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PubMed2004

Biodegradation of mixture of VOC's in a biofilter.

Volatile organic compounds(VOC' s) in air have become major concern in recent years. Biodegradation of a mixture of ethanol and methanol vapor was evaluated in a laboratory biofilter with a bed of compost and polystyrene particles using an acclimated mixed culture. The continuous performance of the biofilter was studied with different proportion of ethanol and methanol at different initial concentration and flow rates. The result showed significant removal for both ethanol and methanol, which were composition dependent. The presence of either compound in the mixture inhibited the biodegradation of the other.

Air Pollutants↗

PubMed2006

Reduced levels of volatile emissions in jasmonate-deficient spr2 tomato mutants favour oviposition by insect herbivores.

Tomato plants release volatile organic compounds (VOCs) following insect or mechanical damage. In this study, the constitutive and wound-induced emission levels of VOCs in suppressor of prosystemin-mediated responses2 (spr2) mutant plants, compromised in linolenic acid (LA) and jasmonic acid (JA) synthesis, and in 35S::prosystemin (35S::prosys) plants, having upregulated direct defence responses, were compared. The spr2 mutants produced constitutively lower levels of VOCs, which were nonetheless increased in response to (a)biotic damage, although at lower levels than wild-type (Wt) and 35S::prosys plants. No significant differences in VOC emissions were detected between the latter two genotypes, thereby suggesting that systemin does not regulate indirect defence responses, whereas differences in fatty acid composition in spr2 plants led to the predominant emission of saturated C6 volatiles in response to wounding. The expression of 1-deoxy-D-xylulose 5-phosphate synthase (DXS2), a key gene involved in VOC synthesis in the chloroplast, was only upregulated in Manduca sexta L.-damaged Wt and 35S::prosys plants. However, its expression was restored in spr2 plants by exogenous LA or JA, suggesting that abated VOC emissions in spr2 plants are correlated with lowered DXS2 expression. Bioassays with two different insects showed that adult females significantly preferred spr2 plants, indicating that lowered levels of VOCs in tomato influence plant selection by insects during oviposition.

Animals↗

PubMed1998

Determination of benzene and associated volatile compounds in mainstream cigarette smoke.

There is continuing interest, by health professionals and individuals, in the composition of mainstream tobacco smoke. Regular official surveys of tar, nicotine and carbon monoxide yields are from time to time supplemented by special surveys of specific components. In this study, gas chromatography-mass spectrometry was used to identify and quantify benzene and certain other volatile compounds of interest in the mainstream smoke of 26 cigarette brands on the UK market and of smoke from hand rolled tobacco. Validation of the method adopted demonstrated the ability to identify and to measure reliably the yields of benzene and seven other compounds: toluene, ethylbenzene, m/p-xylene, o-xylene, styrene, isoprene and acrylonitrile. Yields of these analytes were ranked and compared with the tar yields of the brands. In general terms, brands yielding < or = 3 mg of tar yielded proportionately more of the vapour phase analytes than did brands yielding > 3 mg of tar per cigarette. For many of the higher tar brands the yield of vapour phase analyte was approximately proportional to the tar yield. Smoking cigarettes with an average yield of 50 micron of benzene per cigarette has been compared with the occupational maximum exposure limit (16 mg m-3) concentration and with US studies on the home environment. Smoking the majority of brands examined could contribute significantly to the population exposure of benzene and the other volatile organic compounds considered in this study.

Acrylonitrile↗

PubMed2001

Effects of environmental and test conditions on VOC emissions from "wet" coating materials.

In this paper, numerical simulations have been conducted to study the effects of key environmental and test conditions (air velocity, temperature, film thickness, and sample application time) on volatile organic compound (VOC) emissions from a "wet" coating material (wood stain). Simulation results indicate that air velocity and sample application time only significantly affect the emission profiles in the early stage. Film thickness, on the other hand, affects long-term emissions. Temperature can affect both the short-term and long-term emissions.

Air Movements↗

PubMed2003

Weekday/weekend ozone differences: what can we learn from them?

A national analysis of weekday/weekend ozone (O3) differences demonstrates significant variation across the country. Weekend 1-hr or 8-hr maximum O3 varies from 15% lower than weekday levels to 30% higher. The weekend O3 increases are primarily found in and around large coastal cities in California and large cities in the Midwest and Northeast Corridor. Both the average and the 95th percentile of the daily 1-hr and 8-hr maxima exhibit the same general pattern. Many sites that have elevated O3 also have higher O3 on weekends even though traffic and O3 precursor levels are substantially reduced on weekends. Detailed studies of this phenomenon indicate that the primary cause of the higher O3 on weekends is the reduction in oxides of nitrogen (NOx) emissions on weekends in a volatile organic compound (VOC)-limited chemical regime. In contrast, the lower O3 on weekends in other locations is probably a result of NOx reductions in a NOx-limited regime. The NOx reduction explanation is supported by a wide range of ambient analyses and several photochemical modeling studies. Changes in the timing and location of emissions and meteorological factors play smaller roles in weekend O3 behavior. Weekday/weekend temperature differences do not explain the weekend effect but may modify it.

Air Pollutants↗

PubMed2002

Biodegradation of VOCs from printing press air by an on-site pilot plant bioscrubber and laboratory scale continuous yeast cultures.

The volatile organic compound composition (VOCs) of printing press air was found to contain mostly ethanol, but also ethyl acetate, 1-propanol, 2-propanol, 1-methoxy-2-propanol and 3-ethoxy-1-propanol. A pilot plant bioscrubber inoculated with a mixed microbial population was constructed on-site. The bioscrubber was able to treat the polluted gas efficiently. It, however, suffered from strong wall growth and blockages in the column. The efficiencies of the pilot plant and a bioreactor is compared. The yeasts Candida guilliermondii and Saccharomyces cerevisiae known to tolerate ethanol were selected instead of mixed population to avoid the wall growth a nd blockages inthe bioreactor. The removal of the VOCs both individually and as a complex mixture was tested in a microcultivation system and in continuous chemostat cultures with and without cell recycling. The Candida yeast could use all the compounds as a carbon source while growth of S. cerevisiae was markedly slower on the methoxylated and ethoxylated propanols. Best total removal of the VOCs was 99% and achieved by C. guilliermondii. The only compound that was not totally removable in the chemostat experiment with C. guilliermondii was 1-methoxy-2-propanol. In laboratory scale the total and volumetric removal of VOCs by C. guilliermondii was more efficient compared to the pilot plant encouraging to scale up and applying the yeast bioreactor to real field conditions.

Air Pollutants, Occupational↗

PubMed2005

Measurements of OH reactivity and photochemical ozone production in the urban atmosphere.

Measurements of OH reactivity (i.e., OH loss rates) in the troposphere are essential for discussing tropospheric OH photochemistry. In July and August 2003, we observed the total OH reactivity in a suburban area of Tokyo. More than 90% of the data of the measured OH loss rates were higher than the calculated values with simultaneously measured concentrations of various trace species even though the rate coefficient of the OH + NO2 reaction was measured by us. We concluded that this discrepancy is due to the existence of unmeasured volatile organic compounds (VOCs). We estimated the potential of the photochemical ozone production in the case of including the unknown species as VOCs and excluding the missing sink, respectively. When the unknown species were included as VOCs, the potential increases from 32% to 88%. This result indicates the photochemical production rates of ozone in the urban air are substantially greater than expected.

Air Pollutants↗

PubMed2006

Air contaminants in a submarine equipped with air independent propulsion.

The Swedish Navy has operated submarines equipped with air independent propulsion for two decades. This type of submarine can stay submerged for periods far longer than other non-nuclear submarines are capable of. The air quality during longer periods of submersion has so far not been thoroughly investigated. This study presents results for a number of air quality parameters obtained during more than one week of continuous submerged operation. The measured parameters are pressure, temperature, relative humidity, oxygen, carbon dioxide, hydrogen, formaldehyde and other volatile organic compounds, ozone, nitrogen dioxide, particulate matter and microbiological contaminants. The measurements of airborne particles demonstrate that air pollutants typically occur at a low baseline level due to high air exchange rates and efficient air-cleaning devices. However, short-lived peaks with comparatively high concentrations occur, several of the sources for these have been identified. The concentrations of the pollutants measured in this study do not indicate a build-up of hazardous compounds during eight days of submersion. It is reasonable to assume that a substantial build-up of the investigated contaminants is not likely if the submersion period is prolonged several times, which is the case for modern submarines equipped with air independent propulsion.

Air Pollutants, Occupational↗

PubMed2001

An overview of human exposure modeling activities at the USEPA's National Exposure Research Laboratory.

The computational modeling of human exposure to environmental pollutants is one of the primary activities of the US Environmental Protection Agency (USEPA)s National Exposure Research Laboratory (NERL). Assessment of human exposures is a critical part of the overall risk assessment paradigm. In exposure assessment, we analyze the source-to-dose sequence of processes, in which pollutants are released from sources into the environment, where they may move through multiple environmental media, and to human receptors via multiple pathways. Exposure occurs at the environment-human interface, where pollutants are contacted in the course of human activities. Exposure may result in a dose, by which chemicals enter the body through multiple portals of entry, primarily inhalation, ingestion, and dermal absorption. Within the body, absorbed pollutants are distributed to, metabolized within, and eliminated from various organs and tissues, where they may cause toxicologic responses or adverse health effects. The NERL's modeling efforts are directed at improving our understanding of this sequence of processes, by characterizing the various factors influencing exposures and dose, and their associated variabilities and uncertainties. Modeling at the NERL is one of three essential programmatic elements, along with measurements and methods development. These are pursued interactively to advance our understanding of exposure-related processes. Exposure models are developed and run using the best currently available measurement data to simulate and predict population exposure and dose distributions, and to identify the most important factors and their variabilities and uncertainties. This knowledge is then used to guide the development of improved methods and measurements needed to obtain better data to improve the assessment and reduce critical uncertainties. These models and measurement results are tools that can be used in risk assessments and in risk management decisions in order to reduce harmful exposures. Current areas of the NERL's exposure modeling emphasis include: Pollutant concentrations in ambient (outdoor) air using the Third Generation Air Quality Modeling System's Community Multiscale Air Quality model (Models-3/CMAQ); Air flow and pollutant concentrations at local and microenvironmental scales using computational fluid dynamics (CFD); Human inhalation exposure to airborne particulate matter, air toxics, and multipathway exposure to pesticides, using the Stochastic Human Exposure and Dose Simulation (SHEDS) model; Human and ecological exposure and risk assessments of hazardous waste sites using Framework for Risk Analysis in Multimedia Environmental Systems--Multimedia, Multipathway, Multireceptor Risk Assessment (FRAMES-3MRA), one of many software programs available from the NERL's Center for Exposure Assessment Modeling (CEAM); Physiologically based pharmacokinetic (PBPK) modeling of pesticides and volatile organic compounds (VOCs) in the Exposure-Related Dose-Estimating Model (ERDEM). A brief historical overview of the NERL's evolution of human exposure models is presented, with examples of the present state-of-the-science represented by SHEDS and FRAMES-3MRA.

Air Pollutants↗

PubMed2002

Personal exposure to benzene, toluene and xylene in different microenvironments at the Mexico City metropolitan zone.

The Mexico City Metropolitan Zone (ZMCM) population's exposure to benzene, toluene and xylene was measured at different microenvironments to establish basic indicators of the presence and effects of these characteristic volatile organic compounds (VOC). In particular, VOC personal exposures were measured in different microenvironments during a 5-day working week, with 12-h daily periods. We have found a good agreement of our results with the registered VOC levels of the Metropolitan Automated Monitor System (RAMA) for the corresponding period. From our results, we expect to generate useful information to evaluate the health effects of these VOCs on exposed people.

Automation↗

PubMed2003

Flame retardants in the indoor environment -- Part II: release of VOCs (triethylphosphate and halogenated degradation products) from polyurethane.

Organophosphate esters, halogenated and non-halogenated, are frequently used for fire protection of building materials. With regard to toxicological profiles it is desired to avoid human exposure in the indoor environment. Moreover, some hazardous volatile organic compounds detected in indoor air are directly linked to the utilization of flame retardants. In this study, different polyurethane (PUR) products for building and indoor use treated with organophosphate flame retardants were tested in 1 m(3) emission test chambers. Emissions of flame retardants and degradation products were measured under living conditions. A PUR hard foam sample showed area-specific emission rates >100 microg/m(2) h for the compound triethylphosphate. During the tests several chlorinated degradation products of organophophorous flame retardants could be identified in the chamber air.

Air Pollution, Indoor↗

PubMed2004

New endophytic isolates of Muscodor albus, a volatile-antibiotic-producing fungus.

Muscodor albus, an endophytic fungus originally isolated from Cinnamomum zeylanicum, produces a mixture of volatile organic compounds (VOCs) in culture and its spectrum of antimicrobial activity is broad. Using the original isolate of M. albus as a selection tool, it has been possible to find other culturally and biochemically unique wild-type isolates of this organism existing as endophytes in a variety of other plant species, including Grevillea pterifolia (fern-leafed grevillea), Kennedia nigriscans (snake vine) and Terminalia prostrata (nanka bakarra) growing in the northern reaches of the Northern Territory of Australia. Interestingly, none of the new isolates had a culture morphology that was identical to the original isolate, nevertheless each possessed hyphal characteristics that resembled that isolate. Furthermore, their ITS-5.8S rDNA sequences were 96-99 % identical to that of M. albus and the isolates were considered M. albus on the basis of the DNA sequence data. However, the VOCs produced by these new isolates greatly differed in quality from the original strain by virtue of the production of naphthalene, naphthalene, 1,1'-oxybis-, and one or more other compounds. In bioassays with a range of test micro-organisms, including fungi and bacteria, each isolate possessed biological activity but the range of activity was great. Artificial mixtures of some of the VOCs mimicked the effects of the VOCs of the fungus. The value of these observations to the biology and practical uses of M. albus in agriculture and other applications is discussed.

Anti-Bacterial Agents↗

PubMed1997

Secondary organic aerosols: formation potential and ambient data.

Organic aerosols comprise a significant fraction of the total atmospheric particle loading and are associated with radiative forcing and health impacts. Ambient organic aerosol concentrations contain both a primary and secondary component. Herein, fractional aerosol coefficients (FAC) are used in conjunction with measurements of volatile organic compounds (VOC) to predict the formation potential of secondary organic aerosols (SOA) in the Lower Fraser Valley (LFV) of British Columbia. The predicted concentrations of SOA show reasonable accord with ambient aerosol measurements and indicate considerable seasonal variability in SOA potential. Particulate carbon contributes only approx. 3% of total carbon concentrations in the LFV, and it is shown that variability in total carbon concentrations is significantly larger than variability in gas/particle partitioning.

Aerosols↗

PubMed2003

Seasonal cycle of VOCs in apartments.

To assess the adverse health effects of volatile organic compounds (VOCs), epidemiological studies combine the health outcome of individuals with their concomitant VOC exposure. While the latter is representative of the studied period, health effects might also be the result of long-term exposure or emerge in consequence of a peak pollution throughout the year. To address these problems, additional information about the spatiotemporal distribution of VOCs is necessary. The present paper aims at elucidating the spatial and temporal variation of VOC concentrations in Leipzig, Germany. The analysis is based on 1499 indoor and 222 outdoor measurements taken in the period between 1994 and 2001. All data were collected in the frame of epidemiological studies (Diez et al., 1999; Fritz et al., 1998; Schulz et al., 1999). The analysis comprised concentrations of 30 VOCs belonging to the groups of alkanes, cycloalkanes, aromatics, volatile halogenated hydrocarbons, and terpenes. We found that the VOC load in indoor air is, on average, 10 times higher than outdoors. For the studied period there was a clear downward tendency for all VOCs in apartments in Leipzig, except for terpenes which show an upward trend in the period 1996-99. In indoor air we observe an annual cycle for the total VOC concentration as well as the sum concentrations of the above called groups. Highest concentrations occur during the winter months, approximately three times higher than the summer burden. We summarize this finding in a seasonal model, which is fitted to our measurements. Based on the model we develop a procedure for seasonal adjustment, which enables to roughly estimate the annual peak concentration utilizing one monthly observation.

Air Pollution, Indoor↗

PubMed2003

Natural gas and indoor air pollution: a comparison with coal gas and liquefied petroleum gas.

OBJECTIVE: The study was designed to compare the combustion products of coal gas, liquefied petroleum gas and natural gas in relation to indoor air pollution. METHODS: Regular pollutants including B(a)P were monitored and 1-hydroxy pyrene were tested in urine of the enrolled subjects. Radon concentrations and their changes in four seasons were also monitored in the city natural gas from its source plant and transfer stations to final users. To analyze organic components of coal gas, liquefied petroleum gas and natural gas, a high-flow sampling device specially designed was used to collect their combustion products, and semi-volatile organic compounds contained in the particles were detected by gas chromatograph-mass spectrograph (GC/MS). RESULTS: Findings in the study showed that the regular indoor air pollutants particles and CO were all above the standard in winter when heating facilities were operated in the city, but they were lowest in kitchens using natural gas; furthermore, although NO2 and CO2 were slightly higher in natural gas, B(a)P concentration was lower in this group and 1-hydroxy pyrene was lowest in urine of the subjects exposed to natural gas. Organic compounds were more complicated in coal gas and liquefied petroleum gas than in natural gas. The concentration of radon in natural gas accounted for less than 1% of its effective dose contributing to indoor air pollution in Beijing households. CONCLUSION: Compared to traditional fuels, gases are deemed as clean ones, and natural gas is shown to be cleaner than the other two gases.

Air Pollution, Indoor↗

PubMedDate not supplied

A review of the USEPA's single breath canister (SBC) method for exhaled volatile organic biomarkers.

Exhaled alveolar breath can provide a great deal of information about an individual's health and previous exposure to potentially harmful xenobiotic materials. Because breath can be obtained non-invasively and its constituents directly reflect concentrations in the blood, its use has many potential applications in the field of biomarker research. This paper reviews the utility and application of the single breath canister (SBC) method of alveolar breath collection and analysis first developed by the US Environmental Protection Agency (USEPA) in the 1990s. This review covers the development of the SBC technique in the laboratory and its application in a range of field studies. Together these studies specifically show how the SBC method (and exhaled breath analysis in general) can be used to clearly demonstrate recent exposure to volatile organic compounds, to link particular activities to specific exposures, to determine compound-specific uptake and elimination kinetics, and to assess the relative importance of various routes of exposure (i.e. dermal, ingestion, inhalation) in multi-pathway scenarios. Specific investigations covered in this overview include an assessment of exposures related to the residential use of contaminated groundwater, exposures to gasoline and fuel additives at self-service gas stations, swimmers' exposures to trihalomethanes, and occupational exposures to jet fuel.

Biomarkers↗

PubMed2006

Solubilisation of chlorinated solvents by cyclodextrin derivatives: a study by static headspace gas chromatography and molecular modelling.

The capacity of alpha-cyclodextrin (alpha-CD) and four beta-cyclodextrins (beta-CDs) in reducing the volatility of volatile organic compounds (VOCs) and particularly carbon tetrachloride (CT), chloroform (TCM) and dichloromethane (DCM) is investigated by using static headspace gas chromatography (HSGC). The experiments allowed the determination of Henry's law constant (H(c)) in absence and in presence of cyclodextrins (CDs). The use of CDs may lead to a reduction of 95% of the Henry's law constant for some VOCs. The association constants of the inclusion complexes formed between CDs and the three guests are determined using a new method involving an algorithmic treatment bringing the shortening of experimental time required for the determination of the stability constant. The complementarities of the host and the guest are investigated by molecular modelling. The complexation energies obtained are in good agreement with the experimental formation constants. Furthermore, this study shows the effectiveness of CDs in trapping pollutants and reducing their volatility in the viewpoint of pollution prevention.

Chromatography, Gas↗

PubMedDate not supplied

Pesticides in fog.

The discovery of the very acidic nature of fog and clouds has created much interest in sampling, analysing, and elucidating the chemistry of fog, principally because an understanding of the chemical transformations leading to acid fog may provide important clues to the origin of acid rain. Recently, the knowledge of the chemistry of fog has expanded to include carbonyl compounds, volatile organic acids, and alkyl sulphonates. We have discovered that a variety of pesticides and their toxic alteration products are present in fog, and that they occasionally reach high concentrations relative to reported rainwater concentrations. In our experiments, we were able to measure the air-water distribution coefficients of pesticides between the liquid fog and the interstitial gas phase. These measurements reveal that some chemicals are enriched several thousandfold in the suspended liquid fog droplets compared to equilibrium distributions expected from Henry's Law coefficients for pure aqueous solutions.

Air↗