Air Toxics Monitoring

The Vermont Air Quality & Climate Division (AQCD) began operating an air toxics monitoring program in 1993 based on concerns with the potential health risks associated with specific air toxic pollutants or hazardous air contaminants (HAC) in the ambient air. The specific HACs (EPA refers to these compounds as Hazardous Air Polluntants (HAP)) of concern pose human health risks associated with cancer, lung disease and other acute or chronic health problems.  The air toxics that we are exposed to originate mainly from human-made sources, such as mobile sources (e.g. our cars, trucks, lawn and garden equipment, recreational vehicles such as motorboats, ATVs, etc.), larger point sources (e.g. factories, power plants), and smaller area sources (e.g. residential heating, gas stations, dry cleaning, etc.).  There are also natural sources of these air toxic emissions, such as wildfires.  VT AQCD’s goal of informing the public of the potential health risks associated with specific HACs is accomplished through the collection of ambient air toxics samples at 3 permanent sites throughout the state.   Currently, the VT AQCD measures ambient concentrations down to parts per trillion by volume (pptv) and nanogram/M³ (depending on the particular method) of 96 separate HACs.  These include volatile organic compounds (VOC) such as benzene, 1,3 butadiene; carbonyl compounds such as formaldehyde, acetaldehyde; metal compounds such as arsenic, lead; and polycyclic aromatic hydrocarbons (PAH) such naphthalene, benzo-a-pyrene.  (Click on link to view the complete list of Air Toxics)  The VOC samples are collected using 6-liter Silco-treated stainless steel canisters which are analyzed at the Vermont Agriculture & Environmental Lab (VAEL) by gas chromatography/mass spectrometry (GC/MS).  The carbonyl samples are collected using a special cartridge which contains silca gel coated with dinitrophenylhydrazine (DNPH) which is extracted at the VAEL and analyzed by high performance liquid chromatography (HPLC).   The metals samples are collected on 47 mm Teflon filters which are extracted at the VAEL and analyzed by inductively coupled plasma/mass spectrometry (ICP/MS).  The PAH samples are collected on a 104mm quartz fiber filter combined with a polyurethane foam plug (PUF) containing XAD resin both of which are extracted at an EPA contract lab and analyzed by GC/MS.

The permanent monitoring sites are located in Burlington, Rutland and Underhill.  VOC and carbonyl samples at the Rutland and Burlington urban sites are collected every 12 days on a US EPA schedule.  The Burlington site has separate collocated samplers to provide method quality assurance.    At the Underhill rural site, VOC, carbonyl, metals and PAH samples are collected every 6 days on a US EPA schedule.   Since 2004, the Underhill site has participated in US EPA’s National Air Toxics Trends Stations (NATTS) network designated as a rural background site.