Objectives This study is the first step in a larger study that aims to investigate the potential human exposure to hazardous hydrocarbons in air during oil spill combat offshore. The aim was to measure n-hexane, benzene, toluene, ethylbenzene, xylenes and naphthalene evaporated from fresh, light crude oils, and identify determinants significantly influencing the benzene evaporation.

Methods A small scale open oil-on-water exposure system filled with seawater was used to produce a thin oil film (<0.25 mm) on the water surface. Eight light crude oils from the Norwegian continental shelf (NCS) were tested at 2°C and 13°C. Air samples were collected with active thermal desorption tubes (ATD-tubes) for 30 minutes in 5 minute intervals (N = 6) and analysed by gas chromatography mass spectrometry (ATD-GC-MS). The measured air concentrations of each compound were used to calculate an average air concentration of all oils for three time periods; first 5, first 15 and last 15 min of the 30 min of sampling. Linear mixed-effects models were developed by using the benzene concentration for each time period as dependent variables, and potential determinants as fixed effects.

Results Toluene, followed by benzene, ethylbenzene and n-hexane, yielded the highest air concentrations (6.0–11.3 ppm) of the measured VOCs, and declined rapidly with time. Xylenes and naphthalene yielded lower air concentrations (0.1–1.6 ppm) and did not show analogous decline during sampling. Benzene exceeded the short-term occupational exposure limit at both 2°C (3.5 ppm) and 13°C (4.6 ppm) the first 15 minutes of sampling. Benzene content in fresh oil, oil group (condensate/light oil) and wax content in fresh oil were significant determinants explaining 59–78% of the total variance in the outcome variables.