Ground-level ozone in Medicine Hat triggers 3-hr air advisory

By COLLIN GALLANT on June 14, 2023.

cgallant@medicinehatnews.com@CollinGallant

In a spring with an over abundance of smoke, air quality monitors in southeast Alberta denoted an unusual trend Monday afternoon, namely high amounts of ground level ozone.

That, and another rise in levels on Tuesday led to a special air quality statement from Environment Canada after initiated by the local monitoring agency, the Palliser Airshed Society, but only lasted three hours, between 3 and 6 p.m.

The warning was allowed to expire later in the evening after levels dropped.

Lorna Morishita, executive director of the Palliser Airshed, told the News it is the first local ozone warning in at least six years, but such events are not uncommon in major cities.

Locally, it was likely caused by the combination of high heat, sunlight and particulate matter in the air blown in from forest fires in the province and Saskatchewan, she said.

“We don’t always have the extra heat in the spring or at the time of wildfire season,” said Morishita. “We’re particularly susceptible this year.”

Ozone, a molecule comprising three atoms of oxygen, is most well-known for its ability to filter sunlight in the high atmosphere.

Health Canada states that at ground level however, ozone can aggravate existing breathing conditions, cause coughing, shortness of breath and lead to sore throat, nose and eyes.

Monday night’s general air quality was determined between four and seven, or moderate, on a scale of 1 to 11.

Ozone levels hovered at about 79 parts per billion – about three times more than the amount requiring a report Environment Canada – over the three hours in Medicine Hat, with smoke as the determined cause.

Hatters have watched air quality more closely this spring as huge forest fires in northern Alberta have brought heavy smoke to the region at times. Environment Canada has issued a number of special air quality statements, warning those with health conditions, the elderly, children and even all residents to remain indoors or moderate outdoor activities, such as work.

Morishita said that in rural areas, elevated ozone levels are typically caused by lightning in the presence of nitrogen or the pollutant nitrous dioxide that typically comes from the exhaust of burning hydrocarbon fuel in cars or industrial processes.

It forms a substantial component of urban smog but may be more prevalent in remote rural areas than is currently known, said Morishita, because testing is centred in urban areas.

“We don’t measure it in very many places because of the cost involved,” she said.

Palliser Airshed, which has substantial stations in Medicine Hat (Crescent Heights), Brooks and Taber, received funding from the province as well as industrial, oil and gas and municipal partners.

This year the society started targeted measuring of particulate matter in the air at 15 locations after receiving “PurpleAir” monitoring from Environment and Climate Change Canada.

The devices emit a laser that is returned to the unit after bouncing back off particles to provide data about the size and density of smoke in the atmosphere.

They are stationed at Acadia Valley, Bassano, Bow Island, Brooks, Consort, Duchess, Empress, Hanna, Medicine Hat (Crescent Heights and Desert Blume), Milk River, Oyen, Redcliff, Vauxhall and Warner.

Data is available for public viewing at the group’s website (palliserairshed.com).