Man-made chemicals and heavy metals enter the Baltic Sea via waste water treatment plants, leaching from house-hold materials, waste deposits, through atmospheric deposition from industrial plant emissions, and many other sources. Once in the Baltic they can cause various types of damage to the ecosystem. Some are highly visible in the form of oil-spills, for example. Many contaminants degrade slowly and their impacts can magnify as they accumulate in the aquatic food web. The current contamination status is elevated in all parts of the Baltic Sea, mainly driven by polybrominated flame retardants and mercury. Most indicators show stable status since the last assessment.
Thousands of environmentally hazardous substances have been identified as potentially occurring in the Baltic Sea. The most environmentally hazardous substances are those that are persistent, toxic and accumulate in biota. Some hundreds of substances are regularly monitored. Out of these, concentrations of twelve hazardous substance groups are included in the core indicators used in the integrated contamination status assessment.
Indicators used in the assessment
The core indicators cover substances of specific concern to the Baltic Sea as described in the HELCOM Baltic Sea Action Plan and are based on data from the HELCOM monitoring programme (Core indicator reports: HELCOM 2017l-s).
The core indicators have regionally agreed threshold values that are set based on knowledge of the eco-toxicity of the substances, meaning that when the threshold is achieved, the concentration of the substance is so low that it is not expected to cause harm to the marine environment (Box 4.2.1). However, a risk can never be fully excluded even when the threshold is achieved, especially for persistent or bio-accumulating substances, and the long-term goal is to reach zero concentrations for man-made chemicals. The environmental quality standards (EQS) defined in the EU Environmental Quality Standards Directive (EC 2008) linked to the EU Water Framework Directive (EC 2000) are agreed to be used as indicator threshold values.
If several threshold values are available, priority is given in HELCOM to environmental quality standard values for biota, rather than in water or sediment. For many substances, most data is available for biota and this estimate reflects the accumulation of contaminants in the living environment.
Core indicators have also been developed to monitor effects on a top-predator, the white-tailed eagle, as well as to detect trends in oil-spills. Since the previous holistic assessment, HELCOM has further developed the assessment system for hazardous substances, and taken steps towards applying regionally harmonised methods.
The integrated assessment of hazardous substances was done using the CHASE tool which aggregates the indicator results into a quantitative estimate of overall eutrophication status (Supplementary report: HELCOM 2017C).
Integrated status assessment
The pressure on the marine environment from concentration of contaminants is high in all parts of the Baltic Sea (Figure 4.2.1). This is mainly due to a group of brominated flame retardants and mercury, both measured in fish (Figures 4.2.5, 4.2.10).
The polybrominated diphenyl ethers have mainly been used as flame retardants in plastic materials and polyurethane foams, and enter the Baltic Sea through waste water treatment plants and diffuse sources. The main source of heavy metals, such as mercury, is burning of fossil fuels, which enter the Baltic Sea through atmospheric deposition. Mercury is currently legally used in low energy light sources. It is phased out from several previous uses including amalgams in dentistry, electrodes in paper bleaching, and thermometers, for example.
The highest contaminant concentrations, compared to the threshold value, generally occurred for measurements in biota, rather than in sediments or water, except for some areas in the southern Baltic Sea where the highest contaminant concentration were seen in tributyltin in sediment (Table 4.2.1).
The four most contaminated areas in the integrated assessment, using the available core indicator results, were the Arkona Basin, the Eastern Gotland Basin, the northwestern coastal areas of the Bothnian Sea and the Kiel Bay, which all had the highest contamination scores in biota. Results showing differences in contamination status between adjacent coastal and open sea assessment units are probably influenced by differences in data availability, as reflected in the confidence (Figure 4.2.1). If an assessment unit with a low confidence has a low contamination score, this may indicate that the status could be worsened if more data were available.
The overall contamination status has not changed markedly during the six years that have passed since the previous holistic assessment (HELCOM 2010), showing that contamination from hazardous substances still gives cause for concern throughout the Baltic Sea area, but also that the situation is not deteriorating. This is also reflected in the more frequent downward than upward trends for concentrations of hazardous substances. A total of 433 time series at stations were assessed for trends. An upward trend (deteriorating condition) was detected in 11 instances, and downward trends (improving condition) were detected in 62 instances, across the studied substances (Figure 4.2.3).
The integrated results for the geographical areas are regionally comparable, however the variation in confidence needs to be considered. The confidence in the result is lowered if monitoring does not cover all key substances. Assessment units with lower confidence generally showed better status than those with high confidence (Figure 4.2.1). For example, polybrominated diphenyl ethers and mercury were highly influential in areas being assessed as not achieving good status in all areas where they were monitored.
To improve the geographical coverage, the integrated assessment also includes stations covered by data for only one or two years labelled as ‘initial status assessment’ data (Figure 4.2.2, Table 4.2.1). The statistical confidence for these stations is lower than for the stations with longer data series and thus lowers the confidence for the assessment unit. However, concentration between the two types of stations are generally similar and reaching as good a geographical coverage as possible is considered important.
An improvement of the data coverage, both regarding geographical coverage and substances assessed, is anticipated for the updated version of the report to be completed by 2018.
Core indicator results
The core indicators have been evaluated against the commonly agreed threshold values. All threshold values and technical specifications are listed in the supplementary report (HELCOM 2017C).
(HBCDD) is a persistent, bioaccumulating and toxic compound with possible impacts on the reproductive and developmental system. It is a brominated flame retardant which is used as an insulation material in the building industry, or as coating of textiles to improve the fire resistance of the materials. As an example of its concentrations in the area, levels of hexabromocyclododecane in herring were below the threshold value, which is set to protect the marine ecosystem and humans consuming fish from adverse effects (Figure 4.2.4, Core indicator report: HELCOM 2017l). The monitoring of hexabromocyclododecane concentrations shows stable and downward trends.
In addition, several other man-made brominated substances have been found in the environment, but little is yet known on their effects on the environment and human health. To keep up with the developments and the emerging risks from such novel substances, there is a need to continue and develop further collaborative monitoring and mapping of their occurrence and use in the Baltic Sea region (Kemikalieinspektionen 2017a).
Polybrominated diphenyl ethers (PBDE) are toxic and persistent substances that bioaccumulate in the marine foodweb.
The threshold value is an environmental quality standard set to protect both the marine ecosystem and humans consuming fish from adverse effects. Polybrominated diphenyl ethers fail the threshold value in all areas where they are monitored (Figure 4.2.5, Core indicator report: HELCOM 2017m).
The use of polybrominated diphenyl ethers as a flame retardant has been banned in most products in Europe since 2004. Therefore, decreasing concentrations are expected in the future. Out of the thirty stations where trends were assessed, downward trends were identified in four stations, and one station showed an upward trend.
Polychlorinated biphenyls (PCBs) are persistent, toxic substances and bio-accumulate in the marine foodweb. The substances have been used in a wide variety of applications and manufacturing processes, especially as plasticizers, insulators and flame-retardants. Polychlorinated biphenyls enter the marine environment due to inappropriate handling of waste material or leakage from transformers, condensers and hydraulic systems.
HELCOM has recommended bans and restrictions on transport, trade, handling, use and disposal of polychlorinated biphenyls. The HELCOM Ministerial Declaration of 1998, and the 1995 ‘Declaration of the Fourth international conference of the protection of the North Sea’ called for measures against persistent, bioaccumulating toxic substances like PCBs by the year 2020. The Stockholm Convention on Persistent Organic Pollutants is ratified by the Baltic Sea countries to protect human health and environment.
Non-dioxin-like PCBs were assessed in relation to a threshold value that is based on food safety, showing values above the threshold in some areas (Figure 4.2.6, Core indicator report: HELCOM 2017n). Trends over time were stable or downward (Figure 4.2.3). No full assessment was possible for dioxins, due to data reporting.
Polyaromatic hydrocarbon (PAH) compounds with low-molecular-weight, such as anthracene, are acutely toxic to many marine organisms. High-molecular-weight PAH compounds, such as benzo(a)pyrene, are less toxic but have greater carcinogenic potential. Polyaromatic hydrocarbon compounds enter the marine environment via the release of crude oil products and all types of incomplete combustion of fossil fuels – coal, oil and gas or wood and waste incineration. They are represented in the core indicator by concentration of the substance benzo(a)pyrene in shellfish.
Benzo(a)pyrene concentrations are below the threshold value in all areas where it is measured, indicating that they will not cause adverse effects to the ecosystem or humans consuming shellfish (Figure 4.2.7, Core indicator report: HELCOM 2017o). Trends over time are relatively stable.
When measurements of benzo(a)pyrene are not available, the secondary substances fluoranthene and anthracene can be considered. Initial status assessments show that anthracene concentrations fail the threshold value in the southwestern Baltic Sea.
Perfluorooctane sulphonate (PFOS) is considered a global environmental contaminant, and is a persistent, bioaccumulating and toxic compound with possible effects on the immune, reproductive and developmental systems as well as lipid metabolism in organisms. The substance has been produced since the 1950s and used in the production of fluoropolymers. It is used commercially to provide grease, oil and water resistance to materials such as textiles, carpets, paper and coatings in general. Perfluorooctane sulphonate has also been widely used in firefighting foams.
Concentrations of PFOS are below the threshold values in all the monitored areas (Figure 4.2.8, Core indicator report: HELCOM 2017p). The concentrations in biota, (measured for example in herring) are at a low level. The concentrations are generally stable over time, with a few down ward trends.
The use of perfluorooctane sulphonate has been banned in the EU since 2008 but it has been replaced with other substances, so called per- and polyfluoroalkyl substances (PFAS) which have widespread use. The PFAS substances are often highly persistent and bio-accumulating and are also a cause of concern. Some PFAS substances are listed on the EU candidate list on ‘Substances of very high concern’ under the REACH regulation (ECHA 2017). Inclusion of additional PFAS substances as core indicators should therefore be considered in the future, to keep track of their use and occurrence in the Baltic Sea region (Kemikalieinspektionen 2017b).
Heavy metals are toxic, and some of them, such as cadmium and mercury also bio-accumulate in the marine foodweb. One current source of heavy metals is burning of fossil fuels, leading to atmospheric deposition. Legislations are in place to decrease inputs of mercury, cadmium and lead to the Baltic Sea. The atmospheric deposition of cadmium and mercury to the Baltic Sea has decreased since the 1990s (Figure 4.2.9).
Mercury fails the threshold value in nearly all areas, except in some coastal areas. In areas where the threshold value is failed, the concentration in herring, for example, is at levels where top predators such as seals are at risk of suffering from secondary poisoning (Figure 4.2.10). Cadmium concentrations in both biota and sediment fail the threshold value in many areas and concentrations are clearly elevated from natural background concentrations. Lead concentrations achieve the threshold value in some areas (Figure 4.2.5), and show downward trends in its concentration in biota and sediment at fifteen stations (Figure 4.2.10). All three heavy metals mostly showed stable trends (Figure 4.2.3, Core indicator report: HELCOM 2017q).
Tributyltin (TBT) is a toxic substance known to affect the hormonal function in marine organisms, for example causing imposex in marine snails. Tributyltin has previously been used in paint to prevent biofouling on ships. Its use in such antifouling paints has been banned on a global level by the 2001 International convention on the control of harmful anti-fouling systems on ships (the AFS convention), which entered fully into force in 2008. Most Baltic Sea countries have ratified the AFS Convention. From 1 January 2008, ships bearing an active tributyltin coating on their hulls are no longer allowed in Community ports (EC 2003b).
Indicated by deformed sexual organs in marine snails, concentrations of tributyltin fails the threshold value along coastal areas in the Baltic Proper, The Sound and the Kattegat, but is achieved in the open sea of the Kattegat. Sediment concentrations fails the threshold value in the southwestern Baltic Sea (Figure 4.2.11; Core indicator report: HELCOM 2017r). However, only data from the southwestern Baltic Sea, which represents only a small number of the available monitoring stations for tributyltin in sediments, have been included in this evaluation due to technical data reporting issues.
An updated evaluation with a wider spatial extent, especially in the southern parts of the Baltic Sea, will be presented for the updated version of the report in one years’ time.
Cesium (137Cs) is the greatest contributor of artificial radionuclides to the Baltic Sea. It emits ionizing radiation, which can have effects at the cellular level and lead to internal damage of organisms. 137Cs was deposited in the Baltic Sea after the accident at the Chernobyl nuclear power plant in 1986. Since then it has bio-accumulated in marine flora and fauna and deposited in marine sediments. The concentrations in herring have decreased from the high values in the 1990s in all sub-basins (Figure 4.2.12, Core indicator report: HELCOM 2017s).
The concentrations of radionuclides are below the threshold value when measured in fish in the Arkona Basin, Bay of Mecklenburg and the Kattegat, indicating good status, but they are above the threshold value in all basins when measured in water. Due to the steady half-life of radioactive decay it is expected that concentrations below the threshold value in biota and water may be achieved in all of the Baltic Sea by 2020.
White-tailed eagles are top predators of the food web, which makes them highly vulnerable to hazardous substances that accumulate and magnify through the food web. The white-tailed eagle has suffered for decades from the effects of persistent chemicals in the Baltic Sea environment. Impacts were already apparent in the 1950’s and identified to be mainly due to at that time widely used insecticides (DDTs) and possibly polychlorinated biphenyls (PCBs). Bans on the use of these substances have already been in place for decades and positive development has occurred since the 1980s.
Negative effects of well-known long-standing environmental contaminants, as well as emerging new contaminants can become apparent in white-tailed eagles before they are visible in other species. Parameters describing the number of hatchlings in nests and the proportion of nests producing young (thus the overall productivity) signal effects from contaminants rapidly and forms the basis for the core indicator. While changes in the abundance of adult birds might only occur over a period of several years, an increased mortality of eggs and thus a lowered productivity is an early warning signal of contamination.
The assessment shows that the core indicator ‘White-tailed eagle productivity’ reached the threshold value in most coastal areas of the Baltic Sea. In the Archipelago Sea, the breeding success remained slightly below the threshold, and in the Swedish coast of the Bothnian Sea and the German coast the nestling parameter did not reach the threshold value (Core indicator report: HELCOM 2017t).
Oil is the main fuel in the majority of the ships in the Baltic Sea region, and large amounts of oil are transported across the Baltic Sea. Oil and other petroleum products are released into the sea intentionally or due to negligence, often as oil in bilge water or via dumping of waste oil. Oil may also be released in ship accidents. Most oil spills are detected along the main shipping routes. Oil spills are a serious threat to the marine environment, causing toxic effects and death of marine animals. Even small amounts of oil on the sea surface can harm waterbirds by contaminating their plumage, which reduces their buoyancy and thermal insulation.
Illegal oil spills have been monitored using aerial surveillance since 1988 in the Baltic Sea area. The aerial surveys today are conducted by all HELCOM Contracting Parties with standardised methods, and cover nearly the whole Baltic Sea area. The effort is focused on the busiest shipping routes. The information collated through the aerial surveillance is used in the core indicator on operational oil-spills from ships.
The core indicator evaluation shows that oil spills failed the threshold value in the Bothnian Bay, the Quark, Bothnian Sea, Åland Sea, Eastern Gotland Basin, Kiel Bay and the Great Belt during the assessment period 2011–2015. The threshold values are set based on the volumes of oil spills into each sub-basin during a modern baseline status defined by the reference period 2008–2013, when the estimated volume of oil spills was at a historically low level. The long-term goal in HELCOM is to reach a level of zero oil spills.
Both the number of observed illegal oil spills and the estimated volume of detected oil have decreased in all sub-basins during recent decades. The size of single spills has also shown a decreasing trend, with a significant decrease in spills larger than 10m3. This decrease in oils spills has been achieved although no concomitant decrease in maritime traffic has occurred, indicating that measures conducted to decrease oil spills to the environment have been successful (Core indicator report: HELCOM 2017u).