Ozone: Sky-High Protector but a Vicious Neighbor Down on the Ground

Smog is formed by the reaction of ozone and other atmospheric chemicals with sunlight.

HOUSTON (CN) — A bipolar frenemy that protects you from skin cancer but damages your lungs and makes you sluggish when exercising outside on hot summer days, ozone is oxygen’s enigmatic cousin.

Discovered in lab experiments in the 1800s, ozone, O3, is a gas made of three oxygen atoms, rather than two.

It’s mostly a friend. Ninety percent of the ozone in the atmosphere is in the stratosphere, 6 to 31 miles above the earth’s surface, forming the ozone layer that protects humans from the sun’s ultraviolet radiation.

Its dark side is found in the remaining 10 percent, which forms in the troposphere — from the earth’s surface to 6 to 10 miles above it — when nitrogen dioxide and volatile organic compounds such as benzene, emitted by cars and factories, cook in sunlight on hot summer days.

In sprawling Sunbelt cities such as Houston, where carpooling and mass transit are almost sacrilege, and the population is exploding with people taking advantage of the relatively low cost of living and healthy job market, bringing more vehicles and gridlock, conditions are ripe for bad ozone, also known as smog.

Ozone’s wrath is fickle.

“Ozone is partially due to high temperatures, hot days, calm winds,” said Neil Carman, clean air director for the Sierra Club’s Lone Star Chapter.

“When the winds die to almost nothing, you’ll see peak ozone levels forming. Also clear skies. So it’s a combination of warm temperatures, clear skies, calm winds and a lot of precursors, the volatile organic compounds, the nitrogen oxides.”

Carman keeps daily tabs on some of Texas’ nearly 120 ozone monitors. He said ozone is typically a problem in Houston from April to October, and the peak hours are from 10 a.m. to 6 p.m., with two rush-hour driven spikes, after the morning and evening commutes.

Due to its three oxygen atoms, ozone is unstable, meaning it is much more sensitive to meteorological changes than oxygen.

“Oxygen is stable, but ozone is not. So, for example, if the wind picks up from being calm to like suddenly there’s a breeze coming in from the Gulf of Mexico, 10 to 15 mph, the ozone is instantly breaking down,” Carman said.

“You see it in the monitors. The ozone levels fall. Or if the sunlight is blocked by clouds coming in from the Gulf, the ozone levels will quickly, almost instantly, drop.”

Through Tuesday this week, there have been 15 “ozone-action days” issued for Houston this year, according to Andrew Keese, spokesman for the Texas Commission on Environmental Quality.

The TCEQ advises “sensitive groups” — children, the elderly and people with breathing problems — to limit outdoor activities on such days.

But what are the risks for healthy younger adults?

Dr. Richard Castriotta, Director of Pulmonary and Sleep Medicine at McGovern Medical School at The University of Texas Health Science Center in Houston, said that unlike other air pollutants, ozone is a molecule, so it’s too small to be filtered by masks, and can evade the body’s natural defenses.

“A lot of the other pollutants will get trapped up in our nose and in the back of our throats in mucus membranes before they get down into the lower levels of the lungs,” Castriotta said.

“Ozone gets down pretty quickly. It’s pretty close to the same as oxygen. … It can be irritating to the eyes and the nose, but more importantly, it can get all the way down into the lower lung, into the lung itself, and cause damage there.”

Castriotta said the harm ozone causes is similar to radiation damage. Though he does not believe ozone causes asthma or chronic obstructive pulmonary disease — but aggravates it — empirical evidence shows it can be fatal to those with heart problems.

“All we know is observationally, when there’s high levels of ozone there’s an increase in the number of heart attacks among susceptible individuals. So the presumption is that it’s connected,” he said.

He coughed. “Excuse me, I think I’m choking on my ozone here,” he said, laughing.

Even endurance athletes in the prime of their careers can be damaged because ozone kills lung cells, which Castriotta said can regenerate.

“If you are running a marathon then you have to take in a lot more air to satisfy your oxygen needs to do that work. Or if you’re out in the field working in construction and doing aerobic activity out in the fresh air, you’re just breathing in more air and with it you’re breathing in more ozone,” Castriotta said.

Jeff Douse ran his first half-marathon in his freshman year of college, qualified for the Boston Marathon his sophomore year and ran that race as a senior.

Though he ran track in high school for an “awesome” coach, he said he did not get much individual attention.

Running by himself in college, he said, he learned what worked for him and what did not. He enjoyed training so much that in July 2017 he and his wife started RacePace, a running studio in Houston, where coaches backed by upbeat music lead runners through classes on state-of-the art Woodway treadmills, which he calls the “Rolls Royce” of treadmills.

Douse recently gave a presentation to a corporate running club about running in the sauna-like heat and humidity of Houston summers. He told them to get out before sunrise or after sunset, plan their route to go by water faucets, and not to run on concrete and asphalt, which absorb and radiate heat.

Because ozone reduces oxygen uptake to muscles, it affects the body much like extreme humidity.

“I was at the track this morning and it was 100 percent humidity today, and I noticed the effect immediately,” he said. “Running the same speed I ran three weeks earlier felt a lot harder, all else equal, because of that humidity effect.

“So I think ozone is similar, in that if it’s a high-ozone day, you’re going to feel that effect because of the fact that you aren’t able to transport oxygen to those working muscles as efficiently. So you will feel that fatigue factor set in more quickly than you would on a fresh-air day.”

Despite the rash of ozone-action days in Houston this year, experts say the city’s air has improved dramatically since the late 1990s, when Houston briefly took the title of the nation’s worst air quality from Los Angeles, thanks in large part to chemical plant and refinery operators’ pollution-control upgrades.

According to the American Lung Association, Los Angeles now ranks No. 1 among U.S. cities for ozone pollution. New York City is No. 10 and Houston is No. 11.

“The air is getting cleaner but we still have work to do. It used to be in Houston the smog was so bad in the ’80s and ’90s on bad days you would feel it stinging your skin, the same way in Los Angeles, but not anymore,” said Carman, the Sierra Club clean air director.

The U.S. Environmental Protection Agency made it tougher for cities to comply with smog standards in 2015, when it lowered compliance for its eight-hour attainment level for ozone from 75 to 70 parts per billion.

To gauge compliance, the EPA takes the fourth-highest ozone reading averaged over eight hours at a particular monitor — the top three readings are discarded as possible statistical outliers — and averages them over a three-year period.

“So you’ve got to have data that averages no higher than 70 parts per billion for three years,” Carman said.

Houston is nowhere near meeting that standard.

For Houston residents ozone is a frenemy that cannot be avoided at the office, dodged at the neighborhood park, or unfriended on social media.

But as the owner of an indoor running studio, Douse says there are ways to work around it and urged people not to let it stop them from being active.

“If you are exposed in a high-ozone day, you might have a couple days after where you’re coughing and have a scratchy throat; you might even feel nauseous or light headed,” he said. “But the lasting health benefits of exercising and running are going to far outweigh the short-term effects that you might have from ozone exposure.”

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