Air Sampling Campaigns
The most frequent cause of death among adults in the United States is disease of the heart (principally heart attacks), followed by cancer, and cerebrovascular diseases (stroke). Two of the three main causes are related to the function of the cardiovascular system. Long term exposure to elevated levels of particulate matter (PM) pollution have been implicated in the increased risk of the onset of ischemic heart disease and sub-clinical chronic inflammatory lung injury and atherosclerosis. A proposed mechanism for the effects of PM exposure on the cardiovascular system is via an inflammatory response of the endothelium. The exposure of heritable hyperlipidemic rabbits and mice to elevated, environmentally relevant PM concentrations has been shown to accelerate the progression of atherosclerotic plaques and vascular inflammation. Short term exposure to elevated and acute levels of PM was found to cause an increase in fibrogen and inflammatory markers in pulmonary and respiratory system of humans.
The connection of short term PM exposure and the onset of myocardial infarction has been observed in general population studies. Additionally, a cross-over study of 12,865 patients living in Utah showed that short-term exposure to high PM levels contributed to acute coronary disease, especially among the individuals predisposed or with current coronary condition. Acute vasoconstriction was observed in healthy adults after short term exposure to levels of fine particulate pollution and ozone common in urban areas. Although the effects of exposure to ambient pollution in humans have been studied, and the effects of exposure of experimental animals to concentrated ambient particulate material, CAPS, has been reported in several studies, a study of the endothelial function effects of direct, short-term exposure of humans to PM in laboratory conditions have not yet been performed.
Several designs for controlled human exposure have been developed. These include full-body exposure chambers, hoods and masks. Particulate matter generation in these systems employs either on-board production of pollution via previously obtained powder samples (wheat flour, dust, etc.) or the use of the particulate pollution directly extracted and concentrated from ambient atmospheric conditions. The Hansen Lab Group has designed and characterizes the performance of a two-stage PM exposure chamber/environmental chamber for human subjects developed to study the effects of short-term PM exposure as well as serve as an environmental chamber (Figure 7).
Figure 7: 30 m3 Teflon environmental chamber with bank of UV and black lights located above the inflatable bag.
The design of this chamber allows for the measurement of: 1) the concentrations of non-volatile and semi-volatile PM using semi-continuous monitors, 2) time-dependent size distribution, and 3) the concentrations of environmentally relevant gases, including CO, CO2, NOx, and O3. Additionally, the current design allows for the pretreatment (photochemically aging) of PM or atmospheric gases mixtures. The system allows scientists to investigate the influence of various conditions on ozone and PM production.
The Hansen Lab also uses a human exposure/environmental chamber to test and validate new semi-continuous instruments designed to measure PM and its components. These instruments are ultimately placed into the field where they are used in air sampling campaigns designed to investigate source apportionment. The Hansen Lab Group operates a sampling site in Lindon, Utah (Figure 8). Recently, the Hansen Lab investigated the sources of elevated concentrations of formaldehyde (CH2O) observed in the Bountiful, Utah. Formaldehyde was measured using a newly designed and built Broad Band Cavity Enhanced Absorption Spectrometer.
he U.S. Environmental Protection Agency (EPA) National Air Toxics Trends Station (NATTS) Network has been in place since 2003 and was developed to provide long-term monitoring of hazardous air pollutants (HAPs).[1] Since 2003, the Bountiful, Utah monitoring site has served as one location in the NATTS network. The U.S. EPA has set guidelines for a range of HAPs, and most of these pollutants have been detected in low concentrations in Utah. The Utah Division of Air Quality (DAQ) has sponsored or collaborated on several studies to measure the concentrations of various HAPs in Utah, including formaldehyde. Formaldehyde is a ubiquitous trace compound in the atmosphere. Inhalation of formaldehyde can be irritating to the upper respiratory tract and eyes. Animal studies have shown that inhalation can affect the lungs and impair learning and change behavior.[2] Formaldehyde has been classified as a probable human carcinogen (Group B1) by the U.S. Environmental Protection Agency (EPA) and carcinogen by the International Agency for Research on Cancer (IARC).[3,4] Of 187 compounds that have been identified as HAPs, HCHO contributes over half the total cancer risk and 9% of noncancer risk in the United States (U.S.).[1,5,6] Over 12,000 people year-1 are estimated to develop cancer based on ambient formaldehyde exposure in the US.[7].
Formaldehyde is a volatile organic compound (VOC) that plays a vital role in ozone formation in urban areas. Its photolysis is a source of both OH and HO2 radicals, which both serve to drive tropospheric O3 formation. As a result of HCHO’s carcinogenic nature and role in tropospheric ozone formation, a wealth of research has been done to better elucidate sources of formaldehyde.[8-12] HCHO can be directly emitted into the atmosphere from both anthropogenic and biogenic sources. Secondary production of HCHO occurs during the photooxidation of almost every VOC albeit with varying efficiencies and rates.
Starting in February 2019, an eight-week intensive campaign was started to measure HCHO at the Bountiful, Utah site on a two-hour averaged basis. The components expected to be important to understanding the sources of formaldehyde including benzene, ethylbenzene, toluene, and xylenes (BTEX) were also measured. In addition, the concentrations of NOX (NO, NO2) and O3, were also measured on a two-hour averaged basis. Figure 8 shows the location of the Bountiful sampling site, the five oil refineries located between 2-5 miles to the south, southwest of the sampling site as well as the I-15 interstate and the location of other DAQ permitted VOC emitting point sources. In 2017, the annual average daily traffic count for vehicles passing through the section of I-15 that runs parallel to the sampling site was 168,000. A total of 84% of this traffic was cars, 9.3% was single unit trucks (i.e. vehicle on a single frame including box trucks, camping and recreation vehicles and motor homes) and 6.7% was combination unit trucks (i.e. truck-tractors units traveling with a trailer or multiple trailers).[19]
Figure 8: The locations of various VOC emission sources, oil refineries (red crosses) and industrial (blue circles) with emission strengths (tons year-1) located to the SSW of the Bountiful NATTS sampling site (black star).Green color represents mountains with forest area. Emission strengths are taken from permits issued by the State of Utah Department of Air Quality. Also included is the location of major roadways and forested areas in the area.
In collaboration with researchers from the University of Utah and the Utah Department of Air Quality a positive matrix factorization (PMF) analysis was done using historical data (2004-2015) to better understand the sources of formaldehyde in the region. The historical data set measurements collected every sixth day on a 24-hour basis. The data set collected in 2019 includes two-hour averaged measurements of formaldehyde and some of its possible precursors. The more rapid data collection method used in the 2019 study allows for additional conclusions to be made about sources of formaldehyde in the Bountiful region. To better understand the possible variety of formaldehyde emissions, corresponding back trajectory wind calculations for selected time periods are presented to aid in the understanding of the effects BTEX emission sources on the secondary formation of formaldehyde.
Formaldehyde and NO2 were measured using a newly designed and built Broadband Cavity Enhanced Absorption Spectrometer (BBCEAS) instrument. The BBCEAS leverages long path lengths (1-5 km) by use of multi-reflections in a short instrument footprint (1-2 m).[25] A cage system constructed of carbon-fiber tubes was employed to obtain optical alignment, with structural parts being 3-D printed (laser-sintering or extruded PLA, depending on the function of the part). The instrument has a base path of 98.5 cm and 5 cm diameter highly reflective mirrors from Advanced Thin Films (ATFilms) centered at 365 nm, with a second cavity centered at 455 nm. Light was produced by LEDEngin (blue) and Thorlabs (M340D3) LEDs centered at 450 and 340 nm, respectively, and collected at the rear of the cavity onto optical fibers. An Andor Shamrock SR-303i spectrograph with gated, intensified CCD was used as a detector in the UV region (310-400 nm range, ~0.5 nm FWHM). In the visible region, an Avantes AvaSpec-2048L was used as a detector. Figure 9 shows the instrument.
Figure 9: Illustration of an open -cavity BBCEAS instrument. Not shown is the fiber optic to spectrometer and CCD connection.
The Hansen Lab collaborates with Dr. Ryan Thalman (Snow College) and Dr. Matt Asplund (BYU) to optimize the performance of this new instrument for measurement of a variety of trace gases commonly found in the atmosphere.