Issued by MOA
In order to set technical basis for MRL establishment and risk assessment to human, Ministry of Agriculture formulatedtheGuidelines for Developing ADIs on Pesticide. With approval of the Committee of National Pesticide Residue Standards Evaluation, it is hereby officially released.
Annex:Guidelines for Developing ADIs on Pesticide
Guidelines for Developing ADIs on Pesticide
I. Purpose and scope
In order to set technical basis for MRL establishment and risk assessment to human, and guarantee agro-product quality & safety and the people??s health, Ministry of Agriculture formulatedtheGuidelines for Developing ADIs on Pesticide(theGuidelines).
TheGuidelinesapply to develop acceptabledailyintake (ADI) for pesticide with threshold effect.
1. Acceptable daily intake (ADI)
An estimate of the amount of a substance that can be ingested on a daily basis over a lifetime without appreciable risk to health. It is usually expressed in mg/kgbw, milligrams (of the substance) per kilograms of body weight per day.
2. No-observed-adverse-effectlevel (NOAEL)
The highest concentration or amount of a substance, found by experiment or observation, which causes no detectable adverse alteration of morphology, functional capacity, growth, development, or life span of the target organism under defined conditions.
3. Lowest-observed-adverse-effectlevel (LOAEL)
The lowest concentration or amount of a substance, found by experiment or observation, which causes an adverse alteration of morphology, functional capacity, growth, development, or life span of a target organism distinguishable from normal (control) organisms of the same species and strain under defined conditions of exposure.
4. Benchmarkdose (BMD)
Derived from the dose-response curve, BMD is a dose that produces a predetermined change in response rate of an adverse effect (1%-10% in general) compared to background. In general, a 95% lower confidence limit on the dose at the BMD is applied and called benchmarkdoselowerconfidencelimit,BMDL.
5. Uncertaintyfactor (UF)
When establishing ADI for pesticide, there are uncertainties in extrapolating animal data to humans and uncertainties of database deficiencies. In order to address these uncertainties, a numeral value (equal to or greater than one) is used to divide NOAEL or LOAEL values derived from animal toxicity experimental data to estimate an ADI value for the whole human population, and the numeral value is called uncertainty factor.
III. Procedures of establishing ADI for pesticide
1. Determining NOAEL or BMDL
Based on toxicological analysis and assessment that detect the most sensitive endpoint of the most sensitive animal, data evaluation and statistical analysis shall be conducted to give a NOVEL.
1.1 Comprehensive toxicological evaluation. Based on submitted registration information, comprehensive toxicological analysis and assessment shall be conducted to complete toxicological database. Attention shall be paid to special toxic effects like mutagenicity, reproductive and developmental toxicity, carcinogenicity, and neurotoxicity, etc. Besides registration information, reference data of other reliable sources shall be used, such as evaluation reports of developed countries and international organizations, and published documents and literatures, etc.
1.2 Determining sensitive endpoint. Usually, test data of chronic toxicity, carcinogenicity and two-generation reproductive toxicity, etc. shall be used for establishing ADI. Analysis and evaluation approaches shall be applied to generate the most sensitive endpoint of the most sensitive animal.
1.3 Setting NOAEL. An appropriate test approach shall be selected according to the sensitive endpoint for setting NOAEL of ADI. Test data and sensitive endpoint shall be included in NOAEL instruction.
1.4 BMDL as an alternative of NOAEL. When there is a well-established dose-response model, or the NOAEL is unavailable, or the chronic exposure dose of a pesticide is closed to ADI, BMDL is recommended as an alternative of NOAEL.
2. Selecting UF
When establishing ADI, there are uncertainties in extrapolating animal data to humans and uncertainties of database deficiencies. In order to reduce these uncertainties, UF shall be applied.
A 100-fold UF is usually applied in extrapolating animal data to humans (i.e., interspecies difference) and extrapolating average humans data to sensitive sub-groups (i.e., intraspecies variability), with a 10-fold factor to allow for interspecies difference, and another 10-fold factor to allow for intraspecies variability.
Besides interspecies difference and intraspecies variability, the efficiency and validity of toxicological database and the nature of adverse effects shall also be taken into consideration to determine the UF. Based on the specificity of the case and available data, UF could be modified or reduced, as appropriate. For example, when a dose has no maternal toxicity but teratogenicity on test animal, usually a 10-fold UF is added; and when valid data (i.e. human data in particular) is available, the UF of intraspecies variability could be adjusted appropriately.
To determine an UF, analysis and assessment approaches shall be applied for each pesticide in association with experience of experts. Although there may be various uncertainties, or even the data is incomplete, the maximum of UF is 10000 in general. See Table 1 for uncertainty circumstance & UF adopted in ADI deduction.
Table 1 Uncertainty circumstance & UF adopted in ADI deduction
| Uncertainty circumstance
| Extrapolation from experimental animal to average humans, including:
| Toxicokinetics difference
| Toxicodynamic difference
| Extrapolation from average humans to sensitive sub-groups, including:
| Toxicokinetics difference
| Toxicodynamic difference
| Extrapolation from LOAEL to NOAEL
| Deduction from sub-chronic experiment data to chronic data
| Severe toxicity detected
| Incomplete data collections
NOAEL or BMDL is divided by proper UF to give the ADI. The formula of calculating ADI is as following:3. Calculating ADI
1. Establishing provisional ADI
Provisional ADI for pesticide shall be established upon any of the following conditions:
1.1 Limited toxicological data.
1.2 The updated data calls in question and necessity for revising an established pesticide ADI, and a provisional ADI is required during data collection period.
Generally, larger UFs shall be used in establishing provisional ADI.
2. Establishing category ADI
One ADI can be set for the whole category upon any of the following conditions:
2.1 Pesticides are identical in toxic mechanism, target and effect;
2.2 Pesticides are similar in chemical structure;
3. Exemption of establishing ADI
When there is adequate evidence that the pesticide is risk-free of chronic exposure, ADI formation can be exempted.