Photo: Olga Gordeeva /Mostphotos.

Together with colleagues at Stockholm University, Emma Undeman, researcher at the Baltic Sea Centre, has written four reports compiling the current science on the organic contaminants PCBs, dioxins, brominated flame retardants, PFOS and diclofenac (an active pharmaceutical ingredient). The reports provide description of current knowledge regarding where the substances come from, how they are transported and how the concentrations in the Baltic Sea have changed over time.

Better knowledge of sources and transportation

Researcher Emma Undeman and her colleagues at Stockholm University have compiled the current research on important groups of contaminants in four new reports. Photo: Henrik Hamrén.

HELCOM (Helsinki Commission) has the task of developing a plan for how to further reduce the levels of hazardous substances in the Baltic Sea. In order to implement effective measures, one must know what the most important sources are and which route the chemicals take to the sea. The reports will contribute to HELCOM's work in this field.

– We must identify the major sources of the hazardous substances and understand how they move in the ecosystems to be able to do something about the problem, says Emma Undeman. An important question is often how much sources in the Baltic Sea region contributes to the total inputs to the Baltic Sea. Many hazardous substances are transported long-distances  from polluted areas via air. Then local, or even regional efforts are not enough, but global cooperation is required.

The levels of many classical pollutants have decreased over time. Dioxins and PCBs, which were released in large quantities until the 1970s, have fallen sharply, but in some places levels still exceed levels considered safe by HELCOM. Other substances identified as environmental pollutants more recently are also of concern.

– The levels of PFOS, a substance that today is largely banned, are now in most cases below the threshold defined by HELCOM when measured in biota. But data is scarce, in particular in other matrices. There is also concern regarding the thousands of other PFASs that are still used in society, in some cases as replacement for PFOS, says Emma Undeman. The pharmaceutical ingredient diclofenac is also used extensively and sometimes occurs in high concentrations along the coast, but data is limited and the analytical methods used are often not sensitive enough, she continues.

Major lack of knowledge about dioxins and flame retardants

Although many hazardous substances in the Baltic Sea are well studied, there are still knowledge gaps. This applies, for example, to dioxins, one of the most toxic substances we know of, and which have been studied in the Baltic Sea for several decades.

– Quantifying sources of dioxins is a challenge, says Emma Undeman. There are still large knowledge gaps here that hinder effective measures. As with many hazardous substances, we have focused on management of emissions from larger industries. And the levels have decreased, especially close to previous point sources. But in recent years, the decline has been slower. This means that there are other sources aswell. It is likely that the official statistics underestimate dioxin emissions. For example, small-scale combustion, such as wood burning, can be a larger source than the Baltic Sea countries report.

Banned brominated flame retardants (PBDEs) also occur in concentrations above the limit values. Here it is also uncertain which the most imporant source is.

– It is surprising that it is still unclear where the biggest emissions come from, says Emma Undeman. Different scientific studies come to quite different conclusions. For example the importance of PBDE emissions indoors that escape to the outdoor air, versus those from landfills. Estimating emissions is difficult, even for such a well-studied group of chemicals as PBDEs. In addition, the threshold concentration defined ​​for PBDE in living organisms is low compared to current levels in the marine environment. It will take a very long time for levels to decline below them - between 20 and 40 years according to an estimate in the report.

The PCBs are also difficult to manage. Emissions have largely ceased, but they continue to circulate in the environment because they break down so slowly. When the levels in the air decrease, they are released back from the soil where they were once deposited from air, and in addition emissions continue from e.g. old buildings and electronics in landfills. From there, they slowly leak into the environment.

Emissions to wastewater after human use is the major source of diclofenac in the Baltic Sea. Photo: Artesia Wells /Mostphotos.

Major differences between the Baltic Sea countries

The Baltic Sea countries are different and both handling, legislation and lifestyle affect how hazardous substances are spread.

– There are sometimes large differences between the countries, for example how they handle waste and wastewater, says Emma Undeman.

The use and availability of certain drugs also vary widely, such as the prescription of diclofenac in tablet form. The total prescribed quantityis low in Denmark and Finland compared to Sweden, which in turn has a moderate prescription rate compared to the Baltic states. Diclofenac is available without a prescription in creams in all countries around the Baltic Sea, but information about sales of these products is lacking, so the significance of this source is still unclear.

In Poland, a comparatively large fraction of solid waste is stored in landfills, which are therefore likely significant sources of several hazardous substances, while Sweden and Germany handle waste better through recycling and controlled incineration.

– Landfills are generally problematic as toxic substances can leak directly to the environment via leachate or evaporation. They can also be formed or spread to the atmosphere if a landfill inadvertently starts to burn, she says.

Together, the reports produced for HELCOM provide an updated overview of our knowledge regarding sources and distribution patterns for some problematic groups of environmental pollutants.

– The reports do not provide answers to all questions, there is still a lot we do not know. But they point to knowledge gaps that researchers and authorities need to prioritize in order to move forward in the action work, concludes Emma Undeman.

Text: Maria Lewander