I don't take it seriously.
I read the article and nowhere do they have any data or empirical evidence showing what effects, if any, 22 parts per million has on the human body. For that, they link this article from another site that still doesn't have any data.
Interesting site though. Here are some of the heavies who run that organization:
...He is a 2001 recipient of an award from Fairness and Accuracy in Media’s Project Censored for his story, Plutonium Pancakes....
...Mr. Featherstone has been National Grassroots Coordinator of the Endangered Species Coalition...
...He is our token urbanite. He and his family have developed a unique urban area that revolves around integrating the arts with living and working spaces.
...Ms. Christianson also studied theatre and dance while in college, which helped her later gain professional experience in marketing, grant writing, and business. She has several years experience in administration, having worked for an international engineering firm in Seattle. She also started a "green" team in this office and introduced sustainable concepts to the corporate office.
Not the type I trust to disseminate studies or any type of information for that matter.