From the Union of Concerned Scientists:
Disregarding and misrepresenting recommendations from their own scientists, the Environmental Protection Agency (EPA) recently proposed new air pollution standards that do not sufficiently protect public health. The new rules apply to particulate matter pollution, sources of which include agricultural activity, vehicle exhaust, and emissions from coal-fired power plants. Over 2,000 recent studies have linked particulate matter exposure to heart disease, respiratory ailments, and premature death.
The Union of Concerned Scientists has organizaed a campaign to educate and take action regarding this issue. Read the complete explanation at the UCS Web site.