Oil mist and vapour concentrations from drilling fluids: inter- and intra-laboratory comparison of chemical analyses.

OBJECTIVES: There are no recognized analytical methods for measuring oil mist and vapours arising from drilling fluids used in offshore petroleum drilling industry. To inform the future development of improved methods of analysis for oil mist and vapours this study assessed the inter- and intra-laboratory variability in oil mist and vapour analysis. In addition, sample losses during transportation and storage were assessed. METHODS: Replicate samples for oil mist and vapour were collected using the 37-mm Millipore closed cassette and charcoal tube assembly. Sampling was conducted in a simulated shale shaker room, similar to that found offshore for processing drilling fluids. Samples were analysed at two different laboratories, one in Norway and one in the UK. Oil mist samples were analysed using Fourier transform infrared spectroscopy (FTIR), while oil vapour samples were analysed by gas chromatography (GC). RESULTS: The comparison of replicate samples showed substantial within- and between-laboratory variability in reported oil mist concentrations. The variability in oil vapour results was considerably reduced compared to oil mist, provided that a common method of calibration and quantification was adopted. The study also showed that losses can occur during transportation and storage of samples. CONCLUSIONS: There is a need to develop a harmonized method for the quantification of oil mist on filter and oil vapour on charcoal supported by a suitable proficiency testing scheme for laboratories involved in the analysis of occupational hygiene samples for the petroleum industry. The uncertainties in oil mist and vapour measurement have substantial implications in relation to compliance with occupational exposure limits and also in the reliability of any exposure-response information reported in epidemiological studies.

Comparison of the SidePak personal monitor with the Aerosol Particle Sizer (APS).

The aim of this study was to compare the performance of the TSI Aerodynamic Particle Sizer (APS) and the TSI portable photometer SidePak to measure airborne oil mist particulate matter (PM) with aerodynamic diameters below 10 µm, 2.5 µm and 1 µm (PM(10), PM(2.5) and PM(1)). Three SidePaks each fitted with either a PM(10), PM(2.5) or a PM(1) impactor and an APS were run side by side in a controlled chamber. Oil mist from two different mineral oils and two different drilling fluid systems commonly used in offshore drilling technologies were generated using a nebulizer. Compared to the APS, the SidePaks overestimated the concentration of PM(10) and PM(2.5) by one order of magnitude and PM(1) concentrations by two orders of magnitude after exposure to oil mist for 3.3-6.5 min at concentrations ranging from 0.003 to 18.1 mg m(-3) for PM(10), 0.002 to 3.96 mg m(-3) for PM(2.5) and 0.001 to 0.418 mg m(-3) for PM(1) (as measured by the APS). In a second experiment a SidePak monitor previously exposed to oil mist overestimated PM(10) concentrations by 27% compared to measurements from another SidePak never exposed to oil mist. This could be a result of condensation of oil mist droplets in the optical system of the SidePak. The SidePak is a very useful instrument for personal monitoring in occupational hygiene due to its light weight and quiet pump. However, it may not be suitable for the measurement of particle concentrations from oil mist.

Effect of drilling fluid systems and temperature on oil mist and vapour levels generated from shale shaker.

Workers in the drilling section of the offshore petroleum industry are exposed to air pollutants generated by drilling fluids. Oil mist and oil vapour concentrations have been measured in the drilling fluid processing areas for decades; however, little work has been carried out to investigate exposure determinants such as drilling fluid viscosity and temperature. A study was undertaken to investigate the effect of two different oil-based drilling fluid systems and their temperature on oil mist, oil vapour, and total volatile organic compounds (TVOC) levels in a simulated shale shaker room at a purpose-built test centre. Oil mist and oil vapour concentrations were sampled simultaneously using a sampling arrangement consisting of a Millipore closed cassette loaded with glass fibre and cellulose acetate filters attached to a backup charcoal tube. TVOCs were measured by a PhoCheck photo-ionization detector direct reading instrument. Concentrations of oil mist, oil vapour, and TVOC in the atmosphere surrounding the shale shaker were assessed during three separate test periods. Two oil-based drilling fluids, denoted 'System 2.0' and 'System 3.5', containing base oils with a viscosity of 2.0 and 3.3-3.7 mm(2) s(-1) at 40°C, respectively, were used at temperatures ranging from 40 to 75°C. In general, the System 2.0 yielded low oil mist levels, but high oil vapour concentrations, while the opposite was found for the System 3.5. Statistical significant differences between the drilling fluid systems were found for oil mist (P = 0.025),vapour (P < 0.001), and TVOC (P = 0.011). Increasing temperature increased the oil mist, oil vapour, and TVOC levels. Oil vapour levels at the test facility exceeded the Norwegian oil vapour occupational exposure limit (OEL) of 30 mg m(-3) when the drilling fluid temperature was ≥50°C. The practice of testing compliance of oil vapour exposure from drilling fluids systems containing base oils with viscosity of ≤2.0 mm(2) s(-1) at 40°C against the Norwegian oil vapour OEL is questioned since these base oils are very similar to white spirit. To reduce exposures, relevant technical control measures in this area are to cool the drilling fluid <50°C before it enters the shale shaker units, enclose shale shakers and related equipment, in addition to careful consideration of which fluid system to use.

Modeling of oil mist and oil vapor concentration in the shale shaker area on offshore drilling installations.

The objective of this study was to develop regression models to predict concentrations of oil mist and oil vapor in the workplace atmosphere in the shale shaker area of offshore drilling installations. Collection of monitoring reports of oil mist and oil vapor in the mud handling areas of offshore drilling installations was done during visits to eight oil companies and five drilling contractors. A questionnaire was sent to the rig owners requesting information about technical design of the shaker area. Linear mixed-effects models were developed using concentration of oil mist or oil vapor measured by stationary sampling as dependent variables, drilling installation as random effect, and potential determinants related to process technical parameters and technical design of the shale shaker area as fixed effects. The dataset comprised stationary measurements of oil mist (n = 464) and oil vapor (n = 462) from the period 1998 to 2004. The arithmetic mean concentrations of oil mist and oil vapor were 3.89 mg/m(3) and 39.7 mg/m(3), respectively. The air concentration models including significant determinants such as viscosity of base oil, mud temperature, well section, type of rig, localization of shaker, mechanical air supply, air grids in outer wall, air curtain in front of shakers, and season explained 35% and 17% of the total variance in oil vapor and oil mist, respectively. The developed models could be used to indicate what impact differences in technical design and changes in process parameters have on air concentrations of oil mist and oil vapor. Thus, the models will be helpful in planning control measures to reduce the potential for occupational exposure.

Expert assessment of exposure to carcinogens in Norway's offshore petroleum industry.

This study presents and evaluates an expert group's assessment of exposure to carcinogens for defined job categories in Norway's offshore petroleum industry, 1970-2005, to provide exposure information for a planned cohort study on cancer. Three university and five industry experts in occupational hygiene individually assessed the likelihood of exposure to 1836 combinations of carcinogens (n=17), job categories (n=27) and time periods (n=4). In subsequent plenary discussions, the experts agreed on exposed combinations. Agreement between the individual and the panel assessments was calculated by Cohen's kappa index. Using the panel assessment as reference, sensitivity and specificity were estimated. The eight experts assessed 63% of the 1836 combinations in plenary, resulting in 265 (14%) convened exposed combinations. Chlorinated hydrocarbons, benzene and inhalation of mineral oils had the highest number of exposed job categories (n=14, 9 and 10, respectively). The job categories classified as exposed to the highest numbers of carcinogens were the mechanics (n=10), derrick workers (n=6) and process technicians (n=5). The agreement between the experts' individual assessments and the panel assessment was kappa=0.53-0.74. The sensitivity was 0.55-0.86 and specificity 0.91-0.97. For these parameters, there were no apparent differences between the university experts and the industry experts. The resulting 265 of 1836 possible exposure combinations convened as "exposed" by expert assessment is presented in this study. The experts' individual ratings highly agreed with the succeeding panel assessment. Correlation was found between years of experience of the raters and agreement with the panel. The university experts and the industry experts' assessments had no apparent differences. Further validation of the exposure assessment is suggested, such as by new sampling data or observational studies.

Inter-rater agreement in the assessment of exposure to carcinogens in the offshore petroleum industry.

OBJECTIVES: To evaluate the reliability of an expert team assessing exposure to carcinogens in the offshore petroleum industry and to study how the information provided influenced the agreement among raters. METHODS: Eight experts individually assessed the likelihood of exposure for combinations of 17 carcinogens, 27 job categories and four time periods (1970-1979, 1980-1989, 1990-1999 and 2000-2005). Each rater assessed 1836 combinations based on summary documents on carcinogenic agents, which included descriptions of sources of exposure and products, descriptions of work processes carried out within the different job categories, and monitoring data. Inter-rater agreement was calculated using Cohen's kappa index and single and average score intraclass correlation coefficients (ICC) (ICC(2,1) and ICC(2,8), respectively). Differences in inter-rater agreement for time periods, raters, International Agency for Research on Cancer groups and the amount of information provided were consequently studied. RESULTS: Overall, 18% of the combinations were denoted as possible exposure, and 14% scored probable exposure. Stratified by the 17 carcinogenic agents, the probable exposure prevalence ranged from 3.8% for refractory ceramic fibres to 30% for crude oil. Overall mean kappa was 0.42 (ICC(2,1) = 0.62 and ICC(2,8) = 0.93). Providing limited quantitative measurement data was associated with less agreement than for equally well described carcinogens without sampling data. CONCLUSION: The overall kappa and single-score ICC indicate that the raters agree on exposure estimates well above the chance level. The levels of inter-rater agreement were higher than in other comparable studies. The average score ICC indicates reliable mean estimates and implies that sufficient raters were involved. The raters seemed to have enough documentation on which to base their estimates, but provision of limited monitoring data leads to more incongruence among raters. Having real exposure data, with the inherent variability of such data, apparently makes estimating exposure in a rigid semiquantitative manner more difficult.

Exposure to carcinogens for defined job categories in Norway's offshore petroleum industry, 1970 to 2005.

OBJECTIVES: To identify and describe the exposure to selected known and suspected carcinogenic agents, mixtures and exposure circumstances for defined job categories in Norway's offshore petroleum industry from 1970 to 2005, in order to provide exposure information for a planned cohort study on cancer. METHODS: Background information on possible exposure was obtained through company visits, including interviewing key personnel (n = 83) and collecting monitoring reports (n = 118) and other relevant documents (n = 329). On the basis of a previous questionnaire administered to present and former offshore employees in 1998, 27 job categories were defined. RESULTS: This study indicated possible exposure to 18 known and suspected carcinogenic agents, mixtures or exposure circumstances. Monitoring reports were obtained on seven agents (benzene, mineral oil mist and vapour, respirable and total dust, asbestos fibres, refractory ceramic fibres, formaldehyde and tetrachloroethylene). The mean exposure level of 367 personal samples of benzene was 0.037 ppm (range: less than the limit of detection to 2.6 ppm). Asbestos fibres were detected (0.03 fibres/cm3) when asbestos-containing brake bands were used in drilling draw work in 1988. Personal samples of formaldehyde in the process area ranged from 0.06 to 0.29 mg/m3. Descriptions of products containing known and suspected carcinogens, exposure sources and processes were extracted from the collected documentation and the interviews of key personnel. CONCLUSIONS: This study described exposure to 18 known and suspected carcinogenic agents, mixtures and exposure circumstances for 27 job categories in Norway's offshore petroleum industry. For a planned cohort study on cancer, quantitative estimates of exposure to benzene, and mineral oil mist and vapour might be developed. For the other agents, information in the present study can be used for further assessment of exposure, for instance, by expert judgement. More systematic exposure surveillance is needed in this industry. For future studies, new monitoring programmes need to be implemented.

Exposure to oil mist and oil vapour during offshore drilling in norway, 1979-2004.

OBJECTIVES: To describe personal exposure to airborne hydrocarbon contaminants (oil mist and oil vapour) from 1979 to 2004 in the mud-handling areas of offshore drilling facilities operating on the Norwegian continental shelf when drilling with oil-based muds. METHODS: Qualitative and quantitative information was gathered during visits to companies involved in offshore oil and gas production in Norway. Monitoring reports on oil mist and oil vapour exposure covered 37 drilling facilities. Exposure data were analysed using descriptive statistics and by constructing linear mixed-effects models. RESULTS: Samples had been taken during the use of three generations of hydrocarbon base oils, namely diesel oils (1979-1984), low-aromatic mineral oils (1985-1997) and non-aromatic mineral oils (1998-2004). Sampling done before 1984 showed high exposure to diesel vapour (arithmetic mean, AM = 1217 mg m(-3)). When low-aromatic mineral oils were used, the exposure to oil mist and oil vapour was 4.3 and 36 mg m(-3), and the respective AMs for non-aromatic mineral oils were reduced to 0.54 and 16 mg m(-3). Downward time trends were indicated for both oil mist (6% per year) and oil vapour (8% per year) when the year of monitoring was introduced as a fixed effect in a linear mixed-effects model analysis. Rig type, technical control measures and mud temperature significantly determined exposure to oil mist. Rig type, type of base oil, viscosity of the base oil, work area, mud temperature and season significantly determined exposure to oil vapour. Major decreases in variability were found for the between-rig components. CONCLUSIONS: Exposure to oil mist and oil vapour declined over time in the mud-handling areas of offshore drilling facilities. Exposure levels were associated with rig type, mud temperature, technical control measures, base oil, viscosity of the base oil, work area and season.

[What do we know about chemical hazards in offshore work?]. / Hva vet vi om kjemisk helsefare offshore?

BACKGROUND: Norway has been an oil-producing nation for more than thirty years and a large number of Norwegians have been or are working on oil rigs. There are several chemical substances present on the oil platforms, and these factors may influence workers' health. MATERIAL AND METHODS: The international literature on offshore chemical exposure and health is summarised. RESULTS: The most important groups of chemical substances used on oil rigs are described: crude oil, production chemicals, asbestos and drilling chemicals. Different types of exposure during maintenance work are described as well. Very few exposure data are published. Acute, irritative health effects from chemical exposure are described, as well as chronic health effects like skin disorders and cancer. These workers seem to have a higher risk, that may be related to benzene exposure, of developing acute myelogenous leukemia. INTERPRETATION: Physicians who are treating patients working in the oil industry are advised to be aware of possible adverse health effects from the work environment on the rigs. Further exposure studies and research in this area are highly recommended, as the literature is scarce.