Matti Verta

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

Background, aim and scopeOnce 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 featuresSpecial 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.ResultsThis 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.DiscussionAn 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.ConclusionsIt 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 perspectivesWith 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.

High fish-specific dioxin concentrations in Finland

Dioxin concentrations in a population that frequently eat fish from the Baltic Sea are comparable to those seen in inhabitants of Seveso, Italy, after the accidental release of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in 1976. Individual variations in the congener patterns in human beings are similar to congener patterns in the fish species consumed.

Time trends and congener profiles of PCDD/Fs, PCBs, and PBDEs in Baltic herring off the coast of Finland during 1978-2009.

In Finland, consumption of Baltic fatty fish may lead to high exposure to persistent organic pollutants (POPs), which might have hazardous health effects. Monitoring of POPs in Baltic fish enables the health authorities to keep dietary advice on fish consumption up to date. In this study, which is a compilation of analytical data from earlier studies, time trends and congener profiles of polychlorinated dioxins and furans (PCDD/Fs) and biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) in Baltic herring are reported. Altogether 344 samples of Baltic herring from 1978-2009 were collected across the Finnish coast of the Baltic Sea. The chemical analysis was performed in an accredited testing laboratory with high resolution gas chromatography mass spectrometry. During the 31-year period, PCDD/F and PCB concentrations decreased on approximately 80%, from approximately 20 to 5 pg/g fw, expressed as WHO2005 TEQ. The PBDE concentrations experienced a 4-10 fold increase during late 1980s-early 1990s, and declined to 1978s levels of approximately 2 ng/g fw by 2009. The current concentrations of PCDD/Fs, PCBs and PBDEs in Baltic herring are relatively low, and mostly below EU maximum accepted levels, and are expected to continue decreasing. In the future, it may be possible to re-evaluate the consumption restrictions for this specific Baltic fatty fish.

Interference of contaminated sediment extracts and environmental pollutants with retinoid signaling

Retinoids are known to regulate important processes such as differentiation, development, and embryogenesis. Some effects, such as malformations in frogs or changes in metabolism of birds, could be related to disruption of the retinoid signaling pathway by exposure to organic contaminants. A new reporter gene assay has been established for evaluation of the modulation of retinoid signaling by individual chemicals or environmental samples. The bioassay is based on the pluripotent embryonic carcinoma cell line P19 stably transfected with the firefly luciferase gene under the control of a retinoic acid-responsive element (clone P19/ A15). The cell line was used to characterize the effects of individual chemicals and sediments extracts on retinoid signaling pathways. The extracts of sediments from the River Kymi, Finland, which contained polychlorinated dioxins and furans and polycyclic aromatic hydrocarbons (PAHs), significantly increased the potency of all-trans retinoic acid (ATRA), while no effect was observed with the extract of the sediment from reference locality. Considerable part of the effect was caused by the labile fraction of the sediment extracts. Also, several individual PAHs potentiated the effect of ATRA; on the other hand, 2,3,7,8-tetrachlorodibenzo-p-dioxin and several phthalates showed slightly inhibiting effect. These results suggest that PAHs could be able to modulate the retinoid signaling pathway and that they could be responsible for a part of the proretinoid activity observed in the sediment extracts. However, the effects of PAHs on the retinoic acid signaling pathways do not seem to be mediated directly by crosstalk with aryl hydrocarbon receptor.

Detecting AhR ligands in sediments using bioluminescent reporter yeast.

Sediments polluted with high concentrations of persistent organic pollutants, many of which are ligands of the aryl hydrocarbon receptor (AhR), are currently of concern around the industrialized world. Bioassays that can detect the presence of AhR ligands in environmental samples offer a relatively rapid and cost-effective means of prioritizing samples before more elaborate, laborious, and costly chemical analyses are applied. This paper presents a new bioluminescent yeast assay based on transcriptional activation of AhR. Its applicability for determining AhR ligands in complex environmental samples was demonstrated by analyzing a set of sediment samples from the River Kymi, Finland. The results from the assay are shown to be consistent with those from both a chemical analysis and an H4IIE-luc bioassay. The yeast assay procedure is simple and can be performed within 1 day. The yeasts grow rapidly, are easy to handle, and do not require continuous cell culturing. Moreover, the robustness of the yeast allows the application of the test to crude extracts or even sediment suspensions. The yeast assay described in this paper can be useful in screening and prioritization of samples prior to chemical analysis. Moreover, the strain can be used in the construction of fibre-optic biosensors.

Toxicity screening of novel pulp mill wastewaters in Finnish pulp mills

In the first phase of the study, the toxicity of 18 untreated, pilot treated and secondary treated TCF (total chlorine free), ECF (elementary chlorine free) and chlorine (Cl2) bleaching effluents from 2 pulp mills was assessed by a set of bioassays in order to compare the toxicity with a large number of chemical parameters. The toxicity tests used were: Pseudomonas putida (bacterial) growth inhibition, Vibrio flscheri (bacterial) bioluminescence inhibition, Raphidocelis subcapitata (algal) growth inhibition, Daphnia magna mobility inhibition and zebra fish Brachydanio rerio embryo and sac-fry stage test. Chemical analysis of the wastewaters consisted of BOD7, CODCrTOC, AOX, tot N, tot P, loss on ignition, suspended solids, colour, as well as 25 major and trace elements, phenolic compounds, fatty acids, resin acids and molecular weight (MW) distribution.