Importance of human environmental exposure to hazardous air pollutants from gas flares

Flaring is an accepted practice in the oil and gas industry to dispose of waste gases in Alberta. However, incomplete combustion of these gases produces a variety of volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs). Public health concerns about gas flaring have existed for a number of years. Several facts are notable in attempting to understand what importance VOCs and PAHs from flare gas emissions have in contributing to adverse health effects in humans. Most flare stacks are located in rural areas. Current time-activity studies of humans are lacking in that they have not emphasized characterization of time-activity behavior of rural populations, who would be most susceptible to exposure from these pollutants. Available time-activity studies of primarily urban populations indicate that people spend a majority of time indoors. Numerous VOCs and PAHs measured in gas flare emissions are already present indoors, originating from indoor sources, and almost always at higher levels than outdoors. As humans inhale a majority of air indoors, inhalation exposure would be influenced to a much greater extent from being indoors than outdoors in these instances. Human health risk assessment of hazardous air pollutants emitted from burning flares must take into account indoor and other background exposures to provide useful information for public health decision-makers.