A haze that had lingered in the Baltimore area for several days due to Canadian wildfires began to dissipate Friday, and smoke was likely to continue clearing over the weekend, officials said.
After initially issuing a “Code Orange” air quality alert for much of Maryland Friday, the Maryland Department of the Environment downgraded the threat level to a “Code Yellow” in Central, Southern and Western Maryland indicating conditions had improved.
“Particularly sensitive groups may continue to experience adverse effects, but the general population can return to normal,” the agency stated on its Twitter page.
Maryland’s Eastern Shore, however, remained under a “Code Orange” alert, which indicates the air is unhealthy for sensitive groups like children, older adults and individuals with lung and heart conditions.
The conditions represented a significant improvement from Thursday, when much of the state was under a “Code Red” air quality warning, when the air is considered unhealthy for the general public, and officials recommended residents stay indoors as much as possible and wear a well-fitting N95 mask when outside.
[ What you need to know about unhealthy air quality due to haze ]
Particulate matter, fine particles of dust, soot and smoke, can enter the lungs and bloodstream, causing a range of health effects from breathing difficulties to irregular heartbeats.
Showers and thunderstorms in the forecast Friday are expected to clear some of the residual smoke, according to the Maryland Department of the Environment. In Baltimore, there is a 50% chance of scattered showers and thunderstorms before 8 p.m., according to the National Weather Service.
In a forecast statement, the Maryland Department of the Environment said fine particle concentrations could reach the “Code Orange” level briefly on Saturday morning, before declining to “acceptable” levels.
Saturday, it will be sunny, with a high temperature of 86 in Baltimore. Sunday, the high temperature will reach 90 degrees.
[ Interactive map: Air quality for the Baltimore region and the rest of Maryland and U.S. ]
But over the weekend, ozone — rather than particulate matter — is expected to be the main pollutant of concern for Marylanders, since it will reach “upper moderate” levels, according to MDE.
“Real-time notifications may be issued if high ozone develops,” read the forecast from the agency.
While it is a crucial gas in the atmosphere, ozone is a pollutant at ground level, created by sunlight-driven reactions with chemicals in the air, including those produced by wildfire smoke. Inhaling this pollutant can irritate airways and aggravate lung diseases, among other symptoms.
The issue was discussed during a Johns Hopkins University briefing about the air pollution Friday morning.
“Ozone concentrations tend to be the highest on hot, sunny days and peak in the late afternoon,” said Meredith McCormack, an associate director of pulmonary and critical care medicine in the Johns Hopkins School of Medicine. “In fact, the ozone AQI [air quality index] during the last few days has been in the moderate zone ... so really, we’re getting exposures from multiple types of pollutants at the same time.”
As hundreds of wildfires continue to rage in Canada, in what is shaping up to be the country’s worst wildfire season in recent memory, the threat of smoke pollution and hazy conditions may not be over.
“Air quality impacts are day-to-day and even hour-to-hour, and we can see dramatic swings in the level of air pollution outside,” said Peter DeCarlo, an associate professor of environmental health and engineering at Johns Hopkins University. “These fires are still burning, and they’re gonna continue to burn beyond the next few days. But whether we see impacts here in Baltimore and along the Eastern Seaboard has a lot to do with where the wind is blowing at any given time.”