A conversation with Shari Franjevic, GreenScreen® Program Manager on the updated method
Last week CPA released a new and updated GreenScreen method (version 1.4) to address chemicals, polymers and products. Why did you and your team do this?
Since its launch in 2007, GreenScreen has gone through several revisions, but this update to version 1.4 is particularly significant. Although it was clear how GreenScreen could be applied to single chemicals, users were asking for more guidance on how to assess materials and products which is what we hope we have now achieved with this new update.
We also wanted to address the complexities of polymer hazard assessment with a rigorous and clearly defined approach. We focused on polymers because they are ubiquitous in our economy and environment. We researched previous precedents and ways of assessing the hazards of a polymer, filled in the many gaps, and wove it all together. We also clarified and aligned with definitions used in global regulatory frameworks such as GHS and REACH, so that we have a clear and harmonized way of talking about what we are evaluating.
Now after two years of in-depth research and conversation with experts from around the world, we are happy to finally release this new version of the GreenScreen method, which is openly transparent and free to download from our website. For the first time the GreenScreen method defines how to assess the hazards of both polymers and products in a clear, specific, and standardized way.
What are the key challenges in assessing polymer hazards and how does GreenScreen v1.4 address them?
Assessing polymer hazards is complex!
Polymers are often considered to have low toxicity because they consist of molecules that are too large to be biologically available. In fact, it is for this reason there is a lack of toxicity data available for polymers – existing regulations generally don’t require such information to be provided by manufacturers. However, polymers are really a collection or mixture of polymer chains with different lengths and smaller molecules called oligomers, monomers, and catalysts. These smaller molecules can be more toxic and their presence in the final polymer depends on how complete the reaction is and how “clean” the product is.
Two polymers with the same CAS number made by different manufacturers or processes can have different types and amounts of these small and potentially more hazardous molecules. In addition, the types and amounts of these small molecules can depend on the life cycle stage of some polymers. For example, a thermoset polymer may be sold when partially reacted and then cured (further reacted) in a later stage of the manufacturing chain.
Previous GreenScreen versions did not explicitly address variability in polymer hazards across manufacturers and life cycle stages, nor explicitly recognize polymers as a collection of molecules or provide a single GreenScreen Benchmark™ score for the collection of molecules. Instead, in previous versions a GreenScreen Benchmark score was assigned to the polymer and a separate GreenScreen Benchmark score was assigned to each monomer. Oligomers were noted but not assessed. Since toxicity data are typically not available for the polymer, this usually resulted in the polymer being assigned a Benchmark-U --“Unspecified due to Insufficient Data,” which doesn’t provide the information decision-makers need and want.
In this latest release we really tried to tackle the “missing data” issue by acknowledging that polymers are mixtures of molecules. We based our solution on the precedent of the UN’s GHS framework for assessing mixtures, using ingredient hazards when data are not available for the mixture itself. Maintaining the precautionary approach that GreenScreen was built upon, we evaluate these smaller molecular ingredients in the polymer when they are present at relatively low levels (above 100 ppm). We also included more specific requirements for justifying low hazard scores assigned based on lack of biological availability.
We tackled the polymer identification issue by requiring that polymer assessments be specific to manufacturer, trade name, and life-cycle stage (where relevant) in addition to CAS number. We believe this added specificity with polymer identification will increase clarity, facilitate differentiation between polymers, and inform purchasing decisions.
It was a lot of work and we deeply appreciate the technical peer reviewers who contributed their time and expertise to the process.
How has the GreenScreen assessment of plastic products changed?
The primary difference is in how the polymer is evaluated. The assessment of the polymer itself had no clear method to do a deep dive investigation – until now. Each other ingredient in the plastic product or polymeric material, such as the plasticizers, stabilizers, and lubricants, is assessed separately, as in previous GreenScreen versions.
Will there be any substantial difference in how GreenScreen results for a polymer or product are presented?
No. Similar to chemicals, results for a polymer will be presented in a GreenScreen Assessment Report with a Hazard Summary Table and GreenScreen Benchmark™ score. For a product, a summary of the Benchmark score for each chemical and/or polymer in the product will be provided in an up-front summary, and the individual GreenScreen assessment reports with all the details will be attached.
GreenScreen is used to identify the hazards of a chemical and to find safer alternatives. Will the new methodology allow users to identify safer polymers?
Yes, that is the goal. We now have a more nuanced way to address the fact that polymers are mixtures of molecules of varying sizes and their composition can vary by manufacturer, trade name, and sometimes life-cycle stage. Our new method gives decision makers a clear single score for the polymer taking all these aspects into consideration. We believe this will help users make informed and safer choices.
How does GreenScreen address the issue of end-of-life treatment of polymers? The issue of plastic waste in the oceans and rivers has revealed how persistent this material is in the environment. Does GreenScreen assess this part of the life cycle of polymers?
GreenScreen® for Safer Chemicals is a chemical hazard assessment tool. Persistence is one of the eighteen hazard endpoints evaluated, and high Persistence particularly in combination with toxicity results in a lower Benchmark score.
In addition, the assessment of a chemical or polymer includes an evaluation of environmental transformation products. If a polymer degrades into something that is more persistent and/or toxic than the original polymer, the Benchmark score of the polymer may be downgraded. For example, a polymer used in electronics could end up in an uncontrolled open burning scenario at the end of life, so that would be taken into consideration when assigning a final Benchmark score. For products expected to end up in a landfill, the toxicity of the polymer itself as well as biological degradation products that could leach out of a landfill at the end of life would also be taken into consideration in the Benchmark score.
GreenScreen does not deal with quantity of waste because it does not include an assessment of material flows. A life cycle assessment is distinct from and complementary to a hazard assessment and addresses material and energy flows.
In 2014, CPA released The Plastics Scorecard which used GreenScreen to assess the hazards of polymers. How does the new method compare to The Plastic Scorecard?
The Plastics Scorecard evaluates polymeric materials, i.e, the polymer plus any additives like plasticizers, heat stabilizers, and lubricants, in two ways. The “Progress to Safer Chemicals in Manufacturing Score” is based on the hazards of chemicals used to produce a plastic polymeric material. A score of 0 means a “Chemical of High Concern” or “CoHC” is used as a primary input in each manufacturing stage of the polymeric material. GreenScreen was used to define the criteria for what qualifies as a CoHC. The second metric, the chemical footprint, provides the number and weight percent of CoHCs in a given polymeric material. However, the polymer in the polymeric material was not included as part of the chemical footprint measure, acknowledging the lack of toxicity data typically available and the assumption that long polymer chains generally have low toxicity.
In GreenScreen v1.4, there is now specific guidance on how to score the polymer, using information on small molecules present in the “mixture” if data are lacking on the polymer itself.
Are there any other highlights of GreenScreen v1.4 you want to raise?
We are constantly reviewing the GreenScreen Specified Lists™ and List Translator Map and GreenScreen v1.4 was no exception. The GreenScreen Specified Lists are authoritative lists incorporated into the hazard criteria and presence on a list is used as a line of evidence to classify a hazard as high, moderate, or low in a GreenScreen assessment. The GreenScreen Specified Lists™ and List Translator™ Map are used to generate GreenScreen List Translator™ scores. Our GreenScreen Professionals and Service Providers are instrumental in providing their expertise into this process. We publish a full list of the changes in concert with each GreenScreen version release.
Thanks for sharing your experience, Shari.