- PDF Version (236K) - Print Friendly - Help

Proposals to Amend the New Zealand (Maximum Residue Limits of Agricultural Compounds) Food Standards 2007

11 Proposal to exempt 1, 4-dimethylnapthalene

It is proposed that an MRL exemption be set for 1, 4-dimethylnapthalene when used as a sprout inhibitor for potatoes. It is proposed that Schedule Two of the NZ (MRL) Food Standards 2007 be amended to include the following; this will be the resulting entry for 1, 4-dimethylnapthalene in Schedule Two of the NZ (MRL) Food Standards 2007:

Amendment Rationale

The proposed MRL exemption represents a reassessment of a currently approved use pattern for 1, 4-diemethylnapthalene. As residues in potatoes can’t be distinguished from natural background levels the compound is not suitable to be managed against a concentration limit, and therefore it can be exempted from the requirement of a New Zealand MRL.

Chemical Information

Good Agricultural Practice

1, 4-dimethylnaphthalene is used as a sprout inhibitor for stored potatoes. Application may be throughout potato storage.

Residues Information

1, 4-dimethylnaphthalene (DMN) occurs naturally in potatoes in a role of inhibiting sprout development. Natural levels of DMN are in the order of 1-10mg/kg in pre-sprouting tubers. Prior to sprouting occurs, DMN is metabolised by the tuber to levels below 0.7mg/kg, therefore allowing sprout development. DMN is used as an agricultural compound to maintain the levels of DMN in the stored tubers so sprouting can be inhibiting for longer periods, allowing a greater shelf-life of stored potatoes. Application of DMN is intended to maintain the potato DMN level at a similar range to natural levels. Determining natural residues of DMN from those resulting from the application of DMN as an agricultural compound is impossible. Therefore it is proposed the 1, 4-dimethylnaphthalene be made exempt from the requirement of an MRL.

Dietary Risk Assessment

No chronic toxicity studies are available. Studies (acute) indicate the compound is of low oral toxicity with an LD₅₀ value of 2g/kg kg (LD₅₀ values = median lethal dose, the dose required to kill 50% of a population of laboratory animals - usually rodents). Additionally, the substance has been demonstrated as negative for mutagenicity in several invitro studies. Levels of 1, 4-dimethylnaphthalene are unlikely to exceed naturally occurring levels in potato tubers at the time of consumption. The toxicity data available for 1, 4-dimethylnaphthalene indicates it is of relatively low toxicity. Given its natural occurrence in the diet, without any recorded adverse effects it is considered that exempting 1, 4-dimethylnaphthalene from an MRL for its use as a sprout inhibitor will not result in any increase in dietary risk.

Toxicological / Public Health Assessment

It has been determined that the use of 1, 4-dimethylnaphthalene as a sprout inhibitor for use on potatoes, according to the good agricultural practice specified above, is very unlikely to pose any health risks from consumption of the harvested commodity.

International MRLs

To meet New Zealand’s obligations under the Agreement on the Application of Sanitary and Phytosanitary Measures the proposed MRL exemption will be notified to the World Trade Organization. Any country may choose to comment if they believe the proposed MRL exemption represents a barrier to their trade.