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AgVetLink, October 2004

Change of policy regarding use of the default MRL

Use of default MRL

In the past, the ACVM Group has made good use of the default maximum residue limit (MRL) of 0.1 ppm in two ways when finalising applications for registration of plant compounds and veterinary medicines.

Firstly, the setting of MRLs was sometimes a very slow process. There have been periods of up to three years between changes to the MRL standard of the day (Regulation 257 of the Food Regulations 1984).

Product registrations were not able to be completed if uses in accordance with label claims meant that residues exceeded the MRL standard, whether or not such residues were a potential health risk. However, it was sometimes possible to set appropriate withholding periods (WHPs), which were longer than that recognised as Good Agricultural Practice (GAP) to ensure compliance with the default MRL, so that the applications could be finalised. Shorter, more appropriate withholding periods could then be set in a change to the registration once the MRL standard changed.

Secondly, the ACVM Group could finalise applications for GAP uses that led to residues in produce of less than 0.1 ppm without the need to put active ingredients into the MRL setting process. This also helped to reduce delays in the process.

Purpose of MRLs

MRLs are set so that regulators can ensure the best practices in the production of foods (i.e. compliance with GAP). Use of the default MRL in the second case mentioned above could compromise this purpose. When residues above GAP expectations but still lower than the regulatory limit of 0.1 ppm were found, regulatory action could not be taken.

New policy

NZFSA has therefore decided to set MRLs at less than the default 0.1 ppm when we have data that establishes the supervised trial median residue that applies to GAP. We are setting this sub-default MRL without holding up registrations. We will be seeking appropriate additional residue data from applicants for new claims if the data is sufficient to allow us to be confident that the default MRL will not be exceeded but insufficient to allow the MRL appropriate to GAP to be set.

We will also (over time) look at existing similar registrations to see if we can set MRLs more appropriate to GAP, but at this time we are not treating this part of the project with high priority.

General MRLs

In the past, some very general MRLs have been set for plant compounds, for example on ‘fruit and vegetables’. These were set on the basis of residue trials on two or three representative crops. Other active ingredients are registered for use on many different crops, and so there are potentially many sources of residues in foods.

Impact of HSNO

The coming into force of the Hazardous Substances (Classes 6, 8 and 9) Controls Regulations 2001 means that food residues must now comply with the requirement that potential intakes of pesticides from consumption of treated produce must not exceed the Potential Daily Exposure values set for foods (PDE_food). These have not yet been set for those plant compounds that have been recently transferred, but the ACVM Group is aware that the default PDE_food is 50% of the Acceptable Daily Exposure (which is estimated in the same way as the internationally recognised Acceptable Daily Intake [ADI]). We are also aware that recently some PDEs_food have been set at 80% of the ADE, so the possible impact of the whole issue is not yet completely clear.

Potential intake calculations

Traditionally, the potential intake of a pesticide is calculated by multiplying the average daily intake of the raw agricultural commodity by the supervised trial median residue (STMR), and dividing by the average weight of an individual. Where no STMR is able to be established, the actual MRL that applies is used in the calculation.

This usually grossly over-estimates the potential intake and, particularly for those substances with general MRLs, sometimes leads to an estimated potential intake for the plant compound that exceeds 50% of the ADI. This may be in breach of the new HSNO Regulations once the PDE_food is established (probably within the next year).

The ACVM Group has identified 12 active ingredients with products that have general MRLs, 9 where the potential intake as currently estimated falls between 50% and 100% of the ADI (which is the probable ADE), and a further 16 with potential intakes as currently estimated exceeding 100% of the ADI.

Realistic estimations

The ACVM Group is starting a project to deal with this potential problem and get more realistic estimations of the potential daily intakes.

We are taking two initial steps. The first is to establish formal policies on how potential intakes of plant compounds are calculated. For example, can we establish a general rule as to what fraction of an MRL should be used in the absence of STMR data?

Secondly, we are aware that some of the products that have general (‘fruit and vegetable’) claims may not actually be used on all food crops as the label suggests, or are sold mainly for use on just a few crops, so a less general claim may enable a lower potential intake to be calculated. This would bring the potential intake back into compliance with the HSNO Regulations.

On this latter issue, we will approach proprietors of products that are potentially in breach of the HSNO Regulations and ask them:

• to indicate what their products are actually being used on, and

• to nominate their preference for which crops could be excluded from use (if necessary) or to specify crops for continued use, with a possible exclusion of use on other crops, to get the estimated potential intake down to (or below) the PDE_food.

We are currently developing the policies and rules around this issue and, once the draft principles have been agreed by NZFSA, we will consult with interested parties (including specific consultation with affected registrants and ERMA New Zealand) to reach agreement on how the issue will be managed.