Determination of Exposure to Bitumen and Fume from Bitumen in the Oil Industry Through Determination of Urinary 1-Hydroxypyrene

Abstract

Since 1986, Shell routinely monitors occupational exposure of its operators to polycyclic aromatic hydrocarbons (PAHs) by determination of urinary 1-hydroxypyrene (1-HOPyr). Up till now, about 100 different studies in a wide variety of industrial settings, involving more than 4,000 samples in total, have been performed. The upper limit of the 95% confidence interval of background levels of 1-HOPyr in 121 workers without occupational exposure to PAHs was 0.51 μ mol/mol creatinine (median 0.11; range < 0.05 to 1.08 μ mol/mol creatinine). Due to the variation in composition of the PAH mixture (in particular the ratio between pyrene and carcinogenic PAHs) to which workers may be exposed in different processes ànd by different routes of exposure, it is not feasible to set a limit value for urinary 1-HOPyr. However, a value of 0.50 μ mol/mol creatinine can be used as an indicator whether or not occupational exposure to PAHs has occurred. This article focuses on a selection of studies in which operators were potentially exposed to to PAHs from bitumen and fume from bitumen. The selected studies involved manufacturing, maintenance of production facilities, and road tanker loading of bitumen. Studies over a number of years in a bitumen manufacturing plant indicated that exposures to PAHs as measured by 1-hydroxypyrene were not statistically significantly different from control values with median values of approximately 0.10 μ mol/mmol creatinine. However, occasionally values just over the the internal reference value (up to 0.72 μ mol/mol creatinine) were observed. Similar observations were made during road tanker loading and maintenance/cleaning operations although the value of 0.50 μ mol/mol creatinine was not exceeded in these studies. In several studies multiple pre- and post-shift samples were collected from individual operators during a number of consecutive days. Detailed analysis of the data strongly suggests that small changes over the shift, as seen during loading, manufacturing, and maintenance operations, were due to confounding factors (such as diet and smoking) rather than occupational exposure to PAHs. Several studies were performed to investigate the role of dermal exposure to PAH in more detail. In these studies industrial hygienists made detailed work observations to assess semi-quantitatively the extent of inhalatory and dermal exposure. In addition, studies in workers digging contaminated soil in which different forms of personal protective equipment providing variable degrees of respiratory and dermal protection during identical tasks, were used to show the effectiveness this equipment. Overal, these studies show that dermal exposure to PAHs may be significant in the total exposure to PAHs and that 1-HOPyr can be used to assess the efficacy of personal protective equipment. With appropriate personal protective equipment, exposure to PAHs, as assessed by the determination of urinary 1-HOPyr, could be reduced to background levels. The contribution of dermal exposure to the total uptake of PAHs, however, proved difficult to quantify exactly. In conclusion, both inhalatory and dermal exposure to PAHs from a variety of sources, including bitumen, can readily be assessed by the determination of 1-HOPyr in urine. Results from biomonitoring indicate that both inhalation and dermal exposure to PAHs during manufacturing and handling of bitumen is negligible.

Keywords:

• biomonitoring
• 1-hydroxypyrene
• bitumen
• biological monitoring
• exposure monitoring