The Stockholm Convention is a global treaty which requires that Parties adopt and introduce measures to reduce releases of POPs - a group of chemicals which persist in the environment - with the aim of reducing human and wildlife exposure.

The chemicals also have the potential to be transported long distances and deposited far away from their place of release including in pristine environments such as the Arctic.

There are currently 22 POP chemicals listed in the Convention. 15 of which are pesticides. The pesticides and industrial chemicals listed in the Convention have been banned in the UK for many years, with some limited exemptions.

Defra says that overall the UK has made good progress against the actions outlined in the 2007 NIP. In terms of future activity, the priority is to gain a better understanding of the potential scale and level of emissions from past (legacy) uses and in-use items containing POPs, particularly when these enter the waste stream. The UK Government will also continue to support research on POPs, which will help to inform future measures needed to achieve further emission reductions.

With regard to the water sector, European Directive 2008/105/EC on environmental quality standards in the field of water policy sets out environmental quality standards relating to the presence in surface water of two groups of priority substances. The substances are selected on account of the risk they pose to, or via, the aquatic environment. Annex I of this Directive currently lists 33 substances broken into two groups:

• Priority substances – required for reduction of discharges and losses;

• Priority hazardous substances – required for the cessation or phase out of discharges, emissions and losses.

The substances addressed by Annex I include POPs, which are classified as priority hazardous substances. Annex I is periodically reviewed and updated - a further 15 substances are currently proposed to be added to the Annex, including dioxins and dioxin-like PCBs.

The Directive places a requirement on member states to establish, for each River Basin District, an inventory of emissions, discharges and losses for substances listed under Annex I. The aim of the inventories is to help provide an evidence base to inform policy decisions and plans to reduce these emissions, discharges and losses and help maintain, or achieve, compliance with the environmental quality standards.

Among new POPs added to the Stockholm Convention since it was first launched is endosulfan which is also classified as a priority hazardous substance under the Water Framework Directive 2000/60/EC which requires environmental quality standards to be set for concentrations in water and sediments.

With regard to current monitoring of POPs in the marine environment , the Centre for Environment, Fisheries and Aquaculture Science (Cefas) undertakes monitoring for some POPs. A range of organic contaminants have been determined in marine mammal tissues alongside the Cetacean Strandings Investigation Programme, funded by Defra. These have included PCBs, a range of organochlorine pesticides (DDT and its breakdown products, HCHs, hexachlorobenzene and dieldrin), polycyclic aromatic hydrocarbons, butyltin compounds, the flame retardants PBDEs and HBCD, PFOS and PFOA.

Within the UK Clean Seas Environment Monitoring Programme, Cefas also undertakes contaminant analyses (PCBs, PBDEs, PAHs) in surface sediments and biota from offshore regions around England and Wales.

To meet the regulatory commitments the UK will develop a set of regularly updated emission inventories to satisfy the requirements of Directive 2008/105/EC on environmental quality standards in the field of water policy. The inventories will include priority and priority hazardous substances listed in table 1 of the Directive, updated in accordance with four-yearly reviews.

Waste water treatment works are main source of dioxin and furan emissions to water

Waste water treatment works are specifically identified in the Plan as the main source of dioxin and furan emissions to water, with figures ranging between 24.1 and 26.2g I-TEQ over the period 1990 to 2010 - the discharges have not been reported consistently year on year.

Overall emission trends for dioxins and furans shows the decline in emissions of dioxins and furans between 1990 and 2010, as stricter controls on industrial sources have taken effect. The Plan says the emissions have started to level off suggesting that it is likely to become increasingly difficult to achieve further significant reductions.

The Environment Agency separately carries out water monitoring for some pesticides listed in the Stockholm Convention. Analysis conducted concerning compliance with the environmental quality standards for Hexachlorocyclohexane (HCH, alpha, beta and gamma (Lindane) isomers) shows a limited number of exceedences for HCH at a limited number of specific sites.

The Plan says that further analysis of the data will be carried out in order to assess the overall significance of these emission and to determine if further action is required to eliminate them.

The Plan also flags up the release of Perfluorooctanesulfonic acid (PFOS) to water from sewage works. A limited sampling and analysis programme was carried out in 2010 to verify the modelling methods used to estimate emissions from sewage works which are reported to the Environment Agency’s Pollution Inventory. The findings, which related to the Calder and Aire rivers, were used to revise UK estimates for annual emissions to water and land from agricultural applications of sewage sludge.

The resulting new annual estimates are around 820kg PFOS to water, with emissions to land and air remaining at 5kg and 0kg respectively.

PeCB water emissions dominated by waste water treatment works

Estimated PeCB releases to land remained moderately high at 233kg in 2010 and were primarily due to the disposal of contaminated ash, notably from diffuse waste combustion sources. Water emissions were dominated by waste water treatment works and reflect the residue emissions from the food chain.

The UK Government’s continuing goal is to protect human health and the environment from the risks posed by POPs and to reduce the total releases derived from anthropogenic sources of each of them. Over the past two decades, the UK Government has taken steps to identify, quantify and manage the major sources of unintentional releases of dioxins, PCBs and HCB listed in the Stockholm Convention.

The Plan says that previous major sources such as waste incinerators and industrial processes have now been controlled via legislation and abatement techniques and continue to be closely regulated.

Current emissions of dioxins, PCBs, HCB and PeCB are dominated by a wide range of smaller diffuse sources - overall the UK has seen a significant decline in emissions for these POPs since 1990. Between 1990 and 2010, emissions to air, water and land have reduced by approximately 65%.

However the Plan says that currently data on emissions of the new POPs added to the Convention is limited and that additionally, there are gaps in the UK Government’s knowledge of potential sources and emissions from previous legacy applications for the new POPs.

Multi-media source inventories have been established to provide a more comprehensive assessment of dioxin, PCB and HCB emissions to air, water and land. These have been expanded to capture emissions for PeCB and work is underway to bring the new POPs into scope of the inventories.

Due to the declining trend in the emissions of the original POPs, the Plan says the UK Government is proposing to reduce the frequency of monitoring for these to allow for the additional work needed on the new POPs. 

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