Persistent organic pollutants are chemicals that are:
- not quickly degraded in the environment
- potentially bioaccumulative
- toxic to humans and/or the environment, and
- spread around the world.
A chemical that has any one of these characteristics will pose some risk to the environment. But when they occur together, these characteristics provide a very strong indication that the chemical can cause environmental harm.
This combination of characteristics also makes it difficult to predict the possible environmental impacts, and more or less impossible to remove the chemicals from the environment once they are in it. Because of this, more than 180 countries have agreed to restrict or ban use of persistent organic pollutants.
Scientists look at whether chemicals have any of the four characteristics of persistent organic pollutants to help work out the risk to the environment. Often, having just the first two or three characteristics is enough to raise concerns. As a precaution, it is generally recommended to avoid using these chemicals.