Are there other persistent organic pollutants? A challenge for environmental chemists.

Water Science and Technology Directorate, Environment Canada, Burlington, Ontario, Canada.
Environmental Science and Technology (Impact Factor: 5.48). 04/2007; 40(23):7157-66. DOI: 10.1021/es078000n
Source: PubMed

ABSTRACT The past 5 years have seen some major successes in terms of global measurement and regulation of persistent, bioaccumulative, and toxic (PB&T) chemicals and persistent organic pollutants (POPs). The Stockholm Convention, a global agreement on POPs, came into force in 2004. There has been a major expansion of measurements and risk assessments of new chemical contaminants in the global environment, particularly brominated diphenyl ethers and perfluorinated alkyl acids. However, the list of chemicals measured represents only a small fraction of the approximately 30,000 chemicals widely used in commerce (>1 t/y). The vast majority of existing and new chemical substances in commerce are not monitored in environmental media. Assessment and screening of thousands of existing chemicals in commerce in the United States, Europe, and Canada have yielded lists of potentially persistent and bioaccumulative chemicals. Here we review recent screening and categorization studies of chemicals in commerce and address the question of whether there is now sufficient information to permit a broader array of chemicals to be determined in environmental matrices. For example, Environment Canada's recent categorization of the Domestic (existing) Substances list, using a wide array of quantitative structure activity relationships for PB&T characteristics, has identified about 5.5% of 11,317 substances as meeting P & B criteria. Using data from the Environment Canada categorization, we have listed, for discussion purposes, 30 chemicals with high predicted bioconcentration and low rate of biodegradation and 28 with long range atmospheric transport potential based on predicted atmospheric oxidation half-lives >2 days and log air-water partition coefficients > or =5 and < or =1. These chemicals are a diverse group including halogenated organics, cyclic siloxanes, and substituted aromatics. Some of these chemicals and their transformation products may be candidates for future environmental monitoring. However, to improve these predictions data on emissions from end use are needed to refine environmental fate predictions, and analytical methods may need to be developed.

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Our findings, combined with those from several other studies, suggest that industrial discharge or dumping, rather than diffuse sources which are often associated with population density, dominates the input of Dechloranes to Lake Ontario. Temporal trends of input differ among lakes. Most sites in Lake Superior are still receiving increasing fluxes of DP and Dec602, while these have been declining in Lake Ontario from the peak around 1990. An important finding of this work is that the relative abundance of the two DP isomers, represented by fsyn, increases with increasing distance from the potential discharge source in Niagara Falls, NY, suggesting the anti-DP isomer is more vulnerable to degradation during the long range atmospheric transport. These results have been published in Yang et al. (Environ. Sci. Technol., 2011, 45, 5156–5163). 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Compared with PCBs, PBDEs, and most Dechloranes, the concentrations of these emerging BFRs depend much weakly on the content of the sediment organic matter (OM). Normalization of the concentration by the OM content does not strengthen the correlations against latitude and longitude, suggesting a source controlled spatial distribution. Comparison among the analytes groups is given in the graph above for the estimated total burden in the Great Lakes sediments. These estimates are provided in this report for comparison purpose only and should be used with caution, because the calculation was based on a limited number of the sampling sites involved in this work. Apparently, PCBs still outweigh others as the dominant contaminant. Dechlorane Plus (DP) have accumulated in a relatively large quantity comparable to that of PBDEs. It is followed by Dec602 and mirex. At present, the accumulations of the emerging BFRs are still much lower than those of PBDEs and Dechloranes. 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