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The Precautionary Principle

 

When we decide to avoid the use of certain chemicals, materials, or building techniques because they may harm our health or cause serious environmental damage, we are employing the precautionary principle. This principle says that we should avoid potentially harmful actions even if we are not scientifically certain of the extent of the potential damage.

The precautionary principle came to prominence in the 1990s, after participants in the United Nations’ Earth Summit of 1992 declared, “Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.” Policymakers have debated finer points on whether the principle should come into play only in the case of “serious or irreversible” damage and whether only “cost-effective” measures should be considered, but either way, the principle (or sometimes, “precautionary approach”) has caught on.

In 2005, San Francisco passed an environmentally preferable purchasing ordinance that requires city agencies to consider the precautionary principle when buying everything from toilet paper to computers to fleet vehicles. The city developed a list of criteria for evaluating potential purchases and updates them regularly as scientific knowledge changes. In 2006, the U.S. Green Building Council (USGBC) embraced precaution when its board of directors referenced the idea within its guiding principles.

The precautionary principle has been embraced by the European Union, where the REACH (Registration, Evaluation, Authorization, and Restriction of Chemical Substances) law requires manufacturers to prove chemicals safe before they can be put on the market. A bill in Congress would set a similar standard in the U.S. In the meantime, organizations such as the Healthy Building Network track potentially harmful chemicals and their use in building materials.

We often hear about the precautionary principle in relation to building materials and the chemicals they contain. Polystyrene insulation is a good example—laced with brominated flame retardants, it also has a high global warming potential in its extruded form due to blowing agents used. The scientific assessment of the human health and environmental impacts of the flame retardant most commonly used in polystyrene is not yet complete, but some experts suggest we move away from polystyrene to avoid potential harm.

Historically, chemicals and other materials have often been assumed “innocent until proven guilty” of environmental harm, with harm often being found and understood long after major and irreversible damage has occurred. In this context, the precautionary principle admirably turns the tables. It is not without critics, however, who argue that it is impractical (since everything carries risks), and doesn’t adequately weigh benefits of new technologies. To put it another way, some argue that not employing a new technology or chemical should also be evaluated using the precautionary principle.

September 1, 2010

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1. Illustration: Peter Harris
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