State and local health officials recommended Wednesday that people with asthma, heart and lung conditions or other respiratory illnesses stay inside through Thursday due to the effects of smoke from the Canadian wildfires that have been casting a hazy pall over the Northeast.

“The health effects for some people may include chest tightness, shortness of breath, wheezing, coughing, eye irritation, chest pain, dizziness or lightheadedness, and other symptoms,” Dr. Manisha Juthani, commissioner of the state Department of Public Health, said in a statement. “We recommend that you avoid any outdoor exercise today if you have an underlying health condition. Be sure to have your medications readily available and seek medical attention if these issues worsen.”

Juthani advised residents to keep windows and doors closed, and warned that children, the elderly, and those with asthma or heart and lung conditions are most at risk for experiencing symptoms from elevated air pollution. Even healthy adults should minimize their outdoor activity, she said.

Earlier Wednesday, the state Department of Energy and Environmental Protection reported that it expected the smoke to elevate microscopic particulate matter known as PM2.5 to an unhealthy level in air across the state. The metric is one of six categories that make up the U.S. Environmental Protection Agency’s Air Quality Index.

AQI values range from 0 to 500. The higher the value, the greater the level of air pollution and the greater the health concern. Values from 101 to 150 indicate air considered “unhealthy for sensitive groups,” and air with values from 151 to 200 earns an “unhealthy” designation.

At 3 p.m. Wednesday, the PM2.5 value for the New London-Groton area was 170. Air was deemed “very unhealthy” or “hazardous” in parts of southwestern Connecticut.

AQI values can be monitored online at AirNow.gov.

The EPA predicted the smoke from wildfires in Quebec and northern Ontario, Canada, will linger in New England ― primarily Connecticut, Rhode Island and Massachusetts ― for a few days.

Wednesday’s poor air quality prompted East Lyme public school officials to cancel all after-school outdoor activities, and Norwich public schools moved recess inside. The Connecticut Interscholastic Athletic Conference, which governs high school sports, postponed Wednesday afternoon’s state tournament games due to the air quality forecast. It noted most of the day’s schedule included boys’ and girls’ lacrosse, a high-intensity aerobic sport. Boys’ and girls’ tennis matches also were postponed.

Dr. Craig Mittleman, chairman of the emergency departments and regional medical director at Lawrence + Memorial and Westerly hospitals, said around noon Wednesday the hospitals had not experienced an increase in emergency room activity due to the smoke. He urged those vulnerable to poor air quality to stay indoors and make use of any ventilating equipment they might have, including air conditioning.

Anyone experiencing shortness of breath under any circumstances should seek medical attention, he advised.

Mittleman said it was not clear that masks are effective in fending off effects of the smoke given the fineness of the particulate matter. The state Department of Public Health suggested those in possession of N95 or KN95 masks consider wearing one while outdoors.

“Outside of a local fire, I can’t remember ever seeing haze this thick ― you can smell and taste it,” Mittleman said. “If anyone with asthma or other conditions is having trouble breathing, if their inhaler or medications aren’t working, an emergency room visit is needed.”

Stephen Mansfield, health director of Ledge Light Health District, and Patrick McCormack, his counterpart with the Uncas Health District, said they were alerting school and municipal officials, day care centers and other institutions to the state health department’s advisories regarding the effects of the smoke.

b.hallenbeck@theday.com