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The Risk of Multiple Sclerosis Among Petroleum Workers Exposed to Crude Oil and Other Hydrocarbons

Kirkeleit, Jorunn1; Riise, Trond1,2; Aarseth, Jan2; Farbu, Elisabeth3; Midgard, Rune4; Mygland, Aase5; Morland, Tore Jorgen6; Eikeland, Randi7; Telstad, Wenche8; Forland, Per Tore3; Morten Myhr, Kjell2

doi: 10.1097/01.ede.0000391847.81987.48
Abstracts: ISEE 22nd Annual Conference, Seoul, Korea, 28 August–1 September 2010: Solvent Exposure in Petrochemical Industry

1University of Bergen, Bergen, Norway; 2The Norwegian Multiple Sclerosis Competence Centre, Haukeland University Hospital, Bergen, Norway; 3Stavanger University Hospital, Stavanger, Norway; 4Molde Hospital, Molde, Norway; 5Sorlandet Hospital, Kristiansand, Norway; 6Telemark Hospital, Skien, Norway; 7Sorlandet Hospital, Arendal, Norway; and 8Central Hospital of Sogn and Fjordane, Forde, Norway.

Abstracts published in Epidemiology have been reviewed by the societies at whose meetings the abstracts have been accepted for presentation. These abstracts have not undergone review by the Editorial Board of Epidemiology.


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Environmental factors are likely to play an important role in the development of multiple sclerosis (MS). Offshore workers in the Norwegian petroleum industry are exposed to a number of chemical factors, such as organic solvents, mineral oils, and other hydrocarbons, suggested to contribute to an increased risk. Further, recently there has been a concern in the society about a perceived excess of MS in this industry. We therefore estimated the risk of MS in this population compared with the general working population in Norway.

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Using the Norwegian Registry of Employers and Employees, we included all 27,919 offshore workers registered from 1981 to 2003 and 366,114 referents from the general working population matched by gender, age, and community of residence. Based on the workers industrial classification codes for their first registered engagement in the offshore-related petroleum industry, we categorized the workers into 4 job categories. A diagnosis of MS among these workers was ascertained by linkage to the Norwegian MS-registry and discharge files from neurological departments covering the counties where the workers resided; resulting in a total of 733 patients with onset of disease after start of their working engagement. The risk of MS according type of occupation was estimated prospectively using Cox proportional hazard regression model including age, gender, level of education, and year of employment as covariates.

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There was no excess risk of MS among the offshore workers compared with the general working population. The workers in the 2 job categories assumed to have the most extensive contact to hydrocarbons (production and drilling) had a nonsignificantly decreased risk (RR = 0.54, 95% CI: 0.24.1–1.21 and RR = 0.92, 95% CI: 0.46–1.86).

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These findings do not support a major etiological role of crude oil, organic solvents, or other petroleum-based oil products in the development of MS.

© 2011 Lippincott Williams & Wilkins, Inc.