rates. Stone A had the highest normalized generation rates of crystalline silica, followed by granite, Stone B, and Stone C (no crystalline silica), which likely leads to the same trend of respirable crystalline silica (RCS) exposure when working with these different stones. Manufacturing and adoption of engineered stone products with formulations such as Stone B or Stone C could potentially lower or eliminate RCS exposure risks. Combining all the effects of dust generation rate, size-dependent silica content, and respirable fraction, the highest normalized generation rate of RCS consistently occurs at 3.2-5.6 µm for all the stones containing crystalline silica. Therefore, removing particles in this size range near the generation sources should be prioritized when developing engineering control measures.

Prevention of the Occupational Silicosis Epidemic in Australia: What Do Those Who Assess Workplace Health Risk Think Should Be Done Now?

An Australian National Dust Disease Taskforce was established to address the re-emergence of occupational lung disease, in particular silicosis. Exposure to respirable crystalline silica (RCS) occurs in various industries in Australia. We asked occupational hygienists about their practical experiences and perspectives on RCS exposure and regulatory action. A total of 105 members of the Australian Institute of Occupational Hygienists completed an anonymous questionnaire, which addressed individual characteristics, experience, perceived level of employer awareness, effectiveness of current regulation, and recommendations for improvement, across three main industrial sectors. Based on professional experience, 71% were concerned about the potential for RCS over-exposure. Barriers to adequate exposure control included lack of management commitment and financial resources. The employment of specialist occupational hygiene inspectors was considered to be the most effective regulatory strategy. Given the large number of exposed workers in the construction industry, with only a moderate awareness, there is the potential for significant cost shifting of the burden of occupational lung disease from employers on to individuals and the public health system. A nationally consistent approach to RCS exposure control across all industrial sectors is now recommended, with an increased focus on measuring and controlling exposure.

Elevated exposures to respirable crystalline silica among engineered stone fabrication workers in California, January 2019-February 2020.

Workers fabricating engineered stone face high risk for exposure to respirable crystalline silica (RCS) and subsequent development of silicosis. In response, the California Division of Occupational Safety and Health (Cal/OSHA) performed targeted enforcement inspections at engineered stone fabrication worksites. We investigated RCS exposures and employer adherence to Cal/OSHA's RCS and respiratory protection standards from these inspections to assess ongoing risk to stone fabrication workers. We extracted employee personal air sampling results from Cal/OSHA inspection files and calculated RCS exposures. Standards require that employers continue monitoring employee RCS exposures and perform medical surveillance when exposures are at or above the action level (AL; 25 μg/m3 ); exposures above the permissible exposure limit (PEL; 50 μg/m3 ) are prohibited. We obtained RCS and respiratory protection standard violation citations from a federal database. We analyzed RCS exposures for 152 employees at 47 workplaces. Thirty-eight (25%) employees had exposures above the PEL (median = 89.7 μg/m3 ; range = 50.7-670.7 μg/m3 ); 17 (11%) had exposures between the AL and PEL. Twenty-four (51%) workplaces had ≥1 exposure above the PEL; 7 (15%) had ≥1 exposure between the AL and PEL. Thirty-four (72%) workplaces were cited for ≥1 RCS standard violation. Twenty-seven (57%) workplaces were cited for ≥1 respiratory protection standard violation. Our investigation demonstrates widespread RCS overexposure among workers and numerous employer Cal/OSHA standard violation citations. More enforcement and educational efforts could improve employer compliance with Cal/OSHA standards and inform employers and employees of the risks for RCS exposure and strategies for reducing exposure.

Current global perspectives on silicosis-Convergence of old and newly emergent hazards.

Silicosis not a disease of the past. It is an irreversible, fibrotic lung disease specifically caused by exposure to respirable crystalline silica (RCS) dust. Over 20,000 incident cases of silicosis were identified in 2017 and millions of workers continue to be exposed to RCS. Identified case numbers are however a substantial underestimation due to deficiencies in reporting systems and occupational respiratory health surveillance programmes in many countries. Insecure workers, immigrants and workers in small businesses are at particular risk of more intense RCS exposure. Much of the focus of research and prevention activities has been on the mining sector. Hazardous RCS exposure however occurs in a wide range of occupational setting which receive less attention, in particular the construction industry. Recent outbreaks of silicosis associated with the fabrication of domestic kitchen benchtops from high‐silica content artificial stone have been particularly notable because of the young age of affected workers, short duration of RCS exposure and often rapid disease progression. Developments in nanotechnology and hydraulic fracking provide further examples of how rapid changes in technology and industrial processes require governments to maintain constant vigilance to identify and control potential sources of RCS exposure. Despite countries around the world dealing with similar issues related to RCS exposure, there is an absence of sustained global public health response including lack of consensus of an occupational exposure limit that would provide protection to workers. Although there are complex challenges, global elimination of silicosis must remain the goal.

Occupational exposure to crystalline silica in artificial stone processing

Respirable Crystalline Silica (RCS) is a hazardous substance with known effects that can be well correlated with exposure levels that still persist in many traditional sectors, such as construction or stone processing. In the past decade, exposure scenarios for RCS have been found in the sector of artificial stone processing. The aim of this study is to evaluate the levels of RCS in facilities specialized in the production of artificial stone countertops and other accessories for the furnishing of kitchens, bathrooms, and offices after the introduction of some preventive technical measures such as wet processing or local exhaust ventilation systems. The study involved 51 subjects in four facilities. Personal silica exposure assessment was carried out using GS3 cyclones positioned in the breathing zone during the work shift. Quantitative determination of silica was carried out by X-ray diffraction analysis. Respirable dust levels were in the range 0.046–1.154 mg/m3 with RCS levels within the range <0.003-0.098 mg/m3. The highest exposure was found in dry finishing operations. Although there was a remarkable reduction in RCS exposure levels compared to what was observed in the past before the introduction of preventive measures, the data still showed hazardous exposure levels for some of the monitored activities.

Break-even Analysis of Respirable Crystalline Silica (RCS) Exposure Interventions in the Construction Sector.

We investigated long-term economic impacts of respirable crystalline silica (RCS) removal interventions in the construction at the societal level. We estimated costs and benefits of two RCS exposure interventions, use of "respirators" and "wet method," over a 30-year time period. We identified economic impacts of the interventions under four different scenarios. Under current practices, we estimated that approximately 125 lung cancer cases attributable to RCS exposure would arise in 2060. Under the full exposure removal scenario, we estimated there would be 53 new cases. Over the 30-year time period, the estimated cumulative averted cases are 787 and 482 for respirators and wet method, respectively, which amount to net benefits of $422.13 and $394.92 million. Findings provide important information for policymakers seeking to reduce the economic burden of occupational lung cancer in society.