A Simultaneous Job- and Task-Based Exposure Evaluation of Petroleum Tanker Drivers to Benzene and Total Hydrocarbons

Abstract

A simultaneous job- and task-based exposure study was conducted for tanker drivers delivering petroleum products from several bulk terminals and an agency to retail outlets. Full-shift (job-based) samples and job component tasks samples were collected simultaneously. The tasks sampled included loading, unloading, and travel. Three hundred sixty-six personal charcoal tube samples were collected. Full-shift visual observations of work practices and real-time monitoring using a data logging hydrocarbon analyzer were also conducted. Multiple measurements per worker were made, which permitted an assessment of sampling variability within and between workers. The highest exposures for drivers occurred during unloading at the agency. The mean benzene exposure for agency drivers was 0.88 ppm for full-shift time-weighted average, 2.86 ppm for unloading, and 0.54 ppm for loading. For bulk terminal drivers, the mean benzene level without vapor control was 0.12 ppm for time weighted average, 0.24 ppm for unloading, and 0.33 ppm for loading. The time-weighted average exposure of the agency and bulk terminal drivers based on the data collected and the lognormal model can be expected to exceed threshold limit value-time weighted average of 0.5 ppm for benzene about 70 and 2% of the time, respectively. Agency drivers' unloading and loading tasks accounted for approximately 30% and 7% of the total time, and 95% and 4% of total exposure, respectively. For the bulk terminal drivers, mean unloading and loading tasks constituted 24% and 12% of the total time, and 68% and 19% of the total exposure, respectively. Travel activity accounted for an average of 63% of the total time for agency and 64% for bulk terminal drivers, but only contributed < 1 and 13% of the total exposure, respectively. The actual job-based time-weighted average concentration and the calculated time-weighted average derived from the time-weighted summation of the components tasks are in very good agreement. Within-worker variability was generally higher than between-worker variability. Exposure control strategies are required primarily for unloading at the agencies. Vapor control technology at the terminal effectively reduces exposure (by almost 50%) and fugitive emissions.

Pilot task-based assessment of noise levels among firefighters

“…By combining these two streams of information, typical or worst-case exposures can be estimated for workers with irregular or highly variable job tasks and activities (Smith, Hammond et al 1991). This approach has already been successfully used to evaluate a number of occupational exposures, including ergonomic hazards (Fallentin et al 2001), air contaminants (Johnson, Reynolds et al 2000; Verma, Cheng et al 2004), and noise (Virji, Woskie et al 2009; Neitzel, Daniell et al 2011). …”

Evaluation and Comparison of Three Exposure Assessment Techniques

“…In industries like these, within-worker exposure variability (e.g., variability within and between different work shifts) is high. (16,17) Although trade-based approaches have been used extensively to characterize exposures in the construction industry, (17–22) when within-worker and within-group variability is large, creating groups based on job title may produce groups of workers with very dissimilar exposures. (7,23–25) …”

“…(26) In this approach, workers (27,28) or their supervisors (29) report their tasks for a specific day, a “typical” (29) or “worst case” (30) day, or a longer period, (31,32) or tasks are observed by researchers. (16,33) Time-at-task information is then combined with task-specific exposure levels measured on the same individual or, more commonly, on other individuals conducting the same task, to create an average exposure estimate. (10) …”

“…(48) Finally, task definitions are of critical importance. (26) Some authors have used simple binary measures of task, (33) while others have used limited (16) or more comprehensive (27) sets of tasks, or allowed workers to report tasks in their own words. (49) …”

Occupational exposure to gasoline and the risk of non-Hodgkin lymphoma: A review and meta-analysis of the literature

“…loading and unloading of distribution road tankers, railcars and marine vessels; or maintenance of refinery tanks, gasoline pumps and motor cars -where exposures exceeded 50-100 mg m À3 [56,[59][60][61][62][63][64][65]. Measures to reduce workers' exposure are gradually being adopted and include the introduction of closed process streams in refineries; vapour recovery systems at distribution centres and filling stations; and bottom-, instead of top-, loading distribution tankers [51,57,61,[65][66][67][68].…”