Toxicological Risk Assessment of a Nickel Compound Found on the Surfaces of Replacement Hyperstretch Neoprene (CWU-83P) Neck and Wrist Seals for a Cold water Submersion Survival Suit

Abstract

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: