Concentration models tiers

In addition to the possibility for users to work with their own choices for all settings, MCRA implements four tiers from two documents:

The optimistic and pessimistic basic assessments from the EFSA 2012 Guidance on the Use of Probabilistic Methodology for Modelling Dietary Exposure to Pesticide Residues (EFSA (2012)).
Tier 1 and 2 from the European Commission working document SANTE-2015-10216 rev. 7 (2018) on risk management aspects related to the assessment of cumulative exposure (EC (2018)).

Overview

Table 42 Tier overview for module Concentration models.
Name	EFSA 2012 Optimistic	EFSA 2012 Pessimistic - Acute	EFSA 2012 Pessimistic - Chronic	EC 2018 Tier 1	EC 2018 Tier 2
Default concentration model	Empirical	NonDetectSpikeLogNormal	NonDetectSpikeLogNormal	Empirical	Empirical
Include MRL fallback model	false	true	true	false	false
Censored values replacement	ReplaceByZero	ReplaceByLOR	ReplaceByLOR	ReplaceByLOR	ReplaceByLOR
Sample based	true	true	true	true	true
Impute missing values from available values (if unchecked, missing values are imputed with 0)	false	true	true	true	true
Correlate imputed values with sample potency	false	true	true	true	false
Use occurrence frequencies for imputation	false			true	true
Parametric uncertainty	false	true	false	false	false
Restrict LOR imputation to authorised uses		false	false	false	false
Factor f (f x LOR or f x LOD or LOD + f x (LOQ - LOD)		1	1	0.5	0.5
MRL Factor (f x MRL)		1	1
Apply occurrence pattern percentages				false	true
Substance conversion method				UseMostToxic	DrawRandom
Retain all allocated substances after active substance allocation				true	true
Account for substance authorisations in substance conversions				false	true
Fix duplicate substance allocation inconsistencies				false	false
Use extrapolation rules				true	true
Threshold for extrapolation				10	10
Restrict extrapolations to equal MRLs				true	true
Restrict extrapolations to authorised uses				true	true
Impute water concentrations				true	true
Water concentration value (µg/kg)				0.1	0.05
Restrict water imputation to the five most toxic substances				true	true
Restrict water imputation to authorised uses				false	false
Scale up use frequency to 100%					true
Restrict use percentage up-scaling to authorised uses					true

The sections below describe the settings specified by each tier in detail.

EFSA 2012 Optimistic

Use the optimistic model settings according to the EFSA Guidance 2012. Censored values and missing values are replaced by zero.

Table 43 Tier definition for EFSA 2012 Optimistic.
Name	Setting
Default concentration model	Empirical
Include MRL fallback model	false
Censored values replacement	ReplaceByZero
Sample based	true
Impute missing values from available values (if unchecked, missing values are imputed with 0)	false
Correlate imputed values with sample potency	false
Use occurrence frequencies for imputation	false
Parametric uncertainty	false

EFSA 2012 Pessimistic - Acute

Concentration model settings for acute pessimistic dietary exposure assessments according to the EFSA Guidance 2012. A censored value spike lognormal model is fitted to the positive residue values and censored values are replaced by the LOR. When the number of positives is smaller than 2, the maximum residue limit (if available) is used instead. Missing values are imputed.

Table 44 Tier definition for EFSA 2012 Pessimistic - Acute.
Name	Setting
Default concentration model	NonDetectSpikeLogNormal
Include MRL fallback model	true
Restrict LOR imputation to authorised uses	false
Censored values replacement	ReplaceByLOR
Factor f (f x LOR or f x LOD or LOD + f x (LOQ - LOD)	1
MRL Factor (f x MRL)	1
Sample based	true
Impute missing values from available values (if unchecked, missing values are imputed with 0)	true
Correlate imputed values with sample potency	true
Parametric uncertainty	true

EFSA 2012 Pessimistic - Chronic

Concentration model settings for acute pessimistic dietary exposure assessments according to the EFSA Guidance 2012. A censored value spike lognormal model is fitted to the positive residue values and censored values are replaced by the LOR. When the number of positives is smaller than 2, the maximum residue limit (if available) is used instead. Missing values are imputed.

Table 45 Tier definition for EFSA 2012 Pessimistic - Chronic.
Name	Setting
Default concentration model	NonDetectSpikeLogNormal
Include MRL fallback model	true
Restrict LOR imputation to authorised uses	false
Censored values replacement	ReplaceByLOR
Factor f (f x LOR or f x LOD or LOD + f x (LOQ - LOD)	1
MRL Factor (f x MRL)	1
Sample based	true
Impute missing values from available values (if unchecked, missing values are imputed with 0)	true
Correlate imputed values with sample potency	true
Parametric uncertainty	false

EC 2018 Tier 1

Table 46 Tier definition for EC 2018 Tier 1.
Name	Setting	From input tier	In module
Default concentration model	Empirical
Include MRL fallback model	false
Restrict LOR imputation to authorised uses	false
Censored values replacement	ReplaceByLOR
Factor f (f x LOR or f x LOD or LOD + f x (LOQ - LOD)	0.5
Sample based	true
Impute missing values from available values (if unchecked, missing values are imputed with 0)	true
Correlate imputed values with sample potency	true
Use occurrence frequencies for imputation	true
Parametric uncertainty	false
Apply occurrence pattern percentages	false	EC 2018 Tier 1	Occurrence patterns
Substance conversion method	UseMostToxic	EC 2018 Tier 1	Concentrations
Retain all allocated substances after active substance allocation	true	EC 2018 Tier 1	Concentrations
Account for substance authorisations in substance conversions	false	EC 2018 Tier 1	Concentrations
Fix duplicate substance allocation inconsistencies	false	EC 2018 Tier 1	Concentrations
Use extrapolation rules	true	EC 2018 Tier 1	Concentrations
Threshold for extrapolation	10	EC 2018 Tier 1	Concentrations
Restrict extrapolations to equal MRLs	true	EC 2018 Tier 1	Concentrations
Restrict extrapolations to authorised uses	true	EC 2018 Tier 1	Concentrations
Impute water concentrations	true	EC 2018 Tier 1	Concentrations
Water concentration value (µg/kg)	0.1	EC 2018 Tier 1	Concentrations
Restrict water imputation to the five most toxic substances	true	EC 2018 Tier 1	Concentrations
Restrict water imputation to authorised uses	false	EC 2018 Tier 1	Concentrations

EC 2018 Tier 2

Table 47 Tier definition for EC 2018 Tier 2.
Name	Setting	From input tier	In module
Default concentration model	Empirical
Include MRL fallback model	false
Restrict LOR imputation to authorised uses	false
Censored values replacement	ReplaceByLOR
Factor f (f x LOR or f x LOD or LOD + f x (LOQ - LOD)	0.5
Sample based	true
Impute missing values from available values (if unchecked, missing values are imputed with 0)	true
Correlate imputed values with sample potency	false
Use occurrence frequencies for imputation	true
Parametric uncertainty	false
Apply occurrence pattern percentages	true	EC 2018 Tier 2	Occurrence patterns
Scale up use frequency to 100%	true	EC 2018 Tier 2	Occurrence patterns
Restrict use percentage up-scaling to authorised uses	true	EC 2018 Tier 2	Occurrence patterns
Substance conversion method	DrawRandom	EC 2018 Tier 2	Concentrations
Retain all allocated substances after active substance allocation	true	EC 2018 Tier 2	Concentrations
Account for substance authorisations in substance conversions	true	EC 2018 Tier 2	Concentrations
Fix duplicate substance allocation inconsistencies	false	EC 2018 Tier 2	Concentrations
Use extrapolation rules	true	EC 2018 Tier 2	Concentrations
Threshold for extrapolation	10	EC 2018 Tier 2	Concentrations
Restrict extrapolations to equal MRLs	true	EC 2018 Tier 2	Concentrations
Restrict extrapolations to authorised uses	true	EC 2018 Tier 2	Concentrations
Impute water concentrations	true	EC 2018 Tier 2	Concentrations
Water concentration value (µg/kg)	0.05	EC 2018 Tier 2	Concentrations
Restrict water imputation to the five most toxic substances	true	EC 2018 Tier 2	Concentrations
Restrict water imputation to authorised uses	false	EC 2018 Tier 2	Concentrations

EFSA 2012 Pessimistic

Note

This tier is deprecated and has been replaced by separate acute/chronic tiers.

Concentration model settings for pessimistic dietary exposure assessments according to the EFSA Guidance 2012. A censored value spike lognormal model is fitted to the positive residue values and censored values are replaced by the LOR. When the number of positives is smaller than 2, the maximum residue limit (if available) is used instead. Missing values are imputed.

Table 48 Tier definition for EFSA 2012 Pessimistic.
Name	Setting
Default concentration model	NonDetectSpikeLogNormal
Include MRL fallback model	true
Restrict LOR imputation to authorised uses	false
Censored values replacement	ReplaceByLOR
Factor f (f x LOR or f x LOD or LOD + f x (LOQ - LOD)	1
MRL Factor (f x MRL)	1
Sample based	true
Impute missing values from available values (if unchecked, missing values are imputed with 0)	true
Correlate imputed values with sample potency	true
Parametric uncertainty	true