A review of airborne polycyclic aromatic hydrocarbons (PAHs) and their human health effects

Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds comprised of two or more fused benzene rings arranged in various configurations. PAHs are widespread environmental contaminants formed as a result of incomplete combustion of organic materials such as fossil fuels. The occurrence of PAHs in ambient air is an increasing concern because of their carcinogenicity and mutagenicity. Although emissions and allowable concentrations of PAHs in air are now regulated, the health risk posed by PAH exposure suggests a continuing need for their control through air quality management. In light of the environmental significance of PAH exposure, this review offers an overview of PAH properties, fates, transformations, human exposure, and health effects (acute and chronic) associated with their emission to the atmosphere. Biomarkers of PAH exposure and their significance are also discussed.

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.

Effects of biochar and greenwaste compost amendments on mobility, bioavailability and toxicity of inorganic and organic contaminants in a multi-element polluted soil

Applying amendments to multi-element contaminated soils can have contradictory effects on the mobility, bioavailability and toxicity of specific elements, depending on the amendment. Trace elements and PAHs were monitored in a contaminated soil amended with biochar and greenwaste compost over 60 days field exposure, after which phytotoxicity was assessed by a simple bio-indicator test. Copper and As concentrations in soil pore water increased more than 30 fold after adding both amendments, associated with significant increases in dissolved organic carbon and pH, whereas Zn and Cd significantly decreased. Biochar was most effective, resulting in a 10 fold decrease of Cd in pore water and a resultant reduction in phytotoxicity. Concentrations of PAHs were also reduced by biochar, with greater than 50% decreases of the heavier, more toxicologically relevant PAHs. The results highlight the potential of biochar for contaminated land remediation.

Global atmospheric emissions of polycyclic aromatic hydrocarbons from 1960 to 2008 and future predictions

Global atmospheric emissions of 16 polycyclic aromatic hydrocarbons (PAHs) from 69 major sources were estimated for a period from 1960 to 2030. Regression models and a technology split method were used to estimate country and time specific emission factors, resulting in a new estimate of PAH emission factor variation among different countries and over time. PAH emissions in 2007 were spatially resolved to 0.1° × 0.1° grids based on a newly developed global high-resolution fuel combustion inventory (PKU-FUEL-2007). The global total annual atmospheric emission of 16 PAHs in 2007 was 504 Gg (331-818 Gg, as interquartile range), with residential/commercial biomass burning (60.5%), open-field biomass burning (agricultural waste burning, deforestation, and wildfire, 13.6%), and petroleum consumption by on-road motor vehicles (12.8%) as the major sources. South (87 Gg), East (111 Gg), and Southeast Asia (52 Gg) were the regions with the highest PAH emission densities, contributing half of the global total PAH emissions. Among the global total PAH emissions, 6.19% of the emissions were in the form of high molecular weight carcinogenic compounds and the percentage of the carcinogenic PAHs was higher in developing countries (6.22%) than in developed countries (5.73%), due to the differences in energy structures and the disparities of technology. The potential health impact of the PAH emissions was greatest in the parts of the world with high anthropogenic PAH emissions, because of the overlap of the high emissions and high population densities. Global total PAH emissions peaked at 592 Gg in 1995 and declined gradually to 499 Gg in 2008. Total PAH emissions from developed countries peaked at 122 Gg in the early 1970s and decreased to 38 Gg in 2008. Simulation of PAH emissions from 2009 to 2030 revealed that PAH emissions in developed and developing countries would decrease by 46-71% and 48-64%, respectively, based on the six IPCC SRES scenarios.

Search for past life on Mars: possible relic biogenic activity in martian meteorite ALH84001

Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest that the PAHs are indigenous to the meteorite. High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and Fe-sulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features, including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota.

Organic micropollutants in marine plastics debris from the open ocean and remote and urban beaches

To understand the spatial variation in concentrations and compositions of organic micropollutants in marine plastic debris and their sources, we analyzed plastic fragments (∼10 mm) from the open ocean and from remote and urban beaches. Polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dichloro-diphenyl-trichloroethane and its metabolites (DDTs), polybrominated diphenyl ethers (PBDEs), alkylphenols and bisphenol A were detected in the fragments at concentrations from 1 to 10,000 ng/g. Concentrations showed large piece-to-piece variability. Hydrophobic organic compounds such as PCBs and PAHs were sorbed from seawater to the plastic fragments. PCBs are most probably derived from legacy pollution. PAHs showed a petrogenic signature, suggesting the sorption of PAHs from oil slicks. Nonylphenol, bisphenol A, and PBDEs came mainly from additives and were detected at high concentrations in some fragments both from remote and urban beaches and the open ocean.

Organics Captured from Comet 81P/Wild 2 by the Stardust Spacecraft

Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.

Adsorption of polycyclic aromatic hydrocarbons by carbon nanomaterials

Carbon nanomaterials are novel manufactured materials, having widespread potential applications. Adsorption of hydrophobic organic compounds (HOCs) by carbon nanomaterials may enhance their toxicity and affect the fate, transformation, and transport of HOCs in the environment. In this research, adsorption of naphthalene, phenanthrene, and pyrene onto six carbon nanomaterials, including fullerenes, single-walled carbon nanotubes, and multiwalled carbon nanotubes was investigated, which is the first systematic study on polycyclic aromatic hydrocarbons (PAHs) sorption by various carbon nanomaterials. All adsorption isotherms were nonlinear and were fitted well by the Polanyi-Manes model (PMM). Through both isotherm modeling and constructing "characteristic curve", Polanyi theory was useful to describe the adsorption process of PAHs by the carbon nanomaterials. The three fitted parameters (Q0, a, and b) of PMM depended on both PAH properties and the nature of carbon nanomaterials. For different PAHs, adsorption seems to relate with their molecular size, i.e., the larger the molecular size, the lower the adsorbed volume capacity (Q0), but higher a and b values. For different carbon nanomaterials, adsorption seems to relate with their surface area, micropore volume, and the volume ratios of mesopore to micropore. Quantitative relationships between these sorbent properties and the estimated parameters of PMM were obtained. These relationships may represent a first fundamental step toward establishing empirical equations for quantitative prediction of PAH adsorption by carbon nanomaterials and possibly other forms of carbonaceous (geo-) sorbents, and for evaluating their environmental impact. In addition, high adsorption capacity of PAHs by carbon nanotubes may add to their high environmental risks once released to the environment, and result in potential alteration of PAHs fate and bioavailability in the environment.

Quality assessment of the blue mussel (Mytilus edulis): comparison between commercial and wild types

This study compared species identity, microplastics, chemical and microbial contamination between consumption mussels and wild type mussels, collected at Belgian department stores and Belgian groynes and quaysides, respectively. Species identification based on genetic analysis showed a high number of Mytilus (M.) edulis compared to M. galloprovincialis and M. edulis/galloprovincialis hybrid mussels. The number of total microplastics varied from 2.6 to 5.1 fibres/10 g of mussel. A higher prevalence of orange fibres at quaysides is related to fisheries activities. Chemical contamination of polycyclic aromatic hydrocarbons and polychlorobiphenyls could be related to industrial activities and water turbidity, with maximum concentrations at the quayside of port Zeebrugge. The inverse was noted for Escherichia coli contamination, which was relatively low at Zeebrugge quayside with a total count of 3.9 × 10(2)CFU/100 g tissue, due to limited agricultural effluents. Results of this complementary analysis stress the importance of integrated monitoring and quality assessment.

Ambient particulate pollutants in the ultrafine range promote early atherosclerosis and systemic oxidative stress

Air pollution is associated with significant adverse health effects, including increased cardiovascular morbidity and mortality. Exposure to particulate matter with an aerodynamic diameter of <2.5 microm (PM(2.5)) increases ischemic cardiovascular events and promotes atherosclerosis. Moreover, there is increasing evidence that the smallest pollutant particles pose the greatest danger because of their high content of organic chemicals and prooxidative potential. To test this hypothesis, we compared the proatherogenic effects of ambient particles of <0.18 microm (ultrafine particles) with particles of <2.5 microm in genetically susceptible (apolipoprotein E-deficient) mice. These animals were exposed to concentrated ultrafine particles, concentrated particles of <2.5 microm, or filtered air in a mobile animal facility close to a Los Angeles freeway. Ultrafine particle-exposed mice exhibited significantly larger early atherosclerotic lesions than mice exposed to PM(2.5) or filtered air. Exposure to ultrafine particles also resulted in an inhibition of the antiinflammatory capacity of plasma high-density lipoprotein and greater systemic oxidative stress as evidenced by a significant increase in hepatic malondialdehyde levels and upregulation of Nrf2-regulated antioxidant genes. We conclude that ultrafine particles concentrate the proatherogenic effects of ambient PM and may constitute a significant cardiovascular risk factor.

Export of toxic chemicals - a review of the case of uncontrolled electronic-waste recycling

This paper reviews the concentrations of persistent organic pollutants such as flame retardants (PBDEs), dioxins/furans (PCDD/Fs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and heavy metals/metalloid concentrations of different environmental media at Guiyu, a traditional rice-growing village located in southeastern Guangdong Province (PR China), which has turned into an intensive electronic-waste (e-waste) recycling site. Incomplete combustion of e-waste in open air and dumping of processed materials are the major sources of various toxic chemicals. By comparing with existing data available in other areas and also guidelines adopted in different countries, it is obvious that the environment is highly contaminated by these toxic chemicals derived from the recycling processes. For example, the monthly concentration of the sum of 22 PBDE congeners contained in PM(2.5) (16.8ngm(-3)) of air samples at Guiyu was 100 times higher than published data. In order to safeguard the environment and human health, detailed investigations are urgently needed, especially on tracking the exposure pathways of different toxic chemicals which may affect the workers and local residents especially mothers, infants and children.

Distribution of polycyclic aromatic hydrocarbons (PAHs) in rivers and estuaries in Malaysia: a widespread input of petrogenic PAHs

This is the first publication on the distribution and sources of polycyclic aromatic hydrocarbons (PAHs) in riverine and coastal sediments in South East Asia where the rapid transfer of land-based pollutants into aquatic environments by heavy rainfall and runoff waters is of great concern. Twenty-nine Malaysian riverine and coastal sediments were analyzed for PAHs (3-7 rings) by gas chromatography mass spectrometry. Total PAHs concentrations in the sediment ranged from 4 to 924 ng/g. Alkylated homologues were abundant for all sediment samples. The ratio of the sum of methylphenanthrenes to phenanthrene (MP/P), an index of petrogenic PAHs contribution, was more than unity for 26 sediment samples and more than 3 for seven samples for urban rivers covering a broad range of locations. The MP/P ratio showed a strong correlation with the total PAHs concentrations, with an r2 value of 0.74. This ratio and all other compositional features indicated that Malaysian urban sediments are heavily impacted by petrogenic PAHs. This finding is in contrast to other studies reported in many industrialized countries where PAHs are mostly of pyrogenic origin. The MP/P ratio was also significantly correlated with higher molecular weight PAHs such as benzo[a]pyrene, suggesting unique PAHs source in Malaysia which contains both petrogenic PAHs and pyrogenic PAHs. PAHs and hopanes fingerprints indicated that used crankcase oil is one of the major contributors of the sedimentary PAHs. Two major routes of inputs to aquatic environments have been identified: (1) spillage and dumping of waste crankcase oil and (2) leakage of crankcase oils from vehicles onto road surfaces, with the subsequent washout by street runoff. N-Cyclohexyl-2-benzothiazolamine (NCBA), a molecular marker of street dust, was detected in the polluted sediments. NCBA and other biomarker profiles confirmed our hypothesis of the input from street dust contained the leaked crankcase oil. The fingerprints excluded crude oil, fresh lubricating oil, asphalt, and tire-particles as major contributors.

Contaminants in the Canadian Arctic: 5 years of progress in understanding sources, occurrence and pathways

Recent studies of contaminants under the Canadian Northern Contaminants Program (NCP) have substantially enhanced our understanding of the pathways by which contaminants enter Canada's Arctic and move through terrestrial and marine ecosystems there. Building on a previous review (Barrie et al., Arctic contaminants: sources, occurrence and pathways. Sci Total Environ 1992:1-74), we highlight new knowledge developed under the NCP on the sources, occurrence and pathways of contaminants (organochlorines, Hg, Pb and Cd, PAHs, artificial radionuclides). Starting from the global scale, we examine emission histories and sources for selected contaminants focussing especially on the organochlorines. Physical and chemical properties, transport processes in the environment (e.g. winds, currents, partitioning), and models are then used to identify, understand and illustrate the connection between the contaminant sources in industrial and agricultural regions to the south and the eventual arrival of contaminants in remote regions of the Arctic. Within the Arctic, we examine how contaminants impinge on marine and terrestrial pathways and how they are subsequently either removed to sinks or remain where they can enter the biosphere. As a way to focus this synthesis on key concerns of northern residents, a number of special topics are examined including: a mass balance for HCH and toxaphene (CHBs) in the Arctic Ocean; a comparison of PCB sources within Canada's Arctic (Dew Line Sites) with PCBs imported through long-range transport; an evaluation of concerns posed by three priority metals--Hg, Pb and Cd; an evaluation of the risks from artificial radionuclides in the ocean; a review of what is known about new-generation pesticides that are replacing the organochlorines; and a comparison of natural vs. anthropogenic sources of PAH in the Arctic. The research and syntheses provide compelling evidence for close connectivity between the global emission of contaminants from industrial and agricultural activities and the Arctic. For semi-volatile compounds that partition strongly into cold water (e.g. HCH) we have seen an inevitable loading of Arctic aquatic reservoirs. Drastic HCH emission reductions have been rapidly followed by reduced atmospheric burdens with the result that the major reservoir and transport agent has become the ocean. In the Arctic, it will take decades for the upper ocean to clear itself of HCH. For compounds that partition strongly onto particles, and for which the soil reservoir is most important (e.g. PCBs), we have seen a delay in their arrival in the Arctic and some fractionation toward more volatile compounds (e.g. lower-chlorinated PCBs). Despite banning the production of PCB in the 1970s, and despite decreases of PCBs in environmental compartments in temperate regions, the Arctic presently shows little evidence of reduced PCB loadings. We anticipate a delay in PCB reductions in the Arctic and environmental lifetimes measured in decades. Although artificial radionuclides have caused great concern due to their direct disposal on Russian Shelves, they are found to pose little threat to Canadian waters and, indeed, much of the radionuclide inventory can be explained as remnant global fallout, which was sharply curtailed in the 1960s, and waste emissions released under license by the European reprocessing plants. Although Cd poses a human dietary concern both for terrestrial and marine mammals, we find little evidence that Cd in marine systems has been impacted by human activities. There is evidence of contaminant Pb in the Arctic, but loadings appear presently to be decreasing due to source controls (e.g. removal of Pb from gasoline) in Europe and North America. Of the metals, Hg provokes the greatest concern; loadings appear to be increasing in the Arctic due to global human activities, but such loadings are not evenly distributed nor are the pathways by which they enter and move within the Arctic well understood.

Interstellar polycyclic aromatic hydrocarbons: the infrared emission bands, the excitation/emission mechanism, and the astrophysical implications

This article presents a comprehensive treatment of the polycyclic aromatic hydrocarbon (PAH) hypothesis. The interstellar, infrared spectral features which have been attributed to emission from highly vibrationally excited PAHs are discussed in detail. These include major (most intense) bands at 3040, 1615, "1310," 1150, and 885 cm-1 (3.29, 6.2 "7.7," 8.7, and 11.3 micrometers), minor bands and broad features in the 3200-2700 cm-1 [correction of 3200-2700-1] (3.1-3.7 micrometers), 1600-1100 cm-1 (6.0-9 micrometers) and 910-770 cm-1 (11-13 micrometers) regions, as well as the vibrational quasi-continuum spanning the entire mid-IR and the electronic transitions which contribute to the high-frequency IR continuum. All the major and minor bands, as well as the quasi-continuum, can be attributed to vibrational transitions in molecular-sized PAHs. The latter two broad features probably arise from very large PAHs, PAH clusters, and amorphous carbon particles. A precise match of the interstellar spectra with laboratory spectra is not yet possible because laboratory spectra are not available of PAHs in the forms probably present in the interstellar medium (completely isolated, ionized, some completely dehydrogenated, and containing between about 20 and 40 carbon atoms). The method with which one can calculate the IR fluorescence spectrum from a vibrationally excited molecule is also described in detail. Fluorescence band intensities, relaxation rates, and dependence on molecule size and energy content are treated explicitly. Analysis of the interstellar spectra indicates that the PAHs which dominate the infrared spectra contain between about 20 and 40 carbon atoms. The results obtained with this method are compared with the results obtained using a thermal approximation. It is shown that for high levels of vibrational excitation and emission from low-frequency modes, the two methods give similar results. However, at low levels of vibrational excitation and for the high-frequency modes (for example, the 3040 cm-1, 3.3 micrometers band), the thermal approach overestimates the emission intensities. For calculations of molecular reactions (such as H-loss, deuterium enrichment, and carbon skeleton rearrangement) a thermal approximation is invalid. The relationship between PAH molecules and amorphous carbon particles is presented and their production in circumstellar shells is described. The most likely interstellar PAH molecular structures are discussed and the possibility of destructive reactions with interstellar oxygen and hydrogen atoms is considered in detailed and found to be unimportant. Interstellar PAH size and abundance estimates are made. On the order of a few percent of the available interstellar carbon is tied up in the small (20-40 carbon atom) PAHs which are responsible for the sharp features, and a similar amount is tied up in the larger (200-500 carbon atom) PAHs or PAH clusters and amorphous carbon particles which are responsible for the broad components underlying the 1600-1100 and 900-770 cm-1 (6-9 and 11-13 micrometers) regions. It is shown that the spectroscopic structure these PAHs and PAH-related materials produce in the UV portion of the interstellar extinction curve lie just below current detection limits but fall in the range detectable by the Hubble Space Telescope. Finally, the influence of PAH charge on the ultraviolet, visible, and infrared regions is described.

Effect of prenatal exposure to airborne polycyclic aromatic hydrocarbons on neurodevelopment in the first 3 years of life among inner-city children

Our prospective cohort study of nonsmoking African-American and Dominican mothers and children in New York City is evaluating the role of prenatal exposure to urban pollutants, including polycyclic aromatic hydrocarbons (PAHs) , environmental tobacco smoke (ETS) , and pesticides, in the pathogenesis of neurobehavioral disorders. We used the Bayley Scales of Infant Development to evaluate the effects on child mental and psychomotor development of prenatal exposure to airborne PAHs monitored during pregnancy by personal air sampling. Behavioral development was assessed by the Child Behavior Checklist. We adjusted for potential confounders including sociodemographic factors and prenatal exposure to ETS and chlorpyrifos. Prenatal exposure to PAHs was not associated with psychomotor development index or behavioral problems. However, high prenatal exposure to PAHs (upper quartile) was associated with lower mental development index at age 3 [beta=-5.69; 95% confidence interval (CI), -9.05 to -2.33; p<0.01]. The odds of cognitive developmental delay were also significantly greater for children with high prenatal exposure (odds ratio=2.89; 95% CI, 1.33 to 6.25; p=0.01). General estimated equation analysis showed a significant age times PAH effect on mental development (p=0.01), confirming the age-specific regression findings. Further adjustment for lead did not alter the relationships. There were no differences in effect sizes by ethnicity. The results require confirmation but suggest that environmental PAHs at levels recently encountered in New York City air may adversely affect children's cognitive development at 3 years of age, with implications for school performance.

Remediation approaches for polycyclic aromatic hydrocarbons (PAHs) contaminated soils: Technological constraints, emerging trends and future directions

For more than a decade, the primary focus of environmental experts has been to adopt risk-based management approaches to cleanup PAH polluted sites that pose potentially destructive ecological consequences. This focus had led to the development of several physical, chemical, thermal and biological technologies that are widely implementable. Established remedial options available for treating PAH contaminated soils are incineration, thermal conduction, solvent extraction/soil washing, chemical oxidation, bioaugmentation, biostimulation, phytoremediation, composting/biopiles and bioreactors. Integrating physico-chemical and biological technologies is also widely practiced for better cleanup of PAH contaminated soils. Electrokinetic remediation, vermiremediation and biocatalyst assisted remediation are still at the development stage. Though several treatment methods to remediate PAH polluted soils currently exist, a comprehensive overview of all the available remediation technologies to date is necessary so that the right technology for field-level success is chosen. The objective of this review is to provide a critical overview in this respect, focusing only on the treatment options available for field soils and ignoring the spiked ones. The authors also propose the development of novel multifunctional green and sustainable systems like mixed cell culture system, biosurfactant flushing, transgenic approaches and nanoremediation in order to overcome the existing soil- contaminant- and microbial-associated technological limitations in tackling high molecular weight PAHs. The ultimate objective is to ensure the successful remediation of long-term PAH contaminated soils.

Organic pollutants in microplastics from two beaches of the Portuguese coast

Microplastics pose a threat to coastal environments due to their capacity to adsorb persistent organic pollutants (POPs). These particles (less than 5 mm in size) are potentially dangerous to marine species due to magnification risk over the food chain. Samples were collected from two Portuguese beaches and sorted in four classes to relate the adsorption capacity of pollutants with color and age. Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and DDTs were analysed on pellets through gas chromatography mass spectrometry (GC-MS), and types of plastic were identified using Fourier transformed infra-red spectroscopy (micro-FTIR). Microplastics were mostly polyethylene and polypropylene. Regarding sizes, some fibres ranged from 1 to 5 μm in diameter and were 500 μm in length. The majority of samples collected had sizes above 200 μm. Black pellets, unlike aged pellets, had the highest concentrations of POPs except for PAHs in Fonte da Telha beach. PAHs with higher concentrations were pyrene, phenantrene, chrysene and fluoranthene. Higher concentrations of PCBs were found for congeners 18, 31, 138 and 187. Further investigation is necessary to understand the relationship between plastic degradation and adsorption for different pollutants.

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.

A comparison of mainstream and sidestream marijuana and tobacco cigarette smoke produced under two machine smoking conditions

The chemical composition of tobacco smoke has been extensively examined, and the presence of known and suspected carcinogens in such smoke has contributed to the link between tobacco smoking and adverse health effects. The consumption of marijuana through smoking remains a reality and, among youth, seems to be increasing. There have been only limited examinations of marijuana smoke, including for cannabinoid content and for tar generation. There have not been extensive studies of the chemistry of marijuana smoke, especially in direct comparison to tobacco smoke. In this study, a systematic comparison of the smoke composition of both mainstream and sidestream smoke from marijuana and tobacco cigarettes prepared in the same way and consumed under two sets of smoking conditions, was undertaken. This study examined the suite of chemicals routinely analyzed in tobacco smoke. As expected, the results showed qualitative similarities with some quantitative differences. In this study, ammonia was found in mainstream marijuana smoke at levels up to 20-fold greater than that found in tobacco. Hydrogen cyanide, NO, NO x , and some aromatic amines were found in marijuana smoke at concentrations 3-5 times those found in tobacco smoke. Mainstream marijuana smoke contained selected polycyclic aromatic hydrocarbons (PAHs) at concentrations lower than those found in mainstream tobacco smoke, while the reverse was the case for sidestream smoke, with PAHs present at higher concentrations in marijuana smoke. The confirmation of the presence, in both mainstream and sidestream smoke of marijuana cigarettes, of known carcinogens and other chemicals implicated in respiratory diseases is important information for public health and communication of the risk related to exposure to such materials.

Sorption capacity of plastic debris for hydrophobic organic chemicals

The occurrence of microplastics (MPs) in the ocean is an emerging world-wide concern. Due to high sorption capacity of plastics for hydrophobic organic chemicals (HOCs), sorption may play an important role in the transport processes of HOCs. However, sorption capacity of various plastic materials is rarely documented except in the case of those used for environmental sampling purposes. In this study, we measured partition coefficients between MPs and seawater (KMPsw) for 8 polycyclic aromatic hydrocarbons (PAHs), 4 hexachlorocyclohexanes (HCHs) and 2 chlorinated benzenes (CBs). Three surrogate polymers - polyethylene, polypropylene, and polystyrene - were used as model plastic debris because they are the major components of microplastic debris found. Due to the limited solubility of HOCs in seawater and their long equilibration time, a third-phase partitioning method was used for the determination of KMPsw. First, partition coefficients between polydimethylsiloxane (PDMS) and seawater (KPDMSsw) were measured. For the determination of KMPsw, the distribution of HOCs between PDMS or plastics and solvent mixture (methanol:water=8:2 (v/v)) was determined after apparent equilibrium up to 12 weeks. Plastic debris was prepared in a laboratory by physical crushing; the median longest dimension was 320-440 μm. Partition coefficients between polyethylene and seawater obtained using the third-phase equilibrium method agreed well with experimental partition coefficients between low-density polyethylene and water in the literature. The values of KMPsw were generally in the order of polystyrene, polyethylene, and polypropylene for most of the chemicals tested. The ranges of log KMPsw were 2.04-7.87, 2.18-7.00, and 2.63-7.52 for polyethylene, polypropylene, and polystyrene, respectively. The partition coefficients of plastic debris can be as high as other frequently used partition coefficients, such as 1-octanol-water partition coefficients (Kow) and log KMPsw showed good linear correlations with log Kow. High sorption capacity of microplastics implies the importance of MP-associated transport of HOCs in the marine environment.

Thin-film microextraction

The properties of a thin sheet of poly(dimethylsiloxane) (PDMS) membrane as an extraction phase were examined and compared to solid-phase microextraction (SPME) PDMS-coated fiber for application to semivolatile analytes in direct and headspace modes. This new PDMS extraction approach showed much higher extraction rates because of the larger surface area to extraction-phase volume ratio of the thin film. Unlike the coated rod formats of SPME using thick coatings, the high extraction rate of the membrane SPME technique allows larger amounts of analytes to be extracted within a short period of time. Therefore, higher extraction efficiency and sensitivity can be achieved without sacrificing analysis time. In direct membrane SPME extraction, a linear relationship was found between the initial rate of extraction and the surface area of the extraction phase. However, for headspace extraction, the rates were somewhat lower because of the resistance to analyte transport at the sample matrix/headspace barrier. It was found that the effect of this barrier could be reduced by increasing either agitation, temperature, or surface area of the sample matrix/headspace interface. A method for the determination of PAHs in spiked lake water samples was developed based on the membrane PDMS extraction coupled with GC/MS. A linearity of 0.9960 and detection limits in the low-ppt level were found. The reproducibility was found to vary from 2.8% to 10.7%.

Assessing the combined roles of natural organic matter and black carbon as sorbents in sediments

We hypothesized that two mechanisms, absorption into natural organic matter and adsorption onto combustion-derived black carbon (BC), act in parallel to bind polycyclic aromatic hydrocarbons (PAHs) to Boston Harbor sediments. To focus on BC-adsorption, we removed the non-BC fraction by combusting near shore sediments at 375 degrees C for 24 h under air, leaving ca. 16% of the reduced carbon. The isotherm for pyrene sorption onto our combusted sediment was nonlinear with a Freundlich exponent of 0.62+/-0.12 and a BC-normalized distribution coefficient (microg/ kgBC)/(microg/L)n of 10(6.25)+/-0.14. Pyrene sorption to untreated sediment was reasonably estimated using Kd = f(oc) 10(4.7) + fBC 10(6.25) Cw(0.62-1) where f(oc) was the non-BC organic carbon content, 10(4.7) was the organic carbon-normalized absorption coefficient for pyrene (L/kg(oc)), fBC was the BC content, and Cw was the dissolved pyrene concentration (microg/ L). C/H/N ratios indicated that our environmental BC differed substantially from NIST diesel soot, possibly due to inclusion of larger BC particles from near source atmospheric fallout and urban runoff. The impact of BC on total PAH sorption may explain reports of nonlinear isotherms, Koc values for PAHs that exceed their respective Kow values, and discrepancies in bioavailability between planar and nonplanar sorbates.

Polycyclic aromatic hydrocarbons in urban soils of Beijing: status, sources, distribution and potential risk

We studied the source, concentration, spatial distribution and health risk of 16 polycyclic aromatic hydrocarbons (PAHs) in urban soils of Beijing. The total mass concentration of 16 PAHs ranged from 93 to 13,141 μg kg(-1) with a mean of 1228 μg kg(-1). The contour map of soil PAH concentrations showed that the industrial zone, the historical Hutong district and the university district of Beijing have significantly higher concentrations than those in remainder of the city. The results of sources identification suggested that the primary sources of PAHs were vehicle exhaust and coal combustion and the secondary source was the atmospheric deposition of long-range transported PAHs. The incremental lifetime cancer risks (ILCRs) of exposing to PAHs in the urban soils of Beijing for adult were 1.77 × 10(-6) and 2.48 × 10(-5), respectively under normal and extreme conditions. For child, they were 8.87 × 10(-7) and 6.72 × 10(-6), respectively under normal and extreme conditions.

Chlorinated and polycyclic aromatic hydrocarbons in riverine and estuarine sediments from Pearl River Delta, China

Spatial distribution of chlorinated hydrocarbons [chlorinated pesticides (CPs) and polychlorinated biphenyls (PCBs)] and polycyclic aromatic hydrocarbons (PAHs) was measured in riverine and estuarine sediment samples from Pearl River Delta, China, collected in 1997. Concentrations of CPs of the riverine sediment samples range from 12 to 158 ng/g, dry weight, while those of PCBs range from 11 to 486 ng/g. The CPs concentrations of the estuarine sediment samples are in the range 6-1658 ng/g, while concentrations of PCBs are in the range 10-339 ng/g. Total PAH concentration ranges from 1168 to 21,329 ng/g in the riverine sediment samples, whereas the PAH concentration ranges from 323 to 14,812 ng/g in the sediment samples of the Estuary. Sediment samples of the Zhujiang River and Macao harbor around the Estuary show the highest concentrations of CPs, PCBs, and PAHs. Possible factors affecting the distribution patterns are also discussed based on the usage history of the chemicals, hydrologic condition, and land erosion due to urbanization processes. The composition of PAHs is investigated and used to assess petrogenic, combustion and naturally derived PAHs of the sediment samples of the Pearl River Delta. In addition, the concentrations of a number of organic compounds of the Pearl River Delta samples indicate that sediments of the Zhujiang river and Macao harbor are most likely to pose biological impairment.

Sources, fate, and toxic hazards of oxygenated polycyclic aromatic hydrocarbons (PAHs) at PAH-contaminated sites

In this paper we show that oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) are important cocontaminants that should be taken into account during risk assessment and remediation of sites with high levels of PAHs. The presented data, which have been collected both from our own research and the published literature, demonstrate that oxy-PAHs are abundant but neglected contaminants at these sites. The oxy-PAHs show relatively high persistency and because they are formed through transformation of PAHs, their concentrations in the environment may even increase as the sites are remediated by methods that promote PAH degradation. Furthermore, we show that oxy-PAHs are toxic to both humans and the environment, although the toxicity seems to be manifested through other effects than those known to be important for polycyclic aromatic compounds in general, that is, mutagenicity and carcinogenicity. Finally, we present data that support the hypothesis that oxy-PAHs are more mobile in the environment than PAHs, due to their polarity, and thus have a higher tendency to spread from contaminated sites via surface water and groundwater. We believe that oxy-PAHs should be included in monitoring programs at PAH-contaminated sites, even if a number of other toxicologically relevant compounds that may also be present, such as nitro-PAHs and azaarenes, are not monitored. This is because oxy-PAH levels are difficult to predict from the PAH levels, because their environmental behavior differs substantially from that of PAHs, and oxy-PAHs may be formed as PAHs are degraded.