Today's another Code Red air quality day in the Baltimore area.  Health experts recommend folks stay indoors, particularly those with asthma or other chronic breathing difficulties.  They also urge driving less and avoiding refueling during the daytime, to reduce the release of smog-forming emissions.

Ground-level ozone, commonly called smog, reached unhealthful levels as predicted around 2 pm in the Edgewood area of Harford County, and to a "code orange" level in the Aldino area, meaning levels were high enough to affect sensitive individuals with breathing problems.

The hot summer has made breathing clean air tougher much of the summer. This is the seventh "Code Red" day this summer for the Baltimore area, compared with just one during last year's balmy, rainy summer and four during 2008. And there've been 27 "code orange" days in the B'mroe area - as opposed to 10 last year - when folks with asthma and other chronic lung conditions need to be careful about exerting themselves outdoors.

It should be noted that smog levels have generally improved since the 1980s, as states and the federal government have required cleaner-burning gasoline and more pollution controls on cars and trucks and power plants.

But scientists have found that chronic exposure to even lower levels of ozone can be harmful to health, so the Environmental Protection Agency is considering setting even tighter standards for health air, which is generating push back from industries fearing more costly regulation of their emissions.