SEARCH · PubMed Health

Results for “Volatile Organic Compounds”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60Linked to original sources

PubMed2003

In-tube solid-phase microextraction sampler for long-term storage.

Capillary extractors are proposed as samplers-preconcentrators to overcome losses of volatile organic compounds found using "classical" solid-phase microextraction fiber-holder samplers. A set of equal-size extractors was used to extract in-tube an aqueous solution of benzene, toluene, ethylbenzene and xylenes (BTEX) at 146 ppb. After storage for 6-30 days at 0-4 degrees C (or -15 degrees C) GC analyses were carried out to study BTEX recovery. Results demonstrated that sample preservation was very good: recovery was higher than 98% after 6 days, and more than 95% after 30 days. Capillary extractors, due to their high performance in preserving sample integrity, represent a real breakthrough for on-site sampling of volatile compounds by solid-phase pre-concentration techniques.

Chromatography, Gas↗

PubMed2003

Quantification of chemical vapors in chemosensory research.

Studies of olfaction and chemesthesis often rely on nominal, liquid-phase dilutions to quantify the chemicals tested, even though the associated vapor concentrations constitute the actual stimuli. For more than a decade now, our systematic studies of the olfactory and chemesthetic potency of members of homologous chemical series have routinely included quantification of vapors via gas chromatography. This article depicts the relationships between liquid- and vapor-phase concentrations for 60 volatile organic compounds and summarizes the theoretical and technical factors influencing these relationships. The data presented will allow other investigators working with these materials to express them as vapor concentrations even when they lack the resources to perform the analytical measurements. The paper represents a step toward creation of a practical archive for vapor quantification in chemosensory science.

Calibration↗

PubMed2001

Pre-evaporative fenton remediation of treated municipal wastewater for reuse purposes.

The present study explored the application of evaporative technology as an alternative desalination technique for wastewater treatment plant effluent. In the experiments carried out, it was shown that evaporation allowed for extensive decontamination of wastewater treatment plant effluent as most inorganic and organic contaminants were completely removed. Ammonia could be retained in the concentrate when pH was adjusted to values lower than 4; however this led to increased nitrite volatility due to the formation of nitric oxide. Using an electronic nose, it was observed that evaporation gave rise to a change in odour quality and quantity due to volatilisation of the volatile organic compounds present in the effluent. Remediation of these components was carried out by Fenton oxidation prior to evaporation. A high removal was observed under the applied conditions of Fe2+ = 25 mg l-1, H2O2 = 50 mg l-1, pH = 3 and a reaction time of 2 hours.

Conservation of Natural Resources↗

PubMed2001

Reliability of optimal control strategies for photochemical air pollution.

This study illustrates how consideration of modeling uncertainties can affect optimal control strategies for urban ozone. Control strategies are investigated for illustrative cases of air parcel trajectories ending at Azusa, CA, and Riverside, CA, on August 28, 1987. The control strategies are designed to achieve a specified air quality target with a given reliability, considering uncertainties in the California Institute of Technology's trajectory model and its inputs, including uncertainties in emissions and in the SAPRC-97 chemical mechanism. A decoupled stochastic optimization scheme is used to solve the chance-constrained programming problem. Least-cost control strategies derived using nominal model inputs and parameter values have low reliability for some target O3 concentrations when uncertainties are taken into account. For the case considered, reducing volatile organic compound (VOC) emissions from motor vehicles is identified as the least-cost approach to meeting O3 targets at Azusa. However, the optimal control strategies for Riverside depend on the target O3 concentrations and the level of reliability required. Consideration of model uncertainty is found to shift the focus from VOC controls to nitrogen oxide controls for the Riverside trajectory.

Air Pollution↗

PubMed2003

Risk assessment of sensory irritants in indoor air--a case study in a French school.

Exposure to airborne pollutants can result in adverse health effects. Acute symptoms can for instance comprise of irritation of the eyes or of the respiratory tract (called sensory irritation). In a recent case, health problems were reported in a French school and supposedly attributed to the presence of airborne irritant pollutants. Based on measured concentrations, the risk of developing the described health effects was assessed. Numerous airborne sensory irritants (aldehydes, organic acids, volatile organic compounds (VOCs), SO(2), NH(3)) were identified and quantified in the indoor air by using active and passive sampling and online monitoring techniques. Reference values based on toxicological properties of compounds (sensory irritants) were taken from the literature. If not available, tentative values were specially developed for this purpose. Concentrations of all sensory irritants remain below their corresponding guideline values and are comparable to literature data. It was concluded that the risk of developing sensory irritation due to the presence of the studied compounds is negligible. This holds both for individual compounds and for the mixture of studied compounds. Limitations of the employed sampling strategy, and of existing sampling and analytical techniques, which do not allow for analysing more reactive compounds-which are strong sensory irritants-may play a role. New sampling techniques need to be developed. Psychosocial factors (group behaviour, increased attention to sensory irritation) should also be taken into account when dealing with health complaints on sensory irritation.

Air Pollution, Indoor↗

PubMed2002

Reclamation of treated domestic wastewater using biological membrane assisted carbon filtration (BioMAC).

Membrane processes are increasingly used as an advanced treatment technique for the reclamation of treated domestic wastewater. Despite their inherent advantages, fouling remains an operational problem, while the removal of dissolved organic components such as volatile organic compounds is negligible. In the present work, the addition of a partially non-submerged biological granular activated carbon filtration to a microfiltration lab-scale reactor was investigated. It was observed that the reactor could be operated under stable flux conditions although regular hydraulic backwashing was necessary. Preferential attached growth of nitrifiers on the activated carbon particles allowed for a complete and very stable nitrification, with permeate total ammonium nitrogen and nitrite levels below 0.2 mg l(-1) regardless of influent concentrations. Chemical oxygen demand of the permeate averaged 5.26 mg O2 l(-1) which is below the Environmental Protection Agency guideline for wastewater reuse. Using an electronic nose, elimination of volatile compounds was assessed. The combined process resulted in complete odour removal, with the permeate odour levels equaling the reference samples (tap water), even during periods of increased reactor load (shock load experiment). A 4.2 log10 CFU and 3.7 log10 CFU removal were observed for total coliforms and E. coli, respectively.

Bioreactors↗

PubMed2002

Cabin air quality: an overview.

In recent years, there have been increasing complaints from cockpit crew, cabin crew, and passengers that the cabin air quality of commercial aircraft is deficient. A myriad of complaints including headache, fatigue, fever, and respiratory difficulties among many others have been registered, particularly by flight attendants on long-haul routes. There is also much concern today regarding the transmission of contagious disease inflight, particularly tuberculosis. The unanswered question is whether these complaints are really due to poor cabin air quality or to other factors inherent intlight such as lowered barometric pressure, hypoxia, low humidity, circadian dysynchrony, work/rest cycles, vibration, etc. This paper will review some aspects relevant to cabin air quality such as volatile organic compounds (VOCs), carbon dioxide (CO2), carbon monoxide (CO), ozone (O3), particulates, and microorganisms, as well as the cabin ventilation system, to discern possible causes and effects of illness contracted inflight. The paper will conclude with recommendations on how the issue of cabin air quality may be resolved.

Aerospace Medicine↗

PubMed1997

Influence of dietary protein supplements on the formation of bacterial metabolites in the colon.

BACKGROUND: To evaluate the influence of increased dietary protein intake on bacterial colonic metabolism in healthy volunteers. METHODS: Short chain fatty acids, ammonia, and volatile organic compounds in faecal samples, and phenols in the urine of five volunteers were measured after one week of basal nutrient intake and and after one week of a diet supplemented with a protein rich food (Fortimel; Nutricia, Zoetermeer, The Netherlands). Paired t tests and factor analysis were used for statistical analysis. RESULTS: Total energy and resistant carbohydrate intake remained unchanged in each study period. The percentage energy intake delivered as dietary protein, increased significantly (from 15.4% to 23.8%; p = 0.007) during supplement intake. A significant increase in faecal ammonia (p = 0.002), faecal valeric acid (p = 0.02), and urinary p-cresol (p = 0.04) was noted during supplementary protein intake. A total of 120 different volatile compounds were isolated from the faecal samples of which 10 increased significantly during dietary protein supplementation. The change in volatile pattern, especially for S containing metabolites, was clearly shown by a factor analysis model which made a distinction between the two dietary regimens for all volunteers. CONCLUSION: An increase in dietary protein leads to altered products formation by colonic metabolism, mainly reflected by an increase in faecal ammonia, faecal volatile S substances, and urinary p-cresol.

Adult↗

PubMed2006

Analysis of expired air of fasting male monks at Mount Athos.

Expired air chemical analysis is investigated as a search and locate method for the early detection of entrapped people under the ruins of collapsed buildings after an earthquake. Fasting individuals were examined as a group that simulates the medical status of some of such victims. Exhaled air from seven fasting male monks (after 63 h) was analysed using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) analysis. Over 150 volatile organic compounds (VOCs) were identified and the 43 most frequent are presented. Acetone showed by far the highest "positive alveolar gradient". Other compounds included phenol, di-limonene, 2-pentanone, isoprene and acetaldehyde. Quantitative results showed a 30-fold increase of acetone concentration (5.8 ppmv) compared to control measurements of a volunteer. Breath acetone was also identified through a portable gas chromatography-ion mobility spectrometer showing possible, under certain conditions, effectiveness of the method in the field.

Adult↗

PubMed2004

Airborne signals prime plants against insect herbivore attack.

Green leafy volatiles (GLV), six-carbon aldehydes, alcohols, and esters commonly emitted by plants in response to mechanical damage or herbivory, induced intact undamaged corn seedlings to rapidly produce jasmonic acid (JA) and emit sesquiterpenes. More importantly, corn seedlings previously exposed to GLV from neighboring plants produced significantly more JA and volatile sesquiterpenes when mechanically damaged and induced with caterpillar regurgitant than seedlings not exposed to GLV. The use of pure synthetic chemicals revealed that (Z)-3-hexenal, (Z)-3-hexen-1-ol, and (Z)-3-hexenyl acetate have nearly identical priming activity. Caterpillar-induced nocturnal volatiles, which are enriched in GLV, also exhibited a strong priming effect, inducing production of larger amounts of JA and release of greater quantities of volatile organic compounds after caterpillar regurgitant application. In contrast, GLV priming did not affect JA production induced by mechanical wounding alone. Thus, GLV specifically prime neighboring plants against impending herbivory by enhancing inducible chemical defense responses triggered during attack and may play a key role in plant-plant signaling and plant-insect interactions.

Animals↗

PubMed2000

Performance characteristics of a regenerative catalytic oxidizer for treating VOC-contaminated airstreams.

A pilot apparatus of a regenerative catalytic oxidizer (RCO) equipped with two electrical heaters and two 20-cm i.d. x 200-cm height regenerative beds was used to treat methyl ethyl ketone (MEK) and toluene, respectively, in an airstream. The regenerative beds were packed with gravel (approximate particle size 1.25 cm, specific area 205 m2/m3, and specific heat capacity 840 J/kg degree C) as a solid regenerative material and K-type thermal couples for measuring solid and gas temperatures, respectively. The catalyst bed temperature was kept around 400 degrees C and the gas superficial velocity was operated at 0.234 m/sec. This investigation measured and analyzed distributions of solid and gas temperatures with operating time and variations of volatile organic compound (VOC) concentrations in the regenerative beds. The overall VOC removal efficiency exceeded 98% for MEK and 95% for toluene. Degradation of VOCs will exist for MEK on the surface of solid material (gravel) in the temperature range of 330-400 degrees C, but toluene does not exhibit this phenomenon.

Air Movements↗

PubMed2005

Plant-plant signaling: ethylene synergizes volatile emission in Zea mays induced by exposure to (Z)-3-hexen-1-ol.

Leaf alcohol (Z)-3-hexen-1-ol (Z-3-ol) is emitted by green plants upon mechanical damage. Exposure of intact maize plants to Z-3-ol induces the emission of a volatile blend that is typically released after caterpillar feeding and attracts natural enemies of the herbivores [herbivore-induced volatile organic compounds (HI-VOC)]. Thus, it has been suggested that Z-3-ol might have a function in indirect plant defense mediating plant-plant signaling and intraplant information transfer. Here, we demonstrate that HI-VOC induction by Z-3-ol is synergized by the phytohormone ethylene. Exposure to Z-3-ol at doses of 100 and 250 nmol induced HI-VOC emission in intact maize plants. HI-VOC emissions increased by 2.5-fold when ethylene was added. The effect of ethylene was more pronounced (5.1- to 6.6-fold) when only total sesquiterpene release was considered. In contrast, ethylene alone had no inductive effect but rather decreased the emission of the constitutive maize volatile linalool. We suggest that ethylene plays a synergistic role in plant-plant signaling mediated by green leaf volatiles.

Ethylenes↗

PubMed2004

Evaluation of soil gas sampling and analysis techniques at a former petrochemical plant site.

Methods for soil gas sampling and analysis are evaluated as part of a research study on soil vapour intrusion into buildings, conducted at a former petro-chemical plant site ("Chatterton site"). The evaluation process was designed to provide information on reliability and selection of appropriate methods for soil gas sampling and analysis, and was based on a literature review of data and methods, and experiments completed as part of the research study. The broader context of this work is that soil gas characterization is increasingly being used for input into risk assessment of contaminated sites, particularly when evaluating the potential intrusion of soil vapour into buildings. There are only a limited number of research studies and protocols addressing soil gas sampling and analysis. There is significant variability in soil gas probe design and sample collection and analysis methods used by practitioners. The experimental studies conducted to evaluate soil gas methods address the permeation or leakage of gases from Tedlar bags, time-dependent sorption of volatile organic compound (VOC)-vapours onto probe surfaces and sampling devices, and analytical and quality control issues for light gas and VOC analyses. Through this work, common techniques for soil gas collection and analysis are described together with implications for data quality arising from the different methods used. Some of the potential pitfalls that can affect soil gas testing are identified, and recommendations and guidance for improved protocols are provided.

Biodegradation, Environmental↗

PubMed2002

Temperature dependence of Henry's law constant in an extended temperature range.

The Henry's law constants H for chloroform, 1,1-dichloroethane, 1,2-dichloropropane, trichloroethene, chlorobenzene, benzene and toluene were determined by the EPICS-SPME technique (equilibrium partitioning in closed systems--solid phase microextraction) in the temperature range 275-343 K. The curvature observed in the ln H vs. 1/T plot was due to the temperature dependence of the change in enthalpy delta H0 during the transfer of 1 mol solute from the aqueous solution to the gas phase. The nonlinearity of the plot was explained by means of a thermodynamic model which involves the temperature dependence of delta H0 of the compounds and the thermal expansion of water in the three-parameter equation ln (H rho TT) = A2/T + BTB + C2, where rho T is the density of water at temperature T, TB = ln(T/298) + (298-T)/T, A2 = -delta H298(0)/R, delta H298(0) is the delta H0 value at 298 K, B = delta Cp0/R, and C2 is a constant. delta Cp0 is the molar heat capacity change in volatilization from the aqueous solution. A statistical comparison of the two models demonstrates the superiority of the three-parameter equation over the two-parameter one ln H vs. 1/T). The new, three-parameter equation allows a more accurate description of the temperature dependence of H, and of the solubility of volatile organic compounds in water at higher temperatures.

Organic Chemicals↗

PubMed2006

Solid-phase microextraction as a novel air sampling technology for improved, GC-olfactometry-based assessment of livestock odors.

Air sampling and characterization of odorous livestock gases is one of the most challenging analytical tasks. This is because of low concentrations, physicochemical properties, and problems with sample recoveries for typical odorants. Livestock operations emit a very complex mixture of volatile organic compounds (VOCs) and other gases. Many of these gases are odorous. Relatively little is known about the link between characteristic VOCs/gases and, specifically, about the impact of characteristic odorants downwind from sources. In this research, solid-phase microextraction (SPME) is used for field air sampling of odors downwind from swine and beef cattle operations. Sampling time ranges from 20 min to 1 h. Samples are analyzed using a commercial gas chromatography-mass spectrometry-olfactometry system. Odor profiling efforts are directed at odorant prioritization, with respect to distance from the source. The results indicate the odor downwind is increasingly defined by a smaller number of high-priority odorants. These "character defining" odorants appear to be dominated by compounds of relatively low volatility, high molecular weight, and high polarity. In particular, p-cresol alone appears to carry much of the overall odor impact for swine and beef cattle operations. Of particular interest is the character-defining odor impact of p-cresol as far as 16 km downwind of the nearest beef cattle feedlot. The findings are highly relevant to scientists and engineers working on improved air sampling and analysis protocols and on improved technologies for odor abatement. More research evaluating the use of p-cresol and a few other key odorants as a surrogate for overall odor dispersion modeling is warranted.

Animals↗

PubMed2006

Processes influencing secondary aerosol formation in the San Joaquin Valley during winter.

Air quality data collected in the California Regional PM10/ PM(2.5) Air Quality Study (CRPAQS) are analyzed to qualitatively assess the processes affecting secondary aerosol formation in the San Joaquin Valley (SJV). This region experiences some of the highest fine particulate matter (PM(2.5)) mass concentrations in California (< or = 188 microg/m3 24-hr average), and secondary aerosol components (as a group) frequently constitute over half of the fine aerosol mass in winter. The analyses are based on 15 days of high-frequency filter and canister measurements and several months of wintertime continuous gas and aerosol measurements. The phase-partitioning of nitrogen oxide (NO(x))-related nitrogen species and carbonaceous species shows that concentrations of gaseous precursor species are far more abundant than measured secondary aerosol nitrate or estimated secondary organic aerosols. Comparisons of ammonia and nitric acid concentrations indicate that ammonium nitrate formation is limited by the availability of nitric acid rather than ammonia. Time-resolved aerosol nitrate data collected at the surface and on a 90-m tower suggest that both the daytime and nighttime nitric acid formation pathways are active, and entrainment of aerosol nitrate formed aloft at night may explain the spatial homogeneity of nitrate in the SJV. NO(x) and volatile organic compound (VOC) emissions plus background O3 levels are expected to determine NO(x) oxidation and nitric acid production rates, which currently control the ammonium nitrate levels in the SJV. Secondary organic aerosol formation is significant in winter, especially in the Fresno urban area. Formation of secondary organic aerosol is more likely limited by the rate of VOC oxidation than the availability of VOC precursors in winter.

Aerosols↗

PubMed2006

Changes in landfill gas quality as a result of controlled air injection.

Air addition has been proposed as a technique for rapid stabilization of municipal solid waste (MSW) in landfills. The objective of this study was to observe the change in concentration of trace constituents of landfill gas in response to air addition. Air injection tests were conducted at a MSW landfill in Florida, and the concentrations of several gaseous constituents at adjacent wells within the waste were measured. The concentrations of methane, carbon dioxide, and oxygen, as well as several trace constituents, were measured both prior to and during air addition. The trace components investigated included a suite of volatile organic compounds (VOCs), nitrous oxide (N20), carbon monoxide (CO), and hydrogen sulfide (H2S). A significant increase in CO was observed in 9 of 14 monitoring points; overall, CO concentrations were found to increase as the ratio of CH4 to CO2 decreased. A significant decrease in H2S was observed at 6 of 14 monitoring points. Air injection did not have a noticeable affect on VOC or N2O concentrations compared to initial levels.

Air Movements↗

PubMed2003

Use of a coupled biological system to treat a chemically complex air stream.

The use of biological systems to remove contaminants from waste streams has been well documented. However, when dealing with complex waste streams, the use of one biological treatment system may not be the best alternative. When treating a complex waste stream, the use of "treatment trains" or "coupled systems" may be advantageous compared with any single biological technology. This article demonstrated that a coupled system was effective in biodegrading a chemically complex mixture of volatile organic compounds (VOCs). A bench-scale system consisting of a liquid bioreactor and a biofilter was used for the biodegradation of acetone, methanol, methyl ethyl ketone, naphthalene, alpha-pinene, and toluene. The bioreactor contained an inert solid support that immobilized a microbial population. The biofiltration portion of the system utilized the same microbial inoculum but employed Douglas fir bark as its solid support. Successful biodegradation of the complex VOC mixture was accomplished with this coupled system with an average VOC removal efficiency of 96% and VOC loading rates as high as 79 g/m3/h for inlet concentrations of > 8,000 ppmv. At elevated flow rates the liquid reactor demonstrated limited removal of some compounds, such as alpha-pinene and toluene, while maintaining excellent removal of other compounds, such as methanol and acetone. The biofilter portion of the system proved very successful in degrading the remaining toluene and alpha-pinene, thus complementing the removal from the bioreactor. This study demonstrates that coupled biological systems may be utilized for a chemically complex VOC-laden air stream that previously may not have been considered for biological treatment.

Air Pollution↗