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Possible Control of EU Priority Substances in Danish Waters 10 Assessment of PAH
10.1 Definition of the reference state10.1.1 IntroductionPolycyclic Aromatic Hydrocarbons (PAH) constitute a group of chemicals comprising several individual substances, which are all characterized by being composed of at least three aromatic (i.e. benzene) rings. They occur as a constituent of oil from fossil sources and as a by-product of incomplete combustion of organic materials. Their intended use in certain products (creosote and other tar products) is mainly due to their impregnating properties. The following five PAHs represent the PAH group in the context of the proposed Directive on priority substances: CAS no: 50-32-8 (benzo(a)pyrene) The list of priority substances also mention separately two other PAHs, namely anthracene (CAS no. 120-12-7) and fluoranthene (CAS no. 206-44-0), the latter exclusively as an indicator of PAH. As these two substances will never occur in isolation from other PAHs, and as they are assessed not to pose separate problems in relation to compliance with the proposed EQS values, they are in this report included in the description and assessment of the PAH group. Environmentally, the PAHs are characterised by low water solubility, low volatility and high affinity to particulate matter, especially organic matter. Anthracene and fluoranthene, which are among the small PAHs (few rings), have a somewhat higher, although still low, water solubility and volatility than the five others. The PAHs are moderately to slowly degradable in the environment depending on the specific substance and the environmental circumstances /1/. 10.1.2 Main uses and pollution sourcesPAHs occur mainly in tar products, e.g. creosote, but also in much lower concentrations in mineral oil e.g. fuel oil. However, today the largest amounts of PAHs are generated as by-products of incomplete combustion of organic materials. Earlier, creosote was used in significant amounts to impregnate wooden materials with critical long-term outdoor uses such as railway sleepers, pylons/masts, wharves and fishing stakes. Creosote contains significant amounts of PAHs. According to information from DEPA creosote was permitted as an industrial wood preservative until 1991, but it has not been sold since 1989. However, some of the creosote-treated wood is still in use for the above-mentioned purposes. Coal tar, which also has a high content of PAH, was earlier distilled and used for a range of products e.g. as a binding material for asphalt, tarring of fishing nets and in roofing felt (tar paper). Later, bitumen was substituted for coal tar for these purposes as the content of PAH in bitumen is somewhat lower. Due to these uses, former locations for tarring of fishing nets, production and storage of roofing felt, and roads and other asphalted surfaces are possible point sources of surface and groundwater contaminated with PAH /2/. PAHs are also found in car tyres and, hence, tyre wear will contribute to the contamination of roads, parking lots etc. with PAH. The Danish Product Register has registered a number of commodities that contain the five priority hazardous substance PAHs. As the total amount is considerable, more than 17,500 tonnes /1/, it is assumed that these commodities include various types of mineral oil (including fuel oil), which, of course, are consumed in huge amounts. 10.1.3 Releases to and state of the aquatic environmentLocations of previous production and use of creosote and other tar products are possible point sources of aquatic contamination, not least the uses where the products were placed directly in the aquatic environment such as wharves and fishing stakes. Further, facilities such as garages, bus terminals, service stations etc. release PAHs and are typically connected to municipal sewage systems. In addition, wastewater effluents from petrochemical industries including refineries are to be considered potential point sources of PAH contamination. However, the most significant releases to the aquatic environment are due to the incomplete combustion of organic materials, including fossil fuels and wood. The PAHs thus generated are emitted to the atmospheric environment from which they will deposited again (by dry or wet deposition) as diffuse contamination onto surfaces including roads, parking lots and roofs etc. from where they can run off into drainage systems during rain events. Urban or road rain runoff discharges are known to contain PAHs in concentrations that often exceed the current Danish water quality criteria for PAH. The PAH content in road runoff is typically related to traffic intensity and includes, in addition to the combustion by-products (main contribution), also a (smaller) contribution from the tear and wear of tyres produced using PAH-containing extender oils. PAHs are included in the point source programme under the National Monitoring and Assessment Programme for the Aquatic and Terrestrial Environment, NOVANA, and therefore a considerable amount of data document the occurrence in municipal sewage effluents and sewage sludge. There are also a number of monitoring data regarding rain runoff discharges and water courses. As to the latter, it should be mentioned that only in one out of 23 samples did the concentration of the four measured priority PAHs exceed the limit of detection. The monitoring data are summarised in Table 10-1. Table 10-1 Monitoring data for PAH substances (average or median values). The values in parenthesis are the 95% percentiles. References: /3/ /4/ /5/ /6/.
* n.d.: no data. Based on the median values in sewage and in stormwater runoff presented in table 10-1, the total Danish releases of PAH to the aquatic environment by sewage effluent and stormwater are estimated to less than 6 kg/year and 21 kg/year respectively. EQS proposal The EQS values proposed for PAH substances are presented in Table 10-2. Table 10-2 Proposed environmental quality standards (EQS) for priority PAH substances.
N.A. = Not applicable. There has not yet been proposed any value for the background concentration of PAH in the aquatic environment. 10.1.4 Existing legislation/regulation and their impactStatutory Order no. 665 of 4 July 1996 from the Ministry of the Environment on restricting the sale. and use of creosote as amended by Statutory Order no. 535 of 18 June 2003 from the Ministry of the Environment, and Statutory Order no. 534 of 16 June 2003 from the Ministry of the Environment on restricting the sale and use of creosote for wood preservation and creosote-treated wood . The Statutory Orders ban the import, sale and use of products containing creosote. However, under specific preconditions such products can be "imported, sold and used as an industrial wood preservative or for professional re-preservation of wood". Similarly, the import, sale and use of creosote-treated wood is generally banned, however, with the exemption of professional and industrial uses such as for railways, electrical power and teletransmission, fencing, and in ports and waterways. Re-use of wood that was treated before 30 June 2003 is also permitted on condition that the wood is marketed as second-hand wood. The five specific priority PAHs are not mentioned in the definition of creosote (while anthracene is) in the above-mentioned Orders, but their use will be regulated indirectly by the Order. Assessment Statutory Order no. 74 of 14 January 2005 from the Ministry of the Environment on cosmetics According to this recent statutory order, benzo(a)pyrene, benzo(k)fluoranthene and benzo(b)fluoranthene are not permitted for use in cosmetic products. Assessment The three priority PAH substances benzo(a)pyrene, benzo(k)fluoranthene and benzo(b)fluoranthene are included in the list of dangerous substances. None of the three substances must be used in aerosol spray cans. Assessment International regulations etc. Directive 2005/69/EC of 16 November 2005 relating to restrictions on the marketing and use of certain dangerous substances and preparations (polycyclic aromatic bydrocarbons on extender oils and tyres). This new EC directive limits the content of benzo(a)pyrene and other PAHs in extender oils for production of tyres and will thereby, in principle, reduce the release to road surfaces and, consequently, also to rain runoff from these surfaces. However, it is not known to what extent these oils already comply with the new requirements. PAHs are included in EC Regulation no. 850 on Persistent Organic Pollutants (POPs) with an obligation to eliminate the substances, and they are among the substances included in the LRTAP Protocol (Long Range Transported Atmospheric Pollutants). 10.1.5 Conclusion on the need for further regulationIn treated sewage effluent, the 95% percentile levels of anthracene, fluoranthene, benzo(a)pyrene and the sum of benzofluoranthenes are all lower than the AA-EQS values. The AA-EQS for the sum of benzo(ghi)perylene and indeno(1,2,3-cd) pyrene is 5 times lower than the LOD in the performed monitoring programme. Hence, it cannot be evaluated whether these substances comply with the EQS value or not. To evaluate the possible need for measures in relation to discharges of stormwater from separate systems the concentrations of the selected PAHs observed in this type of discharges (see table 10.1) should be compared to the MAC-EQS. However, MAC-EQSs have presently only been defined for anthracene, fluoranthene and benzo(a)pyrene. The levels of the two former substances are below the MAC values in effluents from separate stormwater runoff systems while benzo(a)pyrene requires a reduction of 1.4 times to obtain compliance. MAC values for the sum of benzo(ghi)perylene and indeno(1,2,3-cd) pyrene have not been defined, and therefore the evaluation of these two specific PAH-substances cannot be made at present (the AA-EQS is not considered suitable for this purpose). The levels found in surface water are, with the possible exception of the sum of benzo(ghi)perylene and indeno(1,2,3-cd)pyrene, all below the AA-EQS. In summary, there appears to be no need for further national measures to be able to comply with the proposed EQS values for PAH (with a reservation for the sum of benzo(ghi)perylene and indeno(1,2,3-cd) pyrene in stormwater) and, consequently, there is no need for further progressive reduction in Scenario A. In Scenario B, however, there is an obligation to continue the progressive reduction of emissions, discharges and losses beyond the EQS compliance level. As the existing legislation is assessed not to provide any further significant reduction, some possible additional measures are described in Section 10.2. The five substances in the PAH group and anthracene are all classified as priority hazardous substances while fluoranthene is just a priority substance. This implies that the "discharges, emissions and losses" to the aquatic environment must eventually cease. In Scenario A, which only implies an obligation to consider all technical reduction options, there is no time frame for this to be achieved while in Scenario B the time -frame is 20 years from the date of entry into force of the directive. The gradual implementation of technical measures aimed at ceasing/phasing out PAH emissions, discharges and losses is considered also to cover the progressive reduction obligation in Scenario B. Finally, it should be mentioned that as the PAHs are naturally occurring substances there is a need for a background level to be defined because an absolute "zero" will not be possible to obtain. Such a level remains yet to be proposed. 10.2 Possible reduction/elimination measures10.2.1 Technical measures to reduce/eliminate PAHThe use of creosote in Denmark for preservation of wood for particularly demanding purposes is believed to have ceased already about 15 years ago, and much of the remaining creosote-treated wood has probably been replaced within the last few years. Some of it is, however, still in use, but the release of PAH from such, aged materials is assessed to be small and probably not relevant as a target for an action to eliminate the discharges, emissions and losses of PAH into the aquatic environment. PAHs are natural constituents of fossil fuel products and do as such occur in asphalt and bitumen used for road surfaces. Earlier, coal tar was used for this purpose but was already in the mid 1970's replaced by bitumen, which has a lower content of PAH. It is, however, considered outside the scope of the study to suggest a society based on another primary energy source than fossil fuels The use of another material than asphalt for the general paving of roads etc. appears unrealistic in this context and will not be dealt with further in this report. Stormwater runoff Stormwater runoff from roads, other paved surfaces and roofs are today considered the dominant source of release of PAH into the aquatic environment. Therefore, technological measures that can reduce this input should be considered though it appears unrealistic to introduce measures specifically aimed at eliminating PAHs. The majority of the PS/PHS including PAHs are characterised by properties such as lipofilicity and significant sorption onto particulate (organic) matter. Therefore, it is assessed that technological measures that generally aim at retaining suspended particles in surface runoff will substantially reduce the loads of PAH and other PS/PHS on the aquatic environment. 10.2.2 Possible synergies with other (priority) substancesA general action against suspended matter/pollutants in stormwater runoff will not only lead to a significant reduction in PAH inputs to the aquatic environment but also bring down the inputs of most of the other PS/PHS. 10.2.3 Summary and assessment of technical possibilitiesAs the PAHs are classified as priority hazardous substances, PHS, Scenario B requires that the anthropogenic discharges, emissions and losses into the aquatic environment must cease within 20 years after the date when the Daughter Directive enters into force. Considering the already implemented regulations on the use of PAH-containing products other than fossil fuels for power and heating purposes, the present and future dominant source type of PAH release into the aquatic environment is the discharge of stormwater runoff from paved surfaces and roofs. To meet the requirements of ceasing "discharges, emissions and losses" of PAHs within 20 years in Scenario B, action must be taken against the stormwater mediated releases. It is assessed that the only realistic way of doing this is by introducing detention basins and similar technological arrangements by which particulate matter in the effluent is retained prior to the discharge into fresh or coastal surface waters (see Chapter 13). With regard to Scenario A, it is assessed, based on the interpretation of the obligations in the WFD (article 16.8), that such measures are probably not realistic if aimed exclusively at eliminating PAHs (but possibly as a common measure, see Chapter 13). 10.3 Economic AssessmentThe technical assessment concluded that the only realistic measures are general technological measures aimed at retaining suspended particles in surface runoff. Since this type of measure is not substance specific, it is described technically and assessed economically in a separate chapter (Chapter 13). 10.4 Conclusion on PAHAccording to the monitoring data available, the concentrations of PAH in various discharges as well as in surface waters do not pose a problem in relation to compliance with the proposed EQS values. However, reservation is made regarding the sum of benzo(ghi)perylene and indeno(1,2,3-cd) pyrene, for which the EQS is lower than the detection limit in the monitoring programmes and for which a MAC-EQS has not been established (relevant for evaluation of stormwater discharges). With this reservation, there appears to be no need for further national progressive reduction measures in Scenario A while Scenario B implies an obligation to continue the reduction of emissions, discharges and losses of PAH. The PAH group is defined as a priority hazardous substance for which cessation of discharges, emissions and losses to the aquatic environment must be achieved. In Scenario A the time -frame of this is undefined (and there is only an obligation to consider all technical reduction options), while in Scenario B it is 20 years from the date of entry into force of the Daughter Directive. There are no longer any intended uses in Denmark of products with high contents of PAH as the use of creosote ceased already 15 years ago. It is assessed that practically all remaining creosote-treated wood will be replaced within 20 years from now. Today, stormwater discharge, in which the PAH content mainly originates from combustion by-products, is by far the largest direct source of PAH emitted to surface waters in Denmark. Therefore, the most relevant measure to be taken to eliminate PAH discharge, i.e. fulfilling the cessation/phase-out obligation in Scenario B, is the general action against suspended matter/pollutants in stormwater runoff, which is described in Chapter 13. As mentioned before, Scenario B requires cessation measures to be fully implemented within 20 years after entry into force of the Daughter Directive. The stormwater runoff initiative can also be regarded as the main progressive reduction measure in Scenario B. An accelerated replacement of the remaining creosote-treated wood is not considered to give environmental benefits that can justify the costs. With regard to Scenario A, it is assessed, based on the interpretation of the obligations in the WFD (article 16.8), that such measures are probably not realistic if aimed exclusively at eliminating PAHs (but possibly as a common measure, see Chapter 13). 10.5 References/1/ Kjølholt J, Winther Ringgaaard K, Skårup S (2005). Kilder og miljøtilstand for prioriterede stoffer under Vandrammedirektivet. Miljøprojekt nr. XXXX (unpublished). Danish Environmental Protection Agency. /2/ Miljøstyrelsen (2002). Kilder til jordforurening med tjære, herunder benzo(a)pyren i Danmark. Miljøprojekt Nr. 728 /3/ Miljøstyrelsen (2004). Punktkilder 2003. /4/ Miljøstyrelsen (1997). Miljøfremmede stoffer i overfladeafstrømning fra befæstede arealer. Miljøprojekt nr. 355. /5/ Fyns Amt (2004). Vandkvalitet og stoftransport, Vandløbenes biologiske tilstand, Forureningskilder. Rapport, Maj 2004 /6/ Århus Amt (2001). Vandløb og kilder. Vandmiljøovervågning 2000. Rapport, Århus Amt, Natur og miljø. August 2001.
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