Not in the US
In the US, power generation is switching from coal to natural gas. It's hard to get asthma from CO2, the only significant byproduct of burning natural gas.
Your assumption that it can only get worse is completely contrary to US history. Maybe you weren't around in the '60s, but I can tell you that in the LA area by the end of the day you couldn't take a deep breath without coughing from the ozone, and often your eyes were watering. That was ancient history by the '80s. While in the LA area this was due to improvements in cars, other parts of the country also saw air pollution declines because of restrictions on coal burning. While we still have a ways to go, the trend since the '60s has always been in the direction of decreasing pollution.
