Issues in Ecology Number 12 Summer 2004 Box1 Log Kaw The combination of physicalproperties that give [A]gas phas rise to environmentally mobile and ioaccumulative substances is best viewed by a Log Koa the key partition 0 one medium (e.g.air)compared to anothe dium(e.gwater)atequilibrium Forexample B]AqU has if a chemical hasan air-water partition coeffic Br10 PBDE Atrazine B(a)P an indexoftoxicity becausesolubility inoctanol 2 3 4 5 6 micssolubility in biological lipid tissuesand ndicates thepotential for bioaccumulation.Van Log Kow Figure2-Plot of ents,air-wa air.aque entry into the environment (B)aqueous phase contaminantsaccumulateor aretransported asa functionof their physicalchemica micals that partition into the aqueous properties Many toxicchemicalsaremultimedia andpartition intomorethanone environment regardlessofmodeofentry,(C)solid Jt. m Tovis assessed on a case-by-case basis,however,since our ability to list includes 2,863 organic chemicalsproduced or imported at predict such biotransformations in the food web is weak. ng( Since the late 1990s.there has been a major increase in chemicals in comm roe as of 1981 of whichabout2 704an measurement and detection of organicchemicals that are not considered HPVCsbased on production levels greater than 1,000 presently dassifiedaspersistentorganicpollutants inwaters affected tons per year and 7,842 arelow production volumechemicals h rates of 10 to 1000 tons per year. h (PBDEs) operation XeoPmue5 mkehundreds of everyday EU and other ntor 2000.that lis products from non-stick cookware and water-and stain- contained 5,235 substances produced at levels greater than repellent coatings for carpetsand raincoats tocosmetics, 1,000 tons globally. s( s)use nics mental persistence, manu aty,the c found in paints and adhesives as wellas fluids used in Councilof Chemical Associationshas established ntly inusesuch asendosulfan and lindane HPVCs for which f datas etsontoxicity and envi mental fat owever,th full data sets 4 Issues in Ecology Number 12 Summer 2004 assessed on a case-by-case basis, however, since our ability to predict such biotransformations in the food web is weak.10 New emerging organic contaminants of interest Since the late 1990s, there has been a major increase in measurement and detection of organic chemicals that are not presently classified as persistent organic pollutants in waters affected by atmospheric contaminants. These chemicals include: • polybrominated diphenyl ether flame retardants (PBDEs) widely used in polymers and textiles; • fluorinated surfactants used to make hundreds of everyday products from non-stick cookware and water- and stain￾repellent coatings for carpets and raincoats to cosmetics, paper products, and polymers for electronics; • chlorinated naphthalenes (PCNs) used in cable insulation, wood preservation, electronics manufacturing, and dye production; • chlorinated alkanes (also known as chlorinated paraffins) found in paints and adhesives as well as fluids used in cutting and machining metals; and • pesticides currently in use such as endosulfan and lindane. Even this expanded list, however, represents only a tiny fraction of the chemicals in commerce or even of the subset known as “high production volume chemicals” (HPVCs). The U.S. HPVC list includes 2,863 organic chemicals produced or imported at levels greater than 450 tons per year.11 In the European Union, the European Inventory of Existing Commercial Chemical Substances lists 100,195 “existing chemicals” – meaning chemicals in commerce as of 1981 — of which about 2,704 are considered HPVCs based on production levels greater than 1,000 tons per year and 7,842 are low production volume chemicals produced at rates of 10 to 1,000 tons per year.12 The Organization for Economic Cooperation and Development maintains an HPVC list based on a compilation of the U.S., E.U., and other national inventories. In 2000, that list contained 5,235 substances produced at levels greater than 1,000 tons globally. While the majority of these HPVCs are probably not a concern with regard to their environmental persistence, bioaccumulation, and toxicity, the chemical industry has recognized that data are lacking for many of these chemicals. In the absence of data, production volume is assumed to be a surrogate for occupational, consumer, and environmental exposure.13 The International Council of Chemical Associations has established a list of 1,000 HPVCs for which full data sets on toxicity and environmental fate are to be developed by 2004.14 However, this will leave more than 50 percent of high production volume chemicals without full data sets. Box 1 — Physical and Chemical Properties of Atmospherically Transported Organic Chemicals The combination of physical properties that give rise to environmentally mobile and bioaccumulative substances is best viewed by a two-dimensional plot of the key partition coefficients (Figure 2). Partition coefficients describe how much of a contaminant will be in one medium (e.g. air) compared to another medium (e.g. water) at equilibrium. For example, if a chemical has an air-water partition coefficient of 2, then there will be twice as much of the chemical in air than in water when expressed in equivalent concentrations. The octanol-water partition coefficient (Kow) is commonly used as an index of toxicity because solubility in octanol mimics solubility in biological lipid tissues and indicates the potential for bioaccumulation. Van de Meent et al.3 proposed classifying chemicals as either (A) gas phase chemicals that partition into the gas phase regardless of their mode of entry into the environment, (B) aqueous phase chemicals that partition into the aqueous environment regardless of mode of entry, (C) solid phase chemicals that partition into soils and sediments, and (D) multimedia chemicals that partition into more than one environmental medium. To visualize these categories, a global scale multimedia model (similar to GloboPOP4 ) was applied that assumed no degradation except in air (class A), water (class B), and soil (class C). The shaded areas in Figure 2 reflect substances with a wide range of air-water and octanol-water partition coefficients, which indicate their relative affinity for air vs. water or for the lipid tissues of organisms vs. water, respectively. Figure 2 – Plot of the two key partition coefficients, air-water partition coefficients (log Kaw) and octanol-water partition coefficients (log Kow), illustrating predicted environmental media (gas—air, aqueous—water, and solid—soil) where organic contaminants accumulate or are transported as a function of their physical chemical properties5 . Many toxic chemicals are multimedia and partition into more than one medium