An environmental risk assessment profile of two synthetic polymers

A number of environmental fate and effects studies on two distinctly different polycarboxylates were conducted as part of a product stewardship program. These studies led to the development of an environmental risk assessment for the two materials. Polymer emulsion (PE) is a typical anionic, styrene acrylic polymer (MW 50,000-60,000) used in coating applications. Resin polymer (RP), insoluble at neutral pH but increasingly soluble at pH greater than or equal to 8, is a neutral-charged, styrene-acrylic polymer (molecular weight 4,500-9,000) used primarily for graphic arts products. Some amount of both materials will enter the environment given their use and disposal patterns. Their environmental fate is driven by physical-chemical characteristics. Both polymers demonstrated low biodegradation and bioaccumulation potential and strong sorption to soils, sludge, and sediments in laboratory and/or field studies. Ecotoxicity test results on a variety of plant and animal species indicated a very low order of acute and chronic toxicity. The environmental risk assessment included characterization of exposure in relevant environmental matrices, characterization of adverse effects or hazards to receptors for which there are complete exposure pathways, and characterization of risk by comparison of predicted exposure levels to adverse effect threshold levels. Based on conservative exposure assumptions, the safety margins established in this assessment indicate that the use of PE and RP, in both commercial and household applications, presents a very low risk to aquatic organisms in the water column and sediments, as well as to terrestrial plants, invertebrates, and wildlife. These polymers are also compatible with wastewater and solid waste treatment systems.