CHICAGO — The greater Chicago metropolitan area was placed under an Air Quality Alert this week as the Illinois Environmental Protection Agency declared an Air Pollution Action Day, warning that ground-level ozone had reached concentrations classified as "Unhealthy for Sensitive Groups" — and was forecast to worsen into Wednesday. Nearly 9.4 million residents across eight Illinois counties, plus a simultaneously issued alert for Northwest Indiana, were advised to limit prolonged outdoor activity. The alert, confirmed by the National Weather Service Chicago and the Illinois EPA, arrived at the end of May — before the meteorological heart of Chicago's ozone season has even begun. Public health officials and atmospheric scientists are increasingly concerned that what was once a mid-summer problem is becoming a spring-through-fall chronic condition.
