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Human exposure to PFOS and mercury through meat from baltic harbour seals (Phoca vitulina)
Environmental Research 175 (2019) 376–383
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Human exposure to PFOS and mercury through meat from baltic harbour seals (Phoca vitulina)
T
Christian Sonnea,b,∗, Katrin Vorkampb,c, Anders Galatiusa, Line Kyhna, Jonas Teilmanna, Rossana Bossib,c, Jens Søndergaarda,b, Igor Eulaersa,b, Jean-Pierre Desforgesa,b, Ursula Sieberta,d, Rune Dietza,b a
Aarhus University, Department of Bioscience, Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark Aarhus University, Arctic Research Center (ARC), Frederiksborgvej 399, DK-4000, Roskilde, Denmark c Aarhus University, Department of Environmental Science, Frederiksborgvej 399, PO Box 358, DK-4000, Roskilde, Denmark d Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Foundation, Werftstr. 6, DE-25761, Büsum, Germany b
ARTICLE INFO
ABSTRACT
Keywords: Hg Polychlorinated biphenyls Polyfluoroalkyl substances TWI Tolerable weekly intake Human consumption
The overall aim of the present study was to assess human exposure to environmental contaminants from consumption of harbour seal (Phoca vitulina) meat in the southwestern Baltic Sea. For this purpose, muscle tissue from harbour seals (n = 27) was sampled from Danish locations in the period 2005–2015 and analysed for concentrations of total mercury (Hg), organochlorine contaminants such as polychlorinated biphenyls (PCBs) and organochlorine pesticides as well as perfluoroalkyl substances (PFAS) with particular focus on perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Hg, ∑PCB, PFOS and PFOA concentrations in the muscle tissue ranged between 0.27 and 4.76 μg g−1 wet weight (ww; mean: 1.38 μg g−1 ww, n = 27), 12.2–137 ng g−1 ww (mean: 47.5 ng g−1 ww, n = 10), 6.95–33.6 ng g−1 ww (mean: 15.8 ng g−1 ww, n = 10) and 0.16–0.55 ng g−1 ww (mean: 0.28 ng g−1 ww, n = 10), respectively. We compared the concentrations with literature-derived human tolerable weekly intake (TWI) values for mercury (1.3 μg kg−1 week−1), ∑PCB (2.1 μg kg−1 week−1), PFOS (0.013 μg kg−1 week−1) and PFOA (0.006 μg kg−1 week−1). The comparisons showed that the weekly consumption of harbour seal meat by children (weighing 30 kg), women (weighing 60 kg) and men (weighing 80 kg) should not exceed 28, 57 and 76 g (for Hg), 1.3, 2.7 and 3.5 kg (for ∑PCB), 25, 50 and 67 g (for PFOS) and 640, 1290 and 1720 g (for PFOA). In conclusion, Hg and PFOS are the contaminants of most importance in seal meat from this area with respect to existing tolerable intake rates and risks of adverse human health effects.
1. Introduction Given their persistence, toxicity and biomagnification properties, mercury (Hg), per- and polyfluoroalkyl substances (PFASs) such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), and organochlorine (OC) contaminants such as polychlorinated biphenyls (PCBs) and OC pesticides are of concern to wildlife and humans (Murphy et al., 2015). They were used in multiple industrial or agricultural products and processes for several decades, such as paper production, gold mining and fossil burning (Hg), fire-fighting foams and coatings (PFASs), transformers, capacitors and construction
materials (PCBs), and as pesticides (OC pesticides) (AMAP, 2004; Outridge et al., 2011). The toxic effects in vertebrates include immune suppression, cancer, neuro-endocrine disruption, reproductive impairment and disruption of energy metabolism (Dietz et al., 2018a; Letcher et al., 2010; Murphy et al., 2015; Sonne, 2010). Because marine mammals occupy high trophic levels in the marine food web, they are exposed to elevated concentrations of these biomagnifying contaminants (Dietz et al., 2018a). Mercury, OCs and PFAS are ubiquitous in the environment, and the Baltic Sea is among the marine ecosystems with the highest reported contaminant concentrations globally (HELCOM, 2018). The Danish part
∗ Corresponding author. Aarhus University, Faculty of Science and Technology, Department of Bioscience, Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark. E-mail addresses: [email protected] (C. Sonne), [email protected] (K. Vorkamp), [email protected] (A. Galatius), [email protected] (L. Kyhn), [email protected] (J. Teilmann), [email protected] (R. Bossi), [email protected] (J. Søndergaard), [email protected] (I. Eulaers), [email protected] (J.-P. Desforges), [email protected] (U. Siebert), [email protected] (R. Dietz).
https://doi.org/10.1016/j.envres.2019.05.026 Received 4 April 2019; Received in revised form 15 May 2019; Accepted 16 May 2019 Available online 24 May 2019 0013-9351/ © 2019 Elsevier Inc. All rights reserved.
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of the western Baltic receive a large influx of contaminants from Baltic rivers (McLachlan et al., 2007). In line with this a previous study showed high concentrations of PFASs in harbour seal liver in the Wadden Sea are lower than concentrations in the western Baltic (Dietz et al., 2012), but there is no knowledge of environmental contaminants in harbour seal muscle tissue, in the Baltic Sea or elsewhere, although it may be consumed by hunters and consequently pose a health concern. Several harbour seal populations are now large and viable in the Baltic Sea region after successful conservation measures since total protection was enforced in 1977, and former fisheries conflicts reemerge. During the last 10 years, an increasing number of permits to shoot seals depredating fishing gear has been issued (Olsen et al., 2018). These conflicts, leading to the potential availability and use of seal meat for human consumption have raised the question of human health issues. Here, we quantify concentrations of important environmental contaminants and compare these to human tolerable weekly intake (TWI) rates to assess the human health risk related to exposure through seal meat consumption.
included perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), perfluoroheptanesulfonic acid (PFHpS), PFOS, perfluorodecanesulfonic acid (PFDS), perfluoro-1-octanesulfonamide (FOSA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), PFOA, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnA), perfluorododecanoic acid (PFDoA), perfluorotridecanoic acid (PFTrA), and perfluorotetradecanoic acid (PFTeA). The extraction method was based on Ahrens et al. (2009). Approximately 5 g of tissue was homogenised and 1g aliquot was weighted in a polypropylene tube and spiked with 10 ng of an internal standard mixture (S3). Native and labelled compounds were bought as mixtures from Wellington Laboratories (Guelph, ON, Canada). Tissues were extracted with 5 mL of acetonitrile twice for 30 min in an ultrasonic bath at 30 °C. The combined extract was reduced to 2 mL under a stream of nitrogen and 50 μL of acetic acid were added. For clean-up Supelclean ENVI-Carb® cartridges (100 mg, 1 mL, 100–400 mesh, Supelco, USA) were used. The cartridges were conditioned with 2 mL of acetonitrile followed by 1 mL of 20% acetic acid in acetonitrile. Afterwards, the sample extract was added to the cartridge with three times 1 mL of methanol and directly collected into another vial. The extracts were dried under a gentle nitrogen stream and reconstituted in 1 mL of methanol:ammonium acetate (2 mM; 50:50; v:v). Quantification was performed by liquid chromatography tandemmass spectrometry with electrospray ionization in negative mode. Chromatographic separation was performed using a C18 Kinetex column (2.1 × 150 mm, Phenomenex, Torrance, CA, USA) and an Agilent 1200 Series HPLC (Agilent, Palo Alto, CA, USA). The ions monitored for each compound can be found in Table S4. Each batch of samples was analysed with a procedural blank. Recoveries ranged from 75 to 129% (Table S5). The relative standard deviation (RSD) for samples run in duplicate ranged from 5 to 24% (Table S5). The RSDs for PFTeA and PFTrA were higher (44%-47%) because mass-labelled chemical standards are not available and analysis is based on the PFDoA standard. Method detection limits were calculated as three times the standard deviation of procedural blanks (Table S6).
2. Materials and methods 2.1. Sampling We collected muscle tissue from 27 harbour seals from the South Western Baltic Sea during the period 2005–2015, where fishermen had been given permission to shoot seals close to their nets and fykes by the Ministry of Environment and Food of Denmark (Fig. 1). The 27 sternal muscle samples were from 9 adult males, 7 adult females, 4 subadult males, and 7 subadult females. Seals were categorized as adult or subadult based on their length measurement (Harding et al., 2018) (Tables 1 and S1). 2.2. Hg analysis Seal muscle samples (n = 27) were analysed for total Hg using a Milestone DMA-80 Direct Mercury Analyzer (DMA) at the accredited Environmental Trace Element Laboratory of the Department of Bioscience, Aarhus University, Roskilde, Denmark. Prior to the analyses, samples were freeze-dried and homogenised. A 0.020–0.040 g dried subsample was weighed and analysed. Sample concentrations were determined based on a calibration curve prepared from a 1000 ± 4 mg L−1 stock solution (Sigma-Aldrich, Switzerland). Blank samples and aqueous control standards (10 ng and 100 ng Hg prepared from the 1000 ± 4 mg L−1 stock solution) were analysed every 10–15 samples. Subsequently, sample concentrations were corrected for blank sample Hg levels and daily instrument drift (based on control standard results). For quality assurance/quality control (QA/QC), the Certified Reference Material DORM-4 (www.nrc-cnrc.gc.ca) was analysed along with the samples. The measured recovery percentage (mean ± SD) of DORM-4 was 101 ± 2% (n = 7; certified Hg concentration = 0.410 ± 0.055 μg g−1; measured Hg concentration = 0.414 ± 0.008 μg g−1). The laboratory is ISO 17025 accredited for total Hg analyses in biological samples using DMA and regularly participates in the proficiency-testing scheme for Hg in biota arranged by the organisation for Quality Assurance of Information for Marine Environmental Monitoring in Europe (QUASIMEME). Results from the analyses are shown in Table S2.
2.4. OC analysis Organochlorine contaminants were analysed at the Department of Environmental Science, Aarhus University, Roskilde, Denmark. A subsample of each 10 pooled samples (see above) was extracted and cleaned up according to the method by Vorkamp et al. (2004), with few modifications. Ten grams were spiked with recovery standards (CB-3, CB-40 and CB-198; Ultra Scientific, Wesel, Germany, now Agilent; Dr. Ehrenstorfer, Augsburg, Germany, LGC Standards; Cambridge Isotope Laboratories, Tewksbury, MA, USA, respectively), mixed with diatomaceous earth and Soxhlet extracted using n-hexane:acetone (4:1; v:v; Rathburn Chemicals, Walkerburn, UK). The extracts were reduced in volume and purified on a multi-layer column consisting of deactivated aluminium oxide (10% water), activated silica (160 °C for 24 h), with and without H2SO4, and a layer of Na2SO4 on top. After elution with nhexane, the extracts were pre-concentrated, spiked with syringe standards (CB-53 and CB-155, both Ultra Scientific, Agilent) and adjusted to a precise volume of 1 mL. The extracts were analysed by dual column-gas chromatography with electron capture detection equipped with a DB-5 and a DB-1701 column (J&W Scientific, both 60 cm long, 0.25 mm inner diameter and 0.25 μm film thickness). Quantification was based on two 9-point stepwise calibration curves. The batch contained one procedural blank and a duplicate of the in-house reference material (fish oil) used for control charts (Table S7). The control charts monitor the long-term precision of the analysis and include warning and action limits (mean ± 2 and 3 standard deviations, respectively) to flag potential quality issues, as further described for these specific analyses by Asmund et al. (2004). The samples had recovery rates of 88–98% (mean 94%, Table S7). Traces of CB-49 and p,p’-DDT were detected in the blank and increased
2.3. PFAS analysis PFAS contaminants were analysed at the Department of Environmental Science, Aarhus University, Roskilde, Denmark. Muscle tissue homogenates were pooled for economic considerations to have a final sample size of ten, representing adults (5 pooled samples each containing two to four specimens) and juveniles (5 pooled samples each containing two-three specimens; Table S3). The PFASs quantified 377
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Fig. 1. Map showing sampling locations for harbour seal muscle samples used in the present study.
the detection limits for these compounds, however, all samples had concentrations above detection limits for all compounds and congeners. The laboratory is ISO 17025 accredited for OC analyses in biological samples and regularly participates in the QUASIMEME proficiencytesting scheme for OCs in biota. The targeted compounds included 22 PCB congeners and the OC pesticides α-, β-, γ-hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), p,p’-DDD, p,p’-DDE, o,p’-DDE, p,p’DDT and o,p’-DDT and trans-nonchlor. A list of congeners and compounds, including their detection limits, is given in Table S7.
half-lives of the compounds in the body. The following TWI muscle values were used for this study: 1.3 μg kg−1 week−1 for Hg, 2.1 μg kg−1 week−1 for ∑PCBs, 0.013 μg kg−1 week−1 for PFOS and 0.006 μg kg−1 week−1 for PFOA (EFSA, 2012; 2018a; Johansen et al., 2004). These are based on the precautionary principle given that recently there is indications that PFAS are likely more toxic than previously thought with respect to cancer, immune and reproductive toxicity. The TWI value for ∑PCB relates back to a provisional tolerable daily intake of 1 μg kg−1 day−1 used by Health Canada for PCBs (Berti et al., 1998). This was later stated to refer to Arochlor mixtures, and a TWI of 2.1 μg kg−1 week−1 was used for the sum of 14 PCB congeners, which comes closer to current congener-specific analyses (AMAP, 2003; Johansen et al., 2004). EFSA (2018b) recently issued a TWI of 2 pg toxicity equivalents kg−1 week−1 for dioxins and dioxin-like PCBs. However, our study only addressed non-dioxin like PCBs for which EFSA has not set a TWI. TWI values for ΣDDT (70 μg kg−1 week−1, provisional TWI set by the World Health Organisation), ΣHCH (2.1 μg kg−1 week−1, set by Health Canada) and HCB (1.2 μg kg−1 week−1, set by the World Health Organisation) are included in Table S7 (Berti et al., 1998; EFSA, 2006a,
2.5. Tolerable weekly intake (TWI) We decided to focus the comparison of contaminant concentrations with human TWI for muscle content of Hg, ∑PCBs, PFOS and PFOA as these were the compounds and compound groups found in the highest concentrations relative to their TWI values and therefore were those posing the highest health risk (EFSA, 2012; 2018a, 2018b; Johansen et al., 2004). Given that the toxicological endpoints are based on longterm exposure, EFSA (2012) recommended, in a scientific opinion on Hg exposure, that TWI is based on chronic exposure and the biological 378
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ww and 5–49 ng g−1 ww, respectively, for Σ10PCBs (Johansen et al., 2004). For comparison, ∑PCB concentrations of 12.2–137 ng g−1 ww were observed in the present study. In the Arctic, communities have been advised to eat tissues from subadult seals rather than adults and to eat less adipose tissue; all in order to reduce the intake of PCBs (Deutch et al. 2006; Johansen et al., 2004; Nielsen et al., 2006; Sonne et al., 2013). The PFAS found in the highest concentration was PFOS, followed by PFTrA and PFUnA (Table S8). In general, concentrations of PFASs were non-significantly higher in subadults than in adults (all p > 0.05). This is likely due to maternal transfer as previously shown for Arctic seals (Letcher et al., 2010; Dietz et al., 2012).
2006b), but not further discussed because of a larger margin between the measured exposure concentrations and the TWI. 2.6. Statistics Analyses of variance (ANOVA) was conducted to test for differences in contaminant loads among age-sex groups (adult male, adult female, subadult male and subadult female) while regression analyses were used to test for a relationship between standard length and contaminant load. The level of significance was set at α= 0.05. Contaminant concentrations and seal standard lengths were ln-transformed prior to statistical analysis in order to approach the assumption of normality and homogeneity of variance. The statistical analyses were performed with the SAS statistical software package (SAS 9.4 and SAS Enterprise Guide 7.1).
3.3. Weekly intake of Hg
Data on the biometric parameters and contaminant concentrations are shown in Table 1. Adult males had the highest concentrations of Hg, however, these were not significantly higher than in subadults and adult females (all p > 0.05) (Table 1). There was no significant relationship between Hg concentration and length of the animals (R2 = 0.06, p = 0.09). Previous studies of Baltic ringed seals (Pusa hispida botnica) showed slightly lower muscle Hg concentrations than in the present study (mean: 1.0 μg g−1 ww; range 0.8–3.0 μg g−1 ww), also, Hg concentrations in Baltic grey seal (Halichoerus grypus) muscle were lower (mean: 0.7 μg g−1 ww; range: 0.4–1.6 μg g−1 ww) (Fant et al., 2001; Nyman et al., 2002). When comparing our results to muscle Hg concentrations in Arctic ringed seals (Pusa hispida) from Greenland and Canada the Hg concentrations are approximately 3 times higher in the Baltic harbour seals of the present study (Dietz et al., 1998; Gaden et al., 2009). This evidently highlights the potential risk in the Baltic, as Hg is a well-known problem for Arctic communities consuming marine mammals with considerably lower Hg concentrations (Dietz et al., 2013, 2018b).
We used the overall muscle Hg mean concentration of 1.38 μg g−1 ww (0.27–4.76 μg g−1 ww) in the TWI calculations. Fig. 2 shows the concentrations of Hg compared to the TWI of 1.3 μg Hg kg−1 from EFSA (2012). Based on the mean concentration of 1.38 μg kg−1 week−1, the weekly amount of meat a man (weighing about 80 kg), a women (weighing about 60 kg) and a child (weighing about 30 kg) can eat is 76, 57 and 28 g, respectively. From the seal with the highest muscle Hg concentration of 4.8 μg g−1 ww, only a maximum of 21, 16 and 8 grams should be consumed per week, while the tolerable intake was 373, 285 and 118 grams for the seal with the lowest value (0.27 μg g−1 ww). However, the long-term exposure is best expressed by the mean concentration in the seals, across both age and sex (Johansen et al., 2004). The risk from consistently exceeding these guidelines includes neurotoxicity and developmental effects leading to reproductive and immune failure in severe cases (Grandjean and Landrigan, 2006). In the Avanersuaq (Thule) municipality in Greenland, Hg TWI is often exceeded 10–20-fold, which is exceptionally high, due to high consumption of narwhal meat that has lower Hg concentrations than the Baltic harbour seals of the present study (Dietz et al., 2018b). Compared to other studies of Baltic seals, harbour seals may even be the species with the highest concentrations of contaminants, however, it will require further analyses to assess which of the species are of most concern with respect to human exposure (Fant et al., 2001; Nyman et al., 2002).
3.2. OCs and PFAS
3.4. Weekly intake of PCBs
The OC group found in highest concentration was ∑PCB which follows is similar to previous studies of OCs in Baltic as well as in Arctic seals (Letcher et al., 2010; Nyman et al., 2002; Routti et al., 2009). Overall, OC concentrations were similar in subadults and adults except for HCB which was higher in adults (Tables 1 and S7). In a study of the Greenland food web, harp seal and ringed seal meat were < 5 ng g−1
We used the overall muscle PCB mean concentration of 47.5 ng g−1 ww (12.2–137 ng g−1 ww) in the TWI calculations. Fig. 3 shows the concentrations of ∑PCB compared with the provisional TWI of 2.1 μg ∑PCB kg−1 (AMAP, 2003; Johansen et al., 2004). Based on the observed mean ∑PCB concentrations in seal meat, weekly consumption for men, women and children should not exceed 3.5, 2.7 and 1.3 kg,
3. Results and discussion 3.1. Mercury
Table 1 Information on the harbour seals from which muscle tissue was collected over the period 2005–2015 and analysed for Hg, PFAs and OCs. Data are given as mean ± SD (min-max). See Tables S2–8 for more information on contaminant concentrations.
Length (cm) Hg (μg g−1 ww) PFASs (ng g−1 ww) PFOS PFTrA PFUnA PFOA OCs (ng g−1 ww) ∑PCBs ∑DDTs trans-nonachlor ∑HCHs HCB
Adult males n = 9
Adult females n = 7
Subadult males n = 4
Subadult females n = 7
157 ± 14 (141–183) 1.63 ± 1.35 (0.42-4.76)
139 ± 10 (126–157) 1.29 ± 0.41 (0.73-1.91)
121 ± 5 (114–125) 1.20 ± 0.39 (0.68-2.08)
116 ± 11 (97–128) 1.31 ± 1.05 (0.27-3.23)
13.9 2.02 1.10 0.27
± ± ± ±
3.4 (10.1-17.5) 0.51 (1.40-2.52) 0.30 (0.86-1.62) 0.16 (0.16.0.55)
17.7 2.57 1.17 0.29
± ± ± ±
11.2 1.60 0.57 0.10
(6.95-33.6) (0.63-4.47) (0.40-1.66) (0.19-0.42)
50.3 30.6 0.99 0.45 0.14
± ± ± ± ±
48.8 22.8 0.83 0.27 0.17
44.7 27.8 0.84 0.33 0.07
± ± ± ± ±
38.3 23.3 0.60 0.22 0.03
(12.2-87.6) (7.03-64.4) (0.25-1.73) (0.09-0.63) (0.04-0.11)
(21.6-137) (15.2-70.6) (0.51-2.46) (0.2-0.88) (0.05-0.45)
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Fig. 2. The relationship between amount of seal meat that can be consumed per week by men, women and children as a function of Hg muscle concentration. The dots refer to results from the present study. The calculation is based on tolerable weekly intake of 1.3 μg kg−1 Hg week−1.
respectively, assuming that the blubber is not consumed, which generally has higher concentrations of lipophilic compounds like PCBs (Johansen et al., 2004). For the pooled group of seals with the highest concentration (137 ng g−1 ww), the intake should not exceed 2.1 kg week−1 for men, 1.6 kg for women and 0.8 kg for children. For the pooled group of seals with the lowest concentration (12.2 μg g−1
ww) it was 24, 18 and 9 kg per week for men, women and children. Again, long-term exposure is best expressed by the mean concentration across both age and sex (Johansen et al., 2004). Furthermore, considering the carcinogenicity of PCBs (IARC, 2016), PCB exposure generally bears a health risk. For ∑DDT, ∑HCH and HCB, the safe margins were higher than for PCBs based on concentrations and TWI (Table S7).
Fig. 3. The relationship between amount of seal meat that can be consumed per week by men, women and children as a function of ∑PCB muscle concentration. The dots refer to results from the present study. The calculation is based on tolerable weekly intake of 2.1 μg kg−1 week−1. 380
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Fig. 4. The relationship between amount of seal meat that can be consumed per week by men, women and children as a function of PFOS muscle concentration. The dots refer to results from the present study. The calculation is based on tolerable weekly intake of 0.013 μg kg−1 week−1.
3.5. Weekly intake of PFOS and PFOA
TWI for relatively small portions of seal meat across all the three agesex groups (children, women and men) while the risk from PFOA exposure was lower and the tolerable intake of seal meat was between those calculated for PFOS and ΣPCB. Weekly seal meat consumption will violate the TWI for PFOS, if 25 g of meat is consumed by children, 50 g by women and 67 g by men, assuming a mean concentration of PFOS of 15.8 ng g−1. For the group of seals with the highest muscle tissue PFOS concentration (33.6 ng g−1 ww), less than 12 g (child), 24 g
We used the overall muscle PFOS mean concentration of 15.8 ng g−1 ww (6.95–33.6 ng g−1 ww) for PFOS and 0.28 ng g−1 ww (0.16–0.55 ng g−1 ww) for PFOA in the TWI calculations. Figs. 4 and 5 show the concentrations of PFOS and PFOA compared with the TWI of 0.013 μg PFOS kg−1 and 0.006 μg PFOA kg−1 from EFSA (2018a). The results for PFOS clearly show a risk similar to that of Hg reaching the
Fig. 5. The relationship between amount of seal meat that can be consumed per week by men, women and children as a function of PFOA muscle concentration. The dots refer to results from the present study. The calculation is based on tolerable weekly intake of 0.006 μg kg−1 week−1. 381
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(women) and 32 g (men) should be consumed in a week while it should not exceed 57 g (child), 114 g (women) and 152 g (men) for the group of seals with lowest muscle concentrations (6.95 ng g−1 ww). For PFOA, the tolerable amount of seal meat would be 640, 1290 and 1720 g for children, women and men, respectively.
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Letcher, R.J., Bustnes, J.O., Dietz, R., Jenssen, B.M., Jørgensen, E.H., Sonne, C., Verreault, J., Vijayan, M.M., Gabrielsen, G.W., 2010. Effects assessment of persistent organohalogen contaminants in arctic wildlife and fish. Sci. Total Environ. 408, 2995–3043. McLachlan, M.S., Holmstrom, K.E., Reth, M., Berger, U., 2007. Riverine discharge of perfluorinated carboxylates from the European continent. Environ. Sci. Technol. 41, 7260–7265. Murphy, S., Barber, J.L., Learmonth, J.A., Read, F.L., Deaville, R., Perkins, M.W., Brownlow, A., Davison, N., Penrose, R., Pierce, G.J., Law, R.J., 2015. Reproductive failure in UK harbour porpoises phocoena phocoena: legacy of pollutant exposure? PLoS One 10, e0131085. Nielsen, E., Larsen, J.C., Ladefoged, O., 2006. Risk Assessment of Contaminant Intake from Traditional Greenland Food Items. Denmark: Danish Veterinary and Food Administration. http://www.dfvf.dk. Nyman, M., Koistinen, J., Fant, M.L., Vartiainen, T., Helle, E., 2002. Current levels of DDT, PCB and trace elements in the Baltic ringed seals (Phoca hispida baltica) and grey seals (Halichoerus grypus). Environ. Pollut. 119, 399–412. Olsen, M.T., Galatius, A., Härkönen, T., 2018. The history and effects of seal-fishery conflicts in Denmark. Mar. Ecol. Prog. Ser. 595, 233–243. Outridge, P.M., Dietz, R., Amyot, M., Barkay, T., Basu, N., Berg, T., Braune, B., Carrie, J., Chételat, J., Cole, A., Constant, P., Dastoor, A., Dommergue, A., Donaldson, S.G., Douglas, T., Durnford, D., Evans, M., Ferrari, C., Gaden, A., Gantner, A.K., Gantner, N., Goodsite, M., Hedman, J., Hintelmann, H., Hobson, K., Johnson, M., Kirk, J., Kroer, N., Krümmel, E., Larose, C., Lean, D., Leech, T., Letcher, R.J., Loseto, L.,
3.6. Considerations Combined effects from Hg, OCs and PFASs are not considered here. Neither are dioxin-like PCBs or dioxins considered, or potential carcinogenicity. However, based on the available data, it is obvious that the risk of contaminant exposure for humans consuming seal meat in Denmark is determined by the presence of Hg and PFOS as less than 67, 50 and 25 g of seal meat consumption is tolerable per week for men, women and children, respectively. Regarding the group of non-dioxin like PCBs alone, there is no realistic risk since as much as 0.5–3.5 kg can be eaten weekly depending on the weight of the consumer and the seal's age, sex and muscle concentrations of ∑PCB, the dominant OC group. This conclusion is based on a provisional TWI which might originally have been set for Aroclor mixtures and which has not been updated recently (Berti et al., 1998; AMAP, 2003; Johansen et al., 2004). In addition to the mercury and industrial chemicals found in the seal meat, infectious diseases including zoonosis should be taken into account when evaluating the appropriateness of the meat for human consumption (Sonne et al., 2018; Tryland et al., 2014). 4. Conclusions The concentrations of Hg and PFOS in muscle tissue of harbour seals from the southwestern Baltic Sea were high in relation to TWI values set by EFSA and only allowed for a weekly consumption of 25, 50 and 67 g of meat in order not to exceed toxic thresholds for children, women and men, respectively. For non-dioxin like PCBs and PFOA, the amount was 1.3–3.5 and 0.6–1.7 kg for children, women and men, in relation to a provisional tolerable weekly intake and an EFSA TWI, respectively. Our study demonstrates that consumption of Danish Baltic Sea harbour seal meat can only be recommended in very small amounts based on Hg and PFOS concentrations alone. Acknowledgements The study was approved by the Danish Nature Agency (SVANA). For funding, we acknowledge the Danish Environmental Protection Agency (supported under the Wildlife Contract) and BONUS BALTHEALTH that has received funding from BONUS (Art. 185), funded jointly by the EU, Innovation Fund Denmark (grants 6180-00001B and 6180-00002B), Forschungszentrum Jülich GmbH, German Federal Ministry of Education and Research (grant FKZ 03F0767A), Academy of Finland (grant 311966) and Swedish Foundation for Strategic Environmental Research (MISTRA). In addition, we are grateful to the laboratory technicians Annegrete Ljungqvist, Inga Jensen and Thomas Hansen who performed the chemical analyses. Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.envres.2019.05.026. References Ahrens, L., Siebert, U., Ebinghaus, R., 2009. Total body burden and tissue distribution of polyfluorinated compounds in harbor seals (Phoca vitulina) from the German Bight. Mar. Pollut. Bull. 4, 520–525. AMAP, 2003. Arctic Monitoring and assessment programme: AMAP assessment 2002 human Health in the arctic. Arctic Monitoring and assessment programme (AMAP), oslo, Norway. www.amap.no. AMAP, 2004. Arctic Monitoring and assessment programme: AMAP assessment 2002 -
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C. Sonne, et al. Macdonald, R.W., Muir, D.C.G., Munthe J, J., Nielsen, T.G., O'Hara, T., Pacyna, J., Poissant, L., Poulain, A., Rigét, F., Rognerud, S., Ryzhkov, A., Scheuhammer, T., Skov, H., Sonne, C., Sørensen, S., Steenhuisen, F., Steffen, A., Stern, G., Stow, J., Sundseth, K., Travnikov, O., Verta, M., Wang, F., Wängberg, I., Wilson, S.J., Zdanowicz, C., 2011. Mercury in the Arctic. Arctic Monitoring and Assessment Programme (AMAP), Oslo, Norway. Xiv + 193. Routti, H., van Bavel, B., Letcher, R.J., Arukwe, A., Chu, S., Gabrielsen, G.W., 2009. Concentrations, patterns and metabolites of organochlorine pesticides in relation to xenobiotic phase I and II enzyme activities in ringed seals (Phoca hispida) from Svalbard and the Baltic Sea. Environ. Pollut. 157, 2428–2434. Sonne, C., 2010. Health effects from long-range transported contaminants in Arctic top predators: an integrated review based on studies of polar bears and relevant model species. Environ. Int. 36, 461–491. Sonne, C., Dietz, R., Letcher, R.J., 2013. Chemical cocktail party in East Greenland: a first time evaluation of human organohalogen exposure from consumption of ringed seal
and polar bear tissues and possible health implications. Toxicol. Environ. Chem. 95, 853–859. Sonne, C., Andersen-Ranberg, E., Rajala, E.L., Agerholm, J.S., Bonefeld-Jørgensen, E., Desforges, J.P., Eulaers, I., Jenssen, B.M., Koch, A., Rosing-Asvid, A., Siebert, U., Tryland, M., Mulvad, G., Härkönen, T., Acquarone, M., Nordøy, E.S., Dietz, R., Magnusson, U., 2018. Seroprevalence for Brucella spp. in Baltic ringed seals (Phoca hispida) and East Greenland harp (Pagophilus groenlandicus) and hooded (Cystophora cristata) seals. Vet. Immunol. Immunopathol. 198, 14–18. Tryland, M., Nesbakken, T., Robertson, L., Grahek‐Ogden, D., Lunestad, B.T., 2014. Human pathogens in marine mammal meat – a Northern perspective. Zoonosis Public Health 61, 377–394. Vorkamp, K., Christensen, J.H., Glasius, M., Rigét, F., 2004. Persistent halogenated compounds in black guillemots (Cepphus grylle) from Greenland - levels, compound patterns and spatial trends. Mar. Pollut. Bull. 48, 111–121.
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Human exposure to PFOS and mercury through meat from baltic harbour seals (Phoca vitulina)
T
Christian Sonnea,b,∗, Katrin Vorkampb,c, Anders Galatiusa, Line Kyhna, Jonas Teilmanna, Rossana Bossib,c, Jens Søndergaarda,b, Igor Eulaersa,b, Jean-Pierre Desforgesa,b, Ursula Sieberta,d, Rune Dietza,b a
Aarhus University, Department of Bioscience, Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark Aarhus University, Arctic Research Center (ARC), Frederiksborgvej 399, DK-4000, Roskilde, Denmark c Aarhus University, Department of Environmental Science, Frederiksborgvej 399, PO Box 358, DK-4000, Roskilde, Denmark d Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Foundation, Werftstr. 6, DE-25761, Büsum, Germany b
ARTICLE INFO
ABSTRACT
Keywords: Hg Polychlorinated biphenyls Polyfluoroalkyl substances TWI Tolerable weekly intake Human consumption
The overall aim of the present study was to assess human exposure to environmental contaminants from consumption of harbour seal (Phoca vitulina) meat in the southwestern Baltic Sea. For this purpose, muscle tissue from harbour seals (n = 27) was sampled from Danish locations in the period 2005–2015 and analysed for concentrations of total mercury (Hg), organochlorine contaminants such as polychlorinated biphenyls (PCBs) and organochlorine pesticides as well as perfluoroalkyl substances (PFAS) with particular focus on perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Hg, ∑PCB, PFOS and PFOA concentrations in the muscle tissue ranged between 0.27 and 4.76 μg g−1 wet weight (ww; mean: 1.38 μg g−1 ww, n = 27), 12.2–137 ng g−1 ww (mean: 47.5 ng g−1 ww, n = 10), 6.95–33.6 ng g−1 ww (mean: 15.8 ng g−1 ww, n = 10) and 0.16–0.55 ng g−1 ww (mean: 0.28 ng g−1 ww, n = 10), respectively. We compared the concentrations with literature-derived human tolerable weekly intake (TWI) values for mercury (1.3 μg kg−1 week−1), ∑PCB (2.1 μg kg−1 week−1), PFOS (0.013 μg kg−1 week−1) and PFOA (0.006 μg kg−1 week−1). The comparisons showed that the weekly consumption of harbour seal meat by children (weighing 30 kg), women (weighing 60 kg) and men (weighing 80 kg) should not exceed 28, 57 and 76 g (for Hg), 1.3, 2.7 and 3.5 kg (for ∑PCB), 25, 50 and 67 g (for PFOS) and 640, 1290 and 1720 g (for PFOA). In conclusion, Hg and PFOS are the contaminants of most importance in seal meat from this area with respect to existing tolerable intake rates and risks of adverse human health effects.
1. Introduction Given their persistence, toxicity and biomagnification properties, mercury (Hg), per- and polyfluoroalkyl substances (PFASs) such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), and organochlorine (OC) contaminants such as polychlorinated biphenyls (PCBs) and OC pesticides are of concern to wildlife and humans (Murphy et al., 2015). They were used in multiple industrial or agricultural products and processes for several decades, such as paper production, gold mining and fossil burning (Hg), fire-fighting foams and coatings (PFASs), transformers, capacitors and construction
materials (PCBs), and as pesticides (OC pesticides) (AMAP, 2004; Outridge et al., 2011). The toxic effects in vertebrates include immune suppression, cancer, neuro-endocrine disruption, reproductive impairment and disruption of energy metabolism (Dietz et al., 2018a; Letcher et al., 2010; Murphy et al., 2015; Sonne, 2010). Because marine mammals occupy high trophic levels in the marine food web, they are exposed to elevated concentrations of these biomagnifying contaminants (Dietz et al., 2018a). Mercury, OCs and PFAS are ubiquitous in the environment, and the Baltic Sea is among the marine ecosystems with the highest reported contaminant concentrations globally (HELCOM, 2018). The Danish part
∗ Corresponding author. Aarhus University, Faculty of Science and Technology, Department of Bioscience, Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark. E-mail addresses: [email protected] (C. Sonne), [email protected] (K. Vorkamp), [email protected] (A. Galatius), [email protected] (L. Kyhn), [email protected] (J. Teilmann), [email protected] (R. Bossi), [email protected] (J. Søndergaard), [email protected] (I. Eulaers), [email protected] (J.-P. Desforges), [email protected] (U. Siebert), [email protected] (R. Dietz).
https://doi.org/10.1016/j.envres.2019.05.026 Received 4 April 2019; Received in revised form 15 May 2019; Accepted 16 May 2019 Available online 24 May 2019 0013-9351/ © 2019 Elsevier Inc. All rights reserved.
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of the western Baltic receive a large influx of contaminants from Baltic rivers (McLachlan et al., 2007). In line with this a previous study showed high concentrations of PFASs in harbour seal liver in the Wadden Sea are lower than concentrations in the western Baltic (Dietz et al., 2012), but there is no knowledge of environmental contaminants in harbour seal muscle tissue, in the Baltic Sea or elsewhere, although it may be consumed by hunters and consequently pose a health concern. Several harbour seal populations are now large and viable in the Baltic Sea region after successful conservation measures since total protection was enforced in 1977, and former fisheries conflicts reemerge. During the last 10 years, an increasing number of permits to shoot seals depredating fishing gear has been issued (Olsen et al., 2018). These conflicts, leading to the potential availability and use of seal meat for human consumption have raised the question of human health issues. Here, we quantify concentrations of important environmental contaminants and compare these to human tolerable weekly intake (TWI) rates to assess the human health risk related to exposure through seal meat consumption.
included perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), perfluoroheptanesulfonic acid (PFHpS), PFOS, perfluorodecanesulfonic acid (PFDS), perfluoro-1-octanesulfonamide (FOSA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), PFOA, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnA), perfluorododecanoic acid (PFDoA), perfluorotridecanoic acid (PFTrA), and perfluorotetradecanoic acid (PFTeA). The extraction method was based on Ahrens et al. (2009). Approximately 5 g of tissue was homogenised and 1g aliquot was weighted in a polypropylene tube and spiked with 10 ng of an internal standard mixture (S3). Native and labelled compounds were bought as mixtures from Wellington Laboratories (Guelph, ON, Canada). Tissues were extracted with 5 mL of acetonitrile twice for 30 min in an ultrasonic bath at 30 °C. The combined extract was reduced to 2 mL under a stream of nitrogen and 50 μL of acetic acid were added. For clean-up Supelclean ENVI-Carb® cartridges (100 mg, 1 mL, 100–400 mesh, Supelco, USA) were used. The cartridges were conditioned with 2 mL of acetonitrile followed by 1 mL of 20% acetic acid in acetonitrile. Afterwards, the sample extract was added to the cartridge with three times 1 mL of methanol and directly collected into another vial. The extracts were dried under a gentle nitrogen stream and reconstituted in 1 mL of methanol:ammonium acetate (2 mM; 50:50; v:v). Quantification was performed by liquid chromatography tandemmass spectrometry with electrospray ionization in negative mode. Chromatographic separation was performed using a C18 Kinetex column (2.1 × 150 mm, Phenomenex, Torrance, CA, USA) and an Agilent 1200 Series HPLC (Agilent, Palo Alto, CA, USA). The ions monitored for each compound can be found in Table S4. Each batch of samples was analysed with a procedural blank. Recoveries ranged from 75 to 129% (Table S5). The relative standard deviation (RSD) for samples run in duplicate ranged from 5 to 24% (Table S5). The RSDs for PFTeA and PFTrA were higher (44%-47%) because mass-labelled chemical standards are not available and analysis is based on the PFDoA standard. Method detection limits were calculated as three times the standard deviation of procedural blanks (Table S6).
2. Materials and methods 2.1. Sampling We collected muscle tissue from 27 harbour seals from the South Western Baltic Sea during the period 2005–2015, where fishermen had been given permission to shoot seals close to their nets and fykes by the Ministry of Environment and Food of Denmark (Fig. 1). The 27 sternal muscle samples were from 9 adult males, 7 adult females, 4 subadult males, and 7 subadult females. Seals were categorized as adult or subadult based on their length measurement (Harding et al., 2018) (Tables 1 and S1). 2.2. Hg analysis Seal muscle samples (n = 27) were analysed for total Hg using a Milestone DMA-80 Direct Mercury Analyzer (DMA) at the accredited Environmental Trace Element Laboratory of the Department of Bioscience, Aarhus University, Roskilde, Denmark. Prior to the analyses, samples were freeze-dried and homogenised. A 0.020–0.040 g dried subsample was weighed and analysed. Sample concentrations were determined based on a calibration curve prepared from a 1000 ± 4 mg L−1 stock solution (Sigma-Aldrich, Switzerland). Blank samples and aqueous control standards (10 ng and 100 ng Hg prepared from the 1000 ± 4 mg L−1 stock solution) were analysed every 10–15 samples. Subsequently, sample concentrations were corrected for blank sample Hg levels and daily instrument drift (based on control standard results). For quality assurance/quality control (QA/QC), the Certified Reference Material DORM-4 (www.nrc-cnrc.gc.ca) was analysed along with the samples. The measured recovery percentage (mean ± SD) of DORM-4 was 101 ± 2% (n = 7; certified Hg concentration = 0.410 ± 0.055 μg g−1; measured Hg concentration = 0.414 ± 0.008 μg g−1). The laboratory is ISO 17025 accredited for total Hg analyses in biological samples using DMA and regularly participates in the proficiency-testing scheme for Hg in biota arranged by the organisation for Quality Assurance of Information for Marine Environmental Monitoring in Europe (QUASIMEME). Results from the analyses are shown in Table S2.
2.4. OC analysis Organochlorine contaminants were analysed at the Department of Environmental Science, Aarhus University, Roskilde, Denmark. A subsample of each 10 pooled samples (see above) was extracted and cleaned up according to the method by Vorkamp et al. (2004), with few modifications. Ten grams were spiked with recovery standards (CB-3, CB-40 and CB-198; Ultra Scientific, Wesel, Germany, now Agilent; Dr. Ehrenstorfer, Augsburg, Germany, LGC Standards; Cambridge Isotope Laboratories, Tewksbury, MA, USA, respectively), mixed with diatomaceous earth and Soxhlet extracted using n-hexane:acetone (4:1; v:v; Rathburn Chemicals, Walkerburn, UK). The extracts were reduced in volume and purified on a multi-layer column consisting of deactivated aluminium oxide (10% water), activated silica (160 °C for 24 h), with and without H2SO4, and a layer of Na2SO4 on top. After elution with nhexane, the extracts were pre-concentrated, spiked with syringe standards (CB-53 and CB-155, both Ultra Scientific, Agilent) and adjusted to a precise volume of 1 mL. The extracts were analysed by dual column-gas chromatography with electron capture detection equipped with a DB-5 and a DB-1701 column (J&W Scientific, both 60 cm long, 0.25 mm inner diameter and 0.25 μm film thickness). Quantification was based on two 9-point stepwise calibration curves. The batch contained one procedural blank and a duplicate of the in-house reference material (fish oil) used for control charts (Table S7). The control charts monitor the long-term precision of the analysis and include warning and action limits (mean ± 2 and 3 standard deviations, respectively) to flag potential quality issues, as further described for these specific analyses by Asmund et al. (2004). The samples had recovery rates of 88–98% (mean 94%, Table S7). Traces of CB-49 and p,p’-DDT were detected in the blank and increased
2.3. PFAS analysis PFAS contaminants were analysed at the Department of Environmental Science, Aarhus University, Roskilde, Denmark. Muscle tissue homogenates were pooled for economic considerations to have a final sample size of ten, representing adults (5 pooled samples each containing two to four specimens) and juveniles (5 pooled samples each containing two-three specimens; Table S3). The PFASs quantified 377
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Fig. 1. Map showing sampling locations for harbour seal muscle samples used in the present study.
the detection limits for these compounds, however, all samples had concentrations above detection limits for all compounds and congeners. The laboratory is ISO 17025 accredited for OC analyses in biological samples and regularly participates in the QUASIMEME proficiencytesting scheme for OCs in biota. The targeted compounds included 22 PCB congeners and the OC pesticides α-, β-, γ-hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), p,p’-DDD, p,p’-DDE, o,p’-DDE, p,p’DDT and o,p’-DDT and trans-nonchlor. A list of congeners and compounds, including their detection limits, is given in Table S7.
half-lives of the compounds in the body. The following TWI muscle values were used for this study: 1.3 μg kg−1 week−1 for Hg, 2.1 μg kg−1 week−1 for ∑PCBs, 0.013 μg kg−1 week−1 for PFOS and 0.006 μg kg−1 week−1 for PFOA (EFSA, 2012; 2018a; Johansen et al., 2004). These are based on the precautionary principle given that recently there is indications that PFAS are likely more toxic than previously thought with respect to cancer, immune and reproductive toxicity. The TWI value for ∑PCB relates back to a provisional tolerable daily intake of 1 μg kg−1 day−1 used by Health Canada for PCBs (Berti et al., 1998). This was later stated to refer to Arochlor mixtures, and a TWI of 2.1 μg kg−1 week−1 was used for the sum of 14 PCB congeners, which comes closer to current congener-specific analyses (AMAP, 2003; Johansen et al., 2004). EFSA (2018b) recently issued a TWI of 2 pg toxicity equivalents kg−1 week−1 for dioxins and dioxin-like PCBs. However, our study only addressed non-dioxin like PCBs for which EFSA has not set a TWI. TWI values for ΣDDT (70 μg kg−1 week−1, provisional TWI set by the World Health Organisation), ΣHCH (2.1 μg kg−1 week−1, set by Health Canada) and HCB (1.2 μg kg−1 week−1, set by the World Health Organisation) are included in Table S7 (Berti et al., 1998; EFSA, 2006a,
2.5. Tolerable weekly intake (TWI) We decided to focus the comparison of contaminant concentrations with human TWI for muscle content of Hg, ∑PCBs, PFOS and PFOA as these were the compounds and compound groups found in the highest concentrations relative to their TWI values and therefore were those posing the highest health risk (EFSA, 2012; 2018a, 2018b; Johansen et al., 2004). Given that the toxicological endpoints are based on longterm exposure, EFSA (2012) recommended, in a scientific opinion on Hg exposure, that TWI is based on chronic exposure and the biological 378
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ww and 5–49 ng g−1 ww, respectively, for Σ10PCBs (Johansen et al., 2004). For comparison, ∑PCB concentrations of 12.2–137 ng g−1 ww were observed in the present study. In the Arctic, communities have been advised to eat tissues from subadult seals rather than adults and to eat less adipose tissue; all in order to reduce the intake of PCBs (Deutch et al. 2006; Johansen et al., 2004; Nielsen et al., 2006; Sonne et al., 2013). The PFAS found in the highest concentration was PFOS, followed by PFTrA and PFUnA (Table S8). In general, concentrations of PFASs were non-significantly higher in subadults than in adults (all p > 0.05). This is likely due to maternal transfer as previously shown for Arctic seals (Letcher et al., 2010; Dietz et al., 2012).
2006b), but not further discussed because of a larger margin between the measured exposure concentrations and the TWI. 2.6. Statistics Analyses of variance (ANOVA) was conducted to test for differences in contaminant loads among age-sex groups (adult male, adult female, subadult male and subadult female) while regression analyses were used to test for a relationship between standard length and contaminant load. The level of significance was set at α= 0.05. Contaminant concentrations and seal standard lengths were ln-transformed prior to statistical analysis in order to approach the assumption of normality and homogeneity of variance. The statistical analyses were performed with the SAS statistical software package (SAS 9.4 and SAS Enterprise Guide 7.1).
3.3. Weekly intake of Hg
Data on the biometric parameters and contaminant concentrations are shown in Table 1. Adult males had the highest concentrations of Hg, however, these were not significantly higher than in subadults and adult females (all p > 0.05) (Table 1). There was no significant relationship between Hg concentration and length of the animals (R2 = 0.06, p = 0.09). Previous studies of Baltic ringed seals (Pusa hispida botnica) showed slightly lower muscle Hg concentrations than in the present study (mean: 1.0 μg g−1 ww; range 0.8–3.0 μg g−1 ww), also, Hg concentrations in Baltic grey seal (Halichoerus grypus) muscle were lower (mean: 0.7 μg g−1 ww; range: 0.4–1.6 μg g−1 ww) (Fant et al., 2001; Nyman et al., 2002). When comparing our results to muscle Hg concentrations in Arctic ringed seals (Pusa hispida) from Greenland and Canada the Hg concentrations are approximately 3 times higher in the Baltic harbour seals of the present study (Dietz et al., 1998; Gaden et al., 2009). This evidently highlights the potential risk in the Baltic, as Hg is a well-known problem for Arctic communities consuming marine mammals with considerably lower Hg concentrations (Dietz et al., 2013, 2018b).
We used the overall muscle Hg mean concentration of 1.38 μg g−1 ww (0.27–4.76 μg g−1 ww) in the TWI calculations. Fig. 2 shows the concentrations of Hg compared to the TWI of 1.3 μg Hg kg−1 from EFSA (2012). Based on the mean concentration of 1.38 μg kg−1 week−1, the weekly amount of meat a man (weighing about 80 kg), a women (weighing about 60 kg) and a child (weighing about 30 kg) can eat is 76, 57 and 28 g, respectively. From the seal with the highest muscle Hg concentration of 4.8 μg g−1 ww, only a maximum of 21, 16 and 8 grams should be consumed per week, while the tolerable intake was 373, 285 and 118 grams for the seal with the lowest value (0.27 μg g−1 ww). However, the long-term exposure is best expressed by the mean concentration in the seals, across both age and sex (Johansen et al., 2004). The risk from consistently exceeding these guidelines includes neurotoxicity and developmental effects leading to reproductive and immune failure in severe cases (Grandjean and Landrigan, 2006). In the Avanersuaq (Thule) municipality in Greenland, Hg TWI is often exceeded 10–20-fold, which is exceptionally high, due to high consumption of narwhal meat that has lower Hg concentrations than the Baltic harbour seals of the present study (Dietz et al., 2018b). Compared to other studies of Baltic seals, harbour seals may even be the species with the highest concentrations of contaminants, however, it will require further analyses to assess which of the species are of most concern with respect to human exposure (Fant et al., 2001; Nyman et al., 2002).
3.2. OCs and PFAS
3.4. Weekly intake of PCBs
The OC group found in highest concentration was ∑PCB which follows is similar to previous studies of OCs in Baltic as well as in Arctic seals (Letcher et al., 2010; Nyman et al., 2002; Routti et al., 2009). Overall, OC concentrations were similar in subadults and adults except for HCB which was higher in adults (Tables 1 and S7). In a study of the Greenland food web, harp seal and ringed seal meat were < 5 ng g−1
We used the overall muscle PCB mean concentration of 47.5 ng g−1 ww (12.2–137 ng g−1 ww) in the TWI calculations. Fig. 3 shows the concentrations of ∑PCB compared with the provisional TWI of 2.1 μg ∑PCB kg−1 (AMAP, 2003; Johansen et al., 2004). Based on the observed mean ∑PCB concentrations in seal meat, weekly consumption for men, women and children should not exceed 3.5, 2.7 and 1.3 kg,
3. Results and discussion 3.1. Mercury
Table 1 Information on the harbour seals from which muscle tissue was collected over the period 2005–2015 and analysed for Hg, PFAs and OCs. Data are given as mean ± SD (min-max). See Tables S2–8 for more information on contaminant concentrations.
Length (cm) Hg (μg g−1 ww) PFASs (ng g−1 ww) PFOS PFTrA PFUnA PFOA OCs (ng g−1 ww) ∑PCBs ∑DDTs trans-nonachlor ∑HCHs HCB
Adult males n = 9
Adult females n = 7
Subadult males n = 4
Subadult females n = 7
157 ± 14 (141–183) 1.63 ± 1.35 (0.42-4.76)
139 ± 10 (126–157) 1.29 ± 0.41 (0.73-1.91)
121 ± 5 (114–125) 1.20 ± 0.39 (0.68-2.08)
116 ± 11 (97–128) 1.31 ± 1.05 (0.27-3.23)
13.9 2.02 1.10 0.27
± ± ± ±
3.4 (10.1-17.5) 0.51 (1.40-2.52) 0.30 (0.86-1.62) 0.16 (0.16.0.55)
17.7 2.57 1.17 0.29
± ± ± ±
11.2 1.60 0.57 0.10
(6.95-33.6) (0.63-4.47) (0.40-1.66) (0.19-0.42)
50.3 30.6 0.99 0.45 0.14
± ± ± ± ±
48.8 22.8 0.83 0.27 0.17
44.7 27.8 0.84 0.33 0.07
± ± ± ± ±
38.3 23.3 0.60 0.22 0.03
(12.2-87.6) (7.03-64.4) (0.25-1.73) (0.09-0.63) (0.04-0.11)
(21.6-137) (15.2-70.6) (0.51-2.46) (0.2-0.88) (0.05-0.45)
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Fig. 2. The relationship between amount of seal meat that can be consumed per week by men, women and children as a function of Hg muscle concentration. The dots refer to results from the present study. The calculation is based on tolerable weekly intake of 1.3 μg kg−1 Hg week−1.
respectively, assuming that the blubber is not consumed, which generally has higher concentrations of lipophilic compounds like PCBs (Johansen et al., 2004). For the pooled group of seals with the highest concentration (137 ng g−1 ww), the intake should not exceed 2.1 kg week−1 for men, 1.6 kg for women and 0.8 kg for children. For the pooled group of seals with the lowest concentration (12.2 μg g−1
ww) it was 24, 18 and 9 kg per week for men, women and children. Again, long-term exposure is best expressed by the mean concentration across both age and sex (Johansen et al., 2004). Furthermore, considering the carcinogenicity of PCBs (IARC, 2016), PCB exposure generally bears a health risk. For ∑DDT, ∑HCH and HCB, the safe margins were higher than for PCBs based on concentrations and TWI (Table S7).
Fig. 3. The relationship between amount of seal meat that can be consumed per week by men, women and children as a function of ∑PCB muscle concentration. The dots refer to results from the present study. The calculation is based on tolerable weekly intake of 2.1 μg kg−1 week−1. 380
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Fig. 4. The relationship between amount of seal meat that can be consumed per week by men, women and children as a function of PFOS muscle concentration. The dots refer to results from the present study. The calculation is based on tolerable weekly intake of 0.013 μg kg−1 week−1.
3.5. Weekly intake of PFOS and PFOA
TWI for relatively small portions of seal meat across all the three agesex groups (children, women and men) while the risk from PFOA exposure was lower and the tolerable intake of seal meat was between those calculated for PFOS and ΣPCB. Weekly seal meat consumption will violate the TWI for PFOS, if 25 g of meat is consumed by children, 50 g by women and 67 g by men, assuming a mean concentration of PFOS of 15.8 ng g−1. For the group of seals with the highest muscle tissue PFOS concentration (33.6 ng g−1 ww), less than 12 g (child), 24 g
We used the overall muscle PFOS mean concentration of 15.8 ng g−1 ww (6.95–33.6 ng g−1 ww) for PFOS and 0.28 ng g−1 ww (0.16–0.55 ng g−1 ww) for PFOA in the TWI calculations. Figs. 4 and 5 show the concentrations of PFOS and PFOA compared with the TWI of 0.013 μg PFOS kg−1 and 0.006 μg PFOA kg−1 from EFSA (2018a). The results for PFOS clearly show a risk similar to that of Hg reaching the
Fig. 5. The relationship between amount of seal meat that can be consumed per week by men, women and children as a function of PFOA muscle concentration. The dots refer to results from the present study. The calculation is based on tolerable weekly intake of 0.006 μg kg−1 week−1. 381
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(women) and 32 g (men) should be consumed in a week while it should not exceed 57 g (child), 114 g (women) and 152 g (men) for the group of seals with lowest muscle concentrations (6.95 ng g−1 ww). For PFOA, the tolerable amount of seal meat would be 640, 1290 and 1720 g for children, women and men, respectively.
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3.6. Considerations Combined effects from Hg, OCs and PFASs are not considered here. Neither are dioxin-like PCBs or dioxins considered, or potential carcinogenicity. However, based on the available data, it is obvious that the risk of contaminant exposure for humans consuming seal meat in Denmark is determined by the presence of Hg and PFOS as less than 67, 50 and 25 g of seal meat consumption is tolerable per week for men, women and children, respectively. Regarding the group of non-dioxin like PCBs alone, there is no realistic risk since as much as 0.5–3.5 kg can be eaten weekly depending on the weight of the consumer and the seal's age, sex and muscle concentrations of ∑PCB, the dominant OC group. This conclusion is based on a provisional TWI which might originally have been set for Aroclor mixtures and which has not been updated recently (Berti et al., 1998; AMAP, 2003; Johansen et al., 2004). In addition to the mercury and industrial chemicals found in the seal meat, infectious diseases including zoonosis should be taken into account when evaluating the appropriateness of the meat for human consumption (Sonne et al., 2018; Tryland et al., 2014). 4. Conclusions The concentrations of Hg and PFOS in muscle tissue of harbour seals from the southwestern Baltic Sea were high in relation to TWI values set by EFSA and only allowed for a weekly consumption of 25, 50 and 67 g of meat in order not to exceed toxic thresholds for children, women and men, respectively. For non-dioxin like PCBs and PFOA, the amount was 1.3–3.5 and 0.6–1.7 kg for children, women and men, in relation to a provisional tolerable weekly intake and an EFSA TWI, respectively. Our study demonstrates that consumption of Danish Baltic Sea harbour seal meat can only be recommended in very small amounts based on Hg and PFOS concentrations alone. Acknowledgements The study was approved by the Danish Nature Agency (SVANA). For funding, we acknowledge the Danish Environmental Protection Agency (supported under the Wildlife Contract) and BONUS BALTHEALTH that has received funding from BONUS (Art. 185), funded jointly by the EU, Innovation Fund Denmark (grants 6180-00001B and 6180-00002B), Forschungszentrum Jülich GmbH, German Federal Ministry of Education and Research (grant FKZ 03F0767A), Academy of Finland (grant 311966) and Swedish Foundation for Strategic Environmental Research (MISTRA). In addition, we are grateful to the laboratory technicians Annegrete Ljungqvist, Inga Jensen and Thomas Hansen who performed the chemical analyses. Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.envres.2019.05.026. References Ahrens, L., Siebert, U., Ebinghaus, R., 2009. Total body burden and tissue distribution of polyfluorinated compounds in harbor seals (Phoca vitulina) from the German Bight. Mar. Pollut. Bull. 4, 520–525. AMAP, 2003. Arctic Monitoring and assessment programme: AMAP assessment 2002 human Health in the arctic. Arctic Monitoring and assessment programme (AMAP), oslo, Norway. www.amap.no. AMAP, 2004. Arctic Monitoring and assessment programme: AMAP assessment 2002 -
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