Five-Year Study of Volatile Organic Compounds in an Intermountain West Valley Region

The Lewis-Clark Valley (LCV) is an intermountain valley located on the border of Idaho and Washington. The LCV comprises multiple industries, including a pulp paper mill which produces a pungent sulfur smell. Residents of the region may be exposed to higher than normal air toxics because of the valley meteorology and inversions. Weekly air samples were taken throughout the valley via thermal desorption tubes from 2017 to 2021 in order to study the air pollution and possible health concerns. Over 100 volatile organic compounds (VOCs) in the samples were analyzed via thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). The spatial and seasonal distribution of the VOC concentrations were analyzed from several different sample sites throughout the LCV. BTEX (benzene, ethylbenzene, toluene, and xylene), chloroform, dimethyl sulfide, and dimethyl disulfide were some of the major VOCs observed. The concentration of benzene was as high as 4 ppbv and chloroform was as high as 0.7 ppbv. Benzene and chloroform are known to be human carcinogens. Health risk calculations using the United States Environmental Protection Agency (US EPA) show the residential cancer risk to be at least 2 x 10-6 based on the levels of benzene and chloroform present.