Trends in Concentrations of Polybrominated Diphenyl Ethers (PBDEs) in Fish and Shellfish

D8 - Concentrations of Contaminants

D8.1 - Concentration of contaminants

Concentrations of polybrominated diphenyl ethers (PBDEs) detected in biota (fish, mussels, oysters) are declining in the majority of areas assessed. The exception is the Skagerrak and Kattegat where concentrations show no statistically significant change. 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.

PBDEs may enter the environment through emissions from manufacturing processes, evaporation from products that contain PBDEs, recycling wastes and leachate from waste disposal sites (Figure 1). 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 the marine environment is variable. Some PBDE congeners tend to accumulate in fish and shellfish more than others. PBDE are known to have effects on the nervous, immune and endocrine systems of birds and mammals.

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 PBDEs in biota is determined but not assessed because there are no OSPAR assessment values developed with which to assess status.

Figure 1: Land-based waste dumping site with potential leakage of polybrominated diphenyl ethers (PBDEs) from products containing these flame-retardants

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 products that have been produced are pentaBDE, octaBDE and decaBDE, containing mixtures of different PBDEs relating to the number of bromines attached to the compound. 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 PBDEs 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 great 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. Therefore, only low concentrations of decaBDE are found in fish, in contrast to lower-brominated BDEs, which are more commonly found in marine organisms. PBDEs can potentially photodegrade in the environment (Nyberg et al., 2013).

The use of substance groups pentaBDE and octaBDE 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 electronic products (European Court of Justice, 2008). However, decaBDE is no longer produced within EU (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 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 benefit 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).

PBDE concentrations in biota are calculated but not assessed because there are no OSPAR Background Assessment Concentrations (BACs) or Environmental Assessment Criteria (EACs) developed with which to assess status. There is an Environmental Quality Standard (EQS) derived within European Union to protect marine and freshwater ecosystems as well as humans from adverse effects of chemicals in the aquatic environments. However, the EQS is set for fish at trophic level four and the normalisation process required for OSPAR contaminant data to trophic level four has not yet been agreed.

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 the biota commenced at an OSPAR scale under the Coordinated Environmental Monitoring Programme (CEMP) in 2008.

For each polybrominated diphenyl ether (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 geographic 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 congener in each 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.

Table a: Number of monitoring sites used in the assessment
OSPAR region OSPAR sub-region Trend Status
Arctic Waters Barents Sea 0 4
Norwegian Sea 1 2
Greater North Sea Norwegian Trench 1 4
Northern North Sea 7 10
Skagerrak and Kattegat 5 12
Southern North Sea 11 17
English Channel 3 3
Celtic Seas Irish and Scottish West Coast 7 15
Irish Sea 18 26
Celtic Sea 2 8
Bay of Biscay and Iberian Coast Iberian Sea 21 23

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 biota (fish, mussels and oysters) taken annually (or every few years) from monitoring sites throughout much of the Greater North Sea, Celtic Seas, and Bay of Biscay and Iberian Coast. A few samples are also taken from Arctic Waters. Monitoring site locations are shown in Figure 2. Data recorded between 2010 and 2015 were used to investigate temporal trends in PBDE concentrations and to compare concentrations and patterns between OSPAR contaminants assessment areas. There were too few monitoring sites in Arctic Waters to give sufficient information for a trend assessment for that region.

Figure 2: Monitoring sites used to assess PBDE concentrations in biota by OSPAR contaminants assessment areas (white lines) determined by hydrogeographic principles and expert knowledge not OSPAR internal boundaries

Temporal trends in mean PBDE concentrations were assessed in seven assessment areas where there were more than five years of data. The results indicate that mean concentrations of PBDEs are decreasing in the majority of assessed areas (Figure 3). The Skagerrak and Kattegat is the exception, where concentrations in biota show no statistically significant change.

Mean PBDE concentrations are <1 µg/kg wet weight in ten assessment areas. The assessment areas showing the highest mean concentrations of PBDE in biota are the English Channel and Irish Sea. The lowest concentrations are found in the Iberian Sea. However, the species monitored differ between assessment areas and this may be reflected in the results. In the Iberian Sea only mussels are analysed, which may explain the low mean concentrations of PBDEs, since mussels across the assessment areas show lower concentrations than fish.

Figure 3: Percentage annual change in overall PBDE concentrations in fish and shellfish 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)

There is high confidence in the assessment and sampling methodology and high confidence in the data used.

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 biota samples (fish, mussels and oysters). The number of time series used in each assessment area is shown in Table a. None of the areas in Arctic Waters were considered to have enough monitoring sites to give sufficient information for an assessment. Monitoring sites defined as polluted and assessment areas with too few monitoring sites were excluded from the 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 biota.

Figure a shows the estimated mean PBDE concentration for each assessment area, showing concentrations for the most recent year of available data (usually 2015). Mean PBDE concentrations are all <1 µg/kg wet weight. The assessment areas showing the highest concentrations were the English Channel, Northern North Sea, Southern North Sea and the Irish Sea. The lowest concentrations were found in the Iberian Sea. However, the species monitored differ between assessment areas and this may be reflected in the overall mean for a given area. Samples from the Iberian Sea, the assessment area with the lowest mean PBDE concentration, are taken only from mussels, which is likely to explain the low mean concentrations of PBDEs since mussels across the assessment areas show lower PBDE concentrations than fish on a wet weight basis. The pattern is similar between assessment areas with BDE-47, a tetra-brominated congener (one of the two main components in the penta-commercial mixture) dominating.

Temporal trends in PBDE concentrations were assessed in areas where there were more than five years of data. The results indicate downward trends in the majority of assessment areas (Figure 3). Downward trends are seen in the Southern North Sea, Northern North Sea, English Channel, Irish and Scottish West Coast, Irish Sea, and Iberian Sea. The PBDE congener BDE-99 (the other main congener in the penta-commercial mixture) consistently shows the largest annual decrease in all assessment areas.

Figure a: Mean concentrations of PBDEs in fish and shellfish 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 biota is presented here http://dome.ices.dk/osparmime2016/regional_assessment_biota_organo-bromines.html. In summary, in 11 out of 339 monitoring sites, mean concentrations of PBDE in biota increased over the assessment period (1996–2015). 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

Since PBDEs were regulated, concentrations in fish and shellfish have decreased for the majority of the assessment areas.

Temporal trends in polybrominated diphenyl ether (PBDE) concentrations in biota are declining by approximately 10% per year in six of the seven areas assessed. In one assessment area, the Skagerrak and Kattegat, the trend shows no statistically significant change.

PBDE concentrations in biota vary between the assessed areas. The highest concentrations occur in the English Channel and the Irish Sea, with the lowest in the Iberian Sea. These differences could reflect the contamination load in the respective assessment areas, but could also be influenced by differences in the species monitored. As there are no assessment criteria available for PBDEs in biota, it is not possible to assess the environmental significance of the concentrations observed.

Knowledge Gaps

There is a lack of monitoring data, particularly in Arctic Waters. Cooperation between OSPAR and the Arctic Council’s Arctic Monitoring and Assessment Programme (AMAP) will improve access to data for Arctic Waters.

Assessment values applicable to OSPAR monitoring data for temporal trends and the status of polybrominated diphenyl ethers (PBDEs) in biota need to be developed. A strategy is needed for making data from different monitoring species comparable.

The Environmental Quality Standard (EQS) derived within European Union to protect marine and freshwater ecosystems as well as humans from adverse effects of chemicals in the aquatic environments requires further investigation for use in the OSPAR Maritime Area.

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