Google is blocking search results

I can't see any other way of interpreting this than the fact that Google is obviously blocking search results in the pursuit of environmental regulations and politics.

Type the following into Bing's search form: "united states" "air pollution" graph +improving

and you get almost 64,000 results, including several links to the EPA and to Wikipedia:

Type the same thing into Google and you get 6 results, which are mostly junk: