It’s second-hand smoke writ large. The culprit isn’t a cigarette. It’s a forest.

East Coast residents might feel confident that ever-more-frequent western wildfires pose harm only to those living close to the blaze. It might hit a lot closer to home than you’d think.

Consider the summer of 2023. Canadian wildfires burned more than 40,000 acres, an area the size of Georgia. That smoke climbed into the atmosphere and drifted across the nation.

Now, a recent study by Maryland researchers found that all that smoke might have triggered a nearly 20% increase in hospital visits for heart and lung problems in their state. That was during the six days in June when smoke from 2,100 miles away turned Baltimore skies dark.

Scientists tapped 2 million de-identified patient records from the University of Maryland Medical System. They also analyzed satellite and other data to identify six days during which standards for safe air were exceeded in each of the state’s 23 counties.

The study tracked an 18% increase in doctor visits for complications related to cardiopulmonary or heart-lung conditions, compared with previous years. This included outpatient, emergency rooms, and hospital admissions. Outpatient clinic visits alone rose 55%.

Those patients were more affluent, tended to be older and were nonsmokers, compared with those seeing a doctor on clean-air days. That suggests an unequal access to care.

Of course, states in the path of the smoke between western Canada and Maryland no doubt saw their own impacts from the fires.

Scientists say pollution from wildfires leads to higher death rates. Environmental hazards don’t abide human-made borders.