Chlorinated Paraffins BT - Volume 3 Anthropogenic Compounds Part K

Abstract

Chlorinated paraffins or polychlorinated n-alkanes (PCAs) consist of C10 to C30n-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 chapter reviews the existing data on the production, uses, reactions, methods of quantitative analysis, and levels of PCAs, and includes an assessment of environmental distribution using a steady state non-equilibrium fugacity-based chemical fate models. Short chain PCAs (C10 to C13 with 60-70% chlorine) have similar molecular weight and physical properties (octanol-water partition coefficient, water solubility, vapor pressure) to many persistent organochlorines such as PCBs and toxaphene. Medium chain (C14 to C17) and long chain (C18to C30) PCAs are extremely hydrophobic and nonvolatile and likely to be associated with particles in aquatic systems. The limited biodegradation data suggests that PCAs are less persistent in water, sediments, or biota than other organochlorines. To date there is limited information on the distribution and fate of PCAs in the environment. There have been recent advances in the analysis of C10 to C13 PCAs using high resolution negative ion mass spectrometry. Interlab comparisons have shown that both high resolution and low resolution negative ion mass spectrometry can be employed to determine PCAs in environmental samples, although agreement between laboratories is poor compared with the determination quantitation of PCBs and organochlorine pesticides. There are indications that PCAs are widespread environmental contaminants at ng/l levels in surface waters and ng/g (wet weight) levels in biota. However, environmental measurements of PCAs are very limited at the present time in the USA and Canada and are only slightly more detailed in western Europe. Application of the Equilibrium Criterion Model, Level III (steady state, nonequilibrium) to representative short (C12H20Cl6) and medium chain PCAs, (C16H24Cl10) using the best available physical-chemical property data and estimated degradation rates, showed that that medium chain compound C16H24Cl10 would achieve higher concentrations in sediment and soil than the short chain C12H20Cl6 because of slower degradation rates and lower water solubility. Volatilization from water to air of both compounds was predicted by the model suggesting the possibility of long range transport via atmosphere and oceans. The environmental residence time of C16H24Cl10 is estimated to be 350 days compared to 170 days for C12H20Cl6. Future studies will require better analytical methods and reference materials certified for PCA content. Additional data is needed to evaluate exposure to PCAs in the environment, particularly in light of their continued production and usage around the globe.