Abstract
ABSTRACT We aimed to characterize the black carbon (BC) exposure from eight types of jobs involving diesel engine vehicles—namely, machinery operation, forklift operation, automobile assembly, garbage collection, garbage truck driving, delivery, toll operation, and crane operation—across seven industries. The workers chosen for this study (N = 106) measured their exposure every minute using an AE51 microAethalometer affixed to a microcyclone and also recorded their time-activity patterns and whereabouts in detail during working hours. We then categorized and analyzed 71,987 of these 1-min observations based on four potential exposure determinants: the operation of a diesel engine vehicle (yes or no), proximity to the source of BC (near or far), location of the workplace (indoor or outdoor), and type of work (moving or stationary). Among the participants, the geometric mean (GM) exposure was highest for forklift operators in indoor environments (9.5 µg m–3), followed by toll operators (GM = 7.4 µg m–3), machinery operators (GM = 7.4 µg m–3), and garbage collectors (GM = 5.5 µg m–3). After accounting for the random effects of the individual workers and working dates (evaluated per occupation) as well as the fixed effects of the determinants and their pairwise interaction terms (p < 0.001), we found that all four of the determinants significantly differed in their associated levels of BC exposure. In particular, working near instead of far from diesel engine equipment doubled the average level of exposure. Additionally, upon investigating different combinations of the determinants, we identified proximity to diesel exhaust sources and indoor working conditions as the main factors of BC exposure. Thus, installing diesel particulate filters on diesel engine vehicles effectively reduces exposure. Our findings potentially contribute to the development of a model that predicts the level of exposure for various types of jobs.
Highlights
Exposure to diesel engine exhaust emissions (DE) can occur in most industrial operations, jobs, and tasks where vehicles equipped with diesel engines are used, including trucks, vessels, cranes, and lifting or other machinery
Our results show that increased proximity to diesel engine exhaust sources and indoor work are the main determinants of black carbon (BC) exposure levels
We investigated BC exposure in eight occupations across seven industries and found significant variations in the mean exposure between different types of jobs and tasks (p < 0.001), even within the same industry
Summary
Exposure to diesel engine exhaust emissions (DE) can occur in most industrial operations, jobs, and tasks where vehicles equipped with diesel engines are used, including trucks, vessels, cranes, and lifting or other machinery. Aside from the drivers who operate the diesel vehicles, the workers who assist or work alongside them can be exposed to DE. All motorized transport using diesel fuel are considered important sources of black carbon (BC). BC has been used as an indicator of exposure to DE because of its relevance to health and the availability of suitable measurement devices (HEI, 2010; Janssen et al, 2011). BC consists of pure carbon formed through the incomplete combustion of fossil fuels, biofuel, and biomass, and it is emitted in both anthropogenic and naturally occurring soot (Anenberg et al, 2012). Several epidemiological studies have shown that the airborne BC mass concentration affects the morbidity and mortality of cardiovascular diseases (Zanobetti et al, 2013; Gong et al, 2019) and respiratory diseases (Hua et al, 2014) and causes decreased lung function (Suglia et al, 2008; Shakya et al, 2016; Paunescu et al, 2019)
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