Development of primary reference gas mixtures of 18 volatile organic compounds in hazardous air pollutants (5 nmol/mol level) and their analytical methods

ABSTRACTAmbient air observations of hazardous air pollutant (HAPs), also known as air toxics, derived from routine monitoring networks operated by states, local agencies, and tribes (SLTs), are analyzed to characterize national concentrations and risk across the nation for a representative subset of the 187 designated HAPs. Observations from the National Air Toxics Trend Sites (NATTS) network of 27 stations located in most major urban areas of the contiguous United States have provided a consistent record of HAPs that have been identified as posing the greatest risk since 2003 and have also captured similar concentration patterns of nearly 300 sites operated by SLTs. Relatively high concentration volatile organic compounds (VOCs) such as benzene, formaldehyde, and toluene exhibit the highest annual average concentration levels, typically ranging from 1 to 5 µg/m3. Halogenated (except for methylene chloride) and semivolatile organic compounds (SVOCs) and metals exhibit concentrations typically 2–3 orders of magnitude lower. Formaldehyde is the highest national risk driver based on estimated cancer risk and, nationally, has not exhibited significant changes in concentration, likely associated with the large pool of natural isoprene and formaldehyde emissions. Benzene, toluene, ethylbenzene, and 1,3-butadiene are ubiquitous VOC HAPs with large mobile source contributions that continue to exhibit declining concentrations over the last decade. Common chlorinated organic compounds such as ethylene dichloride and methylene chloride exhibit increasing concentrations. The variety of physical and chemical attributes and measurement technologies across 187 HAPs result in a broad range of method detection limits (MDLs) and cancer risk thresholds that challenge confidence in risk results for low concentration HAPs with MDLs near or greater than risk thresholds. From a national monitoring network perspective, the ability of the HAPs observational database to characterize the multiple pollutant and spatial scale patterns influencing exposure is severely limited and positioned to benefit by leveraging a variety of emerging measurement technologies.Implications: Ambient air toxics observation networks have limited ability to characterize the broad suite of hazardous air pollutants (HAPs) that affect exposures across multiple spatial scales. While our networks are best suited to capture major urban-scale signals of ubiquitous volatile organic compound HAPs, incorporation of sensing technologies that address regional and local-scale exposures should be pursued to address major gaps in spatial resolution. Caution should be exercised in interpreting HAPs observations based on data proximity to minimum detection limit and risk thresholds.

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The U.S. wood products industry is a leader in the production of innovative wood materials. New products are taking shape within a growth industry for fiberboard, plywood, particle board, and other natural material-based energy efficient building materials. However, at the same time, standards for clean air are becoming ever stricter. Emissions of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) during production of wood products (including methanol, formaldehyde, acetylaldehyde, and mercaptans) must be tightly controlled. Conventional VOC and HAP emission control techniques such as regenerative thermal oxidation (RTO) and regenerative catalytic oxidation (RCO) require significant amounts of energy and generate secondary pollutants such as nitrogen oxides and spent carbon. Biological treatment of air emissions offers a cost-effective and sustainable control technology for industrial facilities facing increasingly stringent air emission standards. A novel biological treatment system that integrates two types of biofilter systems, promises significant energy and cost savings. This novel system uses microorganisms to degrade air toxins without the use of natural gas as fuel or the creation of secondary pollutants. The replacement of conventional thermal oxidizers with biofilters will yield natural gas savings alone in the range of $82,500 to $231,000 per year per unit. Widespread use of biofilters across the entire forest products industry could yield fuel savings up to 5.6 trillion Btu (British thermal units) per year and electricity savings of 2.1 trillion Btu per year. Biological treatment systems can also eliminate the production of NOx, SO2, and CO, and greatly reduce CO2 emissions, when compared to conventional thermal oxidizers. Use of biofilters for VOC and HAP emission control will provide not only the wood products industry but also the pulp and paper industry with a means to cost-effectively control air emissions. The goal of this project was to demonstrate a novel sequential treatment technology that integrates two types of biofilter systems – biotrickling filtration and biofiltration – for controlling forest product facility air emissions with a water-recycling feature for water conservation. This coupling design maximizes the conditions for microbial degradation of odor causing compounds at specific locations. Water entering the biotrickling filter is collected in a sump, treated, and recycled back to the biotrickling filter. The biofilter serves as a polishing step to remove more complex organic compounds (i.e., terpenes). The gaseous emissions from the hardboard mill presses at lumber plants such as that of the Stimson Lumber Company contain both volatile and condensable organic compounds (VOC and COC, respectively), as well as fine wood and other very small particulate material. In applying bio-oxidation technology to these emissions Texas A&M University-Kingsville (TAMUK) and Bio•Reaction (BRI) evaluated the potential of this equipment to resolve two (2) control issues which are critical to the industry: • First, the hazardous air pollutant (HAP) emissions (primarily methanol and formaldehyde) and • Second, the fine particulate and COC from the press exhaust which contribute to visual emissions (opacity) from the stack. In a field test in 2006, the biological treatment technology met the HAP and COC control project objectives and demonstrated significantly lower energy use (than regenerative thermal oxidizers (RTOs) or regenerative catalytic oxidizers (RCOs), lower water use (than conventional scrubbers) all the while being less costly than either for maintenance. The project was successfully continued into 2007-2008 to assist the commercial partner in reducing unit size and footprint and cost, through added optimization of water recycle and improved biofilm activity, and demonstration of opacity removal capabilities.

Optimized design and operating parameters for minimizing emissions during voc thermal oxidation

Aircraft turbine engines are a significant source of particulate matter (PM) and gaseous emissions in the vicinity of airports and military installations. Hazardous air pollutants (HAPs) (e.g., formaldehyde, benzene, naphthalene and other compounds) associated with aircraft emissions are an environmental concern both in flight and at ground level. Therefore, effective sampling, identification, and accurate measurement of these trace species are important to assess their environmental impact. This effort evaluates two established ambient air sampling and analysis methods, U.S. Environmental Protection Agency (EPA) Method TO-11A and National Institute for Occupational Safety and Health (NIOSH) Method 1501, for potential use to quantify HAPs from aircraft turbine engines. The techniques were used to perform analysis of the exhaust from a T63 turboshaft engine, and were examined using certified gas standards transferred through the heated sampling systems used for engine exhaust gaseous emissions measurements. Test results show that the EPA Method TO-11A (for aldehydes) and NIOSH Method 1501 (for semivolatile hydrocarbons) were effective techniques for the sampling and analysis of most HAPs of interest. Both methods showed reasonable extraction efficiencies of HAP species from the sorbent tubes, with the exception of acrolein, styrene, and phenol, which were not well quantified. Formaldehyde measurements using dinitrophenylhydrazine (DNPH) tubes (EPA method TO-11A) were accurate for gas-phase standards, and compared favorably to measurements using gas-phase Fourier-transform infrared (FTIR) spectroscopy. In general, these two standard methodologies proved to be suitable techniques for field measurement of turbine engine HAPs within a reasonable (5–10 minutes) sampling period. Details of the tests, the analysis methods, calibration procedures, and results from the gas standards and T63 engine tested using a conventional JP-8 jet fuel are provided.Implications: HAPs from aviation-related sources are important because of their adverse health and environmental impacts in and around airports and flight lines. Simpler, more convenient techniques to measure the important HAPs, especially aldehydes and volatile organic HAPs, are needed to provide information about their occurrence and assist in the development of engines that emit fewer harmful emissions.

Many of the 189 hazardous air pollutants (HAPs) listed in the Environmental Protection Agency regulations can be monitored by frequency agile CO<SUB>2</SUB> DIAL (FACD) systems. These systems can be used to survey industrial and military installations and toxic waste repositories at ranges of a few kilometers from emission sources. FACD systems may become a valuable tool for detection and estimation of a wide array of HAPs. However, in most cases, several of the listed HAPs will be present simultaneously and discrimination of one HAP from another based on differences in spectral characteristics can be challenging for FACD systems. While FACD hardware is mature and is capable of addressing these discrimination issues, multiple-contaminate separation algorithms need to be developed. A one week field test was conducted at Los Banos, California, to gather multiple HAP data that will be used for future algorithm development. A vapor chamber was used to control disseminated concentrations of each HAP and reduce effects of atmospheric turbulence and wind direction and speed. Data was collected for several chemicals injected into the vapor chamber simultaneously. The data and results from the field test are presented and calibration issues are discussed.

Soil Vapor Extraction (SVE) is considered an acceptable method for the remediation of petroleum impacted soils by the State of Florida. Typically, SVE involves applying a vacuum to the vadose zone by a mechanical system to collect volatile organic compounds (VOCs) present in the soil pore space. The collected VOCs include air toxics that are Hazardous Air Pollutants (HAPs). In order to comply with the federal air quality regulations, Florida has instituted a number of policies and procedures concerning HAP emissions from SVE systems. One of the policies includes the collection of off-gas samples for laboratory analysis of HAPs and other compounds. From the laboratory results and estimated air flow rates, an estimate of HAP emissions can be calculated. Unfortunately, as with most laboratory tests, analytical costs are high. They can cost between $125 and $150 per sample. As a result, off-gas sample collection for laboratory analysis occurs sparingly, usually only a few times over the duration of a site's remedial system operational life.

The Nevada Test Site (NTS) is operated by the U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office. From 1951 through 1992, the NTS was the continental testing location for U.S. nuclear weapons. The release of radionuclides from NTS activities has been monitored since the initiation of atmospheric testing. Limitation to under-ground detonations after 1962 greatly reduced radiation exposure to the public surrounding the NTS. After nuclear testing ended in 1992, NTS radiation monitoring focused on detecting airborne radionuclides from historically contaminated soils. These radionuclides are derived from re-suspension of soil (primarily by winds) and emission of tritium-contaminated soil moisture through evapotranspiration. Low amounts of tritium were also emitted to air at the North Las Vegas Facility (NLVF), an NTS support complex in the city of North Las Vegas. To protect the public from harmful levels of man-made radiation, the Clean Air Act, National Emission Standards for Hazardous Air Pollutants (NESHAP) (Title 40 Code of Federal Regulations [CFR] Part 61 Subpart H) (CFR, 2008a) limits the release of radioactivity from a U.S. Department of Energy facility (e.g., the NTS) to 10 millirem per year (mrem/yr) effective dose equivalent to any member of the public. This limit does not include radiation not related to NTS activities. Unrelated doses could come from naturally occurring radioactive elements or from other man-made sources such as medical treatments. The NTS demonstrates compliance with the NESHAP limit by using environmental measurements of radionuclide air concentrations at critical receptor locations. This method was approved by the U.S. Environmental Protection Agency for use on the NTS in 2001 and has been the sole method used since 2005. Six locations on the NTS have been established to act as critical receptor locations to demonstrate compliance with the NESHAP limit. These locations are actually pseudo-critical receptor stations, because no member of the public actually resides at these onsite locations. Compliance is demonstrated if the measured annual average concentration of each detected radionuclide at each of these locations is less than the NESHAP Concentration Levels (CLs) for Environmental Compliance listed in 40 CFR 61, Appendix E, Table 2 (CFR, 2008a). At any one location, if multiple radionuclides are detected then compliance with NESHAP is demonstrated when the sum of the fractions (determined by dividing each radionuclide's concentration by its CL and then adding the fractions together) is less than 1.0. In 2008, the potential dose from radiological emissions to air, from both current and past NTS activities, at onsite compliance monitoring stations was a maximum of 1.9 mrem/yr; well below the 10 mrem/yr dose limit. Air sampling data collected at all six pseudo-critical receptor stations had average concentrations of radioactivity that were a fraction of the CL values listed in Table 2 in Appendix E of 40 CFR 61 (CFR, 2008a). Concentrations ranged from less than 1 percent to a maximum of 19 percent of the allowed NESHAP limit. Because the nearest member of the public resides approximately 20 kilometers (12 miles) from the NTS boundary, concentrations at this location would be only a small fraction of that measured on the NTS. Potential dose to the public from NLVF was also very low at 0.00006 mrem/yr; more than 160,000 times lower than the 10 mrem/yr limit.

The Nevada Test Site (NTS) is operated by the U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office (NNSA/NSO). From 1951 through 1992, the NTS was operated as the nation’s site for nuclear weapons testing. The release of man-made radionuclides from the NTS as a result of testing activities has been monitored since the first decade of atmospheric testing. After 1962, when nuclear tests were conducted only underground, the radiation exposure to the public surrounding the NTS was greatly reduced. After the 1992 moratorium on nuclear testing, radiation monitoring on the NTS focused on detecting airborne radionuclides that are resuspended into the air (e.g., by winds, dust-devils) along with historically-contaminated soils on the NTS. To protect the public from harmful levels of man-made radiation, the Clean Air Act, National Emission Standards for Hazardous Air Pollutants (NESHAP) (40 Code of Federal Regulations 61 Subpart H) limits the release of radioactivity from a U. S. Department of Energy (DOE) facility (e.g., the NTS) to 10 millirem per year (mrem/yr) effective dose equivalent (EDE) to any member of the public. This is the dose limit established for someone living off of the NTS for inhaling radioactive particles that may be carried by wind off of the NTS. This limit assumes that members of the public surrounding the NTS may also inhale “background levels” or radioactive particles unrelated to NTS activities that come from naturally-occurring elements in the environment (e.g., radon gas from the earth or natural building materials) or from other man-made sources (e.g., cigarette smoke). The U. S. Environmental Protection Agency (EPA) requires DOE facilities (e.g., the NTS) to demonstrate compliance with the NESHAP dose limit by annually estimating the dose to a hypothetical member of the public, referred to as the maximally exposed individual (MEI), or the member of the public who resides within an 80-kilometer (50-mile) radius of the facility who would experience the highest annual dose. This dose to a hypothetical person living close to the NTS cannot exceed 10 mrem/yr. C.1 This report has been produced annually for the EPA Region IX, and for the state of Nevada since 1992 and documents that the estimated EDE to the MEI has been, and continues to be, well below the NESHAP dose limit. The report format and level of technical detail has been dictated by the EPA and DOE Headquarters over the years. It is read and evaluated for NESHAP compliance by federal and state regulators. Each section and appendix presents technical information (e.g., NTS emission source estimates, onsite air sampling data, air transport model input parameters, dose calculation methodology, etc.), which supports the annual dose assessment conclusions. In 2005, as in all previous years for which this report has been produced, the estimated dose to the public from inhalation of radiological emissions from current and past NTS activities is shown to be well below the 10 mrem/yr dose limit. This was demonstrated by air sampling data collected onsite at each of six EPA-approved “critical receptor” stations on the NTS. The sum of measured EDEs from the four stations at the NTS boundaries is 2.5 mrem/yr. This dose is 25 percent of the allowed NESHAP dose limit. Because the nearest member of the public resides approximately 20 kilometers (12 miles) from the NTS boundary, this individual receives only a small fraction of this dose. NESHAP compliance does not require DOE facilities to estimate annual inhalation dose from non-DOE activities. Therefore, this report does not estimate public radiation doses from any other sources or activities (e.g., naturally-occurring radon, global fallout).

During the manufacture of wood composites, paper, and to a lesser extent, lumber, large amounts of volatile organic compounds (VOCs) such as terpenes, formaldehyde, and methanol are emitted to air. Some of these compounds are hazardous air pollutants (HAPs). The air pollutants produced in the forest products industry are difficult to manage because the concentrations are very low. Presently, regenerative thermal oxidizers (RTOs and RCOs) are commonly used for the destruction of VOCs and HAPs. RTOs consume large amounts of natural gas to heat air and moisture. The combustion of natural gas generates increased CO2 and NOx, which have negative implications for global warming and air quality. The aforementioned problems are addressed by an absorption system containing a room-temperature ionic liquid (RTIL) as an absorbent. RTILs are salts, but are in liquid states at room temperature. RTILs, an emerging technology, are receiving much attention as replacements for organic solvents in industrial processes with significant cost and environmental benefits. Some of these processes include organic synthesis, extraction, and metal deposition. RTILs would be excellent absorbents for exhausts from wood products facilities because of their unique properties: no measurable vapor pressure, high solubility of wide range of organic compounds, thermal stability to 200°C (almost 400°F), and immisciblity with water. Room temperature ionic liquids were tested as possible absorbents. Four were imidizolium-based and were eight phosphonium-based. The imidizolium-based ionic liquids proved to be unstable at the conditions tested and in the presence of water. The phosphonium-based ionic liquids were stable. Most were good absorbents; however, cleaning the contaminates from the ionic liquids was problematic. This was overcome with a higher temperature (120°C) than originally proposed and a very low pressure (1 kPa. Absorption trials were conducted with tetradecy(trihexyl)phosphonium dicyanamide as the RTIL. It was determined that it has good absorption properties for methanol and α-pinene, is thermally stable, and is relatively easy to synthesize. It has a density of 0.89 g/mL at 20°C and a molecular weight of 549.9 g/mol. Trials were conducted with a small absorption system and a larger absorption system. Methanol, formaldehyde, and other HAPs were absorbed well, nearly 100%. Acetaldehyde was difficult to capture. Total VOC capture, while satisfactory on methanol and α-pinene in a lab system, was less than expected in the field, 60-80%. The inability to capture the broad spectrum of total organics is likely due to difficulties in cleaning them from the ionic liquid rather than the ability of the ionic liquid to absorb. It’s likely that a commercial system could be constructed to remove 90 to 100% of the gas contaminates. Selecting the correct ionic liquid would be key to this. Absorption may not be the main selection criterion, but rather how easily the ionic liquid can be cleaned is very important. The ionic liquid absorption system might work very well in a system with a limited spectrum of pollutants, such as a paint spray line, where there are not very high molecular weight, non volatile, compounds in the exhaust.

We conducted ambient monitoring of various hazardous air pollutants (HAPs) for 2 years (2013-2015) in two adjacent Korean cities in a megacity area: Seoul and Incheon. Measured HAPs included volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), and heavy metals (HMs). The objectives of this study were to evaluate the spatiotemporal variations of HAPs, to prioritize HAPs based on health risks, to identify sources using a receptor-based model, and to estimate source-specific risks. Overall, the HAP levels in Incheon were higher than those in Seoul. The concentrations of combustion-origin HAPs, such as PAHs and some HMs, were significantly higher during the heating period than during the non-heating period. However, most VOCs exhibited an opposite trend. Benzo[a]pyrene showed the highest cancer risk in both cities, followed by formaldehyde, arsenic, and benzene; trichloroethylene was the only species that exceeded the hazard quotient of 1. Cumulative cancer risks were 2.0 × 10-4 in Seoul and 2.7 × 10-4 in Incheon. Major sources and their contributions to each HAP concentration were estimated by positive matrix factorization modeling. Based on source-specific risk assessments, we suggest that both cities should give high priority to the control of traffic pollution and the supply of cleaner fuels in non-residential sectors. Reducing carbonyl concentrations in Seoul and industrial emissions in Incheon is also necessary. Establishing new ambient standards for benzo[a]pyrene and formaldehyde is worth considering as a long-term measure. This study provides scientific information on the occurrence, health risks, and sources of various HAPs in large urban areas.

Characterization and health impact assessment of hazardous air pollutants in residential areas near a large iron-steel industrial complex in Korea

We measured a wide range of hazardous air pollutants (HAPs) simultaneously at five sites over four seasons in 2009–2010 in Ulsan, the largest industrial city in Korea. Target analytes included volatile organic compounds (VOCs), carbonyls, polycyclic aromatic hydrocarbons (PAHs), phthalates, and heavy metals (HMs). The objectives of this study were to evaluate the occurrence and spatiotemporal distributions of HAPs, and to identify important HAPs based on health risk assessment. Industrial emissions affected ambient levels of VOCs and HMs, as demonstrated by spatial distribution analysis. However, concentrations of PAHs and phthalates were relatively uniform at all sites. VOCs and HMs exhibited little seasonal variation, while formaldehyde increased in the summer due to its secondary formation. PAHs exhibited notable seasonal variation; higher in cold seasons and lower in warm seasons. Cumulative cancer risks imposed by 35 HAPs were 4.7 × 10−4 and 1.7 × 10−4 in industrial and residential areas, respectively. The top five major cancer risk drivers appeared to be formaldehyde, benzene, benzo[a]pyrene, As, and Co. The sums of hazard quotients (HQ) derived by 47 HAPs were 10.0 (industrial) and 2.4 (residential). As the individual species, only two HAPs exceeded the HQ of 1, which are As (3.1) and Pb (2.1) in the industrial area. This study demonstrated the importance of a comprehensive monitoring and health risk assessment to prioritize potentially toxic pollutants in the ambient air of a large industrial city.

Evaluating hazardous air pollutants in Australia

Applicability of canisters for sample storage in the determination of hazardous air pollutants