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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Reaction products resulting from esterification of sucrose with saturated C16-18 (even numbered) fatty acids does not accumulate in organisms.

Key value for chemical safety assessment

Additional information

No experimental data determining the bioaccumulation potential of Reaction products resulting from esterification of sucrose with saturated C16-18 (even numbered) fatty acids are available. A log Pow value calculated as ratio of the saturated water solubility (OECD 105) and saturated octanol solubility (no guideline currently available but based on the principles of OECD 105) was measured to be 3.6. This indicates that bioaccumulation cannot per se be excluded. Therefore, all relevant data to evaluate the bioaccumulation potential of the substance are combined in a Weight of Evidence (WoE) approach. These data comprise physico-chemical properties of the parent compounds and degradation products (e.g., log Pow, molecular weight, max diameter), ADME related data as well as calculated/experimental data for biodegradation and bioaccumulation. Based on this data Reaction products resulting from esterification of sucrose with saturated C16-18 (even numbered) fatty acids is not considered to be bioaccumulating.

 

Intrinsic properties and fate

If entering aquatic compartments the substance will be biodegraded ultimately as indicated by studies performed according to OECD guideline 301B (19 -28% in 28 days, 52 -59% in 60 days). Due to the high adsorption potential and surfactant property, the substance is expected to be removed from the water column to a significant degree by adsorption to sewage sludge (Guidance on information requirements and chemical safety assessment, Chapter R.7a, [ECHA 2008]) and extensive biodegraded. Thus, discharged concentration of the substance into the aqueous compartment is likely to be very low. If the substance is released into the water phase, it will tend to bind to sediment and other particulate organic matter, and therefore, the actual dissolved fraction available to fish via water will be reduced (Mackay and Fraser 2000). Thus, the main route of exposure for aquatic organisms such as fish will be via food ingestion or contact with suspended solids.

 

Bioaccumulation via oral uptake

The accumulation of a substance in an organism is determined, not only by uptake, but also by distribution, metabolism and excretion. Accumulation takes place if the uptake rate is faster than the subsequent metabolism and/or excretion.

Fatty acids

As nutritional energy source, fatty acids are absorbed by different uptake mechanisms depending on the chain length. Long chain fatty acids (> C12), such as palmitic and stearic acid, are absorbed into the walls of the intestine villi and assembled into triglycerides, which then are transported in the blood stream via lipoprotein particles (chylomicrons). In the body, fatty acids are commonly known to be easily metabolized by feeding into physiological pathways like the citric acid cycle, sugar synthesis and lipid synthesis. In addition, fatty acids are an integral part of the cell membranes of every living organism from bacteria and algae to higher plants. Thus, the free fatty acids in the UVCB substances as well as the fatty acids generated by hydrolysis of the sugar esters are not considered to be bioaccumulating. This assumption is confirmed by an experimentally determined BCF value for sodium laurate (BCF = 255 L/Kg; Van Egmond et al. 1999) and estimated BCF values calculated for the main components palmitic acid (CAS 57-10-3, BCF = 56.2 L/kg, Arnot-Gobas method) and stearic acid (CAS 57-11-4, BCF = 10 L/kg) using the BCFBAF v3.01 program (BASF 2017 a, b).

Sucrose ester

If taken up by living organisms (which is basically assumed to be via oral uptake since uptake via skin/ gill is considered to be of minor importance based on the surfactant properties) sugar esters will be metabolized and used for biomass and energy production. The initial metabolisation step is an enzymatic hydrolysis sucrose and long-chain fatty acids (C16-18). Enzymes catalyzing this reaction are available in the digestive tract (stomach, intestine) and all relevant body tissues of organisms (e.g., Sova et al. 1970, Sova et al. 2013, Fänge et al. 1980). Daniel et al. (1979) and Shigeoka et al. (1984) investigated the metabolism of sucrose esters in rats.

Daniel et al. (1979) performed metabolic studies in rats with sucrose esters of beef tallow. Given in a single oral dose of 5, 50 or 100 mg/kg indicated that some 80-90% of the sucrose moiety was absorbed from the gastro-intestinal tract. The disposition of radioactivity after the administration of [14C] sucrose tallowate suggested that the esters were hydrolysed before absorption. No evidence was obtained for the accumulation of the esters in the adipose tissue of rats following repeated daily oral administration of [14C] sucrose tallowate.

Similar experiments were conducted by Shigeoka et al.(1984). They also found that the ratio of expired radioactivity to absorbed radioactivity after oral administration of the sucrose esters labelled at the sucrose moiety was similar to that after the administration of [14C] sucrose. A similar correlation between the ester labelled at the fatty-acid moiety and the free [14C] fatty acid was also observed. No intact sucrose ester was detected in the urine. Studies in vitro using everted intestinal sacs showed that there was virtually no transport of 14C-labelled sucrose esters from the mucosal to the serosal solution through the intestinal tissues, and that the enzymes in the intestinal mucosa played a more important role in the hydrolysis of sucrose esters than did those in the digestive fluid. In studies of intestinal absorption through the mesenteric lymphatic system, during the 24 h after ingestion 1.8% of the administered radioactivity was recovered in the lymph after dosing with [U-14C] sucrose monostearate whereas 20% was recovered in the lymph after dosing with sucrose [l-14C] monostearate. This difference in levels of recovery of administered radioactivity indicated that sucrose monostearate was absorbed only after hydrolysis. No intact ester was detected in the lymph or in the portal or femoral blood. The results of all of these experiments show that the sucrose esters are hydrolysed to sucrose and fatty acids prior to intestinal absorption.

Sucrose is commonly known to enter the carbohydrate metabolic pathway via cleavage into glucose and fructose. Extra glucose is stored in the muscles and liver as glycogen. Thus, the sugar component is not considered to bioaccumulate in organisms in terms of accumulation of chemicals, which may reach toxicologically relevant concentrations over time. The fatty acids are metabolized as explained above. This assumption is further supported by an estimated BCF value for sucrose monopalmitate (26446-38-8) of 80 L/Kg using the regression estimated and 6.4 considering metabolism by the Arnot-Gobas method (BCFBAF v3.01 program; BASF 2017c).

 

The available data clearly indicate that the fatty acid and sugar ester components of Reaction products resulting from esterification of sucrose with saturated C16-18 (even numbered) fatty acids do not bioaccumulation in biota, since they are rapidly metabolized after uptake.

 

References

Fänge R, Lundblad G, Slettengren K, Lind J. 1980.Glycosidases in lymphomyeloid (hematopoietic) tissues of elasmobranch fish. Comp Biochem Physiol 67: 527-532

Mackay D, Fraser A. 2000. Bioaccumulation of persistent organic chemicals: mechanisms and models. Environ Poll 110(3): 375-391

Sova VV, Pesentseva MS, Zakharenko AM, Kovalchuk SN, Zvyagintseva TN. 2013. Glycosidases of marine organisms. Biochemistry (Moscow) 78(7): 746-759

Sova VV, Elyakova LA, Vaskovsky VE. 1970. The distribution of laminarinases in marine invertebrates.Comp Biochem Physiol 32: 459-464