Overview of GreenScreen Method

 
Summary

The Chemical Hazard Data Commons uses the GreenScreen® for Safer Chemicals as a framework for characterizing hazards associated with chemicals. The GreenScreen is a transparent, open standard for chemical hazard assessment designed to identify chemicals of high concern and safer alternatives. The GreenScreen:

  • characterizes the hazard level of substances for 20 human and environmental health endpoints and
  • benchmarks chemicals on a 4 point scale from highest to lowest concern (Benchmark 1 to 4)

It prioritizes the elimination of substances with a high hazard of cancer, mutagenicity, reproductive or developmental toxicity or endocrine disruption or are persistent bioaccumulative toxicants (PBTs). Its thresholds and priorities are aligned with GHS, REACH and many other international protocols identifying chemicals of high concern.

The GreenScreen List Translator (GSLT) is a tool for evaluating substances based on hazard lists from a range of governmental and professional scientific bodies.  All chemicals in the Data Commons are automatically screened under this protocol and characterized for hazard level for each list's relevant endpoint(s).. Chemicals identified on hazard lists which meet the GreenScreen criteria for highest concern are scored as LT-1. An LT-P1 score indicates a listing with a significant possibility of meeting the high concern criteria. While LT scores indicate chemicals known to have high hazard, the lack of an LT-1 or P1 score is not an indication of safety.

GreenScreen full assessments are produced by a licensed toxicologist who does a detailed review of the scientific literature to attempt to determine hazard levels for all endpoints and determine the GreenScreen benchmark. They may also use models and studies of analogs where data are scarce.  The Data Commons lists all known public GreenScreen assessments. GreenScreen full assessments, unlike the GreenScreen List Translator, can benchmark chemicals as lower concern.

The GreenScreen is a project of Clean Production Action who is responsible for the licensing of toxicologists to undertake full assessments and automators, including Pharos and the Data Commons, to provide List Translation scores.

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How the GreenScreen works - the Details

The Data Commons supports the two major analysis tools in the GreenScreen process:

  • GreenScreen List Translator (GSLT)
  • GreenScreen full assessment

Both GreenScreen tools begin by assigning hazard levels (very high/high/medium/low/very low) to each of 20 endpoints covering:

  • human health, such as cancer and reproductive toxicity
  • environmental health endpoints, primarily aquatic toxicity
  • physical hazards, specifically flammability and reactivity
  • environmental fate, specifically persistence and bioaccumulation.

They differ in how they assign these hazard levels, and the resulting scores the chemical can receive.

The GreenScreen List Translator (GSLT) assesses chemicals based on hazard lists issued by government and scientific professional bodies, such as the EU’s- CLP GHS H-Statements and California’s Prop 65. The process is as follows:

  • The criteria for each category in each list is assessed and assigned a hazard level for an individual endpoint.  For example, the  IARC Monographs On the Evaluation of Carcinogenic Risks to Humans category of Group 1 - Agent is Carcinogenic to humans receives a “High” for carcinogenicity.
  • Hazard levels are largely based on thresholds established by the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and by the USEPA’s Design for the Environment (DfE)/Safer Choice) program with additional criteria for endpoints not covered by those programs
  • Lists are also characterized as
    • Authoritative - high confidence or
    • Screening - lower confidence due to less comprehensive review, use of estimated data or other factors. 
  • Authoritative lists and screening lists are both further characterized as:
    • A lists: address a single endpoint and translate to one hazard level classification or a single Benchmark Score 
    • B lists: are based upon multiple endpoints or translate to a range of hazard levels or address only a specific form of the substance or a specific exposure route.
  • A chemical receives a hazard level for each endpoint based on the highest hazard assigned by the most authoritative lists. This is what is displayed in the Data Commons chemical profile Hazard Summary Table.
  • An “LT” score is then determined for the chemical based on if these hazard levels meet the criteria for GreenScreen’s highest concern category of Benchmark 1 (see below).

​All chemicals in the Pharos database are automatically screened under this protocol and receive one of the following scores:

  • LT-1 (List Translator Likely Benchmark 1) - The substance is on at least one  Authoritative A list that meets Benchmark 1 criteria.
  • LT-P1 (List Translator Possible Benchmark 1) - On a list that overlaps Benchmark 1 criteria and/or is a lower confidence Authoritative B or Screening list.
  • LT-UNK (List Translator Benchmark Unknown) - Listed only on a GSLT list that does not meet or overlap Benchmark 1 criteria.
  • NoGS (No GreenScreen information) - Not on a GSLT list and there is no public GreenScreen full assessment.

The List Translator is the first step in a GreenScreen Assessment and is also used as a stand alone screening protocol by various program including the Health Product Declaration and LEED

A GreenScreen Assessment is a comprehensive assessment of a chemical. The assessor (known as a Profiler) uses scientific literature, analogs and models to assign a hazard level for each endpoint. Each endpoint hazard level is also assigned a  confidence level based on the quality of the data or strength of the analog.

The Profiler then benchmarks chemicals on a 4 point scale from highest concern (Benchmark 1) to lowest concern (Benchmark 4).

  • BM-1 - Benchmark 1: Avoid ­- Chemical of High Concern
  • BM-2 - Benchmark 2: Use but Search for Safer Substitutes
  • BM-3 - Benchmark 3: Use but Still Opportunity for Improvement
  • BM-4 - Benchmark 4: Prefer­ - Safer Chemical

Benchmark 1 is reserved for substances with a high hazard of any of the following:

  • Carcinogenicity (Cancer)
  • Mutagenicity
  • Reproductive or developmental toxicity
  • Endocrine disruption
  • Persistent and bioaccumulative toxicants (PBTs) or very persistent or very bioaccumulative toxicants  (vPs, vBs and vPvBs) 

High hazards for other endpoints, such as neurotoxicity and respiratory sensitization, receive a Benchmark 2.

This prioritization scheme aligns with a wide range of national and international definitions of substances of high concern, such as the European Union’s Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) and Classification, Labeling and Packaging (CLP) Regulations, and the Stockholm Convention on Persistent Organic Pollutants.

DG - Data gaps: Strict guidelines limit the amount of data gaps. Where there are data gaps, the Profiler will include a worst case scenario to determine the lowest possible Benchmark score if the data gap were filled with the highest possible hazard.  These Benchmarks include a subscript of DG

A chemical that has too many data gaps receives a:

  • BM-U - Benchmark U: Unspecified Due to Insufficient Data

TP - Transformation Products: The Profiler also will identify feasible and relevant environmental transformation products and benchmark them. If the Benchmark score is determined by the transformation products, the Benchmark score will include a subscript of TP

CoHC - Chemicals of High Concern: Version 1.4 of the GreenScreen added special rules for benchmarking polymers which include analysis of residual monomer and/or catalyst present at or above 100 ppm. If the Benchmark score is determined by one of these chemicals, the Benchmark score will include a subscript of CoHC

The Data Commons includes all known public GreenScreen assessments  that are produced by a Licensed GreenScreen Profiler certified by Clean Production Action (CPA).

Learn more: For more detail on GreenScreen procedures and on its usage in industry, reference CPA’s website on the GreenScreen for Safer Chemicals.