Assessing organic contaminants in fish: comparison of a nonlethal tissue sampling technique to mobile and stationary passive sampling devices

As concerns mount over the human health risks associated with consumption of fish contaminated with persistent organic pollutants, there exists a need to better evaluate fish body burdens without lethally sampling many of the important commercial and sport species of interest. The aim of this study was to investigate two novel methods for estimating organic contaminants in fish that are a concern for both fish and human health. The removal of fish adipose fins, commonly done in mark-recapture studies with salmonid species, was evaluated as a nonlethal sampling technique to estimate concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in flathead catfish (Pylodictis olivaris), relative to those found in muscle fillets of the same fish. We also assessed the efficacy of using poly(dimethylsiloxane) (PDMS) as a mobile passive sampling device (PSD) attached directly to wild flathead catfish for assessing location-specific exposure of the fish to waterborne contaminants. The results of this study have demonstrated for the first time that organic contaminant concentrations in adipose fin were highly correlated (R2 = 0.87) with muscle fillet concentrations, indicating that the adipose fin of certain fishes may be used to accurately estimate tissue concentrations without the need for lethal sampling. Moreover, mobile PSDs attached directly to fish and used here for the first time accurately estimated ultratrace concentrations of waterborne PCBs and OCPs without any apparent harm to the fish, indicating that there are no practical or physical barriers to the use of mobile passive samplers attached to aquatic organisms. Among the many practical implications of this research, two potential priority items include the analysis of organic contaminants in farm-raised and sport fish intended for human consumption, without the economic and population losses associated with lethally sampling fish to obtain tissues, and identifying specific areas where fish may be accumulating large portions of their contaminant burden.     

Sampling medium side resistance to uptake of semivolatile organic compounds in passive air samplers

Current theory of the uptake of semivolatile organic compounds in passive air samplers (PAS) assumes uniform chemical distribution and no kinetic resistance within the passive sampling media (PSM) such as polystyrene-divinylbenzene resin (XAD) and polyurethane foam (PUF). However, these assumptions have not been tested experimentally and are challenged by some recently reported observations. To test the assumptions, we performed kinetic uptake experiments indoors using cylindrical PSM that had been concentrically segmented into three layers. Both XAD and PUF were positioned in the same type of sampler housing to eliminate the variation caused by the different housing designs, which enabled us to quantify differences in uptake caused by the properties of the PSM. Duplicated XAD (PUF) samples were retrieved after being deployed for 0, 1 (0.5), 2 (1), 4 (2), 8 (4), 12 (8), and 24 (12) weeks. Upon retrieval, the PSM layers were separated and analyzed individually for PCBs. Passive sampling rates (R) were lower for heavier PCB homologues. Within a homologue group, R for XAD was higher than that for PUF, from which we infer that the design of the "cylindrical can" housing typically used for XAD PAS lowers the R compared to the "double bowl" shelter commonly used for PUF-disk PAS. Outer layers of the PSM sequestered much higher levels of PCBs than inner layers, indicative of a kinetic resistance to chemical transfer within the PSM. The effective diffusivities for chemical transfer within PSM were derived and were found negatively correlated with the partition coefficients between the PSM and air. Based on the results, we conclude that the PSM-side kinetic resistance should be considered when investigating factors influencing R and when deriving R based on the loss of depuration compounds.     

A dynamic model to study the exchange of gas-phase persistent organic pollutants between air and a seasonal snowpack

An arctic snow model was developed to predict the exchange of vapor-phase persistent organic pollutants between the atmosphere and the snowpack over a winter season. Using modeled meteorological data simulating conditions in the Canadian High Arctic, a single-layer snowpack was created on the basis of the precipitation rate, with the snow depth, snow specific surface area, density, and total surface area (TSA) evolving throughout the annual time series. TSA, an important parameter affecting the vapor-sorbed quantity of chemicals in snow, was within a factor of 5 of measured values. Net fluxes for fluorene, phenanthrene, PCB-28 and -52, and alpha- and gamma-HCH (hexachlorocyclohexane) were predicted on the basis of their wet deposition (snowfall) and vapor exchange between the snow and atmosphere. Chemical fluxes were found to be highly dynamic, whereby deposition was rapidly offset by evaporative loss due to snow settling (i.e., changes in TSA). Differences in chemical behavior over the course of the season (i.e., fluxes, snow concentrations) were largely dependent on the snow/air partition coefficients (K(sa)). Chemicals with relatively higher K(sa) values such as alpha- and gamma-HCH were efficiently retained within the snowpack until later in the season compared to fluorene, phenathrene, and PCB-28 and -52. Average snow and air concentrations predicted by the model were within a factor of 5-10 of values measured from arctic field studies, but tended to be overpredicted for those chemicals with higher K(sa) values (i.e., HCHs). Sensitivity analysis revealed that snow concentrations were more strongly influenced by K(sa) than either inclusion of wind ventilation of the snowpack or other changes in physical parameters. Importantly, the model highlighted the relevance of the arctic snowpack in influencing atmospheric concentrations. For the HCHs, evaporative fluxes from snow were more pronounced in April and May, toward the end of the winter, providing evidence that the snowpack plays an important role in influencing the seasonal increase in air concentrations for these compounds at this time of year.     

Exposure to particulate matter,volatile organic compounds,and other air pollutants inside patrol cars

People driving in a vehicle might receive an enhanced dose of mobile source pollutants that are considered a potential risk for cardiovascular diseases. The exposure to components of air pollution in highway patrol vehicles, at an ambient, and a roadside location was determined during 25 work shifts (3 p.m. to midnight) in the autumn of 2001, each day with two cars. A global positioning system and a diary provided location and activity information. Average pollutant levels inside the cars were low compared to ambient air quality standards: carbon monoxide 2.7 ppm, nitrogen dioxide 41.7 microg/m3, ozone 11.7 ppb, particulate matter smaller 2.5 microm (PM2.5) 24 microg/m3. Volatile organic compounds inside the cars were in the ppb-range and showed the fingerprint of gasoline. PM2.5 was 24% lower than ambient and roadside levels, probably due to depositions associated with the recirculating air conditioning. Levels of carbon monoxide, aldehydes, hydrocarbons, and some metals (Al, Ca, Ti, V, Cr, Mn, Fe, Cu, and Sr) were highest in the cars, and roadside levels were higher than ambient levels. Elevated pollutant levels were related to locations with high traffic volumes. Our results point to combustion engine emissions from other vehicles as important sources of air pollutants inside the car.     

Passive air sampling of polychlorinated biphenyls, organochlorine compounds, and polybrominated diphenyl ethers across Asia

Asia is of global importance economically, yet data on ambient persistent organic pollutant levels are still sparse for the region, despite international efforts under the Stockholm Convention to identify and reduce emissions. A large-scale passive air sampling survey was therefore conducted in Asia, specifically in China, Japan, South Korea, and Singapore. Polyurethane foam disks were deployed simultaneously at 77 sites, between Sept 21 and Nov 16, 2004, and analyzed for polychlorinated biphenyls (PCBs), organochlorine compounds (hexachlorobenzene (HCB), dichlorodiphenyltrichloroethanes (DDTs), chlordane), and polybrominated diphenyl ethers (PBDEs). The meteorological conditions prevailing in the region at this time facilitated the assessment of local/regional differences in atmospheric emissions, because large-scale advection effects due to monsoons or dust storms did not occur. Air concentrations estimated assuming an average sampler uptake rate of 3.5 m3/day ranged as follows (pg m(-3)): PCBs, 5-340; HCB, 10-460; DDTs, 0.4-1800; chlordanes, 1-660; PBDEs, < 0.13-340. South Korea and Singapore generally had regionally low concentrations. Elevated concentrations of PCBs, DDTs, and HCB occurred at sites in China, higher than reported in a similar recent sampling campaign in Europe. Chlordane was highest in samples from Japan (which also had elevated levels of PCBs and DDTs) and was also elevated in some Chinese locations. PBDE levels were generally low in the region.     

Comparison of two field sampling procedures (En Core and field methanol extraction) for volatile organic compounds

In-situ Lasagna technology was recently evaluated at a contaminated site at Offutt Air Force Base. The site was contaminated with low levels (<30 mg/kg) of volatile organic compounds (VOCs). Originally, researchers planned to use field methanol extraction for both pre- and post-treatment sampling to evaluate the effectiveness of the technology on contaminant reduction. Precharacterization sampling, however, indicated that concentrations of some contaminants of concern were much lower than expected. Because use of methanol increases the detection limit, it was probable that post-treatment concentrations of these target contaminants would be nondetectable if methanol extraction was used. Project management, therefore, decided to use En Core samplers in addition to field methanol extraction during the pretreatment sampling event. The En Core sampling approach, while yielding a lower detection limit, uses discreet samples along the length of a core, whereas the methanol extraction approach samples the entire length of the core. The concern was that discreet samples may bias results if any "hot spots" were present. The two field sampling procedures, En Core and field methanol extraction, were performed side-by-side during the pretreatment phase of the technology evaluation in order to determine if the concern was valid for this site. Results were compared for four contaminants of concern: trichloroethylene, vinyl chloride, cis-1,2-dichloroethene, and trans-1,2-dichloroethene. The two procedures produced similar results with respect to both the concentration means and the variances, and no bias was evident. This finding supports project management's decision to use only En Core samplers post-treatment due to low concentrations of target contaminants.     

Selected volatile organic compounds in residential air in the city of Ottawa, Canada

Airborne levels of selected volatile organic chemicals (VOCs) that are priorities for exposure assessment under the Canadian Environmental Protection Act (CEPA) 1999 were measured in both indoor air and outdoor air of 75 residential houses, in the city of Ottawa, Canada, during the winter of 2002/2003. The houses were randomly selected using Ottawa 2001 population census data. VOCs were collected on adsorbent tubes and measured by thermal desorption GC/MS. Among 37 chemicals monitored, 17 were detected with a frequency greater than 80% in indoor air; 9 were between 30% and 80%; 7 were between 1% and 30%; and 4 were not detected. Concentrations of VOCs in both indoor and outdoor air are presented. Virtually all of the target VOCs were detected more frequently and were present at significantly higher levels, in indoor air than in outdoor air. As an indication of the contribution of indoor levels of these chemicals, ratios of the concentration found in indoor air to outdoor air (I/O) and the indoor source strength expressed in estimated emission rate per house are also presented. Compared with earlier published studies including a 1991/1992 Canadian national survey of VOCs in residential air, levels of target analytes in indoor air in this study were lower for a number of chemicals, indicating a possible trend toward decreased inhalation exposure to these chemicals in residential environments. This study has yielded up-to-date information on levels of a variety of priority airborne chemicals in residential air, which is being used to estimate current exposure to these substances as input to health risk assessments and risk management actions under CEPA 1999.     

温度、水分、时间和添加剂对烟丝挥发性及半挥发性化学成分的影响

采用改进的全自动吹扫捕集系统,模拟烘丝条件,研究不同温度(110℃～150℃)、时间(5～25 min)、水分(15%～30%)及添加剂(草酸、苹果酸、柠檬酸、磷酸氰二铵及氨)等条件对烟丝挥发性及半挥发性化学成分的影响.结果表明:试验数据与卷烟加工的实际规律基本相符,该系统可以很好地模拟制丝工艺的某些环节及研究制丝工艺参数对烟草化学成分的影响.     

温度、水分、时间和添加剂对烟丝挥发性及半挥发性化学成分的影响

采用改进的全自动吹扫捕集系统,模拟烘丝条件,研究不同温度（110℃~150℃）、时间（5~25 min）、水分（15%~30%）及添加剂（草酸、苹果酸、柠檬酸、磷酸氢二铵及氨）等条件对烟丝挥发性及半挥发性化学成分的影响。结果表明:试验数据与卷烟加工的实际规律基本相符,该系统可以很好地模拟制丝工艺的某些环节及研究制丝工艺参数对烟草化学成分的影响。      

Evaluating differences between measured personal exposures to volatile organic compounds and concentrations in outdoor and indoor air

Accurate estimation of human exposures to volatile organic compounds (VOCs) is a key element of strategies designed to protect public health from the adverse effects of hazardous air pollutants. The focus here is on examining the capability of three different exposure metrics (outdoor community concentrations, indoor residential concentrations, and a simple time-weighted model) to estimate observed personal exposures to 14 VOCs. The analysis is based on 2-day average concentrations of individual VOCs measured concurrently in outdoor (O) air in three urban neighborhoods, indoor (I) air in participant's residences, and personal (P) air near the breathing zone of 71 healthy, nonsmoking adults. A median of four matched P-I-O samples was collected for each study participant in Minneapolis/St. Paul over three seasons (spring, summer, and fall) in 1999 using charcoal-based passive air samplers (3M model 3500 organic vapor monitors). Results show a clear pattern for the 14 VOCs, with P > I > O concentrations. Intra-individual variability typically spanned at least an order of magnitude, and inter-individual variability spanned 2 or more orders of magnitude for each of the 14 VOCs. Although both O and I concentrations generally underestimated personal exposures, I concentrations provided a substantially better estimate of measured P concentrations. Mean squared error (MSE) as well as correlation measures were used to assess estimator performance at the subject-specific level, and hierarchical, mixed effects models were used to estimate the bias and variance components of MSE by tertile of personal exposure. Bias and variance both tended to increase in the upper third of the P exposure distribution for O versus P and I versus P. A simple time-weighted model incorporating measured concentrations in both outdoor community air and indoor residential air provided no improvement over I concentration alone for the estimation of P exposure.     

On the construction, comparison, and variability of airsheds for interpreting semivolatile organic compounds in passively sampled air

Air mass origin as determined by back trajectories often aids in explaining some of the short-term variability in the atmospheric concentrations of semivolatile organic contaminants. Airsheds, constructed by amalgamating large numbers of back trajectories, capture average air mass origins over longer time periods and thus have found use in interpreting air concentrations obtained by passive air samplers. To explore some of their key characteristics, airsheds for 54 locations on Earth were constructed and compared for roundness, seasonality, and interannual variability. To avoid the so-called "pole problem" and to simplify the calculation of roundness, a "geodesic grid" was used to bin the back-trajectory end points. Departures from roundness were seen to occur at all latitudes and to correlate significantly with local slope but no strong relationship between latitude and roundness was revealed. Seasonality and interannual variability vary widely enough to imply that static models of transport are not sufficient to describe the proximity of an area to potential sources of contaminants. For interpreting an air measurement an airshed should be generated specifically for the deployment time of the sampler, especially when investigating long-term trends. Samples taken in a single season may not represent the average annual atmosphere, and samples taken in linear, as opposed to round, airsheds may not represent the average atmosphere in the area. Simple methods are proposed to ascertain the significance of an airshed or individual cell. It is recommended that when establishing potential contaminant source regions only end points with departure heights of less than ～700 m be considered.     

Transfer kinetics of polar organic compounds over polyethersulfone membranes in the passive samplers POCIS and Chemcatcher

Passive samplers for polar organic compounds often use a polyethersulfone (PES) membrane to retain the particulate sorbent material (e.g., in a POCIS; polar organic chemical integrative sampler) or to reduce the sampling rate and thus extend the kinetic regime (e.g., in a Chemcatcher). The transport kinetics over the PES membrane are evaluated here in a short-term (6 days) and a long-term (32 days) experiment with POCIS and Chemcatchers. Passive samplers were placed in a channel with flowing river water that was spiked with 22 organic chemicals including pharmaceuticals, pesticides and biocides; with logK(ow) (logarithmic octanol-water partitioning coefficient) values between -2.6 and 3.8. Samplers were removed at intervals and membranes and sorbent material were extracted and analyzed with LC-MS/MS. Uptake kinetics of the compounds fell between two extremes: (1) charged chemicals and chemicals of low hydrophobicity did not accumulate in PES and rapidly transferred to the sorbent (e.g., diclofenac) and (2) more hydrophobic chemicals accumulated strongly in the PES and appeared in the sorbent after a lag-phase (e.g., diazinon and diuron). Sorption kinetics were modeled with a three-compartment first-order kinetic model to determine uptake and elimination rate constants and partitioning coefficients. Water PES partitioning coefficients fitted with the model correlated well with experimentally determined values and logK(ow). Sampling rates of Chemcatcher (0.02-0.10 L/d) and POCIS (0.02-0.30 L/d) showed similar patterns and correlated well. Thus the samplers are interchangeable in practical applications. Longer lag-phases may pose problems when calculating time-weighted average aqueous concentrations for short passive sampling windows and for a correct integrative sampling of fluctuating concentrations.     

Comparison of media and sampling locations for isolation of Listeria monocytogenes in queso fresco cheese

Listeriosis associated with Hispanic-style soft cheese is an ongoing public health concern. Although rapid detection methods based on molecular and immunological technologies have been applied successfully for detecting Listeria monocytogenes in foods, obtaining isolates of the pathogen is a critical procedure for epidemiologic studies and regulatory analysis. Oxford agar, a medium recommended by the U.S. Food and Drug Administration Bacteriological Analytical Manual (BAM) to isolate L. monocytogenes from cheese, is unable to differentiate L. monocytogenes from other Listeria species. Hence, two selective isolation media, L. monocytogenes blood agar (LMBA) and Rapid 'L. mono agar (RLMA), were compared with Oxford agar for isolating L. monocytogenes from cheese. Queso fresco cheese was inoculated at 10(0) or 10(1) CFU/g with a five-strain mixture of L. monocytogenes or with the five-strain L. monocytogenes mixture and Listeria innocua. Cheese samples were stored at 21, 12, and 4 degrees C and Listeria counts were determined at 3, 7, and 10 days; 7, 10, 14, 21 days; and 2, 4, 8, and 12 weeks postinoculation, respectively. Surface and interior cheese samples as well as liquid exudate produced during storage were assayed individually to determine differences in Listeria contamination at different sampling locations. L. monocytogenes was more easily differentiated from L. innocua on RLMA than LMBA and Oxford agar. Similar L. monocytogenes counts (ca. 10(4) CFU/g) were obtained on the last sampling day on the surface and interior of cheese samples (P > 0.05) for all storage temperatures and both initial inoculation levels, but smaller cell numbers were detected in the exudate produced during storage. In addition, simultaneous inoculation of L. innocua with L. monocytogenes did not affect the final L. monocytogenes counts in the cheese. The amount of exudate released from the cheese and decrease of pH correlated with storage temperature. More exudate was produced and a greater decrease of pH occurred at 21 degrees C than at 12 or 4 degrees C. Our results indicate that RLMA is a suitable medium for isolating L. monocytogenes from queso fresco cheese. Higher counts of L. monocytogenes were obtained from surface and interior samples of cheese than from the exudate of the cheese during storage. In addition, pH may be a useful indicator of improperly stored queso fresco cheese.     

Comparison of microbiota and volatile organic compounds in milk from different sheep breeds

In this study, we compared the microbiota and volatile organic compounds (VOC) present in the milk obtained from 3 different sheep breeds, namely Merino, Lacaune, and Assaf. Udder milk was collected from 21 animals, 7 from each breed. Bacterial microflora was determined metagenomically by extracting the DNA from the milk and analyzing the V3-V4 region of the 16S rRNA gene. Headspace solid-phase microextraction gas chromatography-mass spectrometry method was used to analyze VOC. The metagenomic analysis revealed (for Merino, Lacaune, and Assaf milk, respectively) Firmicutes (66.32, 69.36, and 57.08%), Actinobacteria (19.09, 7.67, and 19.40%), Proteobacteria (13.76, 21.06, and 22.19%), and Bacteroidetes (0.84, 1.91, and 1.33%) phyla in the milk samples. Lactobacillus was highly abundant in the milk of 3 breeds (29.64, 43.50, and 18.70%). The genera constituting more than 2% of all bacteria in all groups were Jeotgalicoccus (7.19, 5.34, and 10.77%), Enterococcus (5.18, 9.78, and 3.64%), and Corynebacterium (4.08, 3.00, and 13.44%). A total of 32 different VOC were identified by headspace solid-phase microextration analysis with 9, 30, and 24 different compounds from Merino, Lacaune, and Assaf breeds, respectively. Although ketone was the most abundant compound in Merino milk (71.84%), hydrocarbons were the most detected in Lacaune and Assaf milk (37.18% and 55.42%, respectively). A positive correlation was found between acetone, which was detected at the highest level in all groups, with Salinicoccus, Alloiococcus, Psychrobacter, and Dietzia. In addition, a negative correlation was found between the Lactobacillus genus, detected at the highest level in all groups, with methyl cyclopentane, 3-methylheptane, octane, decane, 3,3-dimethyloctane, and dodecane. Thus, differences were observed in the bacterial microflora and VOC in the sheep milk from different breeds under different feeding and breeding conditions.     

Comparison between the predicted fate of organic compounds in landfills and the actual emissions

Emissions of organic compounds from landfills depend on the fate of the compounds inside the landfills. This field study was used to investigate the fate in landfills of organic compounds having different physical, chemical, and biological characteristics. For this purpose, a pilot-scale landfill was constructed containing 540 m3 of ordinary household waste, 12 organic compounds were added at the top of the landfill, and leachate and landfill gas samples were continually collected and analyzed. The fate of each compound was theoretically estimated from literature data on the processes which significantly affect the compounds: sorption, dissociation, evaporation, and transformation. These processes could be described by the octanol/water coefficients, Kow, the acid dissociation constants, pKa, the Henry's law constants, H, and the potential of the compounds to be biologically transformed. The use of a ranking score system was suggested as a tool for interpreting the predicted fate of specific compounds caused by several simultaneous processes. A good correlation could be found between the measured emissions and the theoretically evaluated fate. It was concluded that the construction of a pilot-scale landfill is a useful method for studying simultaneous processes in landfills and that the emissions of organic compounds from landfills can be qualitatively predicted from literature data.     

Receptor model comparisons and wind direction analyses of volatile organic compounds and submicrometer particles in an arid, binational, urban air shed

The relationship between continuous measurements of volatile organic compounds sources and particle number was evaluated at a Photochemical Assessment Monitoring Station Network (PAMS) site located near the U.S.-Mexico Border in central El Paso, TX. Sources of volatile organic compounds (VOCs) were investigated using the multivariate receptor model UNMIX and the effective variance least squares receptor model known as Chemical Mass Balance (CMB, Version 8.0). As expected from PAMS measurements, overall findings from data screening as well as both receptor models confirmed that mobile sources were the major source of VOCs. Comparison of hourly source contribution estimates (SCEs) from the two receptor models revealed significant differences in motor vehicle exhaust and evaporative gasoline contributions. However, the motor vehicle exhaust contributions were highly correlated with each other. Motor vehicle exhaust was also correlated with the ultrafine and accumulation mode particle count, which suggests that motor vehicle exhaust is a source of these particles at the measurement site. Wind sector analyses were performed using the SCE and pollutant data to assess source location of VOCs, particle count, and criteria pollutants. Results from this study have application to source apportionment studies and mobile source emission control strategies that are ongoing in this air shed.     

Probabilistic approach to estimating indoor air concentrations of chlorinated volatile organic compounds from contaminated groundwater: a case study in San Antonio, Texas

This paper describes a probabilistic model, based on the Johnson-Ettinger algorithm, developed to characterize the current and historic exposure to tricholorethylene (TCE) and tetrachlorethylene (PCE) in indoor air from plumes of groundwater contamination emanating from the former Kelly Air Force Base in San Antonio, Texas. We estimate indoor air concentration, house by house, in 30?101 homes and compare the estimated concentrations with measured values in a small subset of homes. We also compare two versions of the Johnson-Ettinger model: one used by the Environmental Protection Agency (EPA) and another based on an alternative parametrization. The modeled mean predicted PCE concentration historically exceeded PCE screening levels (0.41 ug/m(3)) in 5.5% of houses, and the 95th percentile of the predicted concentration exceeded screening levels in 85.3% of houses. For TCE, the mean concentration exceeded the screening level (0.25 ug/m(3)) in 49% of homes, and the 95th percentile of the predicted concentration exceeded the screening level in 99% of homes. The EPA model predicts slightly lower indoor concentrations than the alternative parametrization. Comparison with measured samples suggests both models, with the inputs selected, underestimate indoor concentrations and that the 95th percentiles of the predicted concentrations are closer to measured concentrations than predicted mean values.