PCBs have been identified on surfaces and in component materials and equipment from inactive U.S. Navy nuclear submarines commissioned prior to 1970. Health risks associated with PCBs present onboard submarines were estimated for hypothetical crew members and shipyard workers. Median non-cancer hazard quotients for shipyard workers and submarine crew ranged between 0.4-54.6, with the highest quotients estimated for unprotected shipyard workers. Median cancer risk estimates ranged from 7.3 x 10(-6) to 1.1 x 10(-3) with the highest estimated risk calculated for unprotected shipyard workers. Our findings suggest that PCB surface concentrations found onboard inactive nuclear submarines commissioned prior to 1970 may be high enough to constitute a possible risk to the health of persons involved in dismantling of Navy submarines if PCB exposure is not minimized. Potential sources of uncertainty in our risk assessment include the correlation between PCB contamination levels on inactive versus active nuclear submarine vessels, the relationship between wipe sample concentrations and human exposure, dermal contact frequency with PCB-contaminated surfaces, carcinogenicity of PCBs in humans, and uncertainties inherent with the PCB cancer slope factor and oral RfD. Our findings support Navy policy that shipyard workers should wear personal protective equipment when PCB contamination is suspected or has been identified and that IH surveys should continue to identify sources of PCB contamination onboard vessels and reduce PCB contamination to concentrations that are reasonably achievable.

Abstract:Naval Health Research Center/Toxicology was requested to provide comment and endorse an action plan developed by Naval Air Warfare Center Aeronautics Division (NAWCAD) to remove surface nickel from hyperstretch neoprene (CWU-83/P) neck and wrist seals used in cold water submersion survival suits. The nickel compound present on the surface of the seals is most likely nickeldialkyldithiocarbamate which is a common chemical additive used to prevent photoxidation and breakdown of rubber materials. There is no data on the chronic toxicity or carcinogenicity of nickeldialkyldithiocarbamates. The conservative approach for estimating the toxicological risk of nickeldialkyldithiocarbamate exposure to humans is to assume that these compounds have the same toxic properties as soluble nickel compounds. Lifetime average daily dose (LADD) estimates for persons wearing cold water survival suits were calculated using conservative exposure assumptions. Our calculations suggest that the average surface concentrations of Ni present on Hyperstretch neoprene seals do not pose a significant noncancer toxicological risk for humans. It is possible that a person could be exposed to nickeldialkyldithiocarbamate by hand-to-mouth transfer or by inhalation of airborne neoprene seal particles. However, it was assumed that the potential for oral and inhalation exposure to Ni from exposure to neoprene seals is most likely negligible. Dermal contact with Ni-containing materials may cause allergic skin sensitization and contact dermatitis in certain individuals; the surface concentration of Ni that elicits allergic contact dermatitis reactions in humans has not been determined. Acetone at a concentration of 70-75% should be used to wipe excess nickeldialkyldithiocarbamate from the surface of the neoprene seals at least 10 minutes prior to issue. Seals do not need to be cleaned except when prior to issue. Acetone is a solvent for dissolving rubber and frequent cleaning of the seals with acetone may cause rapid degradation of neoprene rubber over time. Persons involved in the cleaning of the neoprene seals should wear a NIOSH-approved respirator with an organic vapor cartridge.Background:

Abstract:Currently, the US Navy uses the solvent HFC-14lb to clean hydraulic gauges in a semiclosed system prior to gauge calibration. The US Navy will not be able to use the solvent HFC141b after 31 December, 2002, because of a ban on its manufacture. The Navy is considering both Vertrel MCA and HFE-71DE as replacements for HFC-141b. Both solvents are azeotropic mixtures consisting of trans 1,2-DCE and either fluorocarbons or ethers. Both Vertrel MCA and HFE-71DE have high vapor pressures, therefore, they are expected to volatilize at room temperature. The potential routes of exposure to solvent during the gauge cleaning process are inhalation of vapors and dermal contact with liquid when pouring new and spent solvents into flasks and containers. At this time, toxicity information is not available for the azeotropic mixtures Vertrel MCA and HFE-71DE. It was decided that the human NOEL data for trans 1,2-DCE is the most appropriate toxicity data for deriving OEL's for Vertrel MCA and HFE-71DE. OEL's were derived using procedures recommended by the National Research Council. The NOEL of 800 ppm trans 1,2-DCE in air for an exposure time of 30 minutes was used as the endpoint for deriving 5, 10, 30, 60, 90, 120, 240, and 480-minute OEL's for Vertrel MCA and HFE-71DE. The derived OEL's for Vetrel MCA and HFE-71DE range between 48 for 5 minute exposures to 0.5 ppm for 8 hour exposures. The derived OEL's for Vertrel MCA and HFE-7IDE are lower than the 8-hour TLV-TWA for trans 1,2-DCE of 200 ppm, but the conservative nature of the recommended OEL's reflect the lack of toxicity information for Vertrel MCA and HFE-71DE and their major ingredients. Naval Health Research Center/Toxicology endorses the use of personal protective equipment when handling or using these chemicals as recommended by Naval Environmental Health Center industrial hygienists.Background:

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