When the mercury climbs above 90 degrees on sticky, sun-drenched days, it's more than the heat and humidity you need to watch out for. Ozone, also known as smog, forms as vehicle exhaust, power plant emissions and other pollution bake in the lower atmosphere.
The Baltimore area is under a Code Orange air-quality alert today, meaning children and adults with breathing or heart ailments shouldn't spend much time outdoors.
This is not to be confused with the Code Red heat alert issued Sunday by the city Health Department, which opens air-conditioned "cooling" centers around town when the temperature gets above 90 degrees.
The B'more area has had five Code Orange days so far this year, thanks to hot spells in April and May. But that's half of what we had in 2009, when we also had one Code Red day - where air quality gets so bad even healthy people are advised to stay indoors or limit strenuous outdoor activities. The year before, 2008, was even worse, with 21 Code Orange days and 4 Code Red days.
While weather plays a big role in summer smog, laws and regulations cranking down on vehicle and power plant emissions appear to be having an effect, officials say, by removing the ingredients needed to make our air hard to breathe.
To see where the smog is and how bad it's been - or going to be - check out the Clean Air Partners website. You can sign up there for air-quality alerts. Also, for those who want to know more, I recommend "The Smog Blog," a daily diary of air quality in the US put together by atmospheric researchers at the University of Maryland Baltimore County. The map below, just one of the graphics on the website, depicts hourly ozone readings nationwide.
(2002 Baltimore Sun photo by Nanine Hartzenbusch; map Courtesy AIRNOW (EPA/Sonoma Technology Inc.) through the US Air Quality Smog Blog)