Dr Hans Sanderson
Aarhus University, Department of Environmental Science
4000 Roskilde, Denmark
Scott Belanger, Research Fellow, The Procter & Gamble Company, Mason OH USA
Monica Lam, Senior Scientist, The Procter & Gamble Company, Mason OH USA
Kristin Connors, Scientist, The Procter & Gamble Company, Mason OH USA
Martin Hansen, Senior Scientist, Aarhus University, 4000 Roskilde, Denmark
Anna M Brun, PhD student, Aarhus University, 4000 Roskilde, Denmark
Objectives: Our overall aim is to support the development of methods to allow accurate and precise aquatic environmental risk assessment of cationic polymers. This will lay the foundation for regulatory acceptance based on improved methods for regulatory assessment and compliance testing of polymers. However, there are significant gaps in the knowledge base. How can we reliably measure the aquatic exposure for these charged compounds? How do we describe environmental exposures and control lab testing exposure concentrations, when dissolved organic carbon (DOC) species such as humic acids can reduce the apparent toxicity of cationic polymers by one or two orders of magnitude? How can we consistently test and describe the toxicity of cationic polymers, which are not expected to pass biological membranes? How do we characterize their impacts in a modern context of the CLP definition substances hazard and toxicity properties? How do we describe the dose-response for materials that are expected to affect the outer membranes of aquatic organisms and functionalities? This proposal seeks to assess a group of closely related but understudied model cationic polymers that are widely used in industry. The level of cationicity is lower than many others that are studied (e.g., wastewater treatment plant flocculating agents) and are probably somewhat more challenging to model. We will determine if these polymers continue the trends established in QSARs of higher nitrogen-containing polymers in order to generalize toxicity and physical-chemical patterns. There are many pertinent and challenging questions regarding cationic polymers. The iTAP project will assess in a realistic and consistent way the environmental threat posed by cationic polymers. Below are the main objectives of the iTAP project, which will be address in the subsequent work packages:
Objective 1) Review: We will assess the various methods and tools currently available in the literature to measure or predict the toxicity and fate properties of cationic polymers (e.g., standard guidelines, sampling and analytical methods, SAR equations, fate models, etc.). We will review various physical chemical properties believed to demonstrate a correlation with effects (e.g., molecular weight, charge density, N-content, #C-N bonds, etc.) and propose which parameters to use in SAR equation development.
Objective 2) Exposure: Clarify the methodological scheme that should/shall be followed when assessing the environmental hazards of cationic polymers environmental hazards. We will assess the definition of the characteristics of appropriate dilution waters (i.e., OECD dilution water, tap water, tap water supplemented with humic acids, or river water) for standards and modified ecotoxicity tests. We will provide recommendations on methods for the appropriate monitoring of bioavailable concentrations, and discuss proposition of mitigation factors to be used when deriving classification from tests run with well-characterized river water or organic carbon amendments. We will discuss proposition of mitigation factors to be used when deriving PNECaqua from results derived from relevant OECD test guidelines. We will attempt to clarify whether or not the toxicity mitigation is similar to, a subset of, or independent of that typically considered in equilibrium partitioning.
Objective 3) Aquatic toxicity: We will update and organize the knowledge base on the aquatic toxicity of cationic polymers. Specifically, we will use the freshwater algae and cyanobacteria growth inhibition test (OECD 201) building on the work of Nolte et al (2017), the water flea acute test (OECD 202) and the reproduction test (OECD 211), lastly, the fish embryo acute toxicity test (OECD 236).
Objective 4) Aquatic risk: We will address environmental risks thorough description of the bulk approach (ECETOC, 2003) and review of exposure models’ applicability to cationic polymers (e.g. EUSES).
ECETOC. Sorptive substances, in: Environmental Risk Assessment of Difficult Substances, Technical Report No. 88, pp. 33-52. European Centre for Ecotoxicology and Toxicology of Chemicals, Brussels, Belgium.
Project Website: www.projects.au.dk/itap