Environmental fate and exposure assessment of water-soluble polymers

Polymers are a diverse group of materials with a wide range of properties, and many polymer types are likely be released to the environment. However, environmental risk assessment methods for polymers are lacking, and little is known about their environmental fate and exposure, particularly for water-soluble polymers. The aim of this thesis was to investigate and apply methods for environmental fate and exposure assessment of water-soluble polymers, and thus develop recommendations for how environmental exposure of water-soluble polymers could be better assessed in practice.
Current methods for environmental risk assessment of chemicals were first reviewed in the context of their applicability to both solid and water-soluble polymers. The need for adaptation of current methods for polymers was identified, as well as development of analytical methods, characterisation of environmental fate parameters for exposure modelling, and in-depth analysis of polymer transformation in the environment.
A lower-tier exposure modelling approach was then developed to identify, group, and prioritise water-soluble polymers released from household products. Preliminary estimates of environmental exposure and risk were obtained for several water-soluble polymer types. The results indicated that polyethers, polyquaterniums, and polyol ethoxylate esters have the potential to pose an unacceptable environmental risk and that these materials should be a priority for further research and risk assessment.
The environmental fate and behaviour of two prioritised polyethers (polyethylene glycol and polypropylene glycol) was then studied, as despite their low persistence and low toxicity, these polymers may be of concern due to their high usage volumes. An analytical method for quantitation of individual polymer chains was first developed, and used to obtain an in-depth understanding of environmental fate behaviour of different polymer chains within the polymer mixtures. Characterisation of soil sorption indicated dependence on polymer molecular weight and functional group, as well as mixture interactions which may impact fate testing. Analysis of environmental transformation mechanisms and kinetics confirmed biodegradation via sequential chain shortening for both polymers, and provided a basis for kinetics modelling of water-soluble polymers in which mixture components are simultaneously broken down and formed. Both sorption and biodegradation data indicated that shorter polyether chains are likely to persist for longer in surface water than larger chains. Overall, these studies provide crucial information on both polymer environmental risk assessment and method development, and current environmental exposure and potential risk of water-soluble polymers.