To accurately quantify the level of outdoor smoke exposure, Stanford Researchers used portable electronic monitors to measure toxic airborne particles. These instruments are designed to detect a hazardous chemical known as particulate matter-2.5 (PM2.5).
This toxic pollutant contains carcinogens amongst other chemicals that may contribute to chronic bronchitis, irregular heartbeats, heart attacks and an assortment of other health conditions. The outcome of the study found that the closer you are to outdoor tobacco smoke, the higher your risk of hazardous inhalation.
They found that brief exposures, multiple times over several hours in an outdoor pub, could lead to a daily average of 35 micrograms of PM2.5 exposure. If someone is in close proximity to a smoker, they could potentially inhale a breath of 1,000 micrograms, which is 50 times more concentrated than the surrounding air. Researchers warn that although outdoor secondhand smoke dissipates quickly, non-smokers should still be aware of their exposure.