Health Care Without Harm has created a decision making process called Green Screen. Following is a summary of the method as described in a paper submitted to the US Green Building Council as it was debating the creation of a credit in the LEED rating system that might limit the use of PVC. The Green Screen is based on four principles:
- Life cycle Thinking - considering the whole life cycle of a product or process and the impacts at all the stages from raw material extraction through to end of life disposal, reuse, or recycling.
- Pollution Prevention - using the prevention of negative pollutants as a goal rather than measuring the quantity of allowable pollution.
- Continuous Environmental Improvement - always looking for the better option as materials evolve and minimizing trade offs along the way toward true sustainability.
- Precautionary Principle - take action on early warnings and seek the safer alternatives
Using the four principles as guiding forces the decision making process is set up in a hierarchy of screens against which a material/chemical is evaluated. Health Care without Harm suggests a screening based upon toxicity and used in this order:
- Chemicals identified as global or regional priorities by international convention.
- Chemicals of regional and international concern because of their physicochemical properties.
- Chemicals with chronic toxicity.
- Chemicals with acuter toxicity.
Anyone can create a set of screens and use this method when selecting materials and assessing chemical compounds. The goals of the people creating the screens will determine the nature of each screen. Health Care Without Harm has human health as a fundamental priority and therefore the screens focus on human health effects including end-of- life concerns. This type of screening requires an analysis of the chemical inputs and outputs at every stage of the products life cycle. And when setting up the screens, the order they are sequenced in is important. The first screen is the most objectionable item and then the sequence follows from most objectionable down to the least objectionable. Each screen represents a criteria that a product/chemical would have to be able to meet and therefore pass through before it could be accepted. So, in this case, the first screen eliminates any product/chemical that contains a chemical that has been identified as a global or regional priority by international convention. If one of these chemicals is found anywhere in the life cycle of the product/chemical then it is rejected. If the product/chemical has not been identified as a priority by an international convention then the next screen is applied and so on until the product/chemical either passes through all the screens and is accepted for use or is rejected by failing to meet the criteria of one of the screens.
These five screens were suggested that could be used to evaluate PVC and other building materials:
- Use or generation as byproduct of persistent organic pollutants (POPs) and ozone depleting chemicals (ODCs)
- Use of US Environmental Protection Agency's (EPA's) list of persistent, bioaccumulative toxics (PBTs) and the Oslo Paris (OSPAR) Convention list of chemicals for priority action across the material's life cycle.
- Use of known carcinogens, mutagens, reproductive toxicants, developmental toxicants, neurological toxicants, endocrine disruptors, and very persistent or very bioaccumulative chemicals in the manufacture of the material.
- Use or byproduct of acutely toxic chemicals in the materials's lifecycle.
- Evaluate positive attributes of a material: Is it biodegradable or easy to close-loop recycle at the end of its use life?
Most of the screens in these two examples are negative, meaning they highlight things to be avoided. But, positive green screens are helpful as well. A green screen can be set up to promote positive sustainable attributes such as recyclability or degradability. And then products and materials can be assessed and compared based on their positive attributes. Green Screens can be used in combination. The Green screen for toxicity and end-of-life concerns could be used along with a positive green screen looking at recyclability. Which screens are used depends on the factors people want to consider in their decision making process.
One fundamental aspect of a green screen is that it includes "knock-out chemicals", meaning the toxicity profile is of such high concern that they are priorities for elimination and therefore when present in the life cycle of a material, exclude the material from consideration for use. And as noted in the conclusion section of the report:
- "In placing life cycle toxicity and end-of-life concerns at the front of their environmental evaluation of a product, hospitals are taking actions consistent with their concern for human health. Recognizing that product life cycles may contribute to adverse health effects in diverse communities and populations, hospitals are seeking products with less toxic impacts across their life cycle. Yet if these concerns are to be addressed, many business sectors must address them if they are to be alleviated."
The goal of this summary is to understand the basic concept of a Green Screen. There are more complex concepts relating to chemicals that need to be understood and evaluated in order to use the screening process. Please read the full text of the referenced paper for a more in depth understanding of "inherent toxicity" and "distinguishing between chemical use and chemical byproducts" in order to understand how these concepts influence a green screen.
USGBC page with link this is the page on the USGBC website that has a link to the document listed above.