Persistent Organic Pollutants (POPs) are listed under the Stockholm Convention, which regulates the elimination/restriction of their production and use, reduction of release, and environmentally sound treatment. In order to promote environmentally sound treatment of POPs waste in Japan, the Law Concerning Special Measures for PCB has been enacted; and technical documents pertaining to treatment of waste containing pesticides and PFOS and describing requirements for the destruction of such substances have been established. In addition, the topic of how treatment of POPs waste should be positioned within the regulations is being taken into consideration and discussions continue about what is desired and what can actually be done. Regarding plastic wastes that contain POPs as brominated flame retardants, we recognize the importance of establishing the methods for its environmentally sound treatment and of designing new measures for how to distinguish these from others. Regarding POPs as fluorinated surfactants, we are discussing the required measures for the analysis, including the establishment of methods for environmentally sound treatment, in order to prepare for regulation of production and use of PFOA in the future. We look forward to cooperation from the research and development area in order to boost impact on effective policy making going forward.

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The number of substances listed in the Stockholm Convention on Persistent Organic Pollutants (POPs) has increased constantly since the Convention was enacted in 2004. Under the Convention, POPs are classified into three categories: Annex A (Elimination), Annex B (Restriction), and Annex C (Unintentional production). This article focuses on some of the new/candidate POPs of the Convention, including polychlorinated naphthalenes (PCNs), hexachlorobutadiene (HCBD), hexabromocyclododecane (HBCDD), and per- and polyfluoroalkyl substances (PFAS). The paper also outlines what types of waste contain these substances, actual waste treatment conditions, and a few of the basic concepts related to waste management in the circulation and disposal processes.

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The garbage generated from our modern lifestyles undergoes intermediate treatment such as incineration, etc. and is then landfilled at waste disposal sites. Often, various substances, including POPs and others, can be accumulating at these sites and may be detected in landfill leachates over the long term. As a result of this study, PFASs, including PFOA and PFOS, have been detected in the order of thousands of ng/L from landfill leachates and concentrations for HBCD and HCBD measured about two orders magnitude lower than those of PFASs. Notably, the concentrations of PCNs in landfill leachates is still unclear. Some reports suggest that activated carbon adsorptions, photocatalysis and high-pressure membranes treatments are effective in removing PFASs from water samples. Insufficient knowledge regarding concentration of POPs and their reduction during the treatment process in landfill leachates suggests that further research, with monitoring and prediction models for landfill fields, is still required.

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Polychlorinated naphthalenes (PCNs) and Hexachlorobutadiene (HCBD) have been designated as part of the new POPs under the Stockholm Convention. These are either intentionally or unintentionally left in various industrial products and disposed of in landfills. Furthermore, PCNs are similar in structure to PCBs and are contained in the incineration residue as combustion by-products. With a target of developing long-term, appropriate management of landfills, we clarify the actual concentration of these POPs in landfill leachates and study the breakdown process in wastewater treatment. In order to efficiently grasp the actual situation occurring in various parts of Japan, we have developed a simultaneous analysis method that uses analysis items such as dioxins, VOCs, and 1,4-dioxane, which already have standard values and are frequently measured. The PCNs concentration in the leachate amounts to several pg/L to several hundred pg/L, the HCBD is less than the Method Detection Limit (0.015　μg/L). PCNs are removed by wastewater treatment and measure several pg/L in the effluent water.

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The concentrations of Per- and Polyfluoroalkyl Substances (PFASs) in the environment or in human serum has markedly decreased since the PFOA Stewardship Program was established and was registered with the Stockholm Convention. An increase in PFHxA has been reported with a decrease in PFOA. As precursors, N-MeFOSA and N-EtFOSA were detected in seawater using Orbitrap-MS and as a result, 5:2 Ketone, 5:3 FTCA, 6:2 FTOH, 6:2 diPAP, and 6:2 FTS were detected. There have also been recent reports of GenX contamination and cases of detection.
　On the one hand, there have been almost no cases of hexabromocyclododecane (HBCD) surveyed at the landfill, but the concentration range still measured <0.0025 to 9ng･L⁻¹. At the sewage treatment plant, the concentration range for the inflow water was at <0.4 to 400ng･L⁻¹ with effluent numbers at 0.14 to 18ng･L⁻¹. It is notable that the concentration level decreased with treatment. In the future, by analyzing various water samples such as from landfill leachate, etc., we intend to address and solve problems with the aim of creating a manual that provides analysis and survey methods.

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This paper summarizes research trends regarding polychlorinated naphthalenes (PCNs) contained in waste incineration residues and in residues generated from industrial heating processes such as fly ash and clinker in cement kilns, residues generated from secondary refining of steel and non-ferrous metals. Research themes currently being undertaken by the authors is also introduced.
　With the exception of some samples, contents contained within the residue were at the same levels. Although many studies and statistical analyses have been conducted based on distribution of homologues and isomers, fully distinguishing between product-based and combustion-based PCNs and identifying the chlorination reaction route seems to still be problematic. It is suggested that thermal dechlorination treatment under reduction conditions is effective in decomposing, dechlorinating, and reducing the toxicity of PCNs. The reported value of the emission factor of PCNs in waste incineration measured as wide as 1 to 48600 μg t⁻¹, which suggests that further study is required.

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In recent years, per- and polyfluoroalkyl substances (PFASs) such as PFOA and PFOS, and polychlorinated naphthalenes (PCNs) have been added to the list of persistent organic pollutants (POPs). Long-term emissions forecasts from landfills of these pollutants would be a significant step toward environmental preservation. We conducted a literature survey staying mindful of carbon chain length and the number of chlorines in terms of the actual status of emissions and the adsorption capacity which greatly affects the mobility of POPs. Regarding PFASs, we also investigated the biological degradation pathway from fluorotelomer alcohols (FTOHs) to gather knowledge on the possibility of production in landfills. It suggests that PCNs with high chlorines and long-chain PFASs may accumulate in a landfill. On the other hand, PCNs with low chlorines and short-chain PFASs may be discharged to landfill leachate at a relatively early stage. Since it is likely that perfluoroalkyl acids (PFAAs) with eight or fewer carbons are produced under anaerobic conditions like that of landfills, comprehensive research/survey will be required, including not only PFOS and PFOA but also precursors.

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