Trends in Concentrations of Polybrominated Diphenyl Ethers (PBDEs) in Sediments
D8 - Concentrations of Contaminants
D8.1 - Concentration of contaminants
Concentrations of polybrominated diphenyl ethers (PBDEs) detected in sediment in the areas assessed either show no statistically significant change (Northern North Sea) or are declining (Irish Sea). The lack of assessment criteria means the environmental significance of the concentrations cannot be assessed.
Area assessed
Printable Summary
Background
Polybrominated diphenyl ethers (PBDEs) are a group of congeners, mainly used as flame retardants in a variety of materials including plastics, textiles, electronic products, building materials, furnishings and vehicles (Figure 1).
PBDEs may enter the environment through emissions from manufacturing processes, evaporation from products that contain PBDEs, recycling wastes and leachate from waste disposal sites. They are widespread and have been detected in air, sediments, surface waters, fish and other marine animals.
PBDEs are toxic, they take a long time to degrade and have the potential to accumulate in fish or shellfish (taken in either directly from the surrounding water or indirectly via food). As a result, some PBDEs were banned or restricted within the European Union starting in 2004. Production of some groups of PBDEs was banned in 2009 by 180 countries that are signatories to the Stockholm Convention.
The spatial distribution of PBDEs in marine sediments is variable. PBDEs do not dissolve in water and bind strongly to soil or sediment. As a result PBDEs in sediment are not very mobile.
The OSPAR Hazardous Substances Strategy has the ultimate aim of achieving concentrations in the marine environment close to zero for man-made synthetic substances, and PBDEs are included in the group of brominated flame retardants on the OSPAR List of Chemicals for Priority Action. The status of PBDE concentrations in sediment is calculated but not assessed because there are no OSPAR assessment values developed with which to assess status.
Figure 1 (i): Polybrominated diphenyl ethers (PBDEs) are a group of compounds mainly used as flame retardants in a variety of materials, including electronic products
Figure 1(ii): Polybrominated diphenyl ethers (PBDEs) are a group of compounds mainly used as flame retardants in a variety of materials, including vehicles
Polybrominated diphenyl ethers (PBDEs) are a group of 209 different congeners. Their main use is as flame retardants in different types of material including plastics, textiles and electronic products. The three major commercial PBDE mixtures that have been produced are pentaBDE, octaBDE and decaBDE. Globally, decaBDE is the most widely used.
PBDEs are flame-retardants of the additive type, which means that they are physically combined with the material being treated rather than chemically combined (as in reactive flame retardants) and are more likely to diffuse out of the products (European Commission, 2001, 2003; Hutzinger and Thoma, 1987 cited in Alaee et al., 2003). Leakage of PBDE occurs during production, use or disposal of such products, and PBDEs are mainly transferred to the ocean via rivers and through diffuse distribution in the atmosphere (OSPAR, 2009). The presence of PBDEs in air samples from Arctic Canada, for example, provides evidence of their long-range transport (de Wit, 2002).
The advantage of these compounds for industry is their high resistance to acids, bases, heat, light, and reducing and oxidising compounds. However, this becomes a disadvantage in the environment where they persist for very long periods. Increased concentrations of these compounds have been measured in environmental samples since the 1970s (de Wit, 2002). PBDEs are toxic, persist in the environment and can bioaccumulate. As a result, the PBDE substances included in the commercial pentaBDE- and octaBDE-mixtures were banned in the European Union in 2004, and since 2009 have been listed under the Stockholm Convention (2009), meaning that a majority of countries worldwide have agreed to phase out these compounds.
PBDE has been reported as neurotoxic, immunotoxic and to affect thyroid hormone receptors in sensitive human populations (de Wit, 2002). Effects on behaviour and learning (Eriksson et al., 2006a,b) and hormonal function (Legler, 2008) have been reported in mammals, while reduced reproductive success has been documented in birds (Fernie et al., 2009).
Smaller PBDE molecules are more toxic and bioaccumulate more readily than larger molecules. Debromination of highly brominated BDEs (such as decaBDE) to these smaller forms is a possibility and justifies monitoring based on a broad set of congeners. All PBDEs are hydrophobic or ultra-hydrophobic substances that do not dissolve in water and bind strongly to soil or sediment (PBDEs are more mobile in the atmosphere because they attach to airborne particulates; dust, soot, smoke and liquid droplets). As a result PBDEs in sediment are not very mobile and unlikely to volatilise from the water phase. The higher the degree of bromination, the lower the water solubility. PBDEs can potentially be photodegraded in the environment (Nyberg et al., 2013).
The use of substance groups pentaBDE and octaBDE mixtures has been banned in the European Union since 2004 (Commission regulation (EC) No 552/2009). At present the use of decaBDE is only restricted in electrical and electronical products (European Court of Justice, 2008). However, decaBDE is no longer produced within European Union (UNEP, 2014). Although there is no production within the European Union, existing stocks of PBDE-containing products may still act as a diffuse source.
In 2009, tetraBDE, pentaBDE, hexaBDE and heptaBDE were listed under the Stockholm Convention (2009). As a result, Parties to the Convention must take action to eliminate the production and use of these compounds.
The Committee for Socio-economic Analysis (SEAC) adopted its final opinion on the proposal from the European Chemicals Agency (ECHA) to restrict the use of decaBDE as a flame retardant in plastics and textiles. SEAC confirmed its draft Opinion of June 2015 that the proposed restriction is the most appropriate European Union-wide measure in terms of its socio-economic cost benefits ratio. Having considered the 14 comments received during the public consultation on the draft Opinion, SEAC supported additional derogations for military aircraft, road vehicles, spare parts for machinery, and agricultural and forestry vehicles.
The European Foods Safety Authority recommended these eight substances of certain interest to monitor: triBDE-28, tetraBDE-47, pentaBDE-99, pentaBDE-100, hexaBDE-153, hexaBDE-154, heptaBDE-183 and decaBDE-209 (EFSA, 2006). These were selected on the basis of analytical feasibility for their measurement, production volumes (as registered in 2006), their occurrence in food and feed, their persistence in the environment and their toxicity. For environmental monitoring within the European Union, environmental quality standards have been derived for these congeners excluding BDE-183 and BDE-209 (European Commission, 2011).
The lack of assessment criteria for PBDEs in sediment makes any evaluation of the environmental significance of the concentrations observed very limited. PBDE concentrations in sediment are calculated, but not assessed because there are no OSPAR Background Assessment Concentrations (BACs) or Environmental Assessment Criteria (EACs) with which to assess status.
For the QSR2010, data analysed for the period 2000–2005 show widespread contamination of the marine environment with PBDEs in all components of marine ecosystems. Regular monitoring of PBDEs in sediments commenced at an OSPAR scale under the Coordinated Environmental Monitoring Programme (CEMP) in 2008.
Polybrominated diphenyl ether (PBDE) concentrations are measured as µg/kg dry weight normalised to 2.5% organic carbon. For each PBDE congener measured at each monitoring site, the time series of concentration measurements was assessed for temporal trends and calculated for status using the methods described in the contaminants online assessment tool (http://dome.ices.dk/osparmime2016/main.html). The results from these individual time series were then synthesised at the assessment area scale in a series of meta-analyses.
Temporal trend assessments included data from those monitoring sites that were representative of general conditions and excluded data from those monitoring sites impacted by a point source of PBDE and baseline monitoring sites where trends would not be expected. The analysis was also restricted to areas where there were at least three monitoring sites with trend information and where those monitoring sites had a reasonable geographical spread.
The temporal trend for each PBDE congener at each monitoring site was summarised by the estimated annual change in log concentration, with its associated standard error. The annual change in log concentration was then modelled by a linear mixed model with a fixed effect:
~ OSPAR contaminants assessment areas
and random effects:
~ congener + congener: OSPAR contaminants assessment area + monitoring site + congener: monitoring site + within-series variation.
The choice of fixed and random effects was motivated by the assumption that the PBDE congeners would have broadly similar trends, since they have similar sources. Thus, the fixed effect measures the common trend in PBDE congeners in each OSPAR contaminants assessment area and the random effects measure variation in trends:
- between congeners common across OSPAR contaminants assessment areas (congener);
- between congeners within OSPAR contaminants assessment areas (congener: contaminants assessment area);
- between monitoring sites common across congeners (monitoring site); and
- residual variation (congener: monitoring site + within-series variation).
There are two residual terms. Within-series variation is the variation associated with the estimate of the trend from the individual time series and is assumed known (and given by the square of the standard error). Congener: monitoring site allows for any additional residual variation.
Evidence of trends in PBDE concentrations at the assessment area scale was then assessed by plotting the estimated fixed effects with point-wise 95% confidence intervals. Differences between congeners were explored by plotting the predicted trend for each congener and for each congener / assessment area combination with point-wise 95% confidence intervals.
There are no assessment criteria for PBDEs, so a meta-analysis of status was not possible. However, a similar analysis was used to explore concentration profiles across congeners at the assessment area scale. The summary measure was the fitted log concentration in the last monitoring year. Baseline monitoring sites were also included in this analysis.
The number of time series used in each assessment area is shown in Table a.
| OSPAR region | OSPAR assessment area | trend | status |
|---|---|---|---|
| Greater North Sea | Northern North Sea | 5 | 9 |
| Southern North Sea | 0 | 27 | |
| English Channel | 0 | 1 | |
| Celtic Seas | Irish and Scottish West Coasts | 2 | 3 |
| Irish Sea | 3 | 9 | |
| Bay of Biscay and Iberian Coast | Iberian Sea | 0 | 15 |
| Gulf of Cadiz | 0 | 14 |
There are no assessment values for PBDEs.
Differences in methodology used for the IA 2017 compared with the QSR 2010
For the IA 2017, a meta-analysis is used to synthesise the individual time series results and provide an assessment of temporal trend and a calculation of status at the assessment area level. Meta-analyses take into account both the estimate of trend or status in each time series and the uncertainty in that estimate. They provide a more objective regional assessment than was possible in the QSR2010, where a simple tabulation of the trend and status at each monitoring site was presented.
Results
Polybrominated diphenyl ether (PBDE) concentrations are measured in sediment samples taken annually (or every few years) from monitoring sites in the Greater North Sea, Celtic Seas, and Bay of Biscay and Iberian Coast. The locations of the PBDE monitoring sites are shown in Figure 2.
Figure 2: Monitoring sites used to assess PBDE concentrations in sediment by OSPAR contaminants assessment areas (white lines) determined by hydrogeographic principles and expert knowledge not OSPAR internal boundaries
The number of time series used in each area assessed is very limited. Some of the PBDE in sediment data for the Greater North Sea, Celtic Seas, and Bay of Biscay and Iberian Coast could not be taken into account, either because some time series include data below concentration levels that can be accurately measured or because time series are too short for analysis. Furthermore, an OSPAR contaminants assessment area was only assessed if at least three monitoring sites had enough years of data and a representative geographic spread across a contaminants assessment area. It is expected that more monitoring sites can be included for future assessments.
Temporal trends in mean PBDE concentrations were assessed in two areas where there were at least five years of data (Figure 3). Mean PBDE concentrations in sediment show no statistically significant change in the Northern North Sea and decreasing in the Irish Sea.
The mean concentrations of PBDE in sediment were analysed for five assessment areas; Northern North Sea, Southern North Sea, Irish Sea, Irish and Scottish West Coasts and the Gulf of Cadiz. Concentrations in sediment are low (<1 µg/kg dry weight) and often below detection levels. The Gulf of Cadiz has the lowest concentrations of PBDE in any assessed area (<0.01 µg/kg dry weight), while the Irish Sea and Southern North Sea have the highest.
There is high confidence in the assessment and sampling methodology and high confidence in the data used.
Figure 3: Percentage annual change in overall PBDE concentrations in sediment in each OSPAR contaminants assessment area
No statistically significant (p <0.05) change in mean concentration (circle), mean concentration is significantly decreasing (downward triangle). 95% confidence limits (lines)
Assessment Area Results
Concentrations of six polybrominated diphenyl ether (PBDE) congeners (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154) are measured in sediment samples for OSPAR’s CEMP. The number of time series used in each assessment area is very limited in all the areas assessed (Table a). None of the areas in Arctic Waters were considered to have enough monitoring sites to give sufficient information for an assessment. The data were used to investigate temporal trends in PBDE concentrations and to compare concentrations and patterns between assessment areas.
No status assessment was made for the PBDEs in sediment.
Figure ashows the estimated mean PBDE concentration for each assessment area, showing concentrations for the most recent year of available data (usually 2015). Mean PBDE concentrations in sediment are low (<1 µg/kg dry weight) and often below detection levels. However, this is not the case in industrialised areas. For those congeners measured, the Gulf of Cadiz has the lowest concentrations of PBDE in any assessed area (<0.01 µg/kg dry weight), while the Irish Sea and Southern North Sea have the highest.
The lack of data for some of the individual PBDE congeners is in most cases indicative of a very low value that cannot be accurately measured. The most common PBDE congener used in flame retardants is BDE-209 and this is found to occur at the highest concentrations in sediments within the OSPAR Maritime Area (>1 µg/kg dry weight).
Figure a: Mean concentrations of PBDEs in sediment for each OSPAR contaminants assessment area for the most recent year of measurements (generally 2015), 95% confidence limits (lines)
Individual Time Series Results per Monitoring Site
A summary of individual time series results at monitoring sites across the OSPAR Maritime Area) for PBDEs in sediment is presented here http://dome.ices.dk/osparmime2016/regional_assessment_sediment_organo-bromines.html. In summary, none of the 27 monitoring sites showed an increase in mean PBDE concentrations in sediment over the assessment period (2010–2015). It should be noted that not all individual time series results are included in the area assessments (see number of time series used in each assessment area in Table a), in accordance with the criteria set out in the Assessment Methods.
Confidence Assessment
There is high confidence in the quality of the data used for this assessment. The data have been collected over many years using established sampling methodologies. The data were screened to ensure that only sites with sufficient spatial coverage and temporal data have been included. Although the synthesis of monitoring site data for the assessment area scale uses new methods they are based on established and internationally recognised protocols for monitoring and assessment per monitoring site, therefore there is also high confidence in the methodology.
Conclusion
Polybrominated diphenyl ether (PBDE) concentrations in sediment are measured at very few monitoring sites in the Greater North Sea, Celtic Seas, and Bay of Biscay and Iberian Coast. As there are no assessment criteria available for PBDEs in sediment, it is not possible to assess the environmental significance of the concentrations observed.
There were enough years of data from some of the monitoring sites in the Northern North Sea and Irish Sea to carry out temporal trend analyses. PBDE concentrations are declining in Irish Sea and show no statistically significant change in the Northern North Sea.
The majority of measured concentrations of PBDE in sediment are low and often below detection levels. The Gulf of Cadiz has the lowest concentrations of PBDE in any assessed area, while the Greater North Sea has the highest.
Knowledge Gaps
There are few monitoring sites for the assessment of temporal trends in polybrominated diphenyl ether (PBDE) concentrations in sediment in the OSPAR contaminants assessment areas, which means the assessment cannot be considered representative for the OSPAR Maritime Area as a whole. Cooperation between OSPAR and the Arctic Monitoring and Assessment Programme (AMAP) will improve access to data for Arctic Waters.
Background Assessment Concentrations (BACs) and Environmental Assessment Criteria (EACs) need to be developed for PBDE concentrations in sediment in order to be able to assess the environmental significance of the concentrations observed.
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Eriksson, P., Fischer, C. & Fredriksson, A. (2006a) Polybrominated diphenyl ethers, a group of brominated flame retardants, can interact with polychlorinated biphenyls in enhancing developmental neurobehavioral defects. Toxicological Sciences, 94, 302-309.
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| Sheet reference | HASEC17/D808 |
|---|---|
| Assessment type | Intermediate Assessment |
| Context (1) | Hazardous Substances |
| Context (2) | OSPAR Agreement 2004-12 OSPAR List of Chemicals for Priority Action (Update 2007) |
| Context (3) | D8 - Concentrations of Contaminants |
| Context (4) | D8.1 - Concentration of contaminants |
| Point of contact | Lucia Viñas, Jose Fumega |
secretariat@ospar.org | |
| Title | Trends in polybrominated flame retardants (PBDE) concentrations in sediments |
| Resource abstract | Common indicator assessment of trends and concentrations of polybrominated diphenyl ethers (PBDEs) in sediment. Applicable to the Greater North Sea, Celtic Seas, Bay of Biscay and Iberian Coast. |
| Linkage | https://www.ospar.org/convention/agreements?q=Agreement+2004-12&t=&a=&s= |
| Topic category | Environment |
| Indirect spatial reference | L3.2.3.1;L3.2.8.1;L3.2.8.2;L3.2.8.3;L3.2.5.1;L3.2.5.2;L3.2.5.3;L3.2.5.4;L3.2.5.5;L3.2.5.6;L3.2.5.7;L3.2.5.8;L3.2.5.9;L3.2.5.10;L3.2.5.11;L3.2.5.12;L3.2.5.13;L3.2.5.14; |
| N Lat | 62.0000008852327 |
| E Lon | 11.0587692133286 |
| S Lat | 36.0002573554926 |
| W Lon | -12.0250000001498 |
| Countries | BE, DE, ES, IE, NL, NO, SE, UK |
| Start date | 2010-01-01 |
| End date | 2015-12-31 |
| Date of publication | 2017-06-30 |
| Conditions applying to access and use | http://www.ospar.org/site/assets/files/1215/ospar_data_conditions_of_use.pdf |
| Data Snapshot | https://odims.ospar.org/documents/316/download |
| Data Results | https://odims.ospar.org/documents/295/download |
| Data Results | http://dome.ices.dk/osparmime2016/regional_assessment_sediment_organo-bromines.html |
| Data Source | http://ices.dk/marine-data/data-portals/Pages/DOME.aspx |
| Data Source | http://dome.ices.dk/osparmime2016/main.html |
| Data Source | http://dome.ices.dk/views/ContaminantsSediment.aspx |
| Data Source | https://odims.ospar.org/search/?title__icontains=contaminants%20-%20sediment&limit=100&offset=0 |