I’m reading Katherine Boo’s masterful "All the Beautiful Forevers," which is about hard living in a Mumbai shanty town, hemmed in between a sewage lake, a plastics factory and the city’s booming international airport.

As it happens, I lived in Mumbai back in the 1960s, and then revisited in 1999, and the difference was marked. Overwhelmed by its constantly swelling population, Mumbai was now choking on fumes from auto rickshaws, cooking fires and diesel trucks — I had a sore throat during my entire visit, and rarely saw the sun.

Things are even worse in New Delhi, with almost 20 million people and what the New York Times describes as “an acrid blanket of gray smog.” It’s not surprising, because the city adds 1,400 vehicles a day to the more than 7 million already registered there. Fine-particle pollution is up 47 percent in the last 10 years, and nitrogen dioxide up 57 percent. This happened despite some effort to close polluting factors, impose emission standards and convert those rickshaws to natural gas.

We should care about this because the latest Global Burden of Diseases, Injuries, and Risk Factors Study, published in December in The Lancet, for the first time includes air pollution as a top 10 risk factor for disease—up there with high blood pressure, tobacco and alcohol.

The Guardian reports, “In 2010, more than 2.1 million people in Asia died prematurely from air pollution, mostly from the minute particles of diesel soot and gasses emitted from cars and trucks.” The study says 1.2 million of those deaths were in East Asia and China, and 712,000 in South Asia, including India. Perhaps it's not surprising that a recent U.S. study declaring that India has the worst air pollution in the world sparked a firestorm in that country, with blame going in all directions. See the video:

Air pollution is, of course, still potent in the U.S. But it's improving, thanks to new federal laws and the work of super-vigilant agencies such as the California Air Resources Board (the only state agency empowered to set its own emission levels). Between 1980 and 2011, the EPA reports, GDP increased 128 percent and vehicle miles traveled jumped 94 percent. Population was up 37 percent and energy use 26 percent, but still emissions of the six principal air pollutants dropped 63 percent (but carbon dioxide emissions were up 21 percent).

The American Lung Association, which prepares an annual “State of the Air” report, says, “Thanks to a drop in particle pollution between 1980 and 2000, life expectancy in 51 U.S. cities increased by five months on average, according to a 2009 analysis.” California’s air is still dirty, but it’s getting better. According to this study, the state had 74 percent fewer unhealthy air days in 2011 than it had in 2000.

The lesson is that reducing auto density is really important, but absent that car exhaust needs to be rigorously controlled. It’s worked in reducing Los Angeles’ legendary smog, and it could work elsewhere in the world. I often point out to people that a modern Hummer produces far less air pollutants than a 1960s Volkswagen Bug, no matter how fuel efficient it might be.

Exhaust smoke is a deadly brew containing carbon monoxide, nitrogen dioxide, sulphur dioxide, benzene, formaldehyde, lead and the tiny particles known as particulate matter (mainly from diesel).

Says the BBC, “There is no doubt that the more you are exposed the greater the risk is likely to be.” And people who already have respiratory ailments such as asthma and bronchitis are especially at risk. One in every 50 heart attacks in London may be air pollution-related, though they probably weren’t identified that way.

Only North America and Europe have tough air pollution laws, yet around the world, 3.2 million people died of air pollution factors in 2010. That’s a big killer, and it’s all around us, in the air we breathe.

Related post on MNN: The worst common air pollutants — and what they do to your body

MNN tease of air pollution: Shutterstock

Jim Motavalli ( @jmotavalli ) writes about cars, technology and the environmental world to anyone curious enough to ask.

Air pollution now a top 10 disease health risk
Air pollution from auto exhaust and other sources now poses one of the most serious health risks.