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DENVER — The brown cloud was back over metro Denver Wednesday. Thankfully, it didn’t stay around long enough to prompt air quality alerts. Air pollution, however, continues to cause problems for the elderly and those suffering from conditions like asthma.

Air testing results show Denver has had four days below government health standards since Jan. 1. That doesn’t necessarily mean more pollution is being emitted, as weather plays a big role.

“Winter time has always been a high-pollution season in Denver,” said Gregg Thomas, director of Denver’s Environmental Quality Division.

Thomas works within Denver’s Department of Public Health and Environment. He says there were three days of concern last winter. But this winter, the four days of sustained smog were grouped closer together, making the brown clouds more noticeable.

Denver air pollution needs to be put into perspective. In the early 1990s — when far fewer people were living in the Denver area — air quality was a lot worse. Now, it’s better, thanks to cleaner emissions technology.

“Our long-term trends of all these pollutants are down anywhere from 20 — in some cases 90 — percent,” Thomas said.

But Thomas says that if technology doesn’t keep up with population growth, higher pollution rates could be on the way.