"Chronic" marijuana smoking, defined as daily use, damages the lungs over a period of time. The end result "looks a lot like chronic bronchitis, which is of course one of the terms we use for chronic obstructive lung disease, or COPD."
Smokers, people with COPD and other chronic lung diseases, as well as people with moderate to severe asthma are among those at high risk for severe illness from Covid-19, including the worst-case scenario of being placed on a ventilator in order to continue breathing.
Signs of lung damage from smoking even just a few cigarettes can show up in a matter of days. While a hit or two of marijuana doesn't compare, there are some unique properties to a joint of weed that are definitely problematic for the lungs even if you're a new smoker, Glass said.
Think of what happens to a cigarette when lit and left in an ashtray -- it will burn quickly all the way down to the filter, with nothing left but ash.
"It's surrounded by paper. It's completely dried out. It is made to burn at a very high temperature."
Now think of how a joint burns -- there's always some weed left, the "roach," as it is called.
"Marijuana burns at a much, much lower temperature than a commercially made cigarette. "Because of that, the person is inhaling a certain amount of unburnt plant material."
That irritates the lungs in the same manner as ragweed, birch and oak pollen does for those allergic to them.
"So right off the bat there are those patients who would be increasingly susceptible to having a bronchospasm or cough because they have a more sensitive airway."
And since a dry cough is a key sign of Covid-19, any cough caused by smoking a joint of weed could easily mimic that symptom, making diagnosis more difficult.