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Environ. Sci. Technol., Vol. 28, No. 4, 1994
0013-936X/94/0927-186A$04.50/0 © 1994 American Chemical Society
ES&T
AQUATIC RISK A S S E S S M E N T OF POLYMERS
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PA and regulatory agencies w o r l d w i d e have published approaches to the ecological assessment of chemicals under regulations such as the U.S. Toxic S u b s t a n c e s Control Act (TSCA), the U.S. Federal Insecticide, Fungicide and Rodenticide Act, and the European Economic Communities (EEC) Directive of Classification, Packaging, and Labelling of Dangerous Substances. Articles on regulatory ecological risk assessment and on determining toxicity to aquatic species have recently been published (2, 2). Regulatory guidance on aquatic risk assessment of nonpolymers such as surfactants, pesticides, or solvents is not new. However, the assessment and regulation of synthetic polymers is significantly different from that for nonpolymers. Synthetic polymers tend not to be readily absorbed by organisms, and the toxicity associated with some polymers may be substantially altered by key aquatic components. For example, the aquatic toxicity of detergent or water treatment polymers can be altered according to the levels of calcium and magnesium (3) or humic acid [4, 5} typically used in laboratory tests. There is a specific need to ensure that aquatic test systems adequately represent polymer toxicity during environmental testing of new products. Recent feature articles in ES&T have outlined broad approaches to pollution prevention through life cycle assessment and ecological engineering (6, 7). In addition, "stagegate" systems for new product development have been widely adopted by manufacturing industries to manage research and development (R&D) of products such as new polymers (8).
ucts because there are inherent advantages to a balanced ecological assessment program for commercial products (9). These advantages include reduced potential product liability a n d enhanced environmental protection through early prediction of unreasonable environmental product characteristics. Business growth opportunities exist in environmentally compatible products if processes for ecological risk assessment are truly aligned with new product R&D. Efficient m a n a g e m e n t of e n v i r o n m e n t a l assessment is clearly prudent in light of the high cost of environmental support. U.S. i n d u s t r y is Polymers that reach aquatic habispending approximately $10 billion tats in significant volumes include per year overall on R&D toward enthose used in cleaning products, as vironmental opportunities on top of dispersing agents in detergents, as significantly higher costs for comwastewater flocculants, and in wapliance with environmental laws ter treatment products for industrial cooling towers. Stage-gate systems (20). are based on predefined developAny process for R&D should be ment phases (stages) as well as decidefined in terms of when key inforsion criteria (gates), which can in- mation should be obtained as well corporate environmental issues for as what information should be obpolymer products. This article detained. A generic paradigm h a s scribes a process for aquatic risk asbeen developed through joint efsessment during R&D of new polyforts by i n d u s t r y , academia, a n d mers (see box). EPA to provide a framework for ecological risk assessment (2 2). ConsisCoordination of assessment tent with this framework, the following process outlines when A s s e s s m e n t of ecological risks information should be obtained (in during product manufacturing, use, this case, in coordination with busitransport, a n d disposal is increasness needs and ecological risk maningly becoming a planning tool duragement) and what should be obing the development of new prodtained (relevant aquatic toxicity and exposure information). Business resource commitments J O H N D. H A M I L T O N increase considerably as products KEVIN H. R E I N E R T are m o v e d t o w a r d scale-up (i.e., transfer of the manufacturing proM I C H A E L B. F R E E M A N cess to a facility) and commercialRohm and Haas Company ization (i.e., sales of p r o d u c t to Spring House, PA 19477-0904 customer). Figure 1 shows the sug-
PRODUCTS
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gested points of initiation and completion of early aquatic risk assessment during a typical (i.e., generic) new product development. To align new product development with environmental testing, the assessment should begin w h e n the new polymer is sufficiently characterized in terms of chemical structure and is considered to be a viable product from a business perspective. The assessment should be completed in time to provide information for regulatory purposes, for environmental d e c i s i o n s r e l a t e d to c u s t o m e r needs, or both. For example, data for EPA TSCA Section 5 Premanufacture Notice
regulations are obtained during new product development for polymers that do not fall under existing polymer e x e m p t i o n r u l e s (22). Most polymer classes that are presently ineligible for test exemption generally i n c l u d e p o l y m e r s t h a t are 500 {14). Figure 2 illustrates the useful approach of grouping polymers according to electronic charge, molecular weight, and solubility. Structural information can also be used to predict the fate of polymer classes in the aquatic environment. Reviews of polymer biodegradability have provided useful generalizations regarding biodégradation potential of polymers (e.g., 15, 16). Large addition polymers (e.g., polyacrylates) w i t h c a r b o n - t o - c a r b o n backbones do not t e n d to biodegrade significantly; however, nonbranched addition polymers with molecular weights of approximately 100,000 kg/year (220,000 lb/year) and at least one other criterion 3 Materials with predicted high solubility
Materials with predicted low solubility
Possible aquatic fate tests
Wastewater treatment Aerobic biodégradation, photolysis, hydrolysis, or adsorption isotherm Measured water solubility Wastewater treatment
John D. Hamilton has been involved with product risk assessment since joining the Rohm and Haas Company in 1989. Presently a group leader in environmental toxicology and ecological risk assessment, he provides modeling, risk assessment, and pollution prevention support to Rohm and Haas product development teams. His R.Sc. degree from Queen's University and M.Sc. degree from McGill University were followed by a Ph.D. in toxicology from the University of Cincinnati.
Production volume of > 454,000 kg/year (1,000,000 lb/year) and at least one other criterion 3 Materials with predicted high solubility
Wastewater treatment Aerobic or anaerobic biodégradation Photolysis, hydrolysis, or adsorption isotherm Measured water solubility Materials with predicted low solubility Wastewater treatment or aerobic biodégradation Anaerobic biodégradation Photolysis, hydrolysis, or adsorption isotherm "Criteria: Exposure via surface drinking water of >70 mg/kg, or release to surface water of 21000 kg/year (2200 lb/year) Adapted from Reference 19.
teria for assessing the degree of biodegradability, beginning with relatively rapid screening-level tests such as the Sturm, OECD, or Closed Bottle "ready biodegradability" tests. These tests have been applied to assess biodegradability in water as well as in sediments, sewage sludge, and soil. Ready biodegradability tests are typically followed by second-tier b i o d é g r a d a t i o n tests s u c h as the Z a h n - W a l l e n s or semicontinuous activated sludge "inherent biodegradability" tests w h e n a polymer in a ready biodegradability test does not reach EEC criteria for ready biodegradability. Framework for assessment As noted above, EPA has developed a framework for ecological risk assessment [11). The framework is intended to enhance consistency across ecological risk assessments in terms of risk assessment problem formulation, data analysis, and characterization of risk. The EPA framework has been recently applied in a broad range of ecological risk assessment case studies of varying complexity, including aquatic risk assessments of chemical discharges {24), and is flexible enough to provide an aquatic risk assessment of polymers during new p r o d u c t d e v e l o p m e n t (Figure 3). Using the terminology developed for the EPA framework, the risk assessment process is based on "stres-
s o r s , " w h i c h are defined as any physical, chemical, or biological entity that could induce an adverse response in an "ecological compon e n t . " An ecological c o m p o n e n t can be any part of an ecological system, including individuals, populations, communities, and the ecosystem itself. For the purpose of aquatic risk ass e s s m e n t for n e w p o l y m e r s , the stressor is polymer exposure and t h e e c o l o g i c a l c o m p o n e n t s are aquatic species. Assessment endpoints are usually the predicted effects on sensitive aquatic species based on laboratory toxicity data. Toxicity and fate data analysis follows problem formulation in the EPA framework and includes the technical evaluation of data on the effects of stressors (i.e., characterization of ecological effects) and the potential for exposure to stressors (i.e., characterization of exposure). Characterization of ecological effects s h o u l d identify the species found to be most sensitive in new polymer toxicity testing in order to protect sensitive species as well as relatively resistant species. Both EPA and industry have developed fate and exposure models that can characterize aquatic exposure during new product development and are a p p l i c a b l e to p o l y m e r d i s c h a r g e s . For e x a m p l e , the WWTREAT Model estimates the percent r e m o v a l of c h e m i c a l s t h a t p a s s through a sewage treatment facility
Kevin H. Reinert is a research section manager responsible for environmental toxicology and ecological risk assessment with the Rohm and Haas Company. During the past 10 years his work has included ecological risk assessment, modeling, litigation support, and waste management issues. He earned an M.S. degree from Rutgers University and a Ph.D. in biological science from the University of North Texas.
Michael B. Freeman is a group leader in formulation chemicals research with Rohm and Haas. Since 1988, he has been involved in studies of the environmental fate and effects of low molecular weight polymers that are used in water treatment, cleaning formulations, and related products. He joined Rohm and Haas in 1980 after obtaining a R.S. degree from the University of Delaware and a Ph.D. in chemistry from the University of Pennsylvania.
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FIGURE 3
Aquatic risk a s s e s s m e n t - p o l y m e r s (4) Problem formulation Stressors: polymers that may reach aquatic ecosystems
(5)
Ecological components: aquatic invertebrates, fish, and algae
(6)
Endpoints: assessment endpoints are effects on sensitive aquatic organisms. Typical measurement endpoints may include laboratory acute and chronic toxicity tests.
(7)
Data analysis
(9) Characterization of ecological effects
Characterization of exposure
Laboratory studies may be used to examine polymer aquatic toxicity.
Based on fate and application information, simple algorithms and computer models may be used to estimate discharge rates and aquatic concentrations.
Risk characterization
(8)
Τ
J
Estimated exposure concentrations may be compared to concentrations of concern using quotient methods where estimated exposure is compared to a toxicity threshold based on a safety factor.
(10) (11)
(12) (13) (14)
(15) (16)
w i t h both p r i m a r y a n d s e c o n d a r y (i.e., a c t i v a t e d s l u d g e ) t r e a t m e n t systems {25), and the Probability Di lution M o d e l h a s b e e n d e v e l o p e d by EPA to provide distributions of predicted aquatic concentrations postdischarge according to variance in receiving water flow [26). In ad dition, EPA's Chemical Engineering Branch has published a m a n u a l that provides algorithms for estimating aquatic discharges from unit opera t i o n s in i n d u s t r y s u c h as cooling t o w e r s (27). T h e s e g e n e r i c algo r i t h m s and m o d e l s are suitable to estimate aquatic exposure during n e w p r o d u c t d e v e l o p m e n t before detailed application or refined fate data are available. Risk characterization follows ex p o s u r e a n d toxicity analysis. Risk c h a r a c t e r i z a t i o n t h a t is u s e d for n e w p r o d u c t s is often based on a quotient a p p r o a c h in w h i c h expo sure is compared to some threshold of toxicity. For e x a m p l e , a n EPA "concentration of c o n c e r n " can be c a l c u l a t e d by d i v i d i n g t h e lowest median acute toxicity value (LC 50 or EC5()) or no-observed-effect concen tration by a safety factor. For aquatic risk assessments u n d e r the TSCA, safety factors range from 10 to 100 w h e n based on the level of data that is typically available for regulatory review during product develop ment (28). Additional toxicity test ing, fate m e a s u r e m e n t s , or refine ments of exposure may be triggered
192 A
during p r o d u c t development w h e n initial estimates of exposure exceed thresholds for toxicity.
(17)
Conclusions
(18)
A l t h o u g h m e a s u r e d information (i.e., t o x i c i t y , fate a n d d i s c h a r g e rate) can be used in the aquatic risk assessment of polymers during n e w p r o d u c t R&D, an early assessment of a q u a t i c risk b a s e d on p o l y m e r structure, electronic charge, molec ular weight, and solubility s h o u l d b e c o n d u c t e d before p r o d u c t i o n v o l u m e s , discharge rates, a n d de v e l o p m e n t c o s t s b e c o m e signifi cant. Systematic c o m m u n i c a t i o n of e n v i r o n m e n t a l risk to p r o d u c t de v e l o p m e n t teams could save longterm d e v e l o p m e n t costs and en hance responsible environmental quality programs.
(19)
(20)
(21)
(22) (23) (24)
Acknowledgments T h i s a r t i c l e is b a s e d o n a n e n v i r o n m e n tal quality p r o g r a m d e v e l o p e d at t h e R o h m a n d H a a s C o m p a n y , a n d o n infor m a t i o n p r o v i d e d b y J. V. N a b h o l z a n d R. B o e t h l i n g of t h e U . S . E n v i r o n m e n t a l Protection Agency. References (1) (2) (3)
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Bascietto, J. et al. Environ. Sci. Tech no!. 1990, 24, 1-15. Blum, D.J.W.; Speece, R. E. Environ. Sci. Technol. 1990, 24, 2 8 4 - 9 3 . Nabholz, J. V.; Miller, P.; Z e e m a n , M. In Environmental Toxicology and Risk Assessment; Landis, W. G.;
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H u g h e s , J. S.; L e w i s , Μ. Α . , E d s . ; American Society for Testing a n d Ma terials: Philadelphia, PA, 1993; ASTM1179, pp. 40-55. Gary, G. Α.; M c M a h o n , J. Α.; Kuc, W. J. Environ. Toxicol. Chem. 1987, 6, 469-74. G o o d r i c h , M . S. Environ. Toxicol. Chem. 1991, 10, 5 0 9 - 1 5 . Curran, M. A. Environ. Sci. Technol. 1993, 27, 4 3 0 - 3 6 . Mitsch, W. Environ. Sci. Technol. 1993, 27, 4 3 8 - 4 5 . Cooper, R. G.; Kleinschmidt, E. J. /. Prod. Innov. Manage. 1 9 9 3 , 10, 90-111. W a t e r h o u s e , B. R. Spectrum: Chemi cal Industry 1992, 26, 1 - 1 1 . Rich, L. A. Res. Technol. Manage. 1993, 36, 1 6 - 2 3 . " F r a m e w o r k for Ecological Risk A s s e s s m e n t " ; U.S. E n v i r o n m e n t a l Pro t e c t i o n A g e n c y : W a s h i n g t o n , DG, 1992; EPA/630/R-92/001. Fed. Regist. 1984, 49, 4 6 0 6 6 - 9 1 . Fed. Regist. 1993, 58, 7 6 7 9 - 7 7 0 1 . Potts, J. E.; Glendinning, R. Α.; Ackart, W. B. " A n Investigation of the Biodegradability of Packaging Plastics"; U.S. Environmental Protection Agency: Washington, DG, 1972; EPA-R2-046. Swift, G. ACS Symp. Ser. 1990, 433, 2-11. Hocking, P. J. Rev. Macromol. Chem. Phys. 1992, C32{\), 3 5 - 5 4 . " O E C D G u i d e l i n e s for T e s t i n g of C h e m i c a l s " ; O r g a n i z a t i o n for Eco nomic Co-operation a n d Develop ment: Paris, France, 1984. " E n v i r o n m e n t a l Effects G u i d e l i n e s " ; U.S. Environmental Protection Agency: Washington, DC, 1985; EPA 560/6-82-002. Boethling, R. "Exposure-based Envi r o n m e n t a l F a t e T e s t i n g for N e w Chemicals u n d e r TSCA"; Society of Environmental Toxicology and Chemistry A n n u a l Meeting Presenta tion, Cincinnati, OH, 1992. " C h e m i c a l F a t e Test G u i d e l i n e s " ; U.S. Environmental Protection Agency: Washington, DC, 1983; EPA 560/6-92-003. Opgenorth, H-J. In The Handbook of Environmental Chemistry; Hutzinger, O., Ed.; Springer-Verlag: N e w York, 1992; Vol. 3, Part F, p p . 3 3 7 - 5 0 . Freeman, M. B.; Bender, T. M. Envi ron. Technol. 1993, 14, 101-12. Official Journal of the European Com munities 1991, 34, 1-78. " A Review of Ecological Assessment Case Studies from a Risk Assessment Perspective"; U.S. Environmental Protection Agency: Washington, DC, 1993; EPA/630/R-92/005. Cowan, C. E. et al. Wat. Res. 1993, 27, 561-73. "User's Guide to P D M 3 " ; U.S. Envi r o n m e n t a l Protection Agency: Wash ington, DC, 1991; EPA Contract No. 68-DP-0166, Versar Inc. "Chemical Engineering Branch Man ual for t h e Preparation of Engineering Assessments"; U.S. Environmental Protection Agency: Washington, DC, 1991; EPA Contract No. 68-D8-0112, IT Environmental Programs. Nabholz, J. V. Sci. Total Environ. 1991, 109/110, 6 4 9 - 6 5 .
