Modeling VOC-odor exposure risk in livestock buildings

This paper describes a novel idea of linking models of exposure, internal dosimetry, and health effects. Risk assessment approach that integrates predicted odor caused by volatile organic compounds (VOC-odor) of toluene/xylene concentrations in human tissues leads to predict exposure risks in livestock buildings. First, VOC transport model was developed to calculate airborne toluene/xylene concentrations. Based on a physiologically based pharmacokinetic (PBPK) model, concentrations within five compartments representing lung, liver, fat, slowly perfused tissues, and rapidly perfused tissues could be quantified. By using a pharmacodynamic (PD) Hill model, we can optimally fit data from rat and human experiments to reconstruct dose-response relationships for accounting human health effects from nose poke and eye irritation. Results demonstrated that peak tissue concentration occurring at 5-10h in that fat contains the highest concentration than other tissues at around 4ppm of toluene and 1.8ppm of xylene. The EC(10) values are 114 and 232ppm, whereas expected risks are estimated to be 0.71% and 0.26% of human exposure to toluene and xylene, respectively. Risk analyses indicate that inhalation exposure in livestock buildings poses no significant threat to human health under the present environmental conditions. This method provides a rigorous and effective approach to relate target tissue concentration to human nose poke or eye irritation. We suggest that our probabilistic framework and methods be taken seriously because they produce general conclusions that are more robust and could offer a risk-management framework for discussion of future establishment of limits for respiratory exposure to VOC-odor.     

Can we trust odor databases? Example of t- and n-butyl acetate

The US EPA has exempted t-butyl acetate from VOC regulations, which increases the likelihood that it may replace other solvents in some settings. This investigation probes its chemosensory properties. In Study 1, subjects (n = 29) sought to detect the odor of t-butyl acetate and of n-butyl acetate in forced-choice testing of stable concentrations, analytically confirmed. Subjects sniffed from cones with a high enough volumetric flow to insure against dilution by nonodorized air. A subject made hundreds of judgments, enough for a psychometric function for each material. The points of 50% detection above chance (“threshold”) occurred at 8 and 2 ppb for t-butyl acetate and n-butyl acetate, respectively. In study 2, subjects (n = 26) sought to detect vapor with the eye via chemesthesis (sensory irritation) in 10-s exposures. Detection at 50% occurred at 177 and 113 ppm for t-butyl acetate and n-butyl acetate, respectively, more than 10,000 times above that for odor detection. The protocols produced results of uncommon precision compared to those in often-misleading archival databases. The nose exhibits much higher sensitivity than the databases indicate. The collections rarely exhibit accuracy better than ±1000%. Collection of accurate data for a VOC can ironically bring on stricter regulation for just it, a situation that calls for a strategy to improve the database by collection of new data, importation of better data, and development of quantitative structure–activity modeling.     

Control of Photochemical Smog by Alteration of Initial Reactant Ratios

This paper is an endeavor to show how several experimenters have quite closely equaled the results of the other, and how the results from these various laboratories can, by a change of coordinate system, be related to each other in a systematic manner. Only after demonstrating where the Los Angeles Civic Center atmosphere is in relation to these coordinates and the contours, or gradients, of these various effects, eye irritation and oxidant, is it possible to predict the photochemical effect of a reduction of olefins (hydrocarbons) or the reduction of nitric oxide. In addition, a study of the variation in eye irritation with irradiation time, demonstrates that the time at which eye irritation measurements are taken is important in understanding the entire photochemical mechanism underlying the “smog” problem in the summertime in Los Angeles     

Industrial odor sources and air pollutant concentrations in Globeville,a Denver,Colorado neighborhood

An odor of unknown origin described as a “tar” or “asphalt” smell has become unbearable for many of Globeville, CO, residents over the past few years. Residents report during odor events burning eyes and throat, headaches, skin irritation, and problems sleeping. This study was undertaken to identify the potential sources of the odor and the concentrations of air pollutants making up the odor by conducting meteorological correlations and sampling for a panel of volatile organic compounds (VOCs), sulfur gases, and polycyclic aromatic hydrocarbons (PAHs) in the neighborhood and near suspected sources. Wind speed and direction data collected every 1 min in the neighborhood indicate that when the odor is noticed, the community is directly downwind of a wood preservation facility and an asphalt roofing facility. Air samples collected during high-intensity odor events have shown concentrations of methylene chloride, hexane, toluene, naphthalene, dibenz[a,h]anthracene, benzo[g,h,i]perylene, and indeno[1,2,3-cd]pyrene, each at least two times higher than background concentrations. Naphthalene and the other PAHs are known pollutants emitted from wood treatment processes, and are known to have a coal tar odor. Naphthalene was present in a sample collected directly adjacent to the Koppers facility and was not present in any background samples. Single-compound odor and health thresholds, however, were never surpassed. Given the technical and regulatory challenges of sampling odors and controlling emissions, it is recommended that Globeville residents and neighboring industry pursue a “good neighbor policy” to solve the odor issue. Specific offending industrial processes could be identified for which there exist cost-effective control technologies that would reduce exposure to odors and air toxics in Globeville.

Implications: Meteorological correlations and samples of volatile organic compounds (VOCs), sulfur gases, and polycyclic aromatic hydrocarbons (PAHs) in the Globeville, CO, neighborhood and near suspected sources during odor events indicate potential industrial sources of a transient and noxious odor. Legislative approaches have proven unfruitful and no health or odor thresholds were typically violated. New approaches are warranted to address odor mixture effects in neighborhoods near industrial facilities.     

Assessment of the Contribution of Chemical Species to The Eye Irritation Potential of Photochemical Smog

Eye irritation measurements are available from smog chamber solar Irradiations of selected hydrocarbon-nitrogen oxide mixtures. These results have been used to compute eye irritation intensity parameters for formaldehyde, acrolein, peroxyacetyl nitrate, and peroxypropionyl nitrate. Peroxypropionyl nitrate is the most irritating of these four substances. The relative contribution of various pairs of eye Irritants in ambient air mixtures to eye irritation has been calculated from the ambient air concentrations and the eye irritation intensity parameters. The relative contribution of the four eye irritants to a "typical" ambient air mixture has been computed. Formaldehyde appears to be the single most significant eye irritant. Other potential ambient air eye irritants are discussed. The relationships between the hydrocarbon control strategies and eye irritation are considered.     

Formaldehyde Dose-Response in Healthy Nonsmokers

Industrial, commercial, and domestic levels of formaldehyde exposure range from <0.1 to >5.0 ppm. Irritation of the eyes and upper respiratory tract predominate, and bronchoconstriction is described in case reports. However, pulmonary function and irritant symptoms together have not been assessed over a range of HCHO concentrations in a controlled environment. We investigated dose response in both symptoms and pulmonary function associated with 3-h exposures to 0.0-3.0 ppm HCHO in a controlled environmental chamber. Ten subjects were randomly exposed to 0.0, 0.5, 1.0, and 2.0 ppm HCHO at rest plus 2.0 ppm HCHO with exercise and nine additional subjects were randomly exposed to 0.0,1.0,2.0, and 3.0 ppm HCHO at rest plus 2.0 ppm HCHO with exercise. Significant dose-response relationships in odor and eye irritation were observed (p < 0.05). Nasal flow resistance was increased at 3.0 ppm (p < 0.01), but not at 2.0 ppm HCHO. There were no significant decrements in pulmonary function (FVC, FEV₁, FEF_25-75%, SGaw) or increases in bronchial reactivity to methacholine (log PD_35SGaw) with exposure to 0.5-3.0 ppm HCHO at rest or to 2.0 ppm HCHO with exercise.     

Deodorization of pig manure using lignin peroxidase with different electron acceptors

Odor pollution is a big environmental problem caused by large-scale livestock production in China, and developing a practical way to reduce these odors is pressing. In this study, a combination of 0.2–1.0 U/mL lignin peroxidase (LiP) and one of three peroxides (H₂O₂, CaO₂, 2Na₃CO₃·3H₂O₂) was examined for its efficiency in reducing the release of eight chemicals (propionic acid, isobutyric acid, isocaproic acid, isovaleric acid, phenol, p-cresol, indole, and skatole), NH₃, H₂S, and odor intensity from pig manure. The results showed an approximately 90% reduction in p-cresol, 40–60% reduction in odor intensity, 16.5–40% reduction in indolic compounds, and 25–40% reduction in volatile fatty acids. Being the electron acceptors of LiP, 2Na₃CO₃·3H₂O₂ and CaO₂ performed better than H₂O₂ in reducing the concentration of eight chemicals, NH_3, H₂S, and odor intensity from pig manure. The effect of deodorization can last for up to 72 hr.

Implications: In China, one of the major environmental problems caused by confined feeding is odor pollution, which brings a major threat to the sustainability, profitability, and growth of the livestock industry. To couple the LiP with the electron acceptors, a low–cost, simple, and feasible method for odor removal was established in this study. Based on the study results, a practical treatment method was provided for odor pollution and supply the farm operators a more flexible time to dispose treated manure.     

Characterization of livestock odors using steel plates, solid-phase microextraction, and multidimensional gas chromatography-mass spectrometry-olfactometry

Livestock operations are associated with emissions of odor, gases, and particulate matter (PM). Livestock odor characterization is one of the most challenging analytical tasks. This is because odor-causing gases are often present at very low concentrations in a complex matrix of less important or irrelevant gases. The objective of this project was to develop a set of characteristic reference odors from a swine barn in Iowa and, in the process, identify compounds causing characteristic swine odor. Odor samples were collected using a novel sampling methodology consisting of clean steel plates exposed inside and around the swine barn for < or =1 week. Steel plates were then transported to the laboratory and stored in clean jars. Headspace solid-phase microextraction was used to extract characteristic odorants collected on the plates. All of the analyses were conducted on a gas chromatography-mass spectrometry-olfactometry system where the human nose is used as a detector simultaneously with chemical analysis via mass spectrometry. Multidimensional chromatography was used to isolate and identify chemicals with high-characteristic swine odor. The effects of sampling time, distance from a source, and the presence of PM on the abundance of specific gases, odor intensity, and odor character were tested. Steel plates were effectively able to collect key volatile compounds and odorants. The abundance of specific gases and odor was amplified when plates collected PM. The results of this research indicate that PM is major carrier of odor and several key swine odorants. Three odor panelists were consistent in identifying p-cresol as closely resembling characteristic swine odor, as well as attributing to p-cresol the largest odor response out of the samples. Further research is warranted to determine how the control of PM emissions from swine housing could affect odor emissions.     

A Strategy for the Evaluation of Sensory and Pulmonary Irritation Due to Chemical Emissions from Indoor Sources

Abstract

Sensory and pulmonary irritation are physiological responses to chemical exposure which result in characteristic, measurable changes in respiratory activity in mice. A standard method has been applied to the estimation of sensory irritation associated with a specific chemical exposure. This method has been correlated with human responses to these chemicals. Symptoms associated with chemical irritants are consistent with complaints due to problems with indoor air quality, which may include eye and upper respiratory tract irritation, headaches, and nausea. A stepwise strategy for assessing the contribution of indoor products to sensory and pulmonary irritation is discussed in the current paper. The strategy includes product emissions testing using dynamic environmental chambers, the selection of suspected irritants for respiratory irritation testing, respiratory irritation testing of individual compounds and representative mixtures using synthesized atmospheres, and the evaluation of test data to determine those compounds which may contribute to sensory and pulmonary irritation in humans. The current strategy is being applied to evaluate carpet system materials and their constituent chemicals.     

Preventive control of odor emissions through manipulation of operational parameters during the active phase of composting

Better understanding of the effects of key operational parameters or environmental factors on odor emission is of critical importance for minimizing the generation of composting odors. A series of laboratory experiments was conducted to examine the effects of various operating conditions on odor emissions. The results revealed that airflow rates that were too high or too low could result in higher total odor emissions. An optimal flowrate for odor control would be approximately 0.6 L/min.kg dry matter with intermittent aeration and a duty cycle of 33%. Temperature setpoint at 60°C appeared to be a turning point for odor emission. Below this point, odor emissions increased with increasing temperature setpoint; conversely, odor emissions decreased with increasing temperature setpoint above this point. With regard to the composting material properties, odor emissions were greatly affected by the initial moisture content of feedstock. Both peak odor concentration and emission rate generally increased with higher initial moisture content. Odor emission was significant only at moisture levels higher than 65%. An initial moisture level below 45% is not recommended due to concern with the resulting lower degree of biodegradation. Biodegradable volatile solids content (BVS) of feedstock had pronounced effect on odor emissions. Peak odor concentration and emission rate increased dramatically as BVS increased from 45% to 65%, thus, total odor emission increased exponentially with BVS.     

Photochemical Reactivities of Paraffinic Hydrocarbon-Nitrogen Oxide Mixtures Upon Addition of Propylene or Toluene

Effects associated with photochemical air pollution were measured during irradiation of n-butane-nitrogen oxide or n-butane-ethane-nitrogen oxide mixtures, with small amounts of propylene or toluene added. The effects measured including nitrogen dioxide and oxidant dosages, yields of formaldehyde and peroxy-acetyl nitrate, and eye irritation response. The results obtained clearly show that beneficial effects result from selective changes in hydrocarbon composition as well as from reduction of total hydrocarbon concenfration. Exclusion of olefins and alkylbenzenes was highly effective in reducing oxidant dosage, formaldehyde and peroxyacetyl nitrate concentrations, and eye irritation response. The only penalty was a modest increase in nitrogen dioxide dosage. A large reduction in nitrogen oxide concentration reduced nitrogen dioxide dosage and eye irritation response, but with the penalty of a large increase in oxidant dosage. The desirability of preferentially reducing olefins and alkylbenzenes rather than paraffinic hydrocarbons, acetylene, and benzene is strongly supported by this study. Research and development efforts should be directed toward preferential hydrocarbon control by mechanical or catalytic control     

Characterization of odor released during handling of swine slurry: Part I. Relationship between odorants and perceived odor concentrations

Odor emission from livestock production systems is a major nuisance in many rural areas. This study aimed at determining the major airborne chemical compounds responsible for the unpleasant odor perceived in swine facilities during slurry handling, and at proposing predictive models of odor concentration (OC) based on the concentrations of specific odorants in the air. A multivariate data analysis strategy involving principal components analysis and multiple linear regressions was implemented to analyze the relationships between concentration of 35 gases (measured by GC/MS or gas detection tubes), and the overall OC perceived by sensory analysis. The study compiled data on the concentration of odor and odorants, measured in the headspace of 24 unstored and stored slurry samples collected from three different types of production units on 8 commercial swine farms. Among all the measured constituents, OC was found to have the highest correlation with the sulfur containing compounds (i.e. hydrogen sulfide, dimethylsulfide, dimethyldisulfide, dimethyltrisulfide). The concentration of hydrogen sulfide accounted for 68% of the variation in OC above the stirred slurry samples. The highest concentrations of volatile organic compounds were observed for phenols and indoles, which made a significant contribution to the overall OC when the slurry was fresh. The contribution of ammonia to the OC was only significant in the absence of hydrogen sulfide. The precision of predictive models of OC based on the concentration of specific odorants in the air was satisfactory (R² between 0.66 and 0.89). Hence, this study suggests that monitoring of specific odor compounds released from agitated swine slurry can be used to predict the concentration of odor perceived close to the source (e.g. at storage units), allowing the assessment of odor nuisance potentials.     

Prospects for Exhaust Control by Engine Modification

In order to assist in assessing potential odor problems arising from chemical manufacturing operations, the odor thresholds of 53 commercially important odorant chemicals have been determined using a standardized and defined procedure. The odor threshold data previously available have shown wide variation reflecting the diversity of procedures and techniques used. Factors that may affect the odor threshold measurement include the mode of presentation of the stimulus to the observer, the influence of extraneous odorants in the presentation system, the type of observer used, the definition of the odor response, the treatment of the data obtained, and the chemical purity of the odorant. The experimental approach used has minimized these variations. The odorants were presented to a trained odor panel in a static air system utilizing a low odor background air as the dilution medium. The odor threshold is defined as the first concentration at which all panel members can recognize the odor. The effect of chemical purity has been determined by measuring the odor threshold of materials representing different modes of manufacture or after purification by gas chromatographic procedures. The threshold concentrations range over six orders of magnitude. Trimethylamine exhibited the lowest threshold (0.00021 ppm volume); methylene chloride was not recognizable below 214 ppm. Of the 53 chemicals, sulfur bearing compounds exhibit low threshold values on the order of parts per billion. Aside from the sulfides, it is not possible to anticipate the odor threshold of a material based on its chemical structure or functionality.     

Gas Chromatographic Analysis of Incinerator Effluents

Comparative gas cleaning performance of a pilot-scale venturi scrubber with throat dimensions of 6 in. wide × 1 2 in. long × 1 2 in. deep was obtained for the following three methods of water injection: a system of spray nozzles located along each short side of the throat (Figure 2a); a continuous slot located immediately above the nozzles, along each short side of the throat (Figure 2b); and a weir located 2 ft above the spray nozzles along long side of the throat (Figure 2c). For each method of water injection the gas cleaning performance, as a function of the pressure drop, was measured by two tests: absorption of SO₂ and collection efficiency for particles of methylene blue of controlled size.     

Occurrence and formation of trihalomethanes in marine aquaria studied using solid-phase microextraction gas chromatography-mass spectrometry

The occurrence and formation of chlorinated and brominated trihalomethanes (THMs) were studied in artificial saltwater and natural seawater marine aquaria as well as in groundwater and surface waters. A new headspace solid-phase microextraction method was used, which included gas chromatography-mass spectrometry and provided method detection limits of less than 0.1 microg/L, with a signal-to-noise ratio of 3 to 5. The results showed that disinfection by using either chlorine or ozone caused a significant formation of THMs in situ. Speciation of the THMs was a strong function of the water matrix, with initial bromide concentrations playing a pivotal role. These results provide a tool for understanding and monitoring the formation of key disinfection byproducts in marine aquaria that may cause respiratory, eye irritation, or other health concerns.     

National crop loss assessment network: quality assurance program

A quality assurance program was incorporated into the National Crop Loss Assessment Network (NCLAN) program, designed to assess the economic impacts of gaseous air pollutants on major agricultural crops in the United States. To satisfy US EPA requirements that all environmental data collected be of known and documented quality, adequate for the intended use, the quality assurance program developed standardized research and monitoring protocols among sites, and included a range of audit and review procedures. The goal of the quality assurance program was to quantitatively describe the overall quality of data collected in terms of precision, accuracy, completeness, representativeness, and comparability. From this program, it can be concluded that (1) project data quality objectives were valuable for determining the acceptability of data from diverse sites, (2) standardized protocols ensured data comparability among research sites, (3) independent on-site audits served to evaluate protocol adherence, and (4) precision and accuracy measurements provided a way to assess data quality, determine data acceptability, and indicate the need for instrument adjustment or repair.     

Filters and Filter Media for the Cement Industry

To correlate the odor strength of natural gas with its sulfur analysis, the recognition odor thresholds of 18 sulfur compounds were determined using an untrained panel of 35 peopie. For each test a series of odor concentrations graduated in increments of 10^0.2 was presented to the panel in random order over a range of concentrations above and below the olfactory thresholds of all panelists. Each odor was tested on at least three different days. Desired odor concentrations were produced by dynamic blending of gaseous mixtures of the odorous compounds with air. All testing was done out-of-doors during clement weather when no ambient odors were apparent. The range of olfactory response was found to be much greater for certain compounds than for others. Branching of the hydro-carbon chain increased odor strength. Certain compounds appeared to evoke anomalous responses.     

On the Determination of Odor Thresholds in Air Pollution Control—An Experimental Field Study on Flue Gases from Sulfate Cellulose Plants

From the hygienic point of view, not only the health hazards caused by air pollutants but also the odor from emitted flue gases should be reduced to a minimum. An effective control of the risk of odor at ground level presupposes knowledge of the source concentration of the odoriferous gas as well as its odor threshold. This threshold has to be estimated empirically, as the flue gases often contain a complex mixture of different odoriferous substances, the odor thresholds of which are in most cases unknown. For this purpose a method has been developed for estimating the odor thresholds of flue gases emitted, from different industrial processes. The method, afield method, is based on an exposure procedure, a number of subjects compare different concentrations of the flue gas with samples of fresh air and decide at what concentration the flue gas is no longer noticeable. The gas samples used are neither compressed, nor absorbed or heated before the exposure test. The method has been used in two studies on gases from Swedish sulfate cellulose plants. In order to estimate the effect on the odor threshold of different deodorizing measures, gas samples were taken not only from the stack but also from different phases in the production process. The results and a brief discussion on the practical applications of the method are given.     

Consultant Guide/1986

ABSTRACT

To obtain annual odor emission profiles from intensive swine operations, odor concentrations and emission rates were measured monthly from swine nursery, farrowing, and gestation rooms for a year. Large annual variations in odor concentrations and emissions were found in all the rooms and the impact of the seasonal factor (month) was significant (P < 0.05). Odor concentration was low in summer when ventilation rate was high but high in winter when ventilation rate was low, ranging from 362 (farrowing room in July) to 8934 (nursery room in December) olfactory unit (OU) m^?3. This indicates that the air quality regarding odor was significantly better in summer than that in winter. Odor emission rate did not show obvious seasonal pattern as odor concentration did, ranging from 2 (gestation room in November) to 90 (nursery room in April) OU m^?2 sec^?1; this explains why the odor complaints for swine barns have occurred all year round. The annual geometric mean odor concentration and emission rate of the nursery room was significantly higher than the other rooms (P < 0.05). In order to obtain the representative annual emission rate, measurements have to be taken at least monthly, and then the geometric mean of the monthly values will represent the annual emission rate. Incorporating odor control technologies in the nursery area will be the most efficient in reducing odor emission from the farm considering its emission rate was 2 to 3 times of the other areas. The swine grower-finisher area was the major odor source contributing 53% of odor emission of the farm and should also be targeted for odor control. Relatively positive correlations between odor concentration and both H₂S and CO₂ concentrations (R ² = 0.58) means that high level of these two gases might likely indicate high odor concentration in swine barns.

IMPLICATIONS The emissions of air pollutants including odors, greenhouse gases, and toxic gases have become a major environmental issue facing animal farms in the U.S.A. and Canada. To ensure the air quality in the vicinity of intensive livestock farms, air dispersion models have been used to determine setback distances between livestock facilities and neighboring residences based on certain air quality requirement on odor and gases. Due to the limited odor emission data available, none of the existing models can take account of seasonal variations of odor emissions, which may result in great uncertainties in setback distance calculations. Therefore, the obtained seasonal odor and gas emission rates by this study can be used by the government regulatory organizations and researchers in air dispersion modeling to get improved calculation of setback distances.     

Dispersion modeling to compare alternative technologies for odor remediation at swine facilities

The effectiveness of 18 alternative technologies for reducing odor dispersion at and beyond the boundary of swine facilities was assessed in conjunction with an initiative sponsored through agreements between the Attorney General of North Carolina and Smithfield Foods, Premium Standard Farms, and Frontline Farmers. The trajectory and spatial distribution of odor emitted at each facility were modeled at 200 and 400 m downwind from each site under two meteorological conditions (daytime and nighttime) using a Eulerian-Lagrangian model. To predict the dispersion of odor downwind, the geographical area containing the odorant sources at each facility was partitioned into 10-m2 grids on the basis of satellite photographs and architectural drawings. Relative odorant concentrations were assigned to each grid point on the basis of intensity measurements made by the trained odor panel at each facility using a 9-point rating scale. The results of the modeling indicated that odor did not extend significantly beyond 400 m downwind of any of the test sites during the daytime when the layer of air above the earth's surface is usually turbulent. However, modeling indicated that odor from all full-scale farms extended beyond 400 m onto neighboring property in the evenings when deep surface cooling through long-wave radiation to space produces a stable (nocturnal) boundary layer. The results also indicated that swine housing, independent of waste management type, plays a significant role in odor downwind, as do odor sources of moderate to moderately high intensity that emanate from a large surface area such as a lagoon. Human odor assessments were utilized for modeling rather than instrument measurements of volatile organic compounds (VOCs), hydrogen sulfide, ammonia, or particulates less than 10 microm in diameter (PM10) because these physical measurements obtained simultaneously with human panel ratings were not found to accurately predict human odor intensity in the field.