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In a good-quality study conducted to GLP, the bioaccumulation factor (BCF) in freshwater rainbow trout (Oncorhynchus mykiss; reported as Salmo gairdneri) of a C10-12 chlorinated paraffin (58% chlorination) has been determined following exposure to measured concentrations varying from 0.033 to 3.05 mg/L in a dynamic, flow-through system for 60 days. Groups of 30 young fish were exposed to the 58% chlorinated paraffin, mixed with 6-14C-labelled n-undecane (59.1% chlorinated), and the concentration of both radioactivity and parent compound measured in the medium during the study and in the fish at the end of the study period. The BCF values, in the surviving fish, for the C10-12 chlorinated paraffin determined in this study based on radioactivity measurements were 7155, 7816, 3723, 2642 and 1173 at measured concentrations of 0.033, 0.10, 0.35, 1.07 and 3.05 mg/L, respectively. The corresponding values based on parent compound measurements were 7273, 3600, 1629, 991 and 574. The general reduction in BCF with increasing exposure concentration may be related to a lack of solubility of the test material at highest concentrations (Madeley and Maddock, 1983a).

Madeley and Maddock (1983b), using rainbow trout (Oncorhynchus mykiss), found high levels of accumulation in the liver and viscera after exposure to measured concentrations of 3.1 and 14.3 mg/L of a C10-12, 58% chlorinated paraffin. Exposure was for 168 days at 12oC using a flow-through system. The bioconcentration was measured by means of a 14C-labelled chlorinated n-undecane (59.1% wt Cl) mixed into the commercial product. Lower BCFs were observed in the flesh (BCF=1,300-1,600) as compared to liver (2,800-16,000) and viscera (11,700-15,500) and the whole fish BCF was estimated to be 3,600-5,300. These BCFs were based on the amount of 14C-labelled material present in the various organs. A limited number of parent compound analyses were also carried out at various times during the tests, and these indicated that some of the 14C-label present in the liver and viscera may not have been the parent chlorinated paraffin. Therefore, these measured BCFs are likely to represent maximum values. During depuration (168 days), the following half-lives were determined for the chlorinated paraffin: liver 9.9-11.6 days; viscera 23.1- 23.9 days; flesh 16.5-17.3 days; and whole body 18.7-19.8 days. The relatively short half-life observed in the liver is believed to be indicative of rapid metabolism and excretion of the test substance. On days 63-70 of depuration, fish previously exposed to chlorinated paraffins refused to feed and developed behavioural abnormalities. Deaths occurred in both groups previously exposed to chlorinated paraffins and all fish previously exposed to 14.3 mg/L died by day 70 of depuration. In the lower exposure group all abnormal effects ceased after day 70 of depuration. Although no explanation could be found for these events, there were no effects seen at this time or any other time in the control populations and the presence of disease or parasites was eliminated as a possible cause.

Bengtsson et al. (1979) studied the uptake and accumulation of several SCCPs by bleak (Alburnus alburnus). The fish were exposed to 125 mg/L of a C10-13, 49% wt Cl; C10-13, 59% wt Cl; C10-13, 71% wt Cl in brackish water for 14 days at 10oC under semi-static conditions (renewed every 2nd or 3rd day). After exposure, the depuration of the chlorinated paraffins was studied for an additional 7 days. All three chlorinated paraffins were taken up by the fish but uptake was greatest for the lower chlorinated grades over the 14 day exposure period (whole body BCFs of around 800-1,000 can be estimated from the data for the 49% wt Cl and 59% wt Cl compounds, whereas the BCF was around 200 for the 71% wt Cl compound). High levels of chlorinated paraffin were still detected in the fish after the 7 day depuration period.

Fisk et al. (1999) studied the uptake of a C10 and a C12 radiolablelled chlorinated paraffin (64 and 59% chlorination, respectively) by eggs and larvae of Japanese medaka (Oryzias latipes) as part of a 20-day embryo-larval toxicity study. The measured exposure concentrations used were 4.7, 50, 370, 2200 and 5100 mg/L for the C10 chlorinated paraffin and 0.7, 9.6, 55 and 270 mg/L for the C12 chlorinated paraffin. The resulting concentrations in the larvae at approximately 3-days post hatch were 12, 100, 1000, 3000 and 3500 mg/kg respectively for the C10 chlorinated paraffin and 0.74, 7.1, 62 and 460 mg/kg respectively for the C12 chlorinated paraffin. The resulting BCF values were 690-2700 l/kg for the C10 chlorinated paraffin and 740-1700 for the C12 chlorinated paraffin, with the BCF for the C10 chlorinated paraffin appearing to increase with decreasing exposure concentrations. The two highest measured exposure concentrations for the C10 chlorinated paraffin appear to be higher than the experimental water solubility of SCCPs and so the results at these higher exposure concentrations may have been affected by the presence of undissolved test substance (the BCFs for these two concentrations are 690-1364 l/kg compared with BCFs of 2000-2700 l/kg at the three lower concentrations). Similar results were found for the eggs. The exposure period in this experiment is relatively short and no indication is available as to whether equilibrium was reached.

Very high BCFs have been determined for a C10-12, 58% wt Cl chlorinated paraffin in common mussels (Mytilus edulis). The chlorinated paraffin was mixed with a 14C-labelled chlorinated n-undecane (59.1% Cl, 14C-labelled) and concentrations were determined by measurement of radioactivity (both water and mussel). Some parent compound analyses were also carried out at various times during the experiment and the concentrations obtained agreed with those obtained from the 14C radioactivity measurements. Mussels were exposed to the chlorinated paraffin at a concentration of 2.35 μg/L for 147 days followed by 98 days depuration or a concentration of 10.1 μg/L for 91 days followed by 84 days depuration using a flow-through system. Accumulation of the chlorinated paraffin was found to be greatest in the digestive gland, with BCFs being measured as 226,400 and 104,000 at the low and high exposure concentrations, respectively. Whole mussel BCFs were determined as 40,900 and 24,800 at the low and high exposure concentrations, respectively. All tissues expelled the test compound at a similar rate, with half-lives for the whole mussel being calculated as 9.2-9.9 days for the high exposure group and 13.1-19.8 days for the low exposure group. The high exposure concentration (10.1 μg/L) was found to cause a significant number of deaths during the test; 33% of the original 130 exposed mussels died either during the exposure period (23%) or depuration period (10%). Mortalities at the low exposure concentration were not significantly different from controls (Madeley et al, 1983).

Similarly high BCFs (5785-25952) have also been measured in mussels after 60 days exposure to a 58% wt Cl SCCP at concentrations of 0.013-0.93 mg/l (Madeley and Thompson, 1983).

As well as these BCF studies, a number of studies have shown that SCCPs can be taken up by fish in their diet. These studies are summarised in the final RAR (EU, 2000).

A BCF of 7816 for a C10-12 chlorinated paraffin (58% chlorination) in rainbow trout will be taken forward to the risk characterisation.

References (for which no ESR has been created - need to move to reference list in CSR)

Bengsson B E, Svanberg O and Lindén O (1979). Structure related uptake and elimination of some chlorinated paraffins in bleaks Alburnus alburnus. Ambio, 8, 121-122.

Fisk A T, Tomy G T and Muir D C G (1999). The toxicity of C10-, C11-, C12- and C14- polychlorinated alkanes to Japanese medaka (Oryzias latipes) embryos. Environ. Toxicol. Chem., 18, 2894-2902.

Madeley J R and Maddock B G (1983b). The bioconcentration of a chlorinated paraffin in the tissues and organs of rainbow trout (Salmo gairdneri). ICI Confidential Report BL/B/2310.

Madeley J R, Thompson R S and Brown D (1983a). The bioconcentration of a chlorinated paraffin by the common mussel (Mytilus edulis). ICI Confidential Report BL/B/2351.