The European Commission (EC) asked EFSA’s Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF) to review the safety in use of dioctadecyl disulphide.
The EC also asked the CEF panel to assess whether an established specific migration limit (SML) of 3mg/kg of food was still valid.
This assessment was made upon the basis of new information provided by industry, which submitted new toxicological studies to the EC in 2010 asking if the substance is accumulated within the body.
EFSA said that German company Clariant Produkte had informed the EC about their doubts regarding the possible bioaccumulation of the substance, due to its high lipophilicity (ability to dissolve in fat, oils and lipids) and limited water solubility.
Dioctadecyl disulphide is used in polypropylene or polypropylene copolymers as an antioxidant, in tandem with phenolic antioxidants to improve the ageing resistance of plastics.
The CEF panel concluded that a limited daily intake of the substance of up to 0.05 mg per kg of body weight was unlikely to be a cause for safety concern.
Poor gastrointestinal absorbtion
As a plastics additive authorised since 2001 for use in plastics intended to come into contact with food, dioctadecyl disulphide was permitted after a Scientific Committee on Food (SCF) opinion published in 1995.
That opinion reinforced the 0.05mg figure, and was allocated to the substance based on the results of a 90-day oral rat study dating from 1969.
Accordingly, the EC established the 3mg/kg SML upon the basis that a person weighing 60kg may consume up to 1kg of food daily that had been in contact with a packaging material containing dioctadecyl disulphide.
But the EFSA panel said that data from two male rat studies suggested that the substance was poorly absorbed from the gastrointestinal tract.
“The CEF Panel considers that there is no concern regarding the genotoxicity of dioctadecyl disulphide based on negative findings in five in vitro genotoxicity assays and one in vivo micronucleus assay,” it said.
Two 90-day toxicity studies could not be used due to limited data reporting (rat study) and inadequate study design (dog study), EFSA said.
However, in 2 chronic studies the EFSA panel noted that deposits of dioctadecyl disulphide were observed in several organs of both rats and dogs (such as the liver, adrenals, lymph nodes) together with “treatment related evidence of toxicity”.
Treatment-related effects
But the EFSA scientists noted that an inverse dose relationship was seen for both deposition of test material and organ changes evidencing toxicity.
“The panel considered that, due to absence of a positive dose-relationship for the observed effects and the presence of possible treatment-related effects at the lowest dose tested, the results of the study could not be used for the purposes of risk assessment of dioctadecyl disulphide.”
The CEF panel said the 2 studies showed that dioctadecyl disulphide had potential for accumulation, but uncertainties regarding the dose-response relationship and the presence of possible treatment-related effects at lowest dose test levels meant a non-observable adverse effect level (NOAEL) could not be derived.
Therefore, the EFSA panel said it did not agree with the SCF’s allocation of a TDI of 0.05mg per kg of body weight. But given the “absence of genotoxicity” the panel said a limited daily intake up to this level was unlikely to cause safety concerns.
The full EFSA scientific opinion is available here.