Fatty acids, tallow, zinc salts

Endpoint summary

Additional information

No data are available on the bioaccumulation potential of Fatty acids, tallow, zinc salts. The substance is produced by the oleochemistry sector, starting from natural fatty materials, and is a mixture of stearic (C18) and palmitic acid (C16) and monounsaturated C18 fatty acids. Fatty acids, tallow, zinc salts consist of 90% natural fatty acids and 10% zinc.

It is assumed that if taken up by organisms, the substance is changed (at least in part) to the ionic species and that it is this zinc cation that is the determining factor for the biological activities of the zinc compounds. This assumption is in line with the EU Risk Assessment Report for Zinc stearate (ECB, 2008). The free fatty acids are either metabolised via the ß-oxidation pathway in order to generate energy for the cell or reconstituted into glyceride esters and stored in the fat depots in the body (Berg, 2002). The bioaccumulation potential of zinc is discussed below.

Bioaccumulation potential of zinc

In experimental work, high BCF factors are observed at the lowest zinc exposure levels, due to the fact that organisms will concentrate zinc to satisfy internal physiological needs for the essential element. For the same reason of homeostasis, the BCF will strongly decrease when exposure concentrations increase. This results in a general negative relationship between BCF and exposure (McGeer et al 2003). Due to homeostatic control mechanisms, bioaccumulation is not relevant for essential elements in general and for zinc in particular.

On bioaccumulation, the EU risk assessment report (ECB 2008) concludes that “secondary poisoning is considered to be not relevant in the effect assessment of zinc. Major decision points for this conclusion are the following. The accumulation of zinc, an essential element, is regulated in animals of several taxonomic groups, for example in molluscs, crustaceans, fish and mammals. In mammals, one of the two target species for secondary poisoning, both the absorption of zinc from the diet and the excretion of zinc, are regulated. This allows mammals, within certain limits, to maintain their total body zinc level (whole body homeostasis) and to maintain physiologically required levels of zinc in their various tissues, both at low and high dietary zinc intakes. The results of field studies, in which relatively small differences were found in the zinc levels of small mammals from control and polluted sites, are in accordance with the homeostatic mechanism. These data indicate that the bioaccumulation potential of zinc in both herbivorous and carnivorous mammals will be low."

Conclusion

In conclusion, Fatty acids, tallow, zinc salts is assumed to (at least partly) dissociate to zinc ions and free fatty acids if taken up by organisms. The cellular content of zinc is regulated in organisms, and fatty acids are metabolised via well-known pathways. Fatty acids, tallow, zinc salts is thus not expected to bioaccumulate.

References:

Berg, J.M., Tymoczko, J.L. and Stryer, L., Biochemistry, 5^thedition, W.H Freeman and Company, New York, 2002

European Chemicals Bureau (ECB), Risk assessment Zinc distearate CAS-No.: 557-05-1 & 91051-01-3, EINECS-No.: 209-151-9 & 293-049-4, Final report, May 2008, R074_0805_env

McGeer J, Brix KV, Skeaff JM, De Forest DK, Bingham SI, Adams WJ and Green A (2003). Inverse relationship between bioconcentration factors and exposure concentration of metals: implications for hazard assessment of metals in the aquatic environment. Env. Tox. & Chem. 22, nr 5, 1017-1037