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Description of key information

Short description of key information on bioaccumulation potential result: 
Uptake via inhalation is not anticipated for NOM, while dermal absorption is feasible. Significant accumulation in fatty tissue is highly unlikely.

Key value for chemical safety assessment

Additional information

The natural oil monomer consists of esters of the fatty acids palmitic acid (C16), margaric acid (C17) and stearic acid (C18), and C16-C18 fatty acids with one or more methanol side groups on the chain. The methyl groups are likely to hydrolyse readily. Palmitic and stearic acid are endogenous compounds and are present in abundance in our food.  Margaric acid is a naturally occurring dietary fat present in our food, but this fatty acid is not synthesized by the human body.

The fatty acids are anticipated to be distributed, metabolized and excreted in the same way as naturally occurring fatty acids.  Fatty acids with an additional methanol side group are expected to follow these same pathways, with the additional potential for Phase II conjugation of the methanol moieties of these components.   Significant accumulation in fatty tissue is highly unlikely. The anticipated toxicokinetic behaviour of NOM is consistent with the low toxicity of the substance.

Discussion on absorption rate:

Dermal uptake for NOM is possible. Conversely, fatty acids and fatty acid methyl esters are used as penetration enhancers for drug delivery (Chukwumerije et al., 1989; Kogan and Garti, 2006) and thus, it is expected that the fatty acid properties of MPS would allow for dermal penetration. Consistent with the uses for drug delivery, dermal absorption of fatty acids are generally regarded as safe, and the toxicity profile of MPS following dermal testing is consistent with this as well. The dermal absorption of MPS has not been studied to date. However, the permeability of this compound through skin can be estimated with QSAR programs, such as the DermWin model from the US EPA. Using this application, the steady-state flux of a 1% solution of MPS through skin is estimated to be 0.65-240 mg/cm2 surface area of skin, for the various components. The calculated Kp, or rate of penetration via the DermWin model, is calculated to be 1.28-24.4 cm/hr.

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