The Sierra Club launched a lawsuit against Ameren (AEE 0.74%) this week, highlighting an alarming problem that seems to be getting scant attention. The case has to do with particulate-matter emissions from some of Ameren's coal plants, which consistently violate standards set forth under the Clean Air Act. You should care, because that particulate matter is killing people.

Source: Nick Bramhall

Killer air
Particulate matter is basically a bunch of teeny, tiny specs of airborne stuff. It's so small that it can penetrate deep into our lungs, leading to cardiopulmonary disease, cancer, and even death. It kills five times as many people as malaria every year, and almost twice as many as AIDS.

Particulate matter comes from a variety of sources. Some of it arises naturally, from forest fires, for example. But a whole lot of it comes from industry and technology. Vehicle tail pipes spew a ton of it, though less than they once did. Industrial production, especially of consumer goods and pesticides, emits a lot of particulate matter as well. Circling back to Ameren, coal-fired power plants are also big sources of particulate matter.

Some parts of the world have it worse than others. Breathing the air in Beijing all your life would cost you about three years of that life. New Delhi is even worse.

Here in the U.S., things have actually been getting better. After years of decline in American air quality, especially in regions such as the area around Los Angeles, tight regulations under the Clean Air Act helped to turn things around. Vehicle component manufacturers worked wonders in improved combustion and filtration technologies, putting a major dent in tailpipe emissions of particulate matter.

Right now, we actually have the opportunity to go soot-free, but it won't be without pain. While we've made a ton of progress in improving our air quality, it's still not enough. We need to do more to bring the public health threat down to reasonable levels.

The Environmental Protection Agency, or EPA, is about to start enforcing a tighter standard for particulate-matter concentrations. The EPA estimates that achieving the new limit will cost businesses an estimated $53 million to $350 million per year. For some high emitters, like coal-fired power plants, meeting the new requirement could be downright impossible. Watch the following video to find out more about this risk, and what it could mean.