Tendances des teneurs en polybromodiphényléthers (PBDE) dans les sédiments
D8 - Teneurs en contaminants
D8.1 - Teneurs en contaminants
Message clé:
Les teneurs en polybromodiphényléthers (PBDE) relevées dans les sédiments dans les zones évaluées soit ne révèlent aucune modification significative statistiquement (mer du Nord septentrionale) soit ont diminué (mer d’Irlande). 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 (Figure 1).
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. 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 les sédiments marins varie. Les PBDE ne se dissolvent pas dans l’eau et adhèrent fortement au sol et aux sédiments. Les PBDE dans les sédiments ne sont donc pas très mobiles.
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 teneurs en PBDE dans les sédiments est calculé mais pas évalué car aucune valeur d’évaluation OSPAR permettant de le faire n’a été développée.
Figure 1(i): Les polybromodiphényléthers (PBDE) sont un groupe de composés utilisés principalement comme retardateurs de flamme dans diverses matières, notamment les produits électroniques
Figure 1(ii): Les polybromodiphényléthers (PBDE) sont un groupe de composés utilisés principalement comme retardateurs de flamme dans diverses matières, notamment les véhicules
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.
Résultats
Les teneurs en polybromodiphényléthers (PBDE) sont mesurées dans les échantillons de sédiment prélevés tous les ans (ou à quelques années d’intervalle) de sites de surveillance dans la mer du Nord au sens large, les mers Celtiques, le golfe de Gascogne et la côte ibérique. LaFigure 2 indique l’emplacement des sites de surveillance des PBDE.
Figure 2: Sites de surveillance utilisés pour l’évaluation des teneurs en PBDE dans les sédiments 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
La méthodologie d’évaluation et d’échantillonnage et les données utilisées inspirent une confiance élevée.
Le nombre de séries temporelles utilisées dans chaque zone évaluée est très limité. On n’a pas pu prendre en compte certaines données sur les PBDE dans les sédiments pour la mer du Nord au sens large, les mers Celtiques, le golfe de Gascogne et la côte ibérique car soit certaines séries temporelles contiennent des données inférieures aux niveaux des teneurs pouvant être mesurés avec précision soit les séries temporelles sont trop courtes pour pouvoir être analysées. De plus, une zone d’évaluation des contaminants OSPAR n’a été évaluée que si au moins trois sites de surveillance possédaient assez d’années de données et une répartition géographique représentative d’une zone d’évaluation. On prévoit de pouvoir inclure plus de sites de surveillance dans les futures évaluations.
Les tendances temporelles des teneurs moyennes en PBDE dans les sédiments ont été évaluées dans deux zones lorsque des données étaient disponibles pour cinq ans au moins (Figure 3). Les teneurs moyennes en PBDE dans les sédiments ne révèlent aucune modification significative statistiquement dans la mer du Nord septentrionale et une diminution dans la mer d’Irlande.
Les teneurs moyennes en PBDE dans les sédiments ont été analysées pour cinq zones d’évaluation; la mer du Nord septentrionale, la mer du Nord méridionale, la mer d’Irlande, les côtes ouest irlandaise et écossaise et le golfe de Cadix. Les teneurs dans les sédiments sont faibles (<1 µg/kg de poids sec) et souvent inférieures aux niveaux de détection. Les teneurs les plus faibles en PBDE dans toute zone évaluée se trouvent dans le golfe de Cadix (<0,01 µg/kg de poids sec) alors que les plus élevées se trouvent dans la mer d’Irlande et la mer du Nord méridionale.
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)
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
Les teneurs en polybromodiphényléthers (PBDE) dans les sédiments sont mesurées dans très peu de sites de surveillance de la mer du Nord au sens large, des mers Celtiques, du golfe de Gascogne et de la côte ibérique. 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 les sédiments.
Le nombre d’années de données a été suffisant pour certains sites de surveillance dans la mer du Nord septentrionale et la mer d’Irlande pour entreprendre des analyses des tendances temporelles. Les teneurs en PBDE diminuent dans la mer d’Irlande et ne révèlent aucune modification significative statistiquement dans la mer du Nord septentrionale.
La majorité des teneurs en PBDE dans les sédiments mesurées sont faibles et souvent inférieures aux niveaux de détection. Les teneurs en PBDE les plus faibles se trouvent dans le golfe de Cadix dans toute zone d’évaluation tandis que les plus élevées se trouvent dans la mer du Nord au sens large.
Lacunes des connaissances
Il existe peu de sites de surveillance pour l’évaluation des tendances temporelles des teneurs en polybromodiphényléthers (PBDE) dans les sédiments dans les zones d’évaluation des contaminants OSPAR, on ne peut donc pas considérer que l’évaluation est représentative de la zone maritime OSPAR dans son ensemble. 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 y a lieu de développer des teneurs ambiantes d’évaluation (BAC) et des critères d’évaluation environnementale (EAC) pour les teneurs en PBDE dans les sédiments afin de pouvoir évaluer l’importance des teneurs relevées pour le milieu marin.
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