Proposal on limits for chemical exposure in saturation divers’ working atmosphere: the case of benzene

Abstract

Saturation diving is performed under extreme environmental conditions. The divers are confined to a limited space for several weeks under high environmental pressure and elevated oxygen partial pressure. At present, divers are protected against chemical exposure by standard exposure limits only adjusted for the increased exposure length, i.e. from 8 to 24 hours a day and from 5 to 7 days a week. The objective of the present study was to indicate a procedure for derivation of occupational exposure limits for saturation diving, termed hyperbaric exposure limits (HEL). Using benzene as an example, a procedure is described that includes identification of the latest key documents, extensive literature search with defined exclusion criteria for the literature retrieved. Hematotoxicity and leukemia were defined as the critical effects, and exposure limits based upon concentration and cumulative exposure data and corresponding risks of leukemia were calculated. Possible interactions of high pressure, elevated pO₂, and continuous exposure have been assessed, and incorporated in a final suggestion of a HEL for benzene. The procedure should be applicable for other relevant chemicals in the divers’ breathing atmosphere. It is emphasized that the lack of interactions from pressure and oxygen indicated for benzene may be completely different for other chemicals.

Keywords::

• Saturation diving
• breathing atmosphere
• chemical contamination
• hyperbaric exposure limit
• benzene

Acknowledgements

The authors wish to express their sincere thanks to Dr. Jorunn Kirkeleit at University of Bergen, Dept. of Public health and Primary Health Care, Research group for Occupational and Environmental Medicine, for her reviewing and helpful comments during the preparation of the manuscript.

Declaration of interest

This work was funded by Statoil, ExxonMobil and Gassco, Norway. Statoil is a Norwegian oil company operating in the petroleum industry in the North Sea, and is annually in charge of manned underwater services supplied by diving contractors. NUI AS is a competence centre in diving and underwater operations and is 100% owned by Statoil. NUI AS was a minor shareholder in Thelma AS was a small innovation company including environmental and indoor air analysis, occupational health and hyperbaric services. This company is no longer trading. COWI is a consultancy engineering company including environmental and occupational health services.