What do they mean score big on pollution levels?

Question

http://www.forbes.com/2008/03/17/miami-seattle-orlando-biz-logistics-cx_tvr_0317cleanest_slide_5.html?thisSpeed=15000

Answer 1

maybe the pollution  levels are going up or down.

Answer 2

From reading the article it means that they've reduced the pollution levels (smog, greenhouse gas emissions, tainted water etc) in these places and they've basically been given a pat on the back for their efforts.  I guess it means that people with asthma or other breathing difficulties won't have to stay indoors as much when the air is bad making it a cleaner and safer place to live.