Source investigation and risk assessment of air toxics in an environmental justice community

Toxic volatile organic compounds (VOCs) are part of the hazardous air pollutants (HAPs) or air toxics that affect public health. An approach comprising both online and offline measurement techniques was conducted in a community near an industrial complex for method evaluation and risk assessment. During a month-long field test in this environmental justice community, the instrument of thermal desorption (TD) - gas chromatography-mass spectrometry (GCMS) targeting 86 air toxics was intercompared with two other techniques: direct inlet mass spectrometry (proton transfer reaction quadrupole mass spectrometry or PTR-QMS) and flask sampling for evaluating method suitability. TD-GCMS gathering hourly data was deemed the most suitable online device for source investigation and health risk assessment due to its superior accuracy, species coverage, and data continuity. The sensitive detection of plumes as spikes near real-time by TD-GCMS established a strong link between source and receptor, which has proven to be effective for tracing the origins of the plumes. Compared to online measurements, random flask sampling tends to miss most of the emission plumes. The concentration spikes in the TD-GCMS data were further aimed for backward trajectory analysis to guide offline sampling in suspected source areas to confirm emission origins. Although both the online PTR-QMS and TD-GCMS were effective in detecting non-chlorinated species, TD-GCMS proved to be more versatile in detecting both chlorinated and non-chlorinated air toxics with irreplaceable accuracy pivotal for robust hazard assessment resulting from the acute effects, chronic effects, and cancer risks induced by long-term exposure to ambient air toxics.