Environmental chemistry and toxicology of polychlorinated n-alkanes

Polychlorinated-n-alkanes (PCAs) or chlorinated paraffins consist of C10 to C30 n-alkanes with chlorine content from 30% to 70% by mass. PCAs are used as high-temperature lubricants, plasticizers, flame retardants, and additives in adhesives, paints, rubber, and sealants. This review presents the existing data on the environmental chemistry and toxicology of PCAs and a preliminary exposure and risk assessment. There is limited information on the levels, fate, or biological effects of PCAs in the environment. This results both from the difficulty associated with quantifying PCAs, because of the complexity inherent to commercial formulations, and from the limited knowledge of their physicochemical properties and biodegradation rates. There are indications that PCAs are widespread environmental contaminants at ng/L levels in surface waters and ng/g (wet wt) levels in biota. However, environmental measurements of PCAs are very limited in the U.S. and Canada, and are only slightly more detailed in western Europe. Assuming that reported water concentrations are mainly caused by the short chain (C10-C13) compounds, aquatic organisms may be at risk from exposure to PCAs. Fugacity level II modeling for two representative PCAs, using the best available physicochemical property data and estimated degradation rates, suggested that C16C24Cl10 would achieve higher concentrations in biota, sediment, and soil than C12H20Cl6 because of slower degradation rates and lower water solubility. Environmental residence time of C16H24Cl10 is estimated to be 520 d compared to 210 d for C12H20Cl6. Future studies will require better analytical methods and reference materials certified for PCA content. Additional data are needed to evaluate exposure of biota to PCAs in the environment, particularly in light of their continued production and usage around the globe.