First the bad news. Over the last decade, hundreds of peer-reviewed scientific studies from all over the world have clearly established a direct link between dirty air and increased risk of death from lung disease. In 2002, for example, California state scientists estimated that microscopic particles of airborne soot from auto exhaust cause more than 9,300 deaths in the state each year. That’s more Californians than die from AIDS, homicide and traffic accidents combined.

But lung-related death and disease may not be the worst of it. A new study published in the prestigious journal Environmental Health Perspectives found that Toronto residents who live in neighborhoods with the worst traffic-related air pollution had a 40 percent higher risk of death from heart attack and stroke.

Researchers tracked 2,400 patients over 40 at an asthma clinic at Toronto Western Hospital, in a 10-year study that was controlled for factors such as obesity, smoking and lung function—and that mapped patients according to their addresses. When they tracked the addresses of the 298 individuals who died over the course of the study, they saw a pattern emerge.

"When you compared those living in the less polluted areas to those living in the higher pollution areas, the death rate is higher for those in the latter group," said [primary investigator Michael Jerrett of UC Berkeley]. … "Surprisingly, over the last five years, researchers have discovered that air pollution causes heart attacks," he said.

Now the good news. A study funded by the EPA and the Centers for Disease Control found that over the past two decades, cleaner air has added nearly five months to average life expectancy in the United States. It’s the first study to show that reducing air pollution translates into longer life.

"Who would have thought you could get almost half a year in increased life expectancy on average just from cleaning up our air somewhat?" says study co-author Arden Pope, an environmental economist at Brigham Young University in Provo, Utah. "That seems to me like a pretty good investment" in clean-air programs.

Of course, some people won’t accept the facts. Bakersfield Californian blogger Lois Henry recently declared: "Claims about air pollution’s devastating effects on public health are, um, hooey. Or at least largely hooey." She cited studies showing that Californians are actually living longer—which doesn’t mean that air pollution isn’t preventing them from living even longer—and the opinion of an environmental consultant associated with the right-wing Reason Foundation.

Henry took Earthjustice to task for continuing to sue the EPA for stricter air pollution standards in the San Joaquin Valley, which has by some measures the dirtiest air in the country. I could pick a fight with her, but instead I’ll quote one of the comments from her readers:

What have you been smoking?