An excerpt from Green to Gold (pages 52):

"Not long ago, commuters couldn’t see six traffic lights ahead in Los Angeles. Today air quality is not perfect, but it’s much better. Significant air quality controls on factories, cars, and other emissions sources have radically reduced air pollution levels over the past thirty years in the United States, Japan, and Europe. We all can breathe a little easier…While our air is cleaner, it is still not clean in many places. Serious health risks remain for people who suffer from respiratory illnesses like asthma. The European Commission estimated that air pollution causes over 300,000 premature deaths in Europe and costs $100 billion in lost work time."

The Science

The effects of poor air quality are well-known, with measurable increased rates of many ailments such as asthma. What's shifting over time is the definition of 'pollution' with scientists exploring smaller and smaller particles for their ill-effects. Where once "PM10", or 10 micrometer particles were studied closely, now discussion is on even smaller air contaminants, down to "PM2.5". The data on air quality around the world is only getting better and more detailed.

A number of governmental organizations and NGOs track this issue closely, including:

Business response and resources

The Clean Air Act is over 30 years old, so companies have had to manage air pollution for a long time. What's new and interesting is the addition of concerns about indoor air pollution. Big companies have some concern about employee health and periodically, the media picks up on "sick building syndrome" or some other ailment. Companies producing products for offices and indoor spaces are very aware of the trend. Herman Miller tests all its products for "off-gassing" to ensure they do not contribute to poor indoor air quality. See Greenguard for more on indoor air pollution and certification.