CLEVELAND, Ohio -- This summer's near-record heat gave the region its most unhealthy air in years.
An eight-county region recorded 28 days where the pollutant known as ozone reached unhealthy levels. That's double the number from 2011 and easily the highest since 2008, when federal regulators tightened the ozone standard.
The summertime heat wave is the main culprit. Sunlight reacts with emissions from cars, trucks, coal-fired plants, factories and other sources to create ozone, the main ingredient in smog.
Breathing ozone triggers a variety of health problems, including chest pain, coughing, throat irritation, and congestion. Children, older adults and those already suffering respiratory problems can be especially sensitive.
Ozone "almost certainly has a significant (short-term) impact" on the region's health, said Dr. Edward Warren, who specializes in pulmonary and critical-care medicine at MetroHealth System. "At higher concentrations, there's even damage to the cells that are exposed to the ozone -- your eyes, your nose, your throat and your airways."
One of the hottest summers on record caused problems during the ozone-monitoring season, which runs from April 1 to Oct. 31.
On 28 days across eight counties, ozone in the air exceeded 75 parts per million over eight hours, an air-quality health standard set by the U.S. Environmental Protection Agency.
Lake County had 21 days when ozone hit unhealthy levels, followed by Cuyahoga County with 19, Geauga County with nine, Ashtabula County with seven, Lorain County with five, Portage County with two and Medina and Summit counties with one day each.
Lake County's ozone problem stems from the prevailing winds that push pollution in from Cuyahoga County. Ozone worsens during evening rush hour, when sunlight takes full effect on vehicle and industrial pollutants. Sunlight isn't as robust during the morning rush hour.
The eight-county region had only 14 days exceeding the ozone standard in 2011 and 15 in 2010, according to the Northeast Ohio Areawide Coordinating Agency, a federal planning body that monitors air quality in the region.
"We tend to have more (ozone problems) with hot, dry summers," said Heidi Griesmer, spokeswoman for the Ohio Environmental Protection Agency.
It's more evidence that measures like E-Check must continue, officials said. The mandatory tailpipe test is needed because the eight-county region does not meet federal health standards for levels of ozone and particulates in the air.
The region registered two days this year where it hit unhealthy levels of particulates, the same as 2011.
The region is far from meeting the federal ozone standard. By law, the eight counties can have only three days exceeding the standard over three years, Griesmer said. That became a tougher target to hit in 2008, when the air-quality standard for ozone tightened to 75 parts per million from 80 parts per million, she said.
The ozone problem is trending down over time, Griesmer said. In 1999, Ohio's urban areas exceeded the ozone standard on 76 days, compared to 41 in 2012.
This summer's spike in ozone concerned Dr. Sumita Khatri, a specialist in asthma at the Cleveland Clinic.
"Ozone exerts an effect on all people to a certain extent," said Khatri. "Even healthy individuals are affected by poor air quality."
The full effects of breathing ozone aren't felt for 24 to 48 hours, she said. People with allergies or lung conditions will wheeze, cough or feel short of breath, Khatri said.
Studies have shown that high-ozone days result in more emergency visits to the hospital and higher use of asthma medicines, she said.