Hazardous Waste Combustion Research Articles

Extending Multi-Pathway Human Health Risk Assessment from Regional to Country-Wide—A Case Study on Kuwait

Air pollution has emerged as a pressing global issue in recent decades. While criteria pollutants and greenhouse gases contribute to the problem, this article explicitly addresses hazardous air pollutants (HAPs). This work estimates the country-wide cumulative human health impacts from exposure to HAPs. Kuwait is used as the case study due to data availability and non-fragmentation of data. At present, the evaluation of multi-pathway human health risks arising from exposure to HAPs is incomplete, as indirect pathways have not been considered. Furthermore, only a few HAPs, such as benzene, have established ambient air quality standards specifically intended to safeguard human health, leaving many HAPs unregulated. This study considers several pathways (both direct and indirect) and various environmental media (air, water, plants, soil, and animal tissue). The findings indicate that cumulative health risks in the coastal air quality zone are within acceptable limits but are notably higher when compared to the other air quality zones. For cancer risks, only the Ahmadi Hospital, with a cancer risk of 1.09 × 10−5 for the resident adult exposure scenario, slightly exceeds the acceptable risk level of 1 × 10−5. The proposed methodology integrates the results from a country-wide emissions inventory composed of different air quality zones, air dispersion and deposition modeling, multi-pathway transport-and-fate analysis, exposure quantification, and health risk and hazard characterization. It also extends and adapts EPA methodologies initially designed for hazardous waste combustion facilities to additional emission sources and provides a case study for a region seldom subjected to such human health risk assessments.

Methodology for Mobile Toxics Deterministic Human Health Risk Assessment and Case Study

Air toxic emissions from on-road mobile sources are significant contributors to the degradation of air quality in urban and dense population centers. Research led by the United States Environmental Protection Agency (EPA) identified more than 1162 hazardous air pollutants (HAPs) in the exhaust and evaporative emissions from on-road mobile sources. However, less than 70 hazardous air pollutants are monitored by regulatory agencies. HAPs emitted from Mobile Sources are known as Mobile Source Air Toxics (MSATs). The EPA estimates that approximately half of the cancer risk and 74% of noncancer health impacts from air toxics is attributed to mobile sources. The quantification of the risk associated with MSATs exposure remains limited to date, and only a few MSATs have ambient air quality standards to protect human health and welfare. This work presents a novel and validated methodology to quantify the myriad health risks associated with exposure to on-road mobile emissions. This methodology is introduced in the form of a pipelined analysis process, which may be employed in existing and new transportation projects. The proposed new methodology integrates results from three different types of models: on-road vehicle emissions inventory models such as MOVES and IVE, air dispersion models such as AERMOD and SCIPUFF, and risk estimate models for human and ecological receptors such as the 2005 Final U.S. EPA Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities. The result of this research work is a new methodology that provides regulators and risk analysts with a more detailed awareness of the health impacts of MSATs. A case study of Saint Paul, Minnesota, validated the air dispersion modeled results against monitored data, and the agreement was acceptable (i.e., the estimates were within a factor of two of the observations). Three high-population locations in the Saint Paul area were evaluated for human health risk, with the observation that at two of these locations, the Saint Paul—Ramsey Health Center and Anderson Office Building, the calculated cancer risk is in excess of the target risk level of 1.0E-05 for benzo(a)pyrene. The methodology presented in this paper allows regulators, risk analysts, and air quality engineers to better estimate multi-pathway cancer and noncancer risk associated with acute and chronic exposure to MSATs. Moreover, this work provides a science-based aid to policy decision makers when considering factors that most significantly affect population health and ecology.

Quantitative assessment of exposure of heavy metals in groundwater and soil on human health in Reasi district, Jammu and Kashmir.

The assessment of heavy metal contents in environmental sectors is important to estimate the carcinogenic and non-carcinogenic doses and risks for the mankind associated with it. The present work deals with the assessment of the risk exposure related to heavy metal contents in groundwater and soil samples to two different age groups via three different transits, i.e., ingestion, inhalation and dermal. The concentrations of heavy metals (Zn, Cd, Cu, Pb and Cr) were measured in the villages of lower Himalayas of Reasi district by using microwave plasma atomic emission spectrometer. The calculated mean contamination factors of heavy metals in soil samples were as: Zn, 0.73; Cu, 0.70; Pb, 0.74; and Cr, 0.33; which led to pollution load index less than unity. The overall carcinogenic risks have been varied from 6.4E-08 to 5.1E-07 in soil samples and from 7.3E-06 to 1.1E-04 in ground water samples and were found to be well within the range prescribed by USEPA (Screening level ecological risk assessment protocol for hazardous waste combustion facilities, appendix E: toxicity reference values, US Environmental Protection Agency, Washington, D.C., 1999). The mean values of heavy metal contents except lead and chromium in water samples were found to be less than the values prescribed by various agencies. Geo-accumulation Index showed that Pb contribute to the highest contamination (0 < Igeo < 1) among the other heavy metals. Cluster analysis and principal component analysis identified that Zn, Cu, Pb and Cr had a relationship and the presence of these heavy metals could be related to vehicle emissions, traffic sources and industrial sources. The overall mean values of the non-carcinogenic doses and associated hazard risks in soil and water samples calculated for children were found to be higher than the adults which may be due to hand to mouth activities.

The relationship between urinary BTEX metabolites and residence setting among Korean homemakers: the first Korea National Environmental Health Survey (2009\u20132011)

BackgroundBenzene, toluene, ethylbenzene, and xylene (BTEX) are emitted in the combustion or volatilization of hazardous wastes and fossil fuels. Paint, varnishing agents, and cigarette smoke are also sources of BTEX in living environments. Few studies have examined indoor exposure to BTEX using biomarkers, especially in residential settings. In this study, we evaluated the relationship between residence factors and BTEX exposure using biomarkers among Korean homemakers.MethodWe obtained data on 893 non-smoking homemakers older than 19 years from the Korean National Environmental Health Survey (2009–2011). The concentrations of urinary BTEX metabolites (t,t-muconic acid, hippuric acid, mandelic acid, phenylglyoxylic acid, and total methylhippuric acid) were adjusted using the urinary creatinine. Analysis of covariance (ANCOVA) and logistic regression analysis were used to evaluate the associations between residence parameters and urinary BTEX metabolites.ResultsThe geometric mean concentrations of t,t-muconic acid and methylhippuric acid were significantly higher in the group that had remodeled within the previous 6 months (p < 0.05) compared with the no-remodeling group. In logistic regression analyses, the odds ratio for exceeding the median urinary concentration of t,t-muconic acid was significantly higher in the group that had remodeled compared with the no-remodeling group (OR = 1.591, 95% CI = 1.063–2.382). Urinary methylhippuric acid was significantly associated with residing in a home located within 100 m of a major road (OR = 1.399, 95% CI = 1.071–1.826).ConclusionOur study found some significant associations between urinary BTEX metabolites and residence parameters. To find clear associations, additional and more detailed studies are needed.Trial registrationNot applicable (this study does not include healthcare intervention on human participants).

Selected Proceedings from IT3: The International Conference on Thermal Treatment Technologies &amp; Hazardous Waste Combustors, Montreal, Canada, May 12–16, 2008, and Cincinnati, Ohio, May 12–22, 2009Guest Editor: Paul M. Lemieux, Ph.D.Introduction

Environmental Engineering ScienceVol. 27, No. 7 Selected Proceedings from IT3: The International Conference on Thermal Treatment Technologies & Hazardous Waste Combustors, Montreal, Canada, May 12–16, 2008, and Cincinnati, Ohio, May 12–22, 2009Guest Editor: Paul M. Lemieux, Ph.D.IntroductionRoy E. CrossJr.Roy E. CrossJr.*Corresponding author: Technical Market Manager, FGT, Carmeuse Lime & Stone, 3600 Neville Road, Pittsburgh, PA 15225. E-mail:E-mail Address: Roy.Cross@carmeusena.comSearch for more papers by this authorPublished Online:14 Jul 2010https://doi.org/10.1089/ees.2010.2707AboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View article"." , 27(7), p. 537FiguresReferencesRelatedDetails Volume 27Issue 7Jul 2010 InformationCopyright 2010, Mary Ann Liebert, Inc.To cite this article:Roy E. CrossJr..Environmental Engineering Science.Jul 2010.537-537.http://doi.org/10.1089/ees.2010.2707Published in Volume: 27 Issue 7: July 14, 2010PDF download

Minimizing Mercury Emissions in Biosolids Incinerators

Mercury is a persistent bio-accumulative toxicant (PBTs) and thus the United States Environmental Protection Agency (EPA) has established a goal of reducing environmental levels of PBTs in the environment. Proactively, the Water Environment Research Foundation (WERF) provided funding for research related to mercury (Hg) measurement and control in United States Publicly Owned Treatment Works (POTWs) that practice biosolids incineration. In this study, surveys of POTWs determined analytical techniques employed for all matrices, biosolids incinerator design and operational parameters, testing frequency, and historical data. A comprehensive literature review gathered information to summarize current understanding of mercury speciation in combustion gas. This is a critical information piece needed in developing a mercury control strategy. Control technology applied to similar industries of coal fired utilities, municipal waste combustors, medical waste incinerators, hazardous waste combustors, crematories, and industrial boilers is presented in this report. Only limited information is available concerning mercury speciation cycling throughout a biosolids incinerator facility. Mercury control is highly dependent upon understanding and manipulating mercury speciation to advantage. Mass balance studies are an important component of understanding mercury cycling in biosolids incineration, but few studies exist. Guidance for mass balance study design and application is included in this report. This title belongs to WERF Research Report Series . ISBN: 9781843393559 (eBook)

Ultrafine particulates decrease left ventricular performance after ischemia‐reperfusion

Epidemiological studies show a correlation between increased airborne particulates and hospitalization for cardiovascular events, especially in at risk populations. Ultrafine particles (UFP, &lt;100 nm diam) generated from the combustion of hazardous wastes can contain stable free radicals. Given the link between oxidative stress and cardiac disease, we hypothesized that exposure to UFP may exacerbate left ventricular (LV) dysfunction produced by ischemia reperfusion (I/R). Male Brown Norway rats were pretreated (24 hr) i.t. with UFP containing CuO and dichlorobenzene (DCB, 8 mg/kg), silica UFP (8 mg/kg) or vehicle. Rats were anesthetized, ventilated and a pressure volume (PV) catheter placed in the LV. After baseline measures, the LAD was ligated for 90s and released. PV loops were generated 1–60 min post I/R. At 1 min post I/R, control and DCB‐treated rats showed decreased dP/dt max, increased tau, and increased end diastolic volume. Ejection fraction was unchanged in control and reduced in DCB‐treated rats (−45%). LV performance in control rats returned to baseline by 30 min. In DCB‐treated rats LV performance steadily declined for 60 min before stabilizing at reduced levels (dP/dt, −45%; tau, +38%; EF −50% vs baseline). These data indicate that prior exposure to UFP may pose a significant risk in persons with cardiac ischemia. Support: NIH P20‐RR018766

Species Transformation of Trace Elements and Their Distribution Prediction in Dyestuff Residue Incineration

The release of heavy metals from the combustion of hazardous wastes is an environmental issue of increasing concern. The species transformation characteristics of toxic heavy metals and their distribution are considered to be a complex problem of mechanism. The behavior of hazardous dyestuff residue is investigated in a tubular furnace under the general condition of hazardous waste pyrolysis and gasfication. Data interpretation has been aided by parallel theoretical study based on a thermodynamic equilibrium model based on the principle of Gibbs free energy minimization. The results show that Ni, Zn, Mn, and Cr are more enriched in dyestuff residue incineration than other heavy metals (Hg, As, and Se) subjected to volatilization. The thermodynamic model calculation is used for explaining the experiment data at 800°C and analyzing species transformation of heavy metals. These results of species transformation are used to predict the distribution and emission characteristics of trace elements. Although most trace element predictions are validated by the measurements, cautions are in order due to the complexity of incineration systems.

Waste incineration—how big is the health risk? A quantitative method to allow comparison with other health risks

To assess the health risk from a medium-sized waste incinerator and develop a single comparable figure to quantify overall risk. We used a prospective health risk assessment utilizing US Environmental Protection Agency Human Health Risk Assessment Protocol (HHRAP) for Hazardous Waste Combustion Facilities and UK coefficients for the impact of sulphur dioxide and particulates. Calculations were based on a resident population of 25,398 living within 5.5 km of the site. Anxiety, employment, noise, occupational risks, road accidents, and reduced use of landfill were all considered to have a potential, but unquantifiable, effect on health. Stack emissions over 25 years in a population of 25,398 within 5.5 km of the stack would result in an additional 0.018 cancers, 0.46 deaths brought forward due to sulphur dioxide and 0.02 deaths due to fine particles. The overall risk of dying due to emissions in any one year was 2.49 x 10(-7) or 1 in 4 million. To facilitate better public understanding of the comparative risk of incinerator emissions, we propose a simple method of deriving a single annual risk figure allowing comparison with the risk of dying from other causes with which the public is more familiar.

Origin and Health Impacts of Emissions of Toxic By-Products and Fine Particles from Combustion and Thermal Treatment of Hazardous Wastes and Materials

High-temperature, controlled incineration and thermal treatment of contaminated soils, sediments, and wastes at Superfund sites are often preferred methods of remediation of contaminated sites under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 and related legislation. Although these methods may be executed safely, formation of toxic combustion or reaction by-products is still a cause of concern. Emissions of polycyclic aromatic hydrocarbons (PAHs); chlorinated hydrocarbons (CHCs), including polychlorinated dibenzo-p-dioxins and dibenzofurans; and toxic metals (e.g., chromium VI) have historically been the focus of combustion and health effects research. However, fine particulate matter (PM) and ultrafine PM, which have been documented to be related to cardiovascular disease, pulmonary disease, and cancer, have more recently become the focus of research. Fine PM and ultrafine PM are effective delivery agents for PAHs, CHCs, and toxic metals. In addition, it has recently been realized that brominated hydrocarbons (including brominated/chlorinated dioxins), redox-active metals, and redox-active persistent free radicals are also associated with PM emissions from combustion and thermal processes. In this article, we discuss the origin of each of these classes of pollutants, the nature of their association with combustion-generated PM, and the mechanisms of their known and potential health impacts.

Effects of Fly Ash Transition Metal Content and Flue Gas HCl/SO2 Ratio on Mercury Speciation in Waste Combustion

Understanding the transformation of mercury species (elemental and oxidized forms) in stationary combustion sources is of interest to both those responsible for developing control technologies and those responsible for setting regulations. Elemental mercury (Hg0) poses a challenging flue gas control issue, and oxidized forms of mercury (Hg2+) are of concern due to local deposition potential. In a previous study, mercury speciation, or more specifically oxidation of Hg0, was studied in simulated flue gases and in the presence of three-component model fly ashes. Gas-phase studies indicated that oxidation of Hg0 in the presence of hydrogen chloride (HCl) is rather slow, and proceeds at measurable rates only at temperatures >700 °C and HCl concentrations in the range of 100–200 ppm. The effect of fly ash composition was investigated using a fixed-bed reactor containing different synthetic model fly ash components such as alumina (Al2O3), silica (SiO2), ferric oxide (Fe2O3), copper oxide (CuO), and calcium oxide (CaO). Transition metal oxides, CuO and Fe2O3, exhibited significant catalytic activity in the surface-mediated oxidation of Hg0 in the presence of HCl. The observed Hg0 oxidation activities of the two oxides are possibly caused by the Deacon process in which chlorine gas (Cl2) is produced via catalytic oxidation of HCl over these two oxides. In the present follow-up study, the effect of sulfur dioxide (SO2) to HCl ratio on Hg0 oxidation was investigated. The addition of SO2 to the moist flue gas at high SO2:HCl ratios (10:1 to 4:1) caused a decrease in oxidation of Hg0. This is attributed to a scavenging effect of SO2 and H2O on Cl2. Addition of CaO to the synthetic fly ashes also caused a drop in Hg0 oxidation. It is possible that due to the partial removal of HCl by reaction with CaO less HCl is available for the catalytic Deacon reaction. The Hg0 oxidation activity of a cement kiln dust (CKD) sample collected from a full-scale hazardous waste incinerator was also studied. Qualitatively, it exhibited Hg0 oxidation catalytic behavior similar to that observed with CaO-containing model fly ashes. According to this study, only moderate oxidation of Hg0 (40%) can be expected in cement kilns burning hazardous waste. During hazardous and municipal waste combustion, the presence of sufficiently high HCl and/or Cl2 in the gas phase may cause the metallic oxide compounds in the fly ash to be converted into metal chlorides. Additional tests were performed using synthetic fly ashes containing cuprous chloride (CuCl). These results were compared to those obtained using CuO. It was found that CuCl is so reactive that it oxidizes Hg0 even in the absence of HCl in the simulated flue gas. This is contrary to the behavior shown by CuO, which requires the presence of HCl in the flue gas in order for Hg0 oxidation to occur.

Shortcomings in USEPA's Approach for Predicting Risk Due to Consumption of Animal Food Products Impacted by Air Emissions from Hazardous Waste Combustion Facilities: A Case Study Involving Phthalates

As a part of the permitting process for hazardous waste combustion facilities, regulatory agencies are now conducting site-specific, multipathway risk assessments. In accordance with the approach established by the USEPA, the Texas Natural Resource Conservation Commission uses a prospective risk assessment paradigm whereby site-specific activity pattern and land use information is used to determine plausible exposure scenarios and pathways. A set of exposure scenarios defined as receptors (i.e., resident adult, resident child, farmer adult, farmer child, fisher adult and fisher child) is then assumed to be exposed via multiple applicable exposure pathways. In conducting such risk assessments, modeled air emissions of di-n-octyl phthalate (DNOP), at concentrations near or below detectable levels, have been observed to produce an unacceptable hazard in the farmer exposure scenario. Sensitivity analyses indicated that two key parameters affected hazard estimates for DNOP in the farmer scenario: the octanol-water partition coefficient (Kow), which is used to predict bioaccumulation in animal tissue, and the metabolism factor, which is used to account for metabolism and elimination. Evidence indicates that Kow values for highly lipophillie compounds are accurately determined using a slow-stir method. In addition, evidence indicates that the phthalates of interest are extensively metabolized and eliminated. However, current USEPA guidance includes geometric mean Kow values for highly lipophillie compounds derived in part on methods that are outdated and no longer considered accurate. In addition, USEPA guidance only considers metabolism for bis-% ethylhexyl phthalate (BEHP). Collectively, these two shortcomings in the USEPA approach result in a 38-fold underestimation of hazard for BEHP and a 172,000-fold overestimation of hazard for DNOP.

Evolution of hazardous waste combustors MACT standards

AbstractThis year, on July 24, the DC Circuit Court ruled that the EPA had not correctly derived emission standards, and vacated the MACT (Maximum Achievable Control Technology) rule for Hazardous Waste Combustors (HWC) [1, 2]. A major complaint, voiced by the Sierra Club, was that the MACT methodology was misapplied in a manner that produced overly lenient standards. Industry and trade associations argued just the opposite. The Sierra Club won the first round when the court agreed that the emission standards should be based on the average of the best‐performing 12% of units in each category.The next question was, “What will be the regulations until the final standards can be developed?” This caused considerable angst because, if no standards were in place by May 15, 2002, control would revert to case‐by‐case permits by Federal and State regulatory agencies as set forth in Section 112 of the Clean Air Act. Obviously, that would be the antithesis of the Congressional mandate and the objectives of environmental groups. The Sierra Club and most litigants did not want the uncertainties and inconsistencies this would introduce.

Travis and Arms revisited: a second look at a widely used bioconcentration algorithm.

In 1988, Travis and Arms reviewed the literature and collected data to develop a relationship between the octanol-water partition coefficient (Kow) and the uptake of organic compounds into milk and beef (Travis and Arms, 1988). These equations have been utilized for predicting biotransfer factors for organic chemicals when empirical data are lacking. During the external peer review of the draft US Environmental Protection Agency (EPA) guidance entitled Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities (US EPA, 1998) and the development of Superfund's Ecological Soil Screening Levels (US EPA, 2000b), questions challenging the derivation and use of these equations were raised. The primary questions raised were: 1) Are the equations presented in Travis and Arms (1988) for the estimation of transfer of organic compounds from contaminated feed to beef and milk technically valid and reproducible? If so, (2) are the equations appropriate across the entire log Kow range? For these reasons, this study was undertaken to validate the original Travis and Arms equations, to review more recent literature, and. if appropriate, to add to the original Travis and Arms data set to obtain updated equations. This paper presents an evaluation of the original Travis and Arms equations, limitations to their use, and steps to reduce uncertainties associated with their use by updating with more current literature.

Development of a Metabolism Factor for Polycyclic Aromatic Hydrocarbons for Use in Multipathway Risk Assessments of Hazardous Waste Combustion Facilities

As a state authorized to permit hazardous waste combustion facilities, the Texas Natural Resource Conservation Commission (TNRCC) has conducted several site-specific, multipathway risk assessments in support of permitting actions. These risk assessments were carried out in accordance with guidance provided in U.S. Environmental Protection Agency's Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities, Peer Review Draft (HHRAP). This protocol uses a prospective, screening-level, risk assessment paradigm and incorporates conservative default assumptions. In conducting such risk assessments, staff of the Toxicology and Risk Assessment Section have found that modeled emissions of polycyclic aromatic hydrocarbons (PAHs) at concentrations near or below detectable levels can produce unacceptable risk in the “farmer” exposure scenario. In accordance with recommendations in HHRAP, the TNRCC followed a tiered approach, whereby additional site-specific information is incorporated in place of standard default assumptions in cases where the initial screening-level risk assessment yielded unacceptable risk or hazard. Sensitivity analyses indicated that one of the key parameters affecting the risk estimates for PAHs in the farmer exposure scenario was the way in which PAHs were modeled up through the food chain. Therefore, refinement of the model focused on the development of a PAH-specific metabolism factor, as described in the article.

Characterization of organic emissions from hazardous waste incineration processes under the new EPA draft Risk Burn Guidance: measurement issues

EPA's recently published draft Risk Burn Guidance recommends that hazardous waste combustion facilities complete a mass balance of the total organics (TOs) that may be emitted from the combustor. TOs, consisting of three distinct fractions (volatile, semivolatile, and nonvolatile organic compounds) are determined using measurement techniques specific to the boiling point (bp) range of each component. Preliminary proof-of-concept tests have been performed to gain further knowledge of the total chromatographable organics (TCO) and gravimetric analysis (GRAV) procedures used to determine the semivolatile and nonvolatile organic fractions. A commercially prepared Method 8270 semivolatile organic standard solution, made up of 112 compounds containing a variety of halogenated, oxygenated, nitrogenated, and sulfonated hydrocarbons, in addition to those hydrocarbons containing only carbon and hydrogen, was used to examine measurement biases of the TCO and GRAV methods. The results indicate that, at least for this particular standard, both methods are accurate, exhibiting biases <±10%. However, these TCO results may be deceiving. TCO measurement biases observed for select individual semivolatile organic compounds are well in excess of the composite bias observed. The composite bias observed may be more a result of a relatively equal number of negative and positive biases that negate each rather than a true indication of TCO measurement bias. Further methods evaluation work is required to support this tenet. Additional tests were performed to verify that the semivolatile organic mass was not redundantly measured by the GRAV procedure. Experiments were also performed to expand the mass of nonvolatile organic material that could be quantified using the TCO procedure. Expanding the TCO working bp range may be a viable alternative to the GRAV technique. It must be cautioned that these results are not fully comprehensive in nature and, as a result, applications of these results are limited.

NEW RULES TARGET WASTE BURNERS

Last September, after years of delay and discussion, the Environmental Protection Agency issued a final regulation that will subject several hundred facilities to a new regime of air pollution standards. Each year, the affected facilities burn a total of 3.3 million tons of hazardous waste. In all, 232 hazardous waste combustors at 172 facilities will be covered. These include 163 on-site process incinerators, 26 commercial incinerators, 33 cement kilns, and 10 aggregate kilns. EPA estimates the new rule will cut emissions of dioxins and furans by 70%, mercury by 55%, cadmium and lead by 88%, and particulates by 42%. The agency also estimates that releases of arsenic, beryllium, and chromium will be reduced by 75%. The regulation will require companies to install equipment that could include filters and other devices to capture particulates and metals; systems to quickly quench hot flue gases to curb dioxin formation; and monitors to continuously measure carbon monoxide, hydrocarbon emissions, ...

Heat and mass transfer in annular liquid jets: III. Combustion within the volume enclosed by the jet

The nonlinear dynamics of and heat and mass transfer processes in annular liquid jets are analyzed by means of a nonlinear system of integrodifferential equations which account for the liquid motion and the gases enclosed by the jet. Both linear and sinusoidal heat and mass addition sources are considered to take place homogeneously within the volume enclosed by the jet's inner interface in an attempt to simulate the combustion of hazardous wastes or materials within this volume. It is shown that the liquid's temperature at the jet's inner interface increases rapidly with linear heat addition, but drops also quickly to its initial value once heat addition is ended, whereas the pressure coefficient and the volume enclosed by the jet increase until they reach a maximum value and then decrease in an oscillatory manner towards their steady values. For the case of sinusoidal heat addition, it is shown that the pressure coefficient and interfacial concentration, temperature and heat and mass fluxes oscillate in a sinusoidal manner with the same frequency as that of the sinusoidal heat source. It is also shown that mass transfer phenomena are much slower than heat transfer ones. For the case of linear mass addition, it is shown that the temperature of the gases enclosed by the jet first decreases because of dilution and then it increases until it reaches a constant value that corresponds to the same temperature for the gases and the flowing liquid. The pressure of the gases enclosed by the jet first increases because of mass addition and then slowly decreases because of mass absorption by the jet.

Comparison of respiratory symptoms among community residents near waste disposal incinerators

A previous survey found that residents near a hazardous waste incinerator reported more respiratory symptoms than residents of a nearby community. To explore the possibility that these findings might have been due to the use of a rural control site, far removed from urban pollution, we expanded the analysis to include reports of respiratory symptoms from residents of six additional communities. Residents of each of four study communities were exposed to the plumes of biomedical, municipal or hazardous waste combustors. For each study community, a comparison community was surveyed that was distant from major point sources of air pollution. Over 4200 respondents were queried by telephone about respiratory symptoms, smoking and other risk factors such as chemical exposures in the workplace and home, and provided a subjective assessment of air quality in their neighborhoods. Differences in symptom prevalence between each study community and its respective control community, as well as a combined control group, were explored, controlling for factors other than community exposure that may affect respiratory health. Results indicate a higher prevalence of all self-reported respiratory symptoms in one community near a hazardous waste incinerator compared with its control community. While this relationship persisted after controlling for perceived air quality and when compared with a combined control group, only respiratory symptoms of long duration remained significant. These results suggest that further examination of the respiratory health of residents living near this waste combustor source is warranted.

CASE HISTORY REVIEW—DEMILITARIZATION COMBUSTION PERMITS*

In May 1993, Administrative Browner of the U.S. Environmental Protection Agency (USEPA) announced that an indirect exposure health risk assessment was required for all hazardous waste combustion facilities seeking a Resource Conservation and Recovery Act permit. These types of risk assessments evaluate the health and environmental effects from inhalation of emissions (direct exposure) and from contact with environmental media and consumption of food products impacted by the emissions (indirect exposure). Completion of an indirect exposure risk assessment is often complicated by the various methodologies available for generating results and by the requirements of the regulating community. To minimize this complexity and to maximize consistency between risk assessments, the USEPA developed a number of detailed guidance documents. Site-specific conditions and toxicological data gaps, however, continue to present challenges not addressed by these guidance documents. This paper presents some of the specific challenges encountered by the U.S. Army Center for Health Promotion and Preventive Medicine when performing indirect exposure health risk assessments for several demilitarization combustion facilities.