Hazardous Substances Thematic Assessment

Many different activities onshore and in the marine ambit can introduce hazardous substances to the marine environment, particularly harbours and industry onshore, aquaculture, shipping, offshore oil and gas exploration at sea

The activities that can potentially introduce hazardous substances into the marine environment are closely linked to urban population size, particular examples being power production, industrial activity wastewater treatment, transport and shipping. Other such activities not linked to urban areas are the use of biocides in agriculture, encompassing pesticides, herbicides, fungicides, etc, and dredging. Tourism can be linked to both urban and rural activities, trending probably towards larger cities for the majority of tourists.

The key human activities affecting levels of hazardous substances are:

Dredging for navigational purposes (physical restructuring of rivers, coastline or seabed):
Many harbours, rivers, river mouths, estuaries and other near-coastal freshwater and marine areas accumulate contaminated sediment. The contamination may go back several decades, resulting from discharges into water by coastal or riverine industries, dumping of industrial and household waste, accidents involving the sinking of ships and loss of cargo at sea, leakage from landfills, dumped munitions, or simply the accumulation of contamination from boats (e.g., tributyltin, copper). Sediment contamination may be severe and will include persistent chemicals phased out decades ago, such as PCBs. The disturbance of sediments for maintenance or capital dredging activities has the potential to remobilize these contaminants. Remobilization can occur at all stages of the dredging process. The dredging itself can lead to the dispersal of contaminated sediment, depending on the technique used (e.g., conventional dredging with an excavator or suction dredging). Where dredged material is relocated to sea disposal sites, there will be some spread of material during the dumping process, typically 5 10%.

Dredging and the dumping of waste and other matters have been well regulated since the Oslo Convention came into force in 1974. OSPAR Guidelines specify best environmental practice (BEP) for managing dredged material, with the most recent version adopted in 2014 (OSPAR Agreement 2014-06). Sediment that is heavily contaminated is considered hazardous waste and must be deposited on land. Dredging is most extensive in countries where large, sediment-loaded rivers meet the ocean, such as the Netherlands, Belgium and France. Approximately 1 500 million tonnes of sediment are dredged in the OSPAR area annually, with the amount increasing slightly over the period 2008-2014 (OSPAR 2022).

Non-renewable energy generation:
Coal combustion in power plants is the most important source of atmospheric mercury, making up 65% of all anthropogenic mercury emissions to the atmosphere. For the entire OSPAR area combined, atmospheric mercury dominates. This and other sectors like refineries and iron mills also discharge other heavy metals such as nickel, vanadium, arsenic, lead, selenium, chromium, and cadmium.

Extraction of non-living resources:
The exploration and production of oil and gas utilises a range of chemical products (see and ). During the drilling phase, drill cuttings which may be polluted by drilling fluids and hydrocarbons build up on the sea floor. The North Sea contains several million tons of such cutting piles, which can be the source of hydrocarbons and heavy metals. OSPAR has put measures in place to reduce the impacts of pollution by oil and/or other substances from cuttings piles (OSPAR Recommendation 2006/5) and to manage the use of organic-phase drilling fluids (OPF) and the discharge of OPF-contaminated cuttings (OSPAR Decision 2000/3).

During the production phase, the water in the oil/gas reservoir will contain traces of petroleum products and be released into the ocean after separation from the bulk petroleum. This is called produced water. After treatment to lower the content of unwanted components, the produced water can either be reinjected into a geological formation or discharged to the sea. Reinjection is considered the Best Environmental Practice, but is not always technically feasible, in which case the water must be discharged to the sea. This constitutes, by volume, the largest discharge from petroleum production (appx. 300 million m³ annually in the OSPAR area; Beyer et al., 2020). These discharges contain dispersed crude oil, polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs) and metals. The PAH compounds are a key risk element. Typically, total PAH water concentrations are 25–350 ng/L within 1 km downstream of a typical oil platform, and background PAH levels have reached 5 10 km downstream (Beyer et al., 2020). Fish samples generally contain low levels of PAH even in the North Sea, although metabolites indicating PAH exposure have been found in fish in the production intensive Tampen area on the northern border between Region I and II (Beyer et al.,2020). could lead to similar constant oil pollution and the ensuing increased shipping in Arctic waters would increase the risk of accidents.

Oil flaring can also introduce combustion products into the environment. The North Sea oil industry has low flaring intensity per barrel of oil (about 1/3 of the global average). For instance, Norway banned non-emergency flaring in 1971.

The extraction of sand and gravel could not only destroy habitats but also remobilise contaminants otherwise bound to undisturbed sediments. Mining with sea disposal of mining waste may also contribute to contamination, in particular mining for metals, as the fine-grained residue from the mining process will contain more metals. This practice occurs in Norway, but not with metal-rich ores (one copper mine with sea disposal is planned, but not yet active). Deep-sea mining for metals may also increase the dispersal of metals to the environment.  The area between Svalbard and Jan Mayen has turned out to be rich in copper and zinc, and Norway began a process towards the possible opening of the seafloor areas for mineral extraction in 2019.

Extraction of living resource:
Fish and shellfish harvesting by trawling have the potential to remobilise contaminants bound to sediments. Trawl doors weigh several tons and create furrows when dragged along the sea bottom; the North Sea especially is criss-crossed by such trawler tracks.  Fishing-boat engines, as well as fish and shellfish processing, also have the potential to introduce hazardous substances.

Aquaculture – marine, including infrastructure:
Aquaculture is an industry of major importance in some areas (e.g., salmon production in Norway, the Faroes and the United Kingdom, and shellfish production in Spain and France). Aquaculture cages are a substantial source of copper input, through leakage from the copper-based paint used for antifouling. Chemicals can be used as antifoulants or to clean facilities, and pharmaceuticals for the treatment or prevention of disease and parasites, especially the removal of salmon lice. In Norway, which has the largest aquaculture industry in OSPAR, several pharmaceuticals and treatment forms have been used over the years. Bathing treatments using organophosphate insecticides such as dichlorvos (until the early 1990s) and later azamethiphos were used extensively until the mid-2010s (Overton et al., 2019). During the 2000s, treatment using food pellets containing flubenzurons (diflubenzuron and teflubenzuron) and bathing treatments using pyrethroids (cypermethrin and deltamethrin), azamethiphos (an organophosphorous substance) and hydrogen peroxide gained popularity. Similar changes also occurred in Scotland during the period 2005-2011 (Murray, 2016). While hydrogen peroxide degrades relatively quickly, flubenzurons and pyrethroids degrade quite slowly and are poisonous to all crustaceans including non-target animals such as shrimp and lobster. Since 2015, the trend has been to make less use of pharmaceutical treatments and increased use of non-medicinal methods (mechanical or thermal delousing) (FHI 2022). In part, this is because of the evolution of resistance in salmon lice (especially to pyrethroids and azamethiphos). In shellfish production, usage of antibiotics such as tetracycline affects the aquatic environment and poses a threat to human beings as well.

Transport (infrastructure, shipping, air and land):
Transport can introduce hazardous substances either directly (e.g., fuel combustion,  antifoulants) or indirectly (e.g. leaks, poorly maintained vessels and equipment). The most obvious source is acute oil pollution episodes from either intentional oil discharges or ship accidents. In recent years, exhaust scrubbers have emerged as a new source of marine pollution. On 1 January 2020, the so-called IMO 2020 regulation came into force, reducing the upper limit of sulphur content in fuel oil from 3,50% to 0,50% globally. Some areas, including the North Sea, have an even stricter limit of 0,10%. However, it is acceptable to use fuel oil with a higher sulphur content but limit the air pollutants by installing exhaust gas cleaning systems (“scrubbers”). This has led to a huge increase in the use of exhaust scrubbers since 2018, mostly of the open-loop type which discharge the water used for scrubbing into the sea. A medium-sized ship (12 MW engine power) discharges approximately 500-1 000 m³ of "used" water per hour. This water is contaminated by PAHs (e.g., naphthalene and phenanthrene) and metals (e.g., nickel and vanadium). The discharged water also has a very low pH (ca. 3), which may increase the toxicity effect of the contaminants. The open scrubbers prevent the atmospheric release of contaminants but instead directly discharge into the sea along shipping routes. Finally, ship paint containing copper (as an antifoulant) is a major source of copper input to marine areas with heavy maritime traffic, as well as to harbours.

Ships and leisure boats also use antifoulant paint to reduce biofouling (growth of marine organisms on the hull). While the use of tributyltin as an antifoulant is now banned, current antifoulants typically contain copper, and account for a substantial part of the input of that metal into the marine environment. Corrosion anodes are typically made of zinc with trace impurities of cadmium and lead.

Urban and Industrial uses:
Society’s need for trade and movement of goods, stable economies, industrial processes, materials, and health and well-being are drivers of industrial uses. Industrial atmospheric emissions and direct discharges into the sea can lead to the input of substances into the environment, and long-range transport can be a major contributor to the North Sea area. In the OSPAR area, as well as globally, discharges of substances like PAHs and PCBs from industry into the air and sea have been strongly reduced during recent decades.

However, other challenging substances remain in use. Perfluorinated alkyl substances (PFAS) are a group of substances manufactured or used in many industrial processes including metal plating, textile industries and the manufacturing of fluoropolymers. Long-chained PFAS such as PFOS and PFOA are known to be highly persistent, to accumulate in the ecosystem, and for their toxicity. While PFOS and PFOA historically were the most widely produced PFAS substances, they were phased out by European industry after 2005 and later placed under restrictions (PFOS by the Stockholm Convention in 2009; PFOA by the EU REACH regulation (Registration, Evaluation, Authorisation and Restriction of Chemicals) in 2019).  However, there are over 4 000 PFAS substances on the market, and little is known about their toxicological effects and environmental fate. Some of these substances can also be transformed into PFOS or other PFAS known to be hazardous. Accordingly, the EU has recently proposed the banning of a wide range of PFAS substances.

Waste and disposal [Urban and industrial uses]:
Society’s need for health and well-being and for industrial goods and materials processing are drivers of waste treatment and disposal. Direct discharges can lead to the input of substances into the environment. In advanced wastewater treatment plants, co-precipitation of some contaminants will occur when phosphor is flocculated, and bacteria can degrade some organic contaminants, but more water-soluble and less degradable contaminants will not be retained. Wastewater treatment plants have been shown to be a major source of PFAS in some areas. Furthermore, plants where contaminated waste is treated appear to be important sources of PFAS.

Sewage is a major pathway for substances used in pharmaceutical and personal care products. More than 100 pharmaceuticals and pharmaceutical metabolites have been detected in coastal waters. The most frequent substances found are antibiotics, followed by non-steroidal anti-inflammatories and analgesics (Gaw et al., 2014). Pharmaceutical metabolites (i.e., the results of the body’s metabolism of these substances) and transformation products can be present in higher concentrations than in the original substance and can also be more toxic (Gaw et al., 2014). Substances originating from personal care products (including soaps, sunscreens, insect/tick repellents and toothpaste) are also found in the environment, in some cases in concentrations large enough to have harmful effects on marine life (Hopkins and Blaney 2016, EU 2016). Wastewater treatment may remove 10-100% of pharmaceuticals and personal care product substances, depending on the properties of the substance and the treatment technology used (Gaw et al., 2014, Hopkins and Blaney 2016).

Tourism and leisure:
Tourism is linked to several of the other activities, and in particular is responsible for a large part of the transport component. Recreational boating is linked to a substantial part of the usage of antifoulant paints, which typically contains copper that leaks into the environment. Poorly maintained vessels have the potential to introduce other hazardous substances such as TBTs and petroleum products. 

Agriculture [Cultivation of living resources]:
Society’s need for food drives the need for agriculture. Agricultural run-off can lead to the input of substances to the environment, such as pesticides and micronutrients used in fields, and growth promoters. The agricultural sector has a long history of using persistent herbicides and pesticides, some of which eventually end up in the marine environment. Many of these substances, such as DDT and organophosphates, have been banned in the OSPAR area since the 1970s-1980s but can still be detected in marine life in many locations. In some places, DDT has been found to increase in shellfish, and this has been linked to DDT mobilisation in the soil owing to increased precipitation (which again is possibly linked to climate change). Older, more toxic insecticides such as organophosphates were replaced by neonicotinoids in the early 1990s (Hladik et al., 2018), but these substances also ended up in the marine environment in concentrations large enough to be a threat in some coastal areas. As a result, the three main neonicotinoids (clothianidin, imidacloprid, and thiamethoxam) were banned in the EU in 2018, but have sometimes been legalised for certain uses (sugar-beet crops).