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Section III Applications of SSDs This section presents various applications of species sensitivity distributions (SSDs) to illustrate the ways in which SSDs are currently used in practice. It has two subsections, A on derivation of environmental quality criteria and B on ecological risk assessment of contaminated ecosystems. The first subsection starts with a description of the true start of adopting SSD-based methods in an international regulatory context. Further, the subsection presents four examples of implementation of SSDs in the derivation of environmental quality criteria, two from North America, and two from Europe. The second subsection presents six examples of applications of SSDs in ecological risk assessment that illustrate the range of environmental problems that can be tackled by SSD-based methods, alone or combined with other methods. The chapters show how SSDs can function in a range of applications, from formal tiered risk assessment schemes to life cycle assessments of manufactured products. The chapters presented here were meant to present the range of applications of SSDs, without attempting complete coverage of all SSD applications. © 2002 by CRC Press LLC A. Derivation of Environmental Quality Criteria © 2002 by CRC Press LLC 10 Effects Assessment of Fabric Softeners: The DHTDMAC Case Cornelis J. van Leeuwen and Joanna S. Jaworska CONTENTS 10.1 Introduction 10.2 DHTDMAC Behavior in Water 10.3 Effects Assessment of DHTDMAC 10.4 Risk Management 10.5 Discussions about the Selection of Species and Testing for Ecotoxicity 10.6 Discussions about the Extrapolation Methodology 10.7 Communication and Validation: The Development of a Common Risk Assessment Language 10.8 Current Activities Abstract — DHTDMAC was a test case for the ecotoxicological risk assessment of chemicals. High political and economic stakes were involved. There is no doubt that the (inter)national discussions on DHTDMAC accelerated the mutual acceptance of the new extrapolation methodologies to assess environmental effects of chemicals based on Species Sensitivity Distributions. These discussions went through a three-step process of (1) confrontation, (2) communication, and (3) cooperation. From a general perspec-tive, the cooperation evolved to European Union (EU)-approved risk assessment meth-odologies. In a more limited sense, the DHTDMAC case resulted in the development and marketing of a new generation of fabric softeners that are readily biodegradable. 10.1 INTRODUCTION DHTDMAC, dihydrogenated-tallow dimethyl ammonium chloride (Figure 10.1), a quaternary ammonium surfactant, has been used as a fabric softener, to the exclusion of almost all other substances, in the household laundry rinsing process. Consequently, the chemical has been widely dispersed and may have contaminated the aquatic and terrestrial environment even after sewage treatment. The technical-grade product © 2002 by CRC Press LLC H3C Cl – (CH2)17CH3 N+ H3C (CH2)17CH3 FIGURE 10.1 Chemical structure of DHTDMAC. contains impurities such as mono- and trialkyl ammonium compounds with varying carbon chain lengths from C14 to C18. The C18 variety is the most abundant. In the Netherlands about 2000 tonnes/year (as active ingredient) were used in the early 1990s. For the whole of Europe the amount used was approximately 50,000 tonnes/year. In 1990, the use of fabric softeners became a political issue as a result of a discussion in the Dutch Parliament. This discussion was the result of disagreements between the detergent industry and representatives of the Dutch Ministry of the Environment (VROM) regarding the conclusions of a report prepared by the Dutch Consultative Expert Group Detergents–Environment (DCEGDE, 1988). An alterna-tive risk assessment on DHTDMAC, including the comments of the detergent indus-try and a reaction by the representatives of VROM, was published in a Dutch journal (Van Leeuwen, 1989). This article catalyzed policy discussions and attracted public attention in the media. In the end, fabric softeners containing DHTDMAC were classified as dangerous for the environment. In the discussions and publications in the 1990s the acronym DTDMAC was most often used, which actually refers to DHTDMAC but with some unsaturated bonds in the alkyl chains. As a result of risk management discussions between the Netherlands Association of Detergent Industries and VROM (VROM/NVZ, 1992; De Nijs and de Greef, 1992; Roghair et al., 1992; Van Leeuwen et al., 1992a) and to reduce the uncertainties in risk assessment for this type of compound, additional research on DHTDMAC was conducted at the National Institute of Public Health and the Environment (RIVM) in the Netherlands. The studies comprised (1) exposure modeling of DHT-DMAC in the Netherlands, (2) chemical analyses of the substance in effluents, sewage sludge, and surface waters, and (3) assessment of ecotoxicological effects. The DHTDMAC case was the first case in which extrapolation methodologies based on Species Sensitivity Distributions (SSDs) were applied in risk assessment of industrial chemicals in the European Union (EU). But the DHTDMAC case was more. It was a classical clash between (1) science (ecotoxicological extrapolation methodology and SSDs), (2) environmental policy (the application of the precau-tionary approach; i.e., how to deal with uncertainties in risk assessment), and (3) the economy (the high market value of the fabric softeners for the chemical industry in the Netherlands and Europe). After this debate, a constructive cooperation followed between industry, VROM and RIVM. This chapter describes these risk evaluations of DHTDMAC and the cooperative actions. Note that the prediction of environmental concentrations is also subject to recent modeling development (e.g., Feijtel et al., 1997; Boeije et al., 2000), but the description of that subject in detail is beyond the scope of this chapter. © 2002 by CRC Press LLC 10.2 DHTDMAC BEHAVIOR IN WATER DHTDMAC is a difficult substance to assess because of (1) its extremely low water solubility (<0.52 pg/l), (2) its high adsorptivity (with strong ionic and hydrophobic interactions), (3) its tendency to form complexes with anionic substances and min-erals, and (4) the formation of precipitates. As is evident from the high variability in the available data sets, all these properties have implications for the estimation of physicochemical parameters, bioavailability, ecotoxicity, and monitoring. For example, reported sorption coefficients to suspended solids vary between 3,833 and 85,000 l/kg (Van Leeuwen, 1989; ECETOC, 1993a). The rate of decomposition of DHTDMAC greatly depends on the presence of sediment, microbial adaptation, and the type of dosing. Degradation is likely to be slow in surface water, where the concentrations are generally lower than those used in laboratory biodegradation tests. Studies with similar cationic surfactants have led the Dutch Consultative Expert Group Detergents–Environment (DCEGDE, 1988) to the conclusion that degradation will probably fail in surface water that has not been adapted; however, after adaptation the substance becomes inherently, completely biodegradable (ECETOC, 1993a). In 1990, no data were available on the anaerobic degradation in aquatic sediments. The laboratory results on aquatic toxicity of DHTDMAC are highly dependent on test conditions, sample preparation, and the presence of impurities. Compared with other surfactants, the chemical appears to be relatively toxic to algae when tested in reconstituted water. In natural waters, effects may be observed at concen-trations two to three orders of magnitude higher. In reconstituted water, the lowest no-observed effect concentration (NOEC) was observed with Selenastrum capricor-nutum (0.006 mg/l). In treated sewage effluents diluted in river water the NOEC for Selenastrum was 20.3 mg/l (Versteeg et al., 1992). Because of the extremely low solubility of DHTDMAC in the reconstituted water experiments, isopropanol was used as a carrier solvent. At this moment there is limited understanding of the physical form of DHTDMAC in this toxicity test. However, opinions have been expressed that this may have a strong impact on the results. In addition, MTTMAC (the derivative mono-tallow trimethyl ammonium chloride) is present in the recon-stituted water studies with commercial-grade DHTDMAC and its contribution to toxicity should be taken into account because it is more toxic than DHTDMAC, but readily biodegradable. 10.3 EFFECTS ASSESSMENT OF DHTDMAC What follows here is a summary of the work done by the Ministry of VROM and RIVM as published in 1992 (Van Leeuwen et al., 1992a). There were two major discussions at that time: (1) a discussion about the validity of the input data (the results of the toxicity tests) and (2) a discussion about the effects assessment (extrap-olation) methods. This is why different sets of toxicity data were used (Table 10.1) and why different effect assessment methods were applied on these data (Table 10.2). The results of the ecotoxicity studies from Roghair et al. (1992), the Dutch Consultative Expert Group Detergents–Environment (DCEGDE, 1988) and Lewis and Wee (1983) are summarized inTable 10.1. The NOECs are nominal concentrations © 2002 by CRC Press LLC ... - tailieumienphi.vn
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