Relevance of the Indicator

Hazardous substances assessment

The status of hazardous substances is assessed using several core indicators. Each indicator focuses on one important aspect of the complex issue. In addition to providing an indicator-based evaluation of PAHs and their metabolites, this indicator will also contribute to the overall hazardous substances assessment along with the other hazardous substances core indicators.


Policy relevance

Benzo(a)pyrene, benzo(b)fluoranthene, benzo(g,h,i)perylene, benzo(k)fluoranthene, indeno(1,2,3-cd), anthracene, pyrene, fluoranthene and naphthalene are identified as priority substances by European Commission (Directive 2008/105/EC).

The maximum levels of benzo(a)pyrene, and also a sum of benzo(a)pyrene, benz(a)anthracene, benzo(b)fluoranthene and chrysene, are regulated in food stuff according to the Commission Regulation (EC) No 835/2011.


Role of PAH and their metabolites in the ecosystem

Polycyclic aromatic hydrocarbons (PAHs) are of concern due to their persistence and potential to accumulate in aquatic organisms, particularly invertebrates, such as bivalves and crustaceans. In most vertebrates, PAHs are fairly rapidly metabolized, but they and their toxic intermediates that emerge during metabolic degradation, can cause deleterious effects in fish.

The PAH compounds identified as priority pollutants include low-molecular-weight PAH compounds, two-ring compounds (naphthalene) and three-ring compounds (acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene) that are acutely toxic to a broad spectrum of marine organisms. The compounds also include high-molecular-weight PAHs with four-ring compounds (fluoranthene, pyrene, benzo(a)anthracene, and chrysene), five-ring compounds (benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, and dibenz(a,h)anthracene), and six-ring compounds (indeno(1,2,3-c,d)pyrene, benzo(g,h,i)perylene) that are less toxic but have greater carcinogenic potential (Kennish 1997).

Indeno(1,2,3-c,d)pyrene and chrysene have been shown to cause carcinogenic effects in experiments on animals (IARC class 2b), and benzo(a)pyrene to cause cancer in humans (IARC class 1). Weakly- or non-carcinogenic PAHs can modify the carcinogenic activity of other PAHs in complex mixtures (Marston et al. 2001). Therefore, synergistic effects of PAHs can be larger than the total levels of PAHs would indicate. Also, PAHs are transformed in the marine environment, e.g. when exposed to sunlight, the mechanism known as phototoxicity is involved, producing reactive and toxic photomodification products (HELCOM 2010). Thus, evaluating the overall environmental status based on PAHs has to take this complexity into consideration.

PAHs tend to associate with particulate material due to their low water solubility and hydrophobic nature. Deposition of these particles can lead to an accumulation of PAHs in the sediment. PAHs are persistent, especially in anaerobic sediments, with the higher molecular weight PAHs being more persistent than the lower molecular weight compounds (Kennish 1997; Webster et al. 2003).

Bioaccumulation of PAHs in marine organisms from sediments is dependent, thermodynamically, on the ratio between adsorption capacity of the sediment and absorption capacity of the organism. Different profiles of contaminants have been observed in organisms of different trophic levels that have been attributed to a partial biotransformation of the contaminants in the organisms of higher trophic levels (Baumard et al. 1998b). Increased levels of neoplastic aberrations or tumors have been found in fish exposed to PAH contaminated sediments. High concentrations of PAHs are also harmful to reproduction of fish and can damage cellular membrane structures (Knutzen 1995). Oxidised PAHs in an organism are known to bind to DNA and/or cause mutations which may lead to cancer.

To evaluate effects of PAH exposure on fish, concentrations of the main metabolites such as 1-hydroxypyrene, 1-hydroxyphenanthrene and 3-hydroxybenzo(a)pyrene can be determined in bile by HPLC with fluorescence detection (HPLC-F), by synchronous fluorescence scanning, gas chromatography with mass selective detection (GC/MS) and also by UPLC/MS/MS (Ariese et al. 2005). PAH metabolites in fish bile reflects the level of exposure during the last few days before sampling, varying to some degree depending on the feeding activity of the fish.


Human pressures linked to the indicator

GeneralMSFD Annex III, Table 2a
Strong linkPAH introduced to the marine environment through spills of petrochemical substances and emissions from fuel consumption and maritime activities

Substances, litter and energy

- Input of other substances (e.g. synthetic substances, non-synthetic substances, radionuclides) – diffuse sources, point sources, atmospheric deposition, acute events

Weak linkAtmospheric deposition may be a significant pathway


Some polyaromatic hydrocarbons (PAHs) are formed naturally, but the majority of PAHs in the marine environment stem from anthropogenic activity. Anthropogenic PAH sources in the marine environment include the release of crude oil products (petrogenic source) and all types of incomplete combustion of fossil fuels – coal, oil and gas or wood and waste incineration (pyrolytic sources) (Neff 2004).

Each source generates a characteristic PAH pattern enabling distinction of the sources in a sample by analyzing the concentration relationships of individual PAH compounds (Baumard et al. 1998, Sicre et al. 1987, Yunker et al. 2002). The PAH contamination in the Gulf of Finland and some areas in the western Baltic Sea (Sound, Belt Sea and Kattegat) have been identified as having a significant contribution of petrogenic PAHs, compared to the rest of the Baltic Sea where pyrolytic sources predominate. PAHs from pyrolytic sources may be introduced through atmospheric deposition, however no reliable information is available on the airborne deposition of PAHs to Baltic Sea surface waters (Pikkarainen 2004). In the areas where petrogenic PAHs are identified as a significant source, PAH contamination is likely to originate from atmospheric deposition combined with shipping activities.

PAH compounds are pervasive in the Baltic Sea. Anthracene has been detected in fish from Swedish monitoring stations selected to reflect reference conditions. Anthracene has also has been measured in sediment from the Stockholm area (with concentrations falling inversely with distance from central Stockholm) and homogeneous coastal samples, indicating small local impact. It has also been measured in detectable concentrations in water areas sampled with the use of passive sampling devices. Fluoranthene is frequently present in fish from Swedish background stations, and also found in sediment and sludge. It has been found in all water samples from Sweden taken by means of passive sampling devices, and it is detectable in groundwater samples (Swedish EPA 2009).

With distance of point sources there are no temporal trends of PAH contamination, mirrored as PAH metabolites detectable in dab and flounder from the North Sea and the western Baltic Sea caught during 1997 and 2004 (Kammann 2007). Lower values than in North Sea (dab, cod, flounder, haddock) and Baltic Sea (flounder, cod, herring, Vuorinen et al. 2006; eelpout) have been detected in Barents Sea (cod) and near Iceland (dab). Higher concentrations are present in fish caught in harbour regions or in coastal areas (eelpout, Kammann and Gercken 2010).