Emission of polycyclic aromatic hydrocarbons in China

Emission of 16 polycyclic aromatic hydrocarbons (PAHs) listed as U.S. Environmental Protection Agency (U.S. EPA) priority pollutants from major sources in China were compiled. Geographical distribution and temporal change of the PAH emission, as well as emission profiles, are discussed. It was estimated that the total PAH emission in China was 25,300 tons in 2003. The emission profile featured a relatively higher portion of high molecular weight (HMW) species with carcinogenic potential due to large contributions of domestic coal and coking industry. Among various sources, biomass burning, domestic coal combustion, and coking industry contributed 60%, 20%, and 16% of the total emission, respectively. Total emission, emission density, emission intensity, and emission per capita showed geographical variations. In general, the southeastern provinces were characterized by higher emission density, while those in western and northern China featured higher emission intensity and population-normalized emission. Although energy consumption in China went up continuously during the past two decades, annual emission of PAHs fluctuated depending on the amount of domestic coal consumption, coke production, and the efficiency of energy utilization.     

Weight of foods and number of portions consumed are not proxies for expressing nutrient intakes in field studies

In order to determine whether simplified indicators for usual consumption of selected food groups, specifically those derived from either the percentage of the number of daily portions, the percentage of total daily weight consumed, or both, could serve as proxies for the conventional expression of daily energy intake, these indicators were computed and compared from food-frequency data in a data set. Food consumption was reported in frequency categories and portion sizes per month, per week, or per day, and the cumulative sum was divided by 365 to provide a daily average. The survey was done in the township of Santa Cruz and three hamlets of a rural county seat in Guatemala. Data from food-frequency questionnaires from 269 individuals (55 men and 214 women aged 16 to 86 years) were analyzed. For foods of plant origin, the percentage of total energy, percentage of total food weight, and percentage of total number of portions consumed showed low correlations (r < .45). When subdivided into specific foods and food groups (fruits and vegetables, red meat, etc.), marked differences were revealed across sites and among different indicators of consumption. Despite the simplicity of calculation, neither the percentage of weight of food in a group nor the percentage of portions consumed could serve reliably as proxies for their contributions to the percentage of total energy in this rural population in Guatemala.     

Demonstration of a method for the direct determination of polycyclic aromatic hydrocarbons in submerged sediments

We describe the development of a novel method for real-time in situ characterization of polycyclic aromatic hydrocarbons (PAHs) in submerged freshwater sediments. Laser-induced fluorescence (LIF) spectroscopy, a mature technique for PAH characterization in terrestrial sediments, was adapted for shipboard use. A cone penetrometer-type apparatus was designed for probe penetration at a constant rate (1 cm/s) to a depth of 3 m. A field-portable LIF system was used for in situ measurements in which the output of a pulsed excimer laser was transmitted by optical fiber to a sapphire window (6.4-mm o.d.) in the probe wall; fluorescent emission was collected by a separate optical fiber for transmission to the spectrometer on deck. Four wavelengths (340, 390, 440, 490 nm) were selected via optical delay lines, and multiple-wavelength waveforms were created. These multiple-wavelength waveforms contain information on the fluorescence frequency, intensity, and emission decay rate. Field testing was conducted at 10 sites in Milwaukee Harbor (total PAH concentrations ranged from approximately 10 to 650 microg/g); conventional sediment core samples were collected concurrently. The core samples were analyzed by EPA methods 3545 (pressurized fluid extraction, PFE) and 8270C (gas chromatography-mass spectrometry, GC-MS) for PAHs. A partial least-squares regression (PLSR) model wasthen created based on laboratory LIF measurements and PFE-GC-MS of the core samples. The PLSR model was applied to the in situ field test data, and 13 of the 16 EPA-regulated PAHs were quantified with a relative error of <30% overall (the remaining three PAHs were found at levels insufficient to quantify). We additionally describe preliminary source apportionment relationships that were revealed by the PLSR model for the in situ LIF measurements.     

Compilation and application of Japanese inventories for energy consumption and air pollutant emissions using input-output tables

Preparing emission inventories is essential to the assessment and management of our environment. In this study, Japanese air pollutant emissions, energy consumption, and CO2 emissions categorized by approximately 400 sectors (as classified by Japanese input-output tables in 1995) were estimated, and the contributions of each sector to the total amounts were analyzed. The air pollutants examined were nitrogen oxides (NOx), sulfur oxides (SOx), and suspended particulate matter (SPM). Consumptions of about 20 fossil fuels and five other fuels were estimated according to sector. Air pollutant emission factors for stationary sources were calculated from the results of a survey on air pollution prevention in Japan. Pollutant emissions from mobile sources were estimated taking into consideration vehicle types, traveling speeds, and distances. This work also counted energy supply and emissions from seven nonfossil fuel sources, including nonthermal electric power, and CO2 emissions from limestone (for example, during cement production). The total energy consumption in 1995 was concluded to be 18.3 EJ, and the annual total emissions of CO2, NOx, SOx, and SPM were, respectively, 343 Mt-C, 3.51 Mt, 1.87 Mt, and 0.32 Mt. An input-output analysis of the emission inventories was used to calculate the amounts of energy consumption and emissions induced in each sector by the economic final demand.     

Particle size distribution and polycyclic aromatic hydrocarbons emissions from agricultural crop residue burning

Laboratory measurements were conducted to determine particle size distribution and polycyclic aromatic hydrocarbons (PAHs) emissions from the burning of rice, wheat, and corn straws, three major agricultural crop residues in China. Particle size distributions were determined by a wide-range particle spectrometer (WPS). PAHs in both the particulate and gaseous phases were simultaneously collected and analyzed by GC-MS. Particle number size distributions showed a prominent accumulation mode with peaks at 0.10, 0.15, and 0.15 μm for rice, wheat, and corn-burned aerosols, respectively. PAHs emission factors of rice, wheat, and corn straws were 5.26, 1.37, and 1.74 mg kg(-1), respectively. It was suggested that combustion with higher efficiency was characterized by smaller particle size and lower PAHs emission factors. The total PAHs emissions from the burning of three agricultural crop residues in China were estimated to be 1.09 Gg for the year 2004.     

Life cycle energy and greenhouse gas analysis of a large-scale vertically integrated organic dairy in the United States

In order to manage strategies to curb climate change, systemic benchmarking at a variety of production scales and methods is needed. This study is the first life cycle assessment (LCA) of a large-scale, vertically integrated organic dairy in the United States. Data collected at Aurora Organic Dairy farms and processing facilities were used to build a LCA model for benchmarking the greenhouse gas (GHG) emissions and energy consumption across the entire milk production system, from organic feed production to post-consumer waste disposal. Energy consumption and greenhouse gas emissions for the entire system (averaged over two years of analysis) were 18.3 MJ per liter of packaged fluid milk and 2.3 kg CO(2 )equiv per liter of packaged fluid milk, respectively. Methane emissions from enteric fermentation and manure management account for 27% of total system GHG emissions. Transportation represents 29% of the total system energy use and 15% of the total GHG emissions. Utilization of renewable energy at the farms, processing plant, and major transport legs could lead to a 16% reduction in system energy use and 6.4% less GHG emissions. Sensitivity and uncertainty analysis reveal that alternative meat coproduct allocation methods can lead to a 2.2% and 7.5% increase in overall system energy and GHG, respectively. Feed inventory data source can influence system energy use by -1% to +10% and GHG emission by -4.6% to +9.2%, and uncertainties in diffuse emission factors contribute -13% to +25% to GHG emission.     

Application of multiple linear regression to analysis of data from factory energy surveys

When energy surveys are carried out in factories, the usual method is to install expensive metering equipment and to measure energy flows to various parts of the plant. The costs involved in conducting surveys by this method are often prohibitively high. This paper describes an alternative survey method which is simple and inexpensive to use. An estimate of energy use for each product is obtained by the use of multiple linear regression to relate total energy consumption data from existing meters to production of the various products. The accuracy of the estimates depends on the form of the data set collected, but in most factories accurate values can be obtained for the major products. In all seventy-three factories where the technique was applied, it led to a useful analysis of total energy consumption. A summary of data collected in the New Zealand food manufacturing industry by application of the method is presented.     

Influence of local human population on atmospheric polycyclic aromatic hydrocarbon concentrations

Literature values of atmospheric polycyclic aromatic hydrocarbon (PAH) concentrations from sampling sites around the world were found, and using a high-resolution human population grid, the population within a 25-km radius of each sampling site was calculated. A regression of concentration vs population revealed much about PAH concentration differences among regions as well as site locations within a continent. The best fit for the regression was for sampling locations in North America. A small amount of scatter was present for the regression of all developed countries indicating slight differences in emission regulations or energy usage. The regression from this plot was used as a benchmark for the expected relationship between PAHs and human population. Sites located within 25 km of a coasttended to have concentrations lower than expected, due to dilution with clean ocean air, while sites near industrial outputs or other point sources had higher than expected concentrations. Sites from developing countries typically had PAH concentrations that were far higher than those of the rest of the world.     

PCDD/F,PCB, HxCBz,PAH, and PM emission factors for fireplace and woodstove combustion in the San Francisco Bay region

Emissions from residential fireplace and woodstove appliances burning fuels available from the San Francisco Bay area were sampled for polychlorinated dibenzodioxins and dibenzofurans (PCDDs/Fs), polychlorinated biphenyls (PCBs), hexachlorobenzene (HxCBz), particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs, and the monosaccharide levoglucosan. Emission factors for these pollutants were determined, the first known characterization of this extent. Common California natural firewoods and manufactured artificial logs were tested under operating conditions intended to reflect domestic use patterns in the Bay area, which are primarily episodic burning for aesthetic reasons. Emission factors were determined by fuel type, fuel weight, mass emission rates, and energy output, highlighting differences between fuel and combustion facility type. Average PCDD/F emissions factors ranged from 0.25 to 1.4 ng toxic equivalency (TEQ)/kg of wood burned for natural wood fuels and 2.4 ng TEQ/kg for artificial logs. The natural wood emission factors are slightly lower than those which had been estimated for the U.S. inventory. Background-corrected PCBs emitted from woodstove/oak combustion (8370 ng/kg) are 3 orders of magnitude higher in mass than total PCDDs/Fs; however, their toxicity (0.014 ng TEQ/kg) is significantly lower. HxCBz emission factors varied from 13 to 990 ng/kg and were likely fuel- and appliance-specific. Relative PAH concentrations of particle-phase compounds and emission factors were consistent with others' findings. A total of 32 PAH compounds, ranging in concentration from 0.06 to 7 mg/kg, amounted to between 0.12 and 0.38% of the PM mass, depending on the wood and facility type. Preliminary analyses suggest relationships between wood combustion markers and PCDD/F levels.     

Source apportionment of polycyclic aromatic hydrocarbons in the urban atmosphere: a comparison of three methods

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in urban atmospheres. Several PAHs are known carcinogens or are the precursors to carcinogenic daughter compounds. Understanding the contributions of the various emission sources is critical to appropriately managing PAH levels in the environment. The sources of PAHs to ambient air in Baltimore, MD, were determined by using three source apportionment methods, principal component analysis with multiple linear regression, UNMIX, and positive matrix factorization. Determining the source apportionment through multiple techniques mitigates weaknesses in individual methods and strengthens the overlapping conclusions. Overall source contributions compare well among methods. Vehicles, both diesel and gasoline, contribute on average 16-26%, coal 28-36%, oil 15-23%, and wood/other having the greatest disparity of 23-35% of the total (gas- plus particle-phase) PAHs. Seasonal trends were found for both coal and oil. Coal was the dominate PAH source during the summer while oil dominated during the winter. Positive matrix factorization was the only method to segregate diesel from gasoline sources. These methods indicate the number and relative strength of PAH sources to the ambient urban atmosphere. As with all source apportionment techniques, these methods require the user to objectively interpret the resulting source profiles.     

Atmospheric deposition of polycyclic aromatic hydrocarbons to Atlantic Canada: geographic and temporal distributions and trends 1980-2001

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants. The semivolatile organic compounds may disperse into the atmosphere by direct input from several sources such as the burning of fossil fuels, from motor vehicle emissions, and forest fires. Once in the atmosphere, they may travel great distances before being deposited to the earth's surface by the scavenging action of rain and snow. Up to 14 PAHs were determined in wet precipitation samples collected monthly from five sites in the four Canadian Atlantic Provinces during 1980-2001. The relatively more volatile PAHs (phenanthrene, fluoranthene, naphthalene, and pyrene) were predominant in the samples. Significant (P < 0.05) spatial variations in the deposition of some PAHs were observed among sites, but there were no consistent geographic patterns. Seasonal patterns were discernible with peak deposition for sigma6&14 PAHs occurring during the colder months of the year (December to March) and coinciding with higher energy consumption for heating and transport. The monthly volume weighed mean concentration for sigma6 PAHs has declined steadily since the mid-1980s at Kejimkujik National Park in southwest Nova Scotia, with a calculated half-life of 6.4 +/- 0.3 years. The maximum annual deposition flux of 20 microg m(-2) yr(-1) reached in 1985 for sigma6 PAHs decreased approximately 1 order of magnitude by the year 2000. The decrease in sigma6&14 PAHs for the region was found to be correlated (P < 0.05) with decreasing sulfate ion concentrations in the precipitation. The implementation of air pollution abatement programs in Canada, the United States, and elsewhere, switching to cleaner sources of energy and improved technology during the pastfew decades is most likely responsible for the observed decline.     

Polycyclic aromatic hydrocarbons in animal-based foods from Shanghai: bioaccessibility and dietary exposure

A total of 175 samples of 18 types of food were collected from markets in Shanghai, China, and the concentrations and bioaccessibility of 15 priority-controlled polycyclic aromatic hydrocarbons (PAHs) in these samples were determined. The mean concentrations of PAHs varied between 2.4 and 47.1?ng?g(-1) wet weight, with the highest being observed in snail and lowest in chicken. The concentrations were lower than the maximum levels of PAH allowed for food per EU regulations. Among the PAHs measured, phenanthrene was the predominant one. Most of the PAHs originated from pyrogenic sources, analysed using molecular indices. The mean bioaccessibility of PAHs varied from 29.0% to 61.2% as measured by simulating the human gastrointestinal digestion process. Linear relationships between the bioaccessibility and lipid contents were observed for most PAH congeners. The daily intake of PAHs by an average Shanghai resident was 848?ng?day(-1) and decreased to 297?ng?day(-1) when the bioaccessibility of PAHs were considered, demonstrating that most intake might have been overestimated. According to the potency equivalent concentrations and screening values of PAHs, consumption of snail and clam, especially snail, should be limited.     

Atmospheric transport and outflow of polycyclic aromatic hydrocarbons from China

A potential receptor influence function (PRIF) model, based on air mass forward trajectory calculations, was applied to simulate the atmospheric transport and outflow of polycyclic aromatic hydrocarbons (PAHs) emitted from China. With a 10 day atmospheric transport time, most neighboring countries and regions, as well as remote regions, were influenced by PAH emissions from China. Of the total annual PAH emission of 114 Gg, 92.7% remained within the boundary of mainland China. The geographic distribution of PRIFs within China was similar to the geographic distribution of the source regions, with high values in the North China Plain, Sichuan Basin, Shanxi, and Guizhou province. The Tarim basin and Sichuan basin had unfavorable meteorological conditions for PAH outflow. Of the PAH outflow from China (8092 tons or 7.1% of the total annual PAH emission), approximately 69.9% (5655 tons) reached no further than the offshore environment of mainland China and the South China Sea. Approximate 227, 71, 746, and 131 tons PAHs reached North Korea, South Korea, Russia-Mongolia region, and Japan, respectively, 2-4 days after the emission. Only 1.4 tons PAHs reached North America after more than 9 days. Interannual variation in the eastward PAH outflow was positively correlated to cold episodes of El Ni?o/Southern Oscillation. However, trans-Pacific atmospheric transport of PAHs from China was correlated to Pacific North America index (PNA) which is associated with the strength and position of westerly winds.     

Polycyclic aromatic hydrocarbons in animal-based foods from Shanghai: bioaccessibility and dietary exposure

A total of 175 samples of 18 types of food were collected from markets in Shanghai, China, and the concentrations and bioaccessibility of 15 priority-controlled polycyclic aromatic hydrocarbons (PAHs) in these samples were determined. The mean concentrations of PAHs varied between 2.4 and 47.1?ng?g^?1 wet weight, with the highest being observed in snail and lowest in chicken. The concentrations were lower than the maximum levels of PAH allowed for food per EU regulations. Among the PAHs measured, phenanthrene was the predominant one. Most of the PAHs originated from pyrogenic sources, analysed using molecular indices. The mean bioaccessibility of PAHs varied from 29.0% to 61.2% as measured by simulating the human gastrointestinal digestion process. Linear relationships between the bioaccessibility and lipid contents were observed for most PAH congeners. The daily intake of PAHs by an average Shanghai resident was 848?ng?day^?1 and decreased to 297?ng?day^?1 when the bioaccessibility of PAHs were considered, demonstrating that most intake might have been overestimated. According to the potency equivalent concentrations and screening values of PAHs, consumption of snail and clam, especially snail, should be limited.     

Predicting bioavailability of sediment-associated organic contaminants for Diporeia spp. and oligochaetes

Biota-sediment accumulation factors (BSAF) were calculated for Diporeia spp. and oligochaete worms exposed to polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) from field-collected sediment. These data were compared to the contaminant fraction extracted from sediment with Tenax resin using a 24 h extraction. A previous laboratory study suggested a linear relationship between log BSAF and the contaminant fraction rapidly desorbed from sediment. However, the BSAF data in our study did not fit this relationship. Better predictive regressions for both PCBs and PAHs were found when the log of the lipid-normalized organism contaminant concentrations were plotted against the log of the Tenax-extracted organic carbon-normalized sediment contaminant concentration. Regression lines for the two species had the same slope, but the Diporeia intercept was 2.3 times larger. When adjusted for a 6 h Tenax extraction, based on a regression between 6 and 24 h Tenax extractions, data from this study and two other studies that included multiple oligochaete species fit a single predictive regression. The exception included some PAHs that fell below the regression line. Thus, a single relationship generally predicted bioaccumulation across sediments, compound classes, oligochaete species, and among laboratories.     

Estimation of atmospheric emissions of six semivolatile polycyclic aromatic hydrocarbons in southern canada and the United States by use of an emissions processing system

Polycyclic aromatic hydrocarbons (PAHs) are toxic compounds that are ubiquitous in the atmospheric environment. The input for an emissions processing system that was originally configured forthe study of criteria air pollutants was updated to calculate emissions of six semivolatile PAHs. The goal of the work was to produce emissions estimates with the spatial and temporal resolution needed to serve as input to a regional air quality model for southern Canada and the U.S. Such modeling is helpful in determining reductions in PAH emissions that may be necessary to protect human and ecosystem health. The total annual emission of the six PAHs (sigma6PAH) for both countries was estimated at 18 273 Mg/year. A total of 90% of these emissions arise from U.S. sources. The top six source types account for 73% of emissions and are related to metal production, open burning, incineration, and forest fires. The emission factors used in this study were derived from published compilations. Although this approach has the advantage of quality control during the compilation process, some compilations include factors from older studies that may overestimate emissions since they do not account for recent improvements in emission control technology. When compared to estimates published in the National Emissions Inventory (NEI) for 2002, the U.S. emissions in this study are higher by a factor of 4 (16 424 vs 4102 Mg/year). The cause of this difference has been investigated, and much of it is likely due to our use of data unavailable in the 2002 NEI but inferred here on the basis of the PAH emissions literature. Augmenting the 2002 NEI with this additional information would bring its reported annual emissions to 8213 Mg/year, which is within a factor of 2 of the estimates herein. The results presented for southern Canada are the first published values for all known PAH sources in that country.     

Spatial distributions and profiles of atmospheric polycyclic aromatic hydrocarbons in two industrial cities in Japan

The spatial distribution and concentration profiles of 39 vapor and particulate polycyclic aromatic hydrocarbons (PAHs) have been investigated in two Japanese industrial cities (Fuji and Shimizu; a summer and winter season in each). The concentrations of particulate PAHs in winter tended to be higher than those in the summer, but for vapor PAHs, this was not the case. Significant correlations (p < 0.01) were found between most of the PAH concentrations monitored in winter, suggesting the presence of common emission sources. To identify PAH spatial distributions and emission sources in the area, we created contour maps for PAHs monitored; this indicates that the distinctive local distributions correspond to the emission sources. PAH profiles based on benzo[e]pyrene (BeP) concentration, especially for certain relatively heavy molecular weight PAHs, showed differential behaviors among divided areas related to potential regional emission sources such as paper-making plants, power plants, and traffic. We conclude that the origins of atmospheric PAHs in the surveyed areas were dominated by not only traffic but also by stationary emission sources such as paper-making plants and power plants and that local distributions were dependent on the local wind direction.     

Polycyclic aromatic hydrocarbons in riverine runoff of the Pearl River Delta (China): concentrations, fluxes, and fate

On the basis of a monthly sampling effort from March 2005 to February 2006, the total concentrations of the sums of 27 and 15 polycyclic aromatic hydrocarbons (defined as sigma27PAHs and sigma15PAHs, respectively) in riverine runoff of the Pearl River Delta (PRD), China, and associated fluxes were determined. No clear temporal and spatial trends of PAH concentrations were found at all eight riverine runoff outlets where the samples were collected. The annual fluxes of sigma27PAHs and sigma15PAHs from the PRD to the coastal ocean were 60.2 and 33.9 metric tons, respectively. Assuming that riverine flux was positively related to the regional emission of PAHs, the annual riverine fluxes from five major rivers in China to the global oceans were estimated, which are quite significant relative to other major rivers of the world. On the basis of mass balance considerations, approximately 87% of sigma15PAHs inputting to the Pearl River Estuary and northern South China Sea was derived from riverine runoff from the PRD. In addition, approcimately 22.3 metric tons of sigma15PAHs annually outflow to open seas, which is equivalent to a concentration of 0.34 pg/L in the global oceans if the PAHs are evenly distributed in the upper 200 m of the water column. A comparison with the global background level of PAHs indicated that approximately 0.4% of PAHs in the open oceans may have been contributed by 1-year discharge from the PRD.     

Atmospheric polycyclic aromatic hydrocarbons in north China: a winter-time study

The contamination and outflow of atmospheric polycyclic aromatic hydrocarbons (PAHs) in the Chinese Northern Plain, a region with a total area of 300 000 km2 and a high PAH emission density, were investigated. Polyurethane foam (PUF) and PM10 samples were collected at 46 sites located in urban, rural (towns or villages), and control (remote mountain) areas in the winter from November 2005 to February 2006. The observed concentrations of atmospheric PAHs were generally higher than those reported for developed countries and southern Chinese cities. It was found that there was no significant difference in air PAH concentrations between the urban and the rural areas (514 +/- 563 ng/m3 and 610 +/- 645 ng/ m3, respectively), while the PAH concentrations at the control sites (57.1 +/- 12.6 ng/m3) were 1 order of magnitude lower than those at the other sites. The primary reason for the similarity in PAH concentrations between urban and rural areas was the fact that the predominant sources of biomass and domestic coal combustion were widely spread over the study area. The partition constants (K(PM10)) of PAHs were significantly correlated to the corresponding values of subcooled liquid-vapor pressure (pL0). However, the regression slopes of log K(PM10) versus log pL0 were much steeper than -1, indicating adsorption dominated over absorption. Three distinct patterns of outflow from the study area were identified by forward trajectory and cluster analysis.     

Biomimetic extraction of PAHs and PCBs from soil with octadecyl-modified silica disks to predict their availability to earthworms

We developed a model to predict the availability of PAHs and PCBs to earthworms (Lumbricus terrestris L.) in soils. We related the uptake of PAHs and PCBs by earthworms to the extraction with octadecyl-modified silica disks (C18 disks). Eleven soils (data set A) were used to develop the model, and 14 additional soils (data set B) were used to validate it independently. The biota-to-soil accumulation factors (BSAFs) of higher molecular weight PAHs (> or =202 g mol(-1)) and PCBs were higher than the corresponding Cl8 disk-soil partition coefficients (Kdisk) in the soils of data set A. This suggested that PAHs and PCBs were not only partitioned between soil and earthworms but also selectively ingested or metabolized. Nevertheless, we could predict the BSAFs of individual PAHs and PCBs for data set A by regression equations of log BSAF on log Kdisk (r=0.47-0.87). To predict the BSAFs of all PAHs and PCBs, respectively, we derived a model for each compound class that uses Kdisk and K(ow) values. Both the compound and the compound-class specific model were suitable to predict the BSAFs of PAHs and PCBs in data set B within a factor of 10-15.