By Amanda Woerner for Life by DailyBurn

These days it’s nearly unfathomable to imagine a marathoner crossing the finish line, only to light up cigarette. And even ordinary exercisers may subject themselves to dirty looks if they puff near their gym. But what if they’re smoking an e-cigarette?

Introduced to the public as a product with the potential to shield smokers from the dangerous effects of Marlboros, e-cigarettes are marketed as a way to get your nicotine fix without inhaling all that lung-blackening smoke that’s been directly linked to cancer and heart disease.