The concentrations of certain environmental toxins, such as DDT and PCB compounds, have subsequently been reduced in the Baltic Sea and its biota after the use of these substances was banned. At the same time, however, it has been acknowledged that the range of such harmful compounds is very extensive. In addition to known environmental toxins, the gamut of hazardous compounds also contains many other chemicals and drugs.
According to current knowledge, the most problematic substances for the Baltic Sea and its organisms are the compounds of mercury and bromine, which are used as flame retardants. Other potentially harmful substances include dioxins, as well as organic tin compounds used in ship hull primer paints and pipeline slime control. The levels of cadmium and lead are also a cause of worry, particularly in the Southern Baltic.
The huge range of substances used in industry and elsewhere in society is constantly expanding and the effects of all these new substances on the ecosystem of the Baltic Sea are not yet known. New causes for concern include, e.g. so-called hormone disruptors and drugs.
Toxins accumulate at the top of the food web
Toxic substances are found everywhere in nature in the Baltic Sea, including the Finnish coast. The Baltic Sea is particularly sensitive to harmful substances because of its relative shallowness and low water volume. In the oceans, toxins and chemicals are mixed in a large body of water and their concentrations are rapidly diluted. However, in the Baltic Sea, contaminants appear to be present in high concentrations.
The most damaging toxic substances to the Baltic Sea ecosystem are the ones that slowly decompose, build up in organisms, and accumulate at the top of the food web in fish, seals, and waterbirds. Even the humans that eat fish also receive their share of such toxins.
Levels of harmful substances in fush are studied.
As a result, the levels of dioxin and mercury in Baltic Sea fish have occasionally exceeded the maximum values for edible fish. However, these high concentrations are beginning to be consigned to history, thanks to the environmental measures which have reduced the levels of these toxins in fish.
Where do these toxic substances originate?
The Baltic Sea is surrounded by western industrial society. Its large population, intensive agriculture, diverse industry, and other business introduce various harmful substances to the Baltic Sea.
Some of the toxic materials are those used in the making of products. Most of these industrial chemicals can be recovered already during the production process. Instead, the substances bound to the product itself may be released into the environment during the product’s life cycle and finally, when the product is discarded.
Various chemicals are also widely used in households, as well as in agriculture and other industries. These chemicals occur in detergents and cleaning agents, adhesives, solvents, corrosion inhibitors, plant protection products, as well as in paints, lubricants, and dyes. Many furniture, textiles, and electrical appliances are treated with flame retardants.
Environmental toxins are also produced as by-products of industrial processes, as well as from incineration and other practices where combustion is incomplete.
The emissions of harmful substances occur at different stages of the product's life cycle. Source: European Environment Agency / Meren pärskäys 2015 (A report by the Finnish Environment Institute).
Harmful substances are transported into the sea by many different routes
Some of the harmful substances that enter the Baltic Sea are transported in wastewater, either from industry or urban centres. Whether the wastewater is discharged directly into the sea or some lake or river, the toxic substances contained in these effluents end up in the Baltic Sea sooner or later.
Some of the contaminants come from diffuse sources, i.e. carried in run-off waters discharged from fields, forests, or built-up urban areas. Environmental toxins also end up in the Baltic Sea due to airborne deposition.
There is no reliable information on the long-term development of the burden on the environment
There is insufficient accurate data about most of the toxic chemical compounds in the Baltic Sea, making it impossible to evaluate the development of its environmental burden. The collection of data on many substances, such as medicines, drugs, and cosmetics, has only begun in the 2010s and the investigation of their effects is still in its infancy.
The emissions and effects of some heavy metals are best known. These include nickel, cadmium, mercury, and lead. More of these metals are introduced to the Baltic Sea from industry than from urban wastewater.