The Impact of COVID-19 on Transit Workers: Perceptions of Employer Responses and Associations with Health Factors

COVID-19 has had a substantial impact on transit workers’ lives, especially among public-facing vehicle operators. The current project examined relationships between workers’ knowledge and perceptions of their employer’s COVID-19 safety responses, job attitudes, and health. We surveyed transit workers (N = 174) between July and August 2020 and followed up 3 months later. Fifty-seven workers responded to the follow-up survey. Surveys addressed workers’ knowledge and perceptions of their employer implementing Centers for Disease Control and Prevention (CDC)-recommended COVID-19 safety responses, COVID-19 risk perceptions, job attitudes, and health factors. Employees reported knowledge of their employer implementing ~8 of 12 CDC-recommended responses. The most reported response was informational poster placements; the least reported was designating a point-person for COVID-19 concerns. Significant associations were found between knowledge of employer safety responses and lower COVID-19 risk perceptions, better job attitudes, and greater mental and global health. Operators (i.e. public-facing workers) reported worse perceptions of employer responses, and higher COVID-19 risk perceptions, work stress, and turnover intentions, compared with non-operators. A time-lagged panel model found that COVID-19 risk perceptions significantly mediated the relationship between public-facing work status and follow-up depression, anxiety, stress, and global health. Results reveal opportunities for transit authorities to broaden and better communicate their responses to emergent occupational safety and health crises.

Aerosol Analysis Using Handheld Raman Spectrometer: On-site Quantification of Trace Crystalline Silica in Workplace Atmospheres

A method for aerosol chemical analysis using handheld Raman spectrometer has been developed and its application to measurement of crystalline silica concentration in workplace atmosphere is described. The approach involves collecting aerosol as a spot sample using a wearable optical aerosol monitor, followed by direct-on-filter quantitative analysis of the spot sample for crystalline silica using handheld Raman spectrometer. The filter cassette of a commercially available optical aerosol monitor (designed to collect aerosol for post-shift analysis) was modified to collect 1.5-mm-diameter spot sample, which provided adequate detection limits for short-term measurements over a few tens of minutes or hours. The method was calibrated using aerosolized α-quartz standard reference material in the laboratory. Two Raman spectrometers were evaluated, one a handheld unit (weighing less than 410 g) and the other a larger probe-based field-portable unit (weighing about 5 kg). The lowest limit of quantification for α-quartz of 16.6 μg m−3 was obtained using the handheld Raman unit at a sample collection time of 1 h at 0.4 l min−1. Short-term measurement capability and sensitivity of the Raman method were demonstrated using a transient simulated workplace aerosol. Workplace air and personal breathing zone concentrations of crystalline silica of workers at a hydraulic fracturing worksite were measured using the Raman method. The measurements showed good agreement with the co-located samples analyzed using the standard X-ray powder diffraction (XRD) method, agreeing within 0.15–23.2% of each other. This magnitude of difference was comparable to the inter- and intra-laboratory analytical precision of established XRD and infrared methods. The pilot study shows that for silica-containing materials studied in this work it is possible to obtain quantitative measurements with good analytical figures of merit using handheld or portable Raman spectrometers. Further studies will be needed to assess matrix interferences and measurement uncertainty for several other types of particle matrices to assess the broader applicability of the method.

Associations of Bitumen Fumes with Lymphocyte Subsets and Cytokines Expression in the Peripheral Blood of Exposed Workers

Objectives The present study aimed to investigate the distribution of lymphocyte subsets and cytokines expression in the peripheral blood of bitumen fumes-exposed workers. Methods In this study, 129 workers from molding and roasting workshops were recruited as the exposed group and 99 office and quality inspection staff were chosen as the control. The polycyclic aromatic hydrocarbons (PAHs) levels of bitumen fumes in individual and fixed-point air samples and the urinary levels of 1-hydroxypyrene (1-OH-P), 1-hydroxynaphthols (1-OH-N) and 2-hydroxynaphthols (2-OH-N) in workers were measured using High Performance Liquid Chromatography. The lymphocyte subsets and serum cytokines concentrations were analyzed by flow cytometry and cytometric bead array, respectively. Results The median values of PAHs were 0.08 mg/m3 for permissible concentration-time weighted average and 0.12 mg/m3 for permissible concentration-short term exposure (PC-STEL) in molding and roasting workshops, which were higher than that in the control area (< 0.01 mg/m3). Multivariate linear regression models were used to adjust for influential covariates, including age, gender, work age, smoking status, and alcohol consumptions. After adjusting for these covariates, we compared levels of urinary PAHs metabolites, the percentages of lymphocyte subsets, and serum cytokines concentrations between the two groups. The 1-OH-P, 1-OH-N, and 2-OH-N levels in the urine of bitumen fumes exposed workers were significantly higher than that in the controls (P < 0.05). Compared with the control group, the percentage of the natural killer (NK) cell (CD56+ cell) was significantly increased in the exposed group (P < 0.001). There was a significant decrease in the percentages of CD3+ T cell, CD4+ T cell, and CD8+ T cell in the exposed group compared to the control (P < 0.001). The serum levels of interleukin-1β (IL-1β) and IL-6 in bitumen fumes exposed workers were significantly higher than that of the controls (P < 0.05). Moreover, positive correlations were observed between the serum levels of IL-1β, IL-6, and urinary 1-OH-P levels in bitumen fumes-exposed workers, respectively (P < 0.05). There were no significant differences in the serum levels of IL-8, tumor necrosis factor-α (TNF-α), macrophage inflammatory protein-1β (MIP-1β) and monocyte chemotactic protein-1 (MCP-1) between the exposed group and the control group (P > 0.05). Conclusion Our study suggested that low dose of bitumen fumes exposure could decrease the percentage of T cell, increase the percentage of NK cell and stimulate the release of serum IL-1β and IL-6 in the peripheral blood of exposed workers. The serum levels of IL-1β and IL-6 were positive correlated with the urinary 1-OH-P levels in bitumen fumes exposed workers. These results may inform the search for potential effective biomarkers and provide evidences for early health monitoring in workers occupationally exposed to bitumen fumes.

Assessment of the Oxidative Potential and Oxidative Burden from Occupational Exposures to Particulate Matter

Oxidative potential (OP) is a toxicologically relevant metric that integrates features like mass concentration and chemical composition of particulate matter (PM). Although it has been extensively explored as a metric for the characterization of environmental particles, this is still an underexplored application in the occupational field. This study aimed to estimate the OP of particles in two occupational settings from a construction trades school. This characterization also includes the comparison between activities, sampling strategies, and size fractions. Particulate mass concentrations (PM4-Personal, PM4-Area, and PM2.5-Area) and number concentrations were measured during three weeks of welding and construction/bricklaying activities. The OP was assessed by the ascorbate assay (OPAA) using a synthetic respiratory tract lining fluid (RTLF), while the oxidative burden (OBAA) was determined by multiplying the OPAA values with PM concentrations. Median (25th–75th percentiles) of PM mass and number concentrations were 900 (672–1730) µg m–3 and 128 000 (78 000–169 000) particles cm–3 for welding, and 432 (345–530) µg m–3 and 2800 (1700–4400) particles cm–3 for construction. Welding particles, especially from the first week of activities, were also associated with higher redox activity (OPAA: 3.3 (2.3–4.6) ρmol min–1 µg–1; OBAA: 1750 (893–4560) ρmol min–1 m–3) compared to the construction site (OPAA: 1.4 (1.0–1.8) ρmol min–1 µg–1; OBAA: 486 (341–695) ρmol min–1 m–3). The OPAA was independent of the sampling strategy or size fraction. However, driven by the higher PM concentrations, the OBAA from personal samples was higher compared to area samples in the welding shop, suggesting an influence of the sampling strategy on PM concentrations and OBAA. These results demonstrate that important levels of OPAA can be found in occupational settings, especially during welding activities. Furthermore, the OBAA found in both workplaces largely exceeded the levels found in environmental studies. Therefore, measures of OP and OB could be further explored as metrics for exposure assessment to occupational PM, as well as for associations with cardiorespiratory outcomes in future occupational epidemiological studies.

Multicomponent Measurement of Respirable Quartz, Kaolinite and Coal Dust using Fourier Transform Infrared Spectroscopy (FTIR): A Comparison Between Partial Least Squares and Principal Component Regressions

Exposure to respirable crystalline silica (RCS) is potentially hazardous to the health of thousands of workers in Great Britain. Both X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy can be used to measure RCS to assess exposures. The current method outlined in the Health and Safety Executive’s (HSE) Methods for the Determination of Hazardous Substances (MDHS) guidance series is ‘MDHS 101 Crystalline silica in respirable airborne dust - Direct-on-filter analyses by infrared spectroscopy or x-ray’. This describes a procedure for the determination of time-weighted average concentrations of RCS either as quartz or cristobalite in airborne dust. FTIR is more commonly employed because it is less expensive, potentially portable and relatively easy to use. However, the FTIR analysis of RCS is affected by spectral interference from silicates. Chemometric techniques, known as Partial Least Squares Regression (PLSR) and Principal Component Regression (PCR), are two computational processes that have the capability to remove spectral interference from FTIR spectra and correlate spectral features with constituent concentrations. These two common chemometric processes were tested on artificial mixtures of quartz and kaolinite in coal dust using the same commercially available software package. Calibration, validation and prediction samples were prepared by collecting aerosols of these dusts onto polyvinylchloride (PVC) filters using a Safety in Mines Personal Dust Sampler (SIMPEDS) respirable cyclone. PCR and PLSR analyses were compared when processing the same spectra. Good correlations between the target values, measured using XRD, were obtained for both the PCR and PLSR models e.g. 0.98–0.99 (quartz), 0.98–0.98 (kaolinite) and 0.96–0.97 (coal). The level of agreement between PCR and PLSR was within the 95% confidence value for each analyte. Slight differences observed between predicted PCR and PLSR values were due to the number of optimal principal components applied to each chemometric process. The presence of kaolinite in these samples caused an 18% overestimation of quartz, for the FTIR, when following MDHS 101 without a chemometric method. Chemometric methods are a useful approach to obtain interference-free results for the measurement of RCS from some workplace environments and to provide a multicomponent analysis to better characterise exposures of workers.