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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Numerous studies have been conducted on bioaccumulation of NP in the aquatic environment but experiments looking at NPEOs are fewer. In the literature, BCF values of 50 – 500 have been cited for NP (Snyder et al., 2001), considering the most sensitive species for accumulation – fathead minnow – and depending whether lipid correction is considered or not. Based on their higher water solubility, NPEOs are expected to bioaccumulate to a lower extent than NP, and this has been shown in a number of studies where measured BCF or BAF values were always well below the REACH level of 2,000 for defining a substance as ‘bioaccumulative’. Higher bioconcentration/bioaccumulation factors have been observed in green algae by Sun et al. (2014), however there are some uncertainties on this data. Indeed, the high BCF in algae were (at least partly) due to absorption and not uptake and bioaccumulation in the study did not increase higher up in the food chain. In general, algae are not considered in the context of bioaccumulation. The weighted average BCF of the NPEO evaluated in the frame of this Chemical Safety Report estimated using the BCFBAF program of EPIWEB 4.1 was equivalent to 40, which is in line with experimental data.

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A field study was conducted to evaluate the concentrations of NP, NPE-1 and NPE-2 in algae, aquatic plants, fish and birds. Samples of macrophytic algae were collected manually from the Chriesbach Creek and the Glatt River (Switzerland) in the summer and autumn of two consecutive years. Both the creek and the river receive secondary effluents from mechanical-biological domestic sewage treatment plants. Some of the most abundant fish species of the area (Squalus cephalus (n = 2), Barbus barbus (n = 1) and Salmo gairnieri (n = 1)) were collected in the Chriesbach Creek, dissected immediately and deep frozen until tissue analysis (muscle, gut, liver, gills, heart, roe and/or brain) was conducted. One wild duck (Anas boscas) was also caught, dissected and its tissues (liver, muscle, guts, stomach, heart and brain) stored for consequent analysis. Dry matter content was determined for each sample. Water samples were also taken (location and number not specified) for NP, NPE-1 and NPE-2 analysis. Steam distillation / cyclohexane extracts were quantified by HPLC. The extraction efficiencies for NP, NPE-1 and NPE-2 were 100, 96 and 82%, respectively. The limit of quantification of the HPLC method was 0.03 mg/kg dry weight (d.w.) based on 10 g of fresh tissue. The highest concentrations were found in the algaeChladophora glomerata, with 38.0, 4.7 and 4.3 mg/kg dw (dry weight) for NP, NPE-1 and NPE-2, respectively. The concentrations in fish were lower (NP: <0.03 – 1.6 mg/kg dw, NPE-1: 0.06 – 7.02 mg/kg dw and NPE-2: <0.03 – 3.07 mg/kg dw). In the duck, the values ranged between <0.03 – 1.20 (NP), <0.03 – 2.10 (NPE-1) and <0.03 – 0.35 (NPE-2) mg/kg dw. The average water concentrations of NP, NPE-1 and NPE-2 in the Chriesbach Creek were 3.9, 24 and 9.4 µg/L (arithmetic mean of three determinations) (Ahelet al., 1993). The authors calculated bioaccumulation factors (BAFs) comparing the measured data on a dry weight basis to concentrations in water and cited other published bioaccumulation or bioconcentration factors (BCFs) expressed as wet weight. This methodology was considered incorrect and the calculations redone by Staples et al.(1998). When all data was expressed on a weight weight basis assuming that fish muscle (the edible portion of the fish) was 85% water /15% dry matter and that algae were 95% water / 5% dry matter, the non-lipid BAFs (NP /NPE-1/NPE-2) were equivalent to 487/10/23 for Cladophora glomerata, 54/2/3 for Fontinalis antipyretica, 32/2/10 for Potamogeton crispus, 7/1/2 for Squalus cephalus, 15/19/37 for Barbus barbus and 6/3/0.8 for Salmo gairdneri. No recalculated values were presented for duck but the original measured values were in the same range as those for fish. These values suggest a relatively low bioaccumulation potential in the aquatic environment and no significant biomagnification in the food chain.

An accumulation study was performed with caged mussels (Mytilus edulis) in the unpolluted waters of a fjord on the Swedish West Coast. Mussels (40-50 mm) taken from a cultivation in an unpolluted area in the Northern part of the coast were stored in submersed tanks with a controlled dosage of wastewater from the outlet of a chemical plant of the Swedish West Coast producing surface active agents. The wastewater was distributed to the tanks in a semi-static system where the water was changed every 4 h. The concentrations of wasterwater were 100, 10 and 1%, respectively. A total of 25 specimen were used per concentration. After 50 days, the mussels were brought to the laboratory and analysed for shell growth and condition. Ten specimen per concentration were prepared and stored at -50°C for chemical analysis. Mussel dry weight was estimated. The concentrations of NP and NP ethoxylates in the frozen samples were analysed by GC-MS. Results were reported based on mussel fresh weight and fat weight. The concentrations of NP, NPE-1, NPE-2 and NPE-3 in the wastewater (100%) were equivalent to 40, 60, 40 and 50 µg/L, respectively. The study results indicated that NP and its short chain ethoxylates bioaccumulated in mussels and that the degree of bioaccumulation was depedent on chain length, as expected based on water solubility. The average bioconcentration factor for the 100, 10 and 1% wastewater concentrations combined was between 300-400 for NP, 100 -200 for NPE-1, 50 -100 for NPE-2 and approximately 50 for NPE-3 (Granmo Å et al., 1991).

To evaluate bioaccumulation potential and identify potential related risks, concentrations of NP, NPE-1, NPE-2, and NPE-3 were determined in the tissues of fish inhabiting various waters in Michigan (USA), namely the Kalamazoo River Basin and Lake Michigan near the mouth of the Kalamazoo River. The Kalamazoo River flows through both urban and rural areas and receives secondary and tertiary WWTP effluents and industrial discharges, including those of paper manufacturing facilities. Sampling along the river was conducted up and downstream of WWTP, whenever possible. Fish were selected based on availability at sampling site, size (weight), migratory behaviour and placement in the food chain. Species analysed included rock bass (Ambloplites rupestris), bluegill sunfish (Lepomis macrochirus),green sunfish (Lepomiscyanellus), smallmouth bass (Micropterus dolomieui), white suckers (Catostomus commersoni), longnose suckers (Maxostoma macrolepidotum) and rainbow smelt (Osmerus mordax). Fish were collected at three occasions between late June and early November 1999 and stored at -20°C for analysis. The digestive/excretory system was chosen for analysis, as this is the area where NP is likely to accumulate. The analysis method involved extraction of samples using exhaustive steam distillation with concurrent liquid extraction. No sampling of water was conducted. The detection limits for NP, NPE-1, NPE-2 and NPE-3 were 3.3, 16.8, 18.2 and 20.6 ng/g, respectively. Concentrations of NP among all sites and species ranged from <3.3 to 29.1 ng/g wet weight (ww) and varied little among sites. NPE-1 was detectable in some samples but at concentrations less than the method detection limit (16.8 ng/g). Concentrations of NPE-2 and NPE-3 in all samples were less than their respective minimum detection levels. Bioconcentration factors were not established. However, the study suggests the presence of nonylphenols in fish but at relatively small concentrations. NP was the predominant compound, with concentrations of NPEs less than those of NP. Fish collected near WWTP effluent discharge sites contained relatively greater concentrations than those collected from more remote areas (Keith TL et al., 2001).

To evaluate bioaccumulation potential and identify potential related risks, concentrations of NP, NPE-1, NPE-2, and NPE-3 were determined in the tissues of fish inhabiting various waters in Michigan (USA). The method involved extraction of samples using exhaustive steam distillation with concurrent liquid extraction. Concentrations of NP among all sites and species ranged from <3.3 to 29.1 ng/g wet weight (ww) and varied little among sites. NPE-1 was detectable in some samples but at concentrations less than the method detection limit (16.8 ng/g). Concentrations of NPE-2 and NPE-3 in all samples were less than their respective minimum detection levels of 18.2 and 20.6 ng/g (Keith TL et al., 2001).

The BCF of the NPEO evaluated in the frame of this Chemical Safety Report was estimated using the BCFBAF program of EPIWEB 4.1, based on the weighted average of the BCFs of the various constituents. A value of 40 was obtained, which is in line with experimental data.