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Risk envelope suitability

There are many parameters which influence the suitability of a previous evaluation (or GAP/use) for use as a risk envelope. For a suitable risk envelope, the following conditions should generally be met:

Parameter Condition Comments

Crop

In most cases, the crop should be identical, or in the same 'primary group' in the crop hierarchy.

In some cases it can be appropriate to use a risk envelope from another crop.

For calculation of PECsoil values when it can be demonstrated that the amount reaching the soil is greater for the previously assessed product.
For GW and SW this is more difficult due to different crop parameterisations within the models.

Application rate

The previously assessed use pattern should have been performed on an identical or higher application rate (g a.s/ha)

These parameters can interact with substance DT50 to change the suitability of a product as a risk envelope.

If the DT50 of the active substance and metabolites were very long, then a lower application rate with a higher number of applications may be suitable for use as a risk envelope, due to accumulation of residues across the applications.

Alternatively, if the DT50 values of the active substance and relevant metabolites are very short, residues would degrade between applications, meaning a single application would be an accurate representation of a multiple application use pattern.

A clear justification is needed to employ these approaches.

Number of applications

The previously assessed use pattern should have an identical or higher number of applications.

Application interval

The previously assessed use pattern should have an identical or shorter application interval than the proposed uses of the new product.

BBCH growth stage/

Application window/

Crop interception

The previously assessed application timing should be similar or occur in a more vulnerable time of year.

BBCH growth stages should typically be similar or earlier, however for some crops a late application with regard to BBCH can be worse due to leaf fall.

The BBCH growth stages should translate as identical or smaller crop interception values than that of the proposed uses of the new product.

Different application windows can occur at more/less vulnerable times of year from a climatic perspective. For example, PECsw via drainflow is sensitive to rainfall, so an application window coinciding with high seasonal rainfall would be expected to be more worst-case than an application window.

If the above conditions are met, a previous product and or GAP/use evaluation is potentially a good candidate for use as a risk envelope. Some of these conditions are highlighted in the example below.

PECsoil, PECgw and PECsw via drainflow:

For PECsoil PECgw and PECsw via drainflow, the important issue is the amount of active substance reaching the soil. This means that the number of applications, application rate, application interval and crop interception are of importance.

PECsw via spray drift:

For PECsw via spray drift, the important issues are the application rate, number of applications, application interval, and method of application. These influence the overall spray drift, surface water loading and ultimately PECsw.

Applications relied upon for risk envelope should be fully described and referenced for CRD with any application and the approach of using a previously authorised product to address a submission should be carefully explained.

It is also good practice to reproduce endpoints and PEC values (where available) from previous products where they are relied upon by applicants, as a risk envelope, into the new product dRR.

The use of the 'risk envelope' is a UK approach therefore this terminology may not be immediately understood by evaluators across the EU.  For core dRRs, consideration that "the assessment of the previously authorised Product X is sufficient to address the risk of the proposed uses of product Z" would be more appropriate. It should be noted that some member states require all products to have a full stand-alone assessment.

Example

Below is a table displaying the main application parameters of interest for previous fate evaluations of the hypothetical active substance 'Y'. Two products are listed, and the representative use from the Community level assessment of substance Y is also provided (considered under the previous Annex I inclusion process).

Evaluation Crop Application rate (g a.s/ha) Number of applications Application interval (days) BBCH timing Crop interception (%)

Product Z

maize

150

2

7

10-19

25

Product X

maize

175

1

N/A

10-19

25

Representative use of substance Y (annex 1)

maize

175

2

7

00-09

0

A new proposed product, Product A, features the following parameters:

Evaluation Crop Application rate (g a.s/ha) Number of applications Application interval (days) BBCH timing Crop interception (%)

Product A

maize

160

2

7

10-19

25

In this case, the new product features applications to the same crop as the previous assessments.

It also has the same number of applications as Product Z and the annex 1 assessment. However, it features a higher use rate than Product Z. Therefore, product Z may not be appropriate for the risk envelope approach.

Product X features a higher use rate than the new product 'A', but features only a single application, and therefore may not be appropriate to use as a risk envelope for Product.

The annex 1 representative use features a higher use rate, identical number of applications and interval to the proposed uses of product A. Is also has an earlier BBCH window which translates to lower crop interception.

In this instance, the annex 1 representative use is demonstrably more worst-case, and can provide a risk envelope for Product A.

In this example, all the multiple application uses have an identical application interval. A shorter application interval would typically be more worst-case, as there is less time between applications for degradation of active substance and metabolites, leading to possible accumulation in soil, impacting upon both PECsoil, PECgw and PECsw (via drainflow).

However: It should be noted that Product X might still be a valid risk envelope for the assessment, despite having fewer applications. If the DT50 values of the active substance and relevant metabolites are very short, residues would degrade between applications, meaning a single application would be an accurate representation of a multiple application use pattern.

Similarly, it may be worth looking at the Product Z assessment, even though it has a lower use rate than the new product A. If high margins of safety have been established in Product Z, the slightly higher use rate of the new Product A may not be an issue. This type of reasoned justification should be well documented in the new dRR/addenda and discussions with ecotoxicology branch should be sought.

Things to look out for

When using the risk envelope, be aware of the following possible issues:

combined drainflow assessment

Updated 2017-05-23