New study done over time suggests that both long- and short-term exposure to diesel and other fuels and pollutants, when combined with higher levels of stress, are causing we humans to experience more respiratory illnesses–and making people with asthma significantly worse.

One study did tests for toxicity of particulate matter in Seattle, Denver, Mesa and other cities. It tested for short-term exposure effects on mortality, hospitalization, inflammation, cardiac function and asthma control–and for long-term effects on artherosclerosis and cardiac incidents. Another tested multiple U.S. and European cities.

As the populations of big cities around the world grow ever larger, the traffic congestion ever worse, and the resulting particulate matter ever denser, we humans have to start thinking hard about whether we want to control our populations by making more people get sick, have heart attacks, etc. (this approach will really add up in costs to society), or whether we want to start thinking about new ways of looking at how we get around and how we manufacture.

Those little paper masks from the medical supply store aren’t the most attractive fashion statements–and we won’t be able to see each other smile.