Pollution sources and occurrences of selected persistent organic pollutants (POPs) in sediments of the Mekong River delta, South Vietnam

The Mekong River delta is one of the largest agricultural land in the Southeast Asia. It plays a very important role for agriculture and fisheries in South Vietnam. However, comprehensive studies on the environmental pollution of persistent organic pollutants (POPs) in Mekong River delta have not been carried out in recent years. In this study, we collected sediment samples from the Mekong River to evaluate the contamination and ecological risks caused by several POPs. The contamination pattern of POPs was DDT>PCBs>CHLs>HCHs>HCB. DDTs are the most abundant pollutants, their concentration ranging from 0.01 to 110 ng/g dry wt, followed by PCBs (0.039-9.2 ng/g dry wt). DDTs and PCBs concentrations were higher in sediment from adjacent to urban areas than those from rural and agricultural sites, suggesting urban areas as important point sources of DDTs and PCBs to the river. Ratio of p,p'-DDT/p,p'-DDE was lower compared to those previously reported. However, some samples still had the ratio higher than 0.5, indicating recent input of DDT into the aquatic environments. This result shows that although the magnitude of contamination decreased over time, recent inputs of DDTs to the river still occur. Some sediment samples had concentrations of DDT compounds higher than the standards from the Canadian Environmental Quality Guideline, suggesting continuous monitoring for POPs contamination in the Mekong River is necessary.     

Persistent organic pollutants in environment of the Pearl River Delta,China: an overview

In the Pearl River Delta of China, the rapidly developing industrial and agricultural activities, municipal development and use of chemicals caused serious environmental problems. This report summarizes the published scientific data on POPs in the environment of the Pearl River Delta, including the levels of POPs in the air, water, soil, river and estuarine sediments, the marine organisms like fish and shellfish in this region. The data preliminarily reveal the state of contamination in this region and give insight into the fate of POPs in this sub-tropical area. However, most research in this area is limited to a few kinds of POP compounds.     

Chemical, biological, and ecotoxicological assessment of pesticides and persistent organic pollutants in the Bahlui River, Romania

Background, aim, and scope  

Current knowledge on environmental impacts of industrial activities in Romania, particularly persistent organic pollutants (POPs), indicates that environmental standards of the European Union are not systematically met. In our study area, additional sources of POPs are agriculture and domestic wastes. Very scarce information is available upon environmental contaminations and effects. In the present study, we investigated the chemical pollution and their eventual impact on the ecosystem by measuring POPs and by using biological indicators of pollution.     

Urban environmental geochemistry of trace metals

As the world's urban population continues to grow, it becomes increasingly imperative to understand the dynamic interactions between human activities and the urban environment. The development of urban environmental geochemistry has yielded a significant volume of scientific information about geochemical phenomena found uniquely in the urban environment, such as the distribution, dispersion, and geochemical characteristics of some toxic and potentially toxic trace metals. The aim of this paper is to provide an overview of the development of urban environmental geochemistry as a field of scientific study and highlight major transitions during the course of its development from its establishment to the major scientific interests in the field today. An extensive literature review is also conducted of trace metal contamination of the urban terrestrial environment, in particular of urban soils, in which the uniqueness of the urban environment and its influences on trace metal contamination are elaborated. Potential areas of future development in urban environmental geochemistry are identified and discussed.     

Passive air sampling for persistent organic pollutants: introductory remarks to the special issue

There have been a number of developments in the need, design and use of passive air samplers (PAS) for persistent organic pollutants (POPs). This article is the first in a Special Issue of the journal to review these developments and some of the data arising from them. We explain the need and benefit of developing PAS for POPs, the different approaches that can be used, and highlight future developments and needs.     

Introducing an integrated climate change perspective in POPs modelling, monitoring and regulation

This paper presents a review on the implications of climate change on the monitoring, modelling and regulation of persistent organic pollutants (POPs). Current research gaps are also identified and discussed.Long-term data sets are essential to identify relationships between climate fluctuations and changes in chemical species distribution. Reconstructing the influence of climatic changes on POPs environmental behaviour is very challenging in some local studies, and some insights can be obtained by the few available dated sediment cores or by studying POPs response to inter-annual climate fluctuations. Knowledge gaps and future projections can be studied by developing and applying various modelling tools, identifying compounds susceptibility to climate change, local and global effects, orienting international policies.Long-term monitoring strategies and modelling exercises taking into account climate change should be considered when devising new regulatory plans in chemicals management.     

Geospatial patterns of hospitalization rates for stroke with comorbid hypertension in relation to environmental sources of persistent organic pollutants: results from a 12-year population-based study

Purpose  

Recent evidence indicates that exposure to persistent organic pollutants (POPs) is emerging as an important risk factor for atherosclerosis-related diseases, including stroke. Hypertension (HTN) is a major risk factor for stroke, and some studies suggest that exposure to POPs is also a risk factor for HTN. We hypothesized that POPs increase the environmental burden of stroke with comorbid HTN.     

Man-made chemicals found in remote areas of the world: the experimental definition for POPs

Members of the United Nations Economic Commission for Europe (UN-ECE) signed a legally binding protocol on persistent organic pollutants (POPs) in February 1998 under the Convention on Long-Range Transboundary Air Pollution. A treaty that intends to control the production, import, export, disposal and use of toxic chemicals that persist for decades in the environment has been formally signed at a conference in May 2001 in Stockholm. The 2001 POP treaty, like the 1998 LRTAP POP protocol, contains a provision on adding further chemicals to the initial group of twelve or fifteen. The occurrence of a compound or a group of compounds in so called remote and pristine areas, e.g. in the Artic or in the Southern Hemisphere, proves its stability under the chemical and biological conditions of the environment. Compounds identified in this way, in samples taken primarily in very remote regions of the planet, are classified by their environmental fate and global distribution as persistent organic pollutants (POPs), regardless of any political assessments.     

Climate change influence on POPs distribution and fate: a case study

Climate change has the potential of affecting the behaviour and distribution of organic pollutants, including POPs. Direct effects of climate change, like temperature increase, modification of wind and precipitation patterns, sea level rise, snow and ice cover, may be very effective in altering the partitioning of POPs among the environmental compartments. Other consequences of future climate scenarios may imply the alteration of degradation rates, soil properties (and hence land use), air-particle partitioning of chemicals and so forth. A case study is here presented to illustrate the major implications of climate change on the long term at the local scale. A dynamic multimedia model was applied to selected PCB and PCDD/F congeners to simulate the effects of climate change on their distribution and fluxes over the next 50 y in the Venice Lagoon (Italy). Different climate change scenarios were tested, finding noticeable variations in POPs concentration even for minor environmental changes. PCBs and PCDFs environmental concentrations may differ by a factor two in a moderate climate change scenario, compared to a situation with stable climate over the next 50 y. However, model results also suggest that if global warming may have the potential of reducing the environmental levels of these chemicals, it would probably enhance their mobility and hence their potential for long range atmospheric transport.     

Contaminant concentrations in breeding and non-breeding northern fulmars (Fulmarus glacialis L.) from the Canadian high arctic

Persistent organic pollutants (POPs) were measured in livers of male and female northern fulmars (Fulmarus glacialis) shortly after egg-laying on northern Devon Island, NU, Canada. Breeding females had lower hepatic POPs (lipid normalised) than breeding males, but non-breeding males and females had similar concentrations. We suspect that breeding females are eliminating some of their POPs during egg formation. Concentrations of measured POPs were lower than those associated with avian health concerns, and there was no evidence that POPs in the birds were contributing to additional breeding stress.     

Occurrence of persistent organic pollutants in sediments and biota from Portugal versus European incidence: A critical overview

Persistent organic pollutants (POPs) are widespread compounds, such as organohalogenated compounds, polycyclic aromatic hydrocarbons (PAHs) and pesticides, which can be found in all types of environmental compartments. Their presence in the aquatic environment is a worldwide problem, with emphasis on sediments which act as depository and consequently as a source of hydrophobic, recalcitrant and harmful compounds. Besides, these pollutants might affect the reproduction and mortality of living organisms, diverging in their potential to bioaccumulate in tissues. The present paper aims to review the occurrence of POPs in sediments and biota from the coastal, estuarine and river areas of Portugal. The list of the studied compounds comprises organohalogenated compounds, PAHs, organometallic compounds, pesticides, sterols, fatty acids and pharmaceutical compounds. The contamination of sediments by various pollutants is presented, such as PAHs up to 7,350 ng g^?1 found in Sado estuary and polychlorinated biphenyls up to 62.2 ng g^?1 in the case of sediments collected in Ria de Aveiro. The occurrence of these persistent toxic substances in sediments demonstrates aquatic contamination from agricultural, industrial and urban discharges and the concern about the potential risks to aquatic organisms, wildlife and humans. In fact, several classes of POPs have also been found in biota, such as polychlorinated biphenyls up to 810.9 ng g^?1 in sentinel fish from the Douro River estuary and pesticides in bivalves from the Sado River estuary. The importance of further systematic research on sediments and biota is here highlighted to compare the contamination of these two reservoirs; to assess their spatial and temporal variation; and to determine other classes of POPs that were not investigated yet (e.g., industrial compounds, estrogens and many classes of pharmaceuticals).     

Primary sources of selected POPs: regional and global scale emission inventories

During the last decade, a number of studies have been devoted to the sources and emissions of Persistent Organic Pollutants (POPs) at regional and global scales. While significant improvements in knowledge have been achieved for some pesticides, the quantitative understanding of the emission processes and emission patterns for "non-pesticide" POPs are still considered limited. The key issues remaining for the non-pesticide POPs are in part determined by their general source classification. For industrial chemicals, such as the polychlorinated biphenyls (PCBs), there is considerable uncertainty with respect to the relative importance of atmospheric emissions from various source categories. For PCBs, temperature is discussed as a potential key factor influencing atmospheric emission levels and patterns. When it comes to the unintentional by-products of combustion and industrial processes (PCDD/Fs), there is still a large uncertainty with respect to the relative contribution of emissions from unregulated sources such as backyard barrel burning that requires further consideration and characterisation. For hexachlorobenzene (HCB), the relative importance of primary and secondary atmospheric emissions in controlling current atmospheric concentrations remains one of the key uncertainties. While these and other issues may remain unresolved, knowledge concerning the emissions of POPs is a prerequisite for any attempt to understand and predict the distribution and fate of these chemicals on a regional and global scale as well as to efficiently minimise future environmental burdens.     

Current issues and uncertainties in the measurement and modelling of air-vegetation exchange and within-plant processing of POPs

Air-vegetation exchange of POPs is an important process controlling the entry of POPs into terrestrial food chains, and may also have a significant effect on the global movement of these compounds. Many factors affect the air-vegetation transfer including: the physicochemical properties of the compounds of interest; environmental factors such as temperature, wind speed, humidity and light conditions; and plant characteristics such as functional type, leaf surface area, cuticular structure, and leaf longevity. The purpose of this review is to quantify the effects these differences might have on air/plant exchange of POPs, and to point out the major gaps in the knowledge of this subject that require further research. Uptake mechanisms are complicated, with the role of each factor in controlling partitioning, fate and behaviour process still not fully understood. Consequently, current models of air-vegetation exchange do not incorporate variability in these factors, with the exception of temperature. These models instead rely on using average values for a number of environmental factors (e.g. plant lipid content, surface area), ignoring the large variations in these values. The available models suggest that boundary layer conductance is of key importance in the uptake of POPs, although large uncertainties in the cuticular pathway prevents confirmation of this with any degree of certainty, and experimental data seems to show plant-side resistance to be important. Models are usually based on the assumption that POP uptake occurs through the lipophilic cuticle which covers aerial surfaces of plants. However, some authors have recently attached greater importance to the stomatal route of entry into the leaf for gas phase compounds. There is a need for greater mechanistic understanding of air-plant exchange and the 'scaling' of factors affecting it. The review also suggests a number of key variables that researchers should measure in their experiments to allow comparisons to be made between studies in order to improve our understanding of what causes any differences in measured data between sites.     

Dioxin- and POP-contaminated sites—contemporary and future relevance and challenges

BACKGROUND, AIM AND SCOPE: Once they have been generated, polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and other persistent organic pollutants (POPs) can persist in soils and sediments and in waste repositories for periods extending from decades to centuries. In 1994, the US EPA concluded that contaminated sites and other reservoirs are likely to become the major source of contemporary pollution problems with these substances. With this in mind, this article is the first in a new series in ESPR under the title 'Case Studies on Dioxin and POP Contaminated Sites--Contemporary and Future Relevance and Challenges', which will address this important issue. The series will document various experiences from sites contaminated with PCDD/F and other POPs. This article provides an overview of the content of the articles comprising the series. In addition, it provides a review of the subject in its own right and identifies the key issues arising from dioxin/POP-contaminated sites. Additionally, it highlights the important conclusions that can be drawn from these examples. The key aim of this article and of the series as a whole is to provide a comprehensive overview of the types of PCDD/F contaminated sites that exist as a result of historical activities. It details the various processes whereby these sites became contaminated and attempts to evaluate their contemporary relevance as sources of PCDD/Fs and other POPs. It also details the various strategies used to assess these historical legacies of contamination and the concepts developed, or which are under development, to effect their remediation. MAIN FEATURES: Special sessions on 'Contaminated sites--Cases, remediation, risk and policy' were held at the DIOXIN conferences in 2006 and 2007, and this theme will be continued at DIOXIN 2008 to be held in Birmingham. Selected cases from the approximately 70 contributions made to these sessions, together with some additional invited case studies are outlined together with the key issues they raise. By evaluating these cases and adding details of experiences published in the current literature, an overview will be given of the different features and challenges of dioxin and POP-contaminated sites. RESULTS: This article provides a systematic categorisation of types of PCDD/F and POP-contaminated sites. These are categorised according to the chemical or manufacturing process, which generated the PCDD/Fs or POPs and also includes the use and disposal aspects of the product life cycle in question. The highest historical PCDD/F and dioxin-like polychlorinated biphenyl (PCB) contamination burdens have arisen as a result of the production of chlorine and of chlorinated organic chemicals. In particular, the production of chlorinated pesticides, PCBs and the related contaminated waste streams are identified being responsible for historical releases of toxic equivalents (TEQs) at a scale of many tonnes. Along with such releases, major PCDD/F contaminated sites have been created through the application or improper disposal of contaminated pesticides, PCBs and other organochlorine chemicals, as well through the recycling of wastes and their attempted destruction. In some extreme examples, PCDD/F contaminated sites have also resulted from thermal processes such as waste incinerators, secondary metal industries or from the recycling or deposition of specific waste (e.g. electronic waste or car shredder wastes), which often contain chlorinated or brominated organic chemicals. The examples of PCDD/F and dioxin-like PCB contamination of fish in European rivers or the impact of contaminated sites upon fishing grounds and upon other food resources demonstrate the relevance of these historical problems to current and future human generations. Many of the recent food contamination problems that have emerged in Europe and elsewhere demonstrate how PCDD/F and dioxin like PCBs from historical sources can directly contaminate human and animal feedstuffs and indeed highlight their considerable contemporary relevance in this respect. Accordingly, some key experiences and lessons learnt regarding the production, use, disposal and remediation of POPs from the contaminated sites are summarised. DISCUSSION: An important criterion for evaluating the significance and risks of PCDD/Fs and other POPs at contaminated sites is their present or future potential for mobility. This, in turn, determines to a large degree their propensity for off-site transport and environmental accessibility. The detailed evaluation of contaminated site cases reveals different site-specific factors, which influence the varied pathways through which poor water-soluble POPs can be mobilised. Co-contaminants with greater water solubility are also typically present at such sites. Hence, pumping of groundwater (pump and treat) is often required in addition to attempting to physically secure a site. At an increasing number of contaminated sites, securing measures are failing after relatively short time spans compared to the time horizon, which applies to persistent organic pollutant contamination. Due to the immense costs and challenges associated with remediation of contaminated sites 'monitored natural attenuation' is increasingly gaining purchase as a conceptual remediation approach. However, these concepts may well prove limited in their practical application to contaminated sites containing persistent organic pollutants and other key pollutants like heavy metals. CONCLUSIONS: It is inevitable, therefore, that dioxin/POP-contaminated sites will remain of contemporary and future relevance. They will continue to represent an environmental issue for future generations to address. The securing and/or remediation of dioxin/POP-contaminated sites is very costly, generally in the order of tens or hundreds of millions of dollars. Secured landfills and secured production sites need to be considered as constructions not made for 'eternity' but built for a finite time scale. Accordingly, they will need to be controlled, supervised and potentially repaired/renewed. Furthermore, the leachates and groundwater impacted by these sites will require ongoing monitoring and potential further remediation. These activities result in high maintenance costs, which are accrued for decades or centuries and should, therefore, be compared to the fully sustainable option of complete remediation. The contaminated site case studies highlight that, while extensive policies and established funds for remediation exist in most of the industrialised western countries, even these relatively well-regulated and wealthy countries face significant challenges in the implementation of a remediation strategy. This highlights the fact that ultimately only the prevention of contaminated sites represents a sustainable solution for the future and that the Polluter Pays Principle needs to be applied in a comprehensive way to current problems and those which may emerge in the future. RECOMMENDATIONS AND PERSPECTIVES: With the continuing shift of industrial activities in developing and transition economies, which often have poor regulation (and weak self-regulation of industries), additional global challenges regarding POPs and other contaminated sites may be expected. In this respect, a comprehensive application of the "polluter pays principle" in these countries will also be a key to facilitate the clean-up of contaminated areas and the prevention of future contaminated sites. The threats and challenges of contaminated sites and the high costs of securing/remediating the problems highlight the need for a comprehensive approach based upon integrated pollution prevention and control. If applied to all polluting (and potentially polluting) industrial sectors around the globe, such an approach will prove to be both the cheapest and most sustainable way to underpin the development of industries in developing and transition economies.     

Neurobehavioral deficits and brain oxidative stress induced by chronic low dose exposure of persistent organic pollutants mixture in adult female rat

Persistent organic pollutants (POPs) are long-lived organic compounds that are considered one of the major risks to ecosystem and human health. Recently, great concerns are raised about POPs mixtures and its potential toxicity even in low doses of daily human exposure. The brain is mostly targeted by these lipophilic compounds because of its important contain in lipids. So, it would be quite interesting to study the effects of exposure to these mixtures and evaluate their combined toxicity on brain cells. The present study was designed to characterize the cognitive and locomotors deficits and brain areas redox status in rat model. An orally chronic exposure to a representative mixture of POPs composed of endosulfan (2.6 μg/kg), chlorpyrifos (5.2 μg/kg), naphthalene (0.023 μg/kg) and benzopyrane (0.002 μg/kg); the same mixture with concentration multiplied by 10 and 100 was also tested. Exposed rats have shown a disturbance of memory and a decrease in learning ability concluded by Morris water maze and the open field tests results and anxiolytic behaviour in the test of light/dark box compared to control. Concerning brain redox homeostasis, exposed rats have shown an increased malondialdehyde (MDA) amount and an alteration in glutathione (GSH) levels in both the brain mitochondria and cytosolic fractions of the cerebellum, striatum and hippocampus. These effects were accompanied by a decrease in levels of cytosolic glutathione S-transferase (GST) and a highly significant increase in superoxide dismutase (SOD) and catalase (CAT) activities in both cytosolic and mitochondrial fractions. The current study suggests that environmental exposure to daily even low doses of POPs mixtures through diet induces oxidative stress status in the brain and especially in the mitochondria with important cognitive and locomotor behaviour variations in the rats.     

The maximum reservoir capacity of soils for persistent organic pollutants: implications for global cycling

The concept of maximum reservoir capacity (MRC), the ratio of the capacities of the surface soil and of the atmospheric mixed layer (AML) to hold chemical under equilibrium conditions, is applied to selected persistent organic pollutants (POPs) in the surface 'skin' (1 mm) of soils. MRC is calculated as a function of soil organic matter (SOM) content and temperature-dependent K(OA) and mapped globally for selected PCB congeners (PCB-28; -153; -180) and HCB, to identify regions with a higher tendency to retain POPs. It is shown to vary over many orders of magnitude, between compounds, locations and time (seasonally/diurnally). The MRC approach emphasises the very large capacity of soils as a storage compartment for POPs. The theoretical MRC concept is compared to reality and its implications for the global cycling of POPs are discussed. Sharp gradients in soil MRC can exist in mountainous areas and between the land and ocean. Exchanges between oceans and land masses via the atmosphere is likely to be an important driver to the global cycling of these compounds, and net ocean-land transfers could occur in some areas.     

Approaches to assess the oral bioaccessibility of persistent organic pollutants: a critical review

Oral bioaccessibility, also known as in vitro gastrointestinal extraction or the physiologically based extraction test (PBET), is an important tool when assessing the risk to humans from persistent organic pollutants (POPs) (and metals). The approach seeks to mimic the processes of human food digestion and thereby assess the bioavailability of POPs (and metals) from materials consumed either accidentally or intentionally in the diet. In vitro conditions are created to simulate various actions in the stomach and intestines (although some methods also include the mouth compartment). This paper reviews the current status of oral bioaccessibility with respect to the release of POPs from soil and related samples of environmental importance. Particular emphasis is placed on the parameters that influence gastrointestinal extraction including gastric and intestinal pH, enzymes, bile salts, food constituents and residence time. In addition, important developments in the use of in vitro gastrointestinal extraction are highlighted. These developments include the use of epithelial Caco-2 cells to mimic the intestinal cell lining, the potential for biotransformation of POPs into estrogenic metabolites as a result of colon microbiota, and the use of in vivo studies to validate existing approaches.     

Seasonal change of persistent organic pollutant concentrations in air at Niigata area,Japan

The concentrations of persistent organic pollutants (POPs), such as HCB, alpha-, beta-, gamma- and delta-HCH, trans- and cis-chlordane (t-CHL, c-CHL), DDE, DDD and DDT, in ambient air have been measured at five sampling points in Niigata area, Japan (Niigata, Maki, Tsubame, Jouzo and Yahiko) during the period from September 1999 to November 2001. HCB, alpha-HCH, t-CHL and c-CHL showed higher concentrations than the other chemicals in all locations. All the POPs except t-CHL and c-CHL collected at urban sites of the Niigata Plain was almost the same in their concentration levels. Higher concentrations of t-CHL and c-CHL in residential areas should be attributed to the past usage of the chemical as a termiticide. At Yahiko (remote site), most of the POPs showed lower concentrations than those measured at the other sampling sites, although alpha-HCH and gamma-HCH were comparable with the concentrations found at the other sampling sites. All POPs except alpha-HCH and gamma-HCH tend to decrease 41-80% in their concentrations from 2000 to 2001. The lower POPs concentrations in winter and the higher POPs concentrations in summer at every sampling point can be partly explained by temperature differences. Applying the equation of the logarithm of the POP partial pressure in air versus reciprocal temperature (lnPa=m/T+b) to our data, linear relations were observed. HCB gave a poor linearity and the smallest slope, while beta-HCH, t-CHL and c-CHL gave good linearities and large slopes in the equation. The results suggest that HCB level is influenced by not only the emission from terrestrial sources but the global-scale background pollution. A peculiar observation is that beta-HCH concentration measured in our study showed large temperature dependence, indicating there could be a source of contamination in the surrounding areas.