Kobe, Japan (CNN) -- For the last several days, I have been in beautiful Kobe, Japan, reporting about the World Health Organization forum on urbanization and health.
Given that more than half the world's population now lives in cities, with the number expected to increase significantly, the implications on individual health are becoming pretty clear. A lot of the discussion here has been specifically on the quality of the air we breathe, and the news has not been great.
For starters, an Environmental Protection Agency report found the air in many cities is simply too dirty to breathe. Think about that: as things stand now, toxic pollution has become a particular disease of the world's urbanites, affecting more than a billion of its citizens.
And, if you look more closely at the impact of pollution, you see more than half the burden on human health is on people in developing countries already crippled with poverty and few resources.
For example, here in Kobe, there is an obvious marriage between the industrial sector filled with at least 15 large factories, and residential areas close by. Walking around the city, you quickly see the consequences of explosive urban growth. The combination of factory emissions with exhaust from trucks, buses and automobiles is proving toxic to human health.
Today, urban pollution kills a million people a year, according to the United Nations. And, conventional wisdom was that it took a long time to develop health problems associated with pollution, but it is simply not the case. A study published in 2007 found that on days when pollution is high, cities see spikes in emergency room visits over the next 24 hours. Just one day.
If you live in a city, chances are you might not even notice just how polluted the air has become. Turns out that within four days of breathing the dirty air in, your body sort of becomes accustomed to it, despite the fact that your airways becomes more inflamed and restricted, and your risk of lung and heart problems start to rise.
The good news is that fixes are being tested in many cities around the world. In Shanghai, coal-free downtown areas have been established, which has already resulted in lower particulate matter. In New York City, there is a ban on idling trucks and buses. And in Bogota, transport management policies have led to increased use of mass transit.
Having spent time in many major cities on every continent in the world, it is safe to say "urbanization" is here to stay. As individuals and as societies, however, it is up to us to try to make the beautiful city we live in a safer and healthier one.