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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Low bioaccumulation potential (BCF = 13 L/kg, read-across from DOCMAC; BCF = 70.8 L/kg, EPIWIN v4.11, BCFBAF v3.01)

Key value for chemical safety assessment

BCF (aquatic species):
13 L/kg ww

Additional information

No experimental data on bioaccumulation are available for MDIPA Esterquat C16-18 and C18 unsatd. According to REACH regulation (Annex XI, 1.5), the study on aquatic bioaccumulation does not need to be conducted for the substance under investigation if data from a structurally closely related material are available. The justification for read-across is given in the overall Endpoint Summary “Bioaccumulation”.

Measured BCF data are available on a structurally closely related substance DODMAC (Dimethyldioctadecylammonium chloride). The target substance MDIPA Esterquat C16-18 and C18 unsatd. differs from DODMAC by the ester linking groups between the alkyl chains (of C18 chain length) and the head group (effectively the dimethylammonium group).

Regarding BCF of the registration substance, the registration substance BCF is expected to be lower than the BCF for DODMAC:

The chemical structure of the target substance MDIPA Esterquat C16-18 and C18 unsatd. includes, in contrast to DODMAC, two polar ester moieties that lower BCF and are biodegradable and/or hydrolysable which also will result in a lower BCF for the registration substance. DODMAC is poorly biodegradable and much more stable than the registration substance. For DODMAC no abiotic degradation is expected, for biotic degradation in water the degradation rate is very low (1.4E-04 day-1) (EU RAR, 2002).

Juvenile fish (Pimephales promelas) were exposed to DODMAC for 24 h under flow-through conditions, followed by a depuration period of 72 h. Without Humic acid, a BCF of 103.8 L/kg could be calculated based on the uptake rate constant (k1) of 1.35 mg/g x h and the depuration rate constant (k2) of 0.013 mg/g x h. With the addition of 1 mg/L and 6.8 mg/L Humic acid, the BCF was 37.5 and 2.8 L/kg, respectively. (Versteeg & Shorter, 1992).

Based on naturally occurring concentrations of dissolved organic carbon (DOC) in the range of 2 to 10 mg/L in rivers and lakes, and 50% of the DOC being fulvic and humic acids (Thurman, 1985 (4)), the BCF obtained with the addition of 1 mg/L Humic acid can be considered to be most relevant.

The measured BCF values for similar substances (DODMAC, DHTDMAC(2)) are 12-32 (BUA Report 191, 1995) and 13-256 (EU RAR, 2002). The conclusion for DODMAC was “bioaccumulation is indicated, but it is assumed that it is low under environmental conditions. A BCF of 13 L/kg is used in the risk assessment…” (EU RAR, 2002).

The calculated BCF value for MDIPA Esterquat C16-18 and C18 unsatd. is 70.8 L/kg (EPIWIN v4.11, BCFBAF v3.01.).

The low bioavailability of the substance (due to rapid and strong sorption to negatively charged surfaces in the aquatic environment) in combination with the rapid (bio)degradation of the bioavailable fraction (mainly due to the hydrolysis of the ester bond), make high bioconcentration factors for the substance even more improbable (Comber et al., 2003 in Hera, 2008).

For MDIPA Esterquat C16-18 and C18 unsatd. a BCF of the same order of magnitude as the BCF of DODMAC (13 L/kg) is expected. The above information is considered as sufficient to support to the conclusion that the bioaccumulation potential of the registration substance is expected to be low (3).

 

(1) for a fatty acid derivative like the registration substance, bioaccumulation potential increases with increasing chain length of the fatty acid (within certain limits). Compound I has the longest fatty acid chain length among the molecules forming the registration substance.

(2) DHTDMAC: Dihydrogenated Tallow Alkyl Dimethyl Ammonium Chloride

(3) REACH Regulation, Annex XIII: a substance fulfils the bioaccumulation criterion when the bioconcentration factor (BCF) is higher than 2000

(4) Thurman EM, Organic Geochemistry of Natural Waters.1985, Springer