238. Occupational Exposures to Diesel Particulate Matter in Minneapolis-St. Paul Transportation Systems

Abstract Questions still exist regarding which indicator better estimates worker’s exposure to diesel particulate matter (DPM) and, especially for ultrafine particles (UFP), how exposure levels and the characteristics of the particles vary in workplaces with different exposure conditions. This study aimed to quantify and characterize DPM exposures in three workplaces with different exposure levels: an underground mine, a subway tunnel, and a truck repair workshop. The same sampling strategy was used and included measurements of the particle number concentration (PNC), mass concentration, size distribution, transmission electron microscopy (TEM), and the characterization of carbonaceous fractions. The highest geometric means (GMs) of PNC and elemental carbon (EC) were measured in the mine [134 000 (geometric standard deviation, GSD = 1.5) particles cm−3 and 125 (GSD = 2.1) µg m−3], followed by the tunnel [32 800 (GSD = 1.7) particles cm−3 and 24.7 (GSD = 2.4) µg m−3], and the truck workshop [22 700 (GSD = 1.3) particles cm−3 and 2.7 (GSD = 2.4) µg m−3]. This gradient of exposure was also observed for total carbon (TC) and particulate matter. The TC/EC ratio was 1.4 in the mine, 2.5 in the tunnel and 8.7 in the workshop, indicating important organic carbon interference in the non-mining workplaces. EC and PNC were strongly correlated in the tunnel (r = 0.85; P < 0.01) and the workshop (r = 0.91; P < 0.001), but a moderate correlation was observed in the mine (r = 0.57; P < 0.05). Results from TEM showed individual carbon spheres between 10 and 56.5 nm organized in agglomerates, while results from the size distribution profiles showed bimodal distributions with a larger accumulation mode in the mine (93 nm) compared with the tunnel (39 nm) and the truck workshop (34 nm). In conclusion, the composition of the carbonaceous fraction varies according to the workplace, and can interfere with DPM estimation when TC is used as indicator. Also, the dominance of particles <100 nm in all workplaces, the high levels of PNC measured and the good correlation with EC suggest that UFP exposures should receive more attention on occupational routine measurements and regulations.

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Occupational Respirable Mine Dust and Diesel Particulate Matter Hazard Assessment in an Underground Gold Mine in Ghana

Journal of Health and Pollution ◽

10.5696/2156-9614-10.25.200305 ◽

2020 ◽

Vol 10 (25) ◽

pp. 200305

Author(s):

Martin K. Mensah ◽

Kwadwo Mensah-Darkwa ◽

Carsten Drebenstedt ◽

Bright V. Annam ◽

Edward K. Armah

Keyword(s):

Particulate Matter ◽

Occupational Exposures ◽

Crystalline Silica ◽

Mine Safety ◽

Dust Exposure ◽

Diesel Particulate Matter ◽

Gold Mine ◽

Diesel Particulate ◽

Silica Dust ◽

Safety And Health

Background. Underground miners can experience occupational health diseases due to exposure to particulate matter hazards. Objectives. The aim of the present study was to examine occupational exposures of underground miners to dust and diesel particulate matter and to identify exposure groups with high potential to develop associated health effects due to the presence of dust and diesel particulate matter (DPM) hazards in an underground gold mine in Ghana. Methods. Purposive sampling was employed using gravimetric air samplers over an 8-hour time weighted average period. The National Institute for Occupational Safety and Health (NIOSH) analytical Chapter Q and 5040 were used in determining crystalline silica dust and diesel particulate matter fractions, respectively. Structured questionnaires were administered to gather data on workers' level of awareness to dust and DPM exposures. Results. It was found that 41% of the sampled groups were exposed to higher crystalline silica levels above the (NIOSH) permissible exposure limit (PEL) level of 0.05 mg/m3. For DPM, 49% of these groups had exposures above the Mine Safety and Health Administration (MSHA) PEL level of 160 μg/m3. Among the 94 mine workers who responded to this study, 62% were found to be aware of the presence and hazardous nature of silica dust, 28% had minimal knowledge and the remaining were found to be unaware. Conclusions. There are varying levels of dust and DPM due to the presence of silica-bearing rocks, the production of diesel fumes and inefficiencies of available mitigation measures. Research carried out over the past decades has found confirmed cases of silicosis and lung cancer due to high dust exposure levels. Rock drillers, blast men and shotcrete operators were found to be exposed to higher levels of dust and diesel particulate matter and are at greater risk of silicosis. Participant Consent. Obtained Ethics Approval. This study was approved by the Ethics Committee of the Kwame Nkrumah University of Science and Technology, Ghana and carried out under full consent of the mining company under study. Competing Interests. The authors declare no competing financial interests.

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