Tendances des teneurs en polybromodiphényléthers (PBDE) dans le poisson, les mollusques et crustacés

D8 - Teneurs en contaminants

D8.1 - Teneurs en contaminants

Message clé:

Les teneurs en polybromodiphényléthers (PBDE) relevées dans le milieu vivant (poisson, moule et huître) ont diminué dans la majorité des zones évaluées. Le Skagerrak et le Kattegat font exception car leurs teneurs ne révèlent aucune modification significative statistiquement. Il n’est pas possible d’évaluer l’importance environnementale des teneurs en l’absence de critères d’évaluation.

Zone Évaluée

Récapitulatif Imprimable

Contexte

Les polybromodiphényléthers (PBDE) sont un groupe de congénères, utilisés principalement comme retardateurs de flamme dans diverses matières, notamment les plastiques, les textiles, les produits électroniques, les matériaux de construction, l’ameublement et les véhicules.

Les émissions provenant des processus de fabrication, l’évaporation à partir de produits contenant des PBDE, le recyclage des déchets et lixiviats de sites d’élimination de déchets sont responsables de la pénétration des PBDE dans le milieu marin (Figure 1). Ils sont très répandus et ont été décelés dans l’air, les sédiments, les eaux de surface, le poisson et autres organismes marins.

Les PBDE sont toxiques, ils mettent longtemps à se dégrader et ont tendance à s’accumuler dans le poisson et les mollusques et crustacés (soit absorbés directement dans les eaux ambiantes soit indirectement par voie alimentaire). Certains PBDE ont donc été interdits ou leur utilisation limitée dans le cadre de l’Union européenne à partir de 2004. La production de certains groupes de PBDE a été interdite en 2009 par 180 pays signataires de la Convention de Stockholm.

La répartition spatiale des PBDE dans le milieu marin varie. Certains congénères des PBDE ont tendance à s’accumuler dans le poisson, les mollusques et crustacés plus que d’autres. On sait que les PBDE ont des effets sur les systèmes nerveux, immunitaire et endocrinien d’oiseaux et de mammifères.

La Stratégie OSPAR substances dangereuses a pour objectif, en dernier ressort, de parvenir à des teneurs dans l’environnement marin qui soient proches de zéro dans le cas des substances de synthèse, et les PBDE sont inclus dans le groupe de retardateurs de flamme bromés figurant dans la Liste OSPAR de produits chimiques devant faire l’objet de mesures prioritaires. Le statut des PBDE dans le milieu vivant est déterminé mais pas évalué car il n’existe pas de valeur d’évaluation permettant de le faire. 

Figure 1: Site de décharge à terre pouvant potentiellement causer des fuites de polybromodiphényléthers (PBDE) provenant de produits contenant ces retardateurs de flamme

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.

Résultats

Les teneurs en polybromodiphényléthers (PBDE) sont mesurées dans le milieu vivant (poisson, moule et huître) prélevé tous les ans (ou à quelques années d’intervalle) de sites de surveillance dans la plus grande partie de la mer du Nord au sens large, des mers Celtiques, du golfe de Gascogne et de la côte ibérique. Quelques échantillons sont également prélevés dans les eaux Arctiques. La Figure 2 indique l’emplacement des sites de surveillance. Les données enregistrées entre 2010 et 2015 ont été utilisées pour étudier les tendances temporelles des teneurs en PBDE et comparer les teneurs et les profils entre les zones d’évaluation des contaminants OSPAR. Le nombre de sites de surveillance dans les eaux Arctiques est trop faible pour fournir des informations suffisantes permettant une évaluation des tendances dans cette région.

Figure 2: Sites de surveillance utilisés pour l’évaluation des teneurs en PBDE dans le milieu vivant par zone d’évaluation des contaminants OSPAR (lignes blanches) déterminés selon des principes hydrogéographiques et des connaissances d’expert plutôt que des limites internes OSPAR

Les tendances temporelles des teneurs moyennes en PBDE ont été évaluées dans sept zones d’évaluation lorsque plus de cinq années de données étaient disponibles. Les résultats indiquent que les teneurs moyennes en PBDE ont diminué dans la majorité des zones évaluées (Figure 3). Le Skagerrak et le Kattegat font exception car les teneurs dans le milieu vivant ne révèlent aucune modification significative statistiquement.

Les teneurs moyennes en PBDE sont <1 µg/kg de poids humide dans dix zones d’évaluation. Les zones d’évaluation révélant les teneurs moyennes en PBDE dans le milieu vivant les plus élevées sont la Manche et la mer d’Irlande. Les teneurs les plus faibles se trouvent dans la mer Ibérique. Les espèces surveillées varient cependant d’une zone d’évaluation à l’autre et ceci pourrait se retrouver dans les résultats. Seule la moule est analysée dans la mer Ibérique ce qui pourrait expliquer les teneurs moyennes faibles en PBDE car les teneurs dans la moule sont plus faibles que dans le poisson pour l’ensemble des zones d’évaluation.

Figure 3: Modification du pourcentage annuel de l’ensemble des teneurs en PBDE dans chaque zone d’évaluation des contaminants OSPAR.

Aucune modification significative statistiquement des teneurs moyennes (p <0,05) (cercle), les teneurs moyennes sont nettement à la baisse statistiquement (triangle inversé). Limites de confiance de 95% (lignes)

La méthodologie d’évaluation et d’échantillonnage et les données utilisées inspirent une confiance élevée.

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

Les teneurs dans le poisson, les mollusques et crustacés ont diminué dans la majorité des zones d’évaluation depuis que les PBDE sont réglementés.

Les tendances temporelles des teneurs en polybromodiphényléthers (PBDE) dans le milieu vivant ont diminué d’environ 10% par an dans six des sept zones évaluées. La tendance ne révèle aucune modification significative statistiquement dans une zone d’évaluation, le Skagerrak et le Kattegat.

Les teneurs en PBDE dans le milieu vivant varient d’une zone d’évaluation à l’autre. Les teneurs les plus élevées se trouvent dans la Manche et la mer d’Irlande et les plus basses dans la mer Ibérique. Ces différences pourraient refléter la charge de contaminants dans les zones d’évaluation respectives mais pourraient également être influencées par les différences entre les espèces surveillées. Il n’est pas possible d’évaluer l’importance des teneurs relevées pour le milieu marin car aucun critère d’évaluation n’est disponible pour les PBDE dans le milieu vivant. 

Lacunes des connaissances

On relève l’absence de données de la surveillance, en particulier pour les eaux Arctiques. Une coopération entre OSPAR et le Programme de surveillance et d’évaluation de l’Arctique (AMAP) permettrait un meilleur accès aux données sur les eaux Arctiques.

Il faudra développer des valeurs d’évaluation applicables aux données de la surveillance pour les tendances temporelles et le statut des polybromodiphényléthers (PBDE) dans le milieu vivant et envisager une stratégie permettant de comparer les données de la surveillance de diverses espèces.

Il faudra étudier de plus près la norme de qualité environnementale (EQS) dérivée dans le cadre de l’Union européenne afin de protéger les écosystèmes marins et d’eau douce ainsi que l’homme des effets des produits chimiques dans les milieux aquatiques pour pouvoir l’utiliser dans la zone maritime OSPAR.

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