Occupational Benzene Exposure in the Norwegian Offshore Petroleum Industry, 2002–2018

Abstract

Purpose Workers on offshore petroleum installations are at risk of being exposed to benzene which is carcinogenic to humans. The present study aimed to assess the time trend of full-shift benzene exposure from 2002 to 2018 in order to characterize benzene exposure among laboratory technicians, mechanics, process operators, and industrial cleaners, and to examine the possible determinants of benzene exposure. Methods A total of 924 measurements of benzene exposure from the Norwegian petroleum offshore industry were included. The median sampling duration was 680 min, ranging from 60 to 940 min. The overall geometric mean (GM) and 95% confidence interval, time trends, and determinants of exposure were estimated using multilevel mixed-effects tobit regression analyses. Time trends were estimated for sampling duration below and above 8 h, both overall and for job groups. The variability of exposure between installation and workers was investigated in a subset of data containing worker identification. Results The overall GM of benzene exposure was 0.004 ppm. When adjusting for job group, design of process area, season, wind speed, and sampling duration, industrial cleaners had the highest exposure (GM = 0.012). Laboratory technicians, mechanics, and process operators had a GM exposure of 0.004, 0.003, and 0.004 ppm, respectively. Overall, the measured benzene exposure increased by 7.6% per year from 2002 to 2018. Mechanics had an annual increase of 8.6% and laboratory technicians had an annual decrease of 12.6% when including all measurements. When including only measurements above 8 h, mechanics had an increase of 16.8%. No statistically significant time trend was found for process operators. Open process area, high wind speed, and wintertime were associated with reduced exposure level. Conclusions An overall increase in measured exposure was observed from 2002 to 2018. The increase may reflect changes in measurement strategy from mainly measuring on random days to days with expected exposure. However, the time trend varied between job groups and was different for sampling duration above or below 8 h. Industrial cleaners had the highest exposure of the four job groups while no differences in exposure were observed between laboratory technicians, mechanics, and process operators. The design of the process area, job group, wind speed, and season were all significant determinants of benzene exposure.

Benzene Exposure From Selected Work Tasks on Offshore Petroleum Installations on the Norwegian Continental Shelf, 2002–2018

“…The annual downward trend of 10% in task-based benzene exposure contrasts with the recently published 7.6% annual upward trend for full-shift benzene exposure among the same group of offshore workers during the same period (2002–2018) ( Ridderseth et al , 2022 ) ( Fig. 2 ).…”

“… Unadjusted time trend for all task-based measurements with a sampling duration below 60 min (solid line) and as a scatterplot (triangles). In addition, the measurements (equal to or above 60 min sampling duration) presented in Ridderseth et al (2022) are included and presented for comparison (dashed line). Unadjusted splines including knots in the years 2007 and 2017.…”

“…However, the implementation of control measures prior to measurements was not sufficiently documented in the measurement reports. On the other hand, the increasing trend for the full-shift measurements might be related to a change in measurement strategy during the last 20 years, from sampling on random days in the first years to a more targeted strategy towards days with expected exposure to benzene ( Ridderseth et al , 2022 ). Studies investigating full-shift exposure in the petroleum industry have commented that a targeted sampling strategy towards days with tasks including benzene exposure is common ( Panko et al , 2009 ; Gaffney et al , 2010 ; Kreider et al , 2010 ; Swaen et al , 2010 ).…”

“…Previous studies have reported full-shift exposure to benzene among offshore petroleum workers to have a geometric mean (GM) ranging from 0.004 ppm to 0.036 mg/m 3 [0.011 ppm], ( Verma et al , 2000 ; Kirkeleit et al , 2006 ; Bråtveit et al , 2007 ; Ridderseth et al , 2022 ). This is below the present occupational exposure limit value (OELV) in the EU of 0.2 ppm (1 ppm in a transitional period until April 2024 and 0.5 ppm until April 2026) for an eight-hour working day ( European Union, 2022 ).…”