Measurements of Outdoor Air Pollution from Secondhand Smoke on the Umbc Campus

Introduction. Individual cigarettes are point sources of air pollution; smoking in groups becomes an area source. Outdoor air pollutants from individual point sources are subject to plume rise if the temperature of the smoke plume is hotter than the surrounding air; however if the plume has a small cross-section, as for a cigarette, it will rapidly cool and lose its upward momentum, and then will subside as the combustion particles and gases are heavier than air. Thus, in the case of no wind, the cigarette plume will rise to a certain height and then descend, and for a group of smokers, for example sitting in an outdoor cafe, on a hospital patio, or in stadium seats, their smoke will tend to saturate the local area with secondhand smoke (SHS). In the case where there is wind, the amount of thermally-induced plume rise is inversely proportional to the wind velocity -doubling the wind velocity will halve the plume rise. In this case, the cigarette plume will resemble a cone tilted at an angle to the vertical. The width of the cone and its angle with the ground will depend upon the wind velocity: a higher wind will create a more horizontal but wider cone (due to increased turbulence), with uncertain impact on exposure to SHS for downwind nonsmokers. If there are multiple cigarette sources, the downwind concentrations will consist of multiple intersecting cones, i.e., overlapping plumes. As the wind direction changes, SHS pollution will be spread in various directions, fumigating downwind nonsmokers.