In the wake of the recent glyphosate discussion, it became clear that there are some misconceptions on what “Maximum Residue Levels” (MRLs) for pesticides actually are, and whether or not they have any toxicological basis (see comments to this post).
So, here’s a brief overview.
Europe
In Europe, the setting of MRLs is regulated by Regulation 396/2005 (EU Parliament, 2005), which also provides the definition of MRLs in Article 2(2d):
‘maximum residue level’ (MRL) means the upper legal level of a concentration for a pesticide residue in or on food or feed set in accordance with this Regulation, based on good agricultural practice and the lowest consumer exposure necessary to protect vulnerable consumers;
That is, the setting of an MRL is driven by two assessments: good agricultural practice (GAP, as defined in Article 2 (2a) of Regulation 396/2005) and the toxicological evaluation of the pesticide in question.
MRLs are thus driven by the toxicological properties of the pesticide in question. They are intended to be sufficiently low, so that the consumption of food with pesticide residues at or below the corresponding MRL is safe even for vulnerable consumers (e.g. infants, but also vegetarians).
A pesticide company that seeks approval to use its product on the European market is submitting the following two items to the European Food Safety Authority (EFSA):
- Toxicological evaluation
- The residues expected on the produced food items after they have been treated with the pesticide according to good agricultural practice
If EFSA concludes that, based on the available toxicological information, the expected residue is not safe, the pesticide is not allowed on the European market. End of story.
This toxicology-driven setting of MRLs would imply that substantial amounts of pesticides with a comparatively low toxicity (according to our current toxicological understanding) would be acceptable. In order to avoid this, MRLs are additionally adjusted to the lowest value that is technically achievable, i.e. to the residues levels that can be achieved when working according to good agricultural practice.
Finally, the MRLs are set to the lowest concentration that can still be determined by state-of-the-art chemical-analytical techniques, if the use of a pesticide according to good agricultural practice would not result in any measurable pesticide residues. The MRL then basically serves as a check on whether farmers and food producers have worked according to best practice.
The Commission sets MRLs for 315 products (listed in Annex I of Regulation 396/2005) in their various forms (fresh, dried, etc.) for the pesticides approved on the European market. In case no substance-specific MRLs have been set (e.g. for pesticides not allowed on the EU market, but found in imported food), a default value of 0.01 mg/kg is used (Regulation 396/2005, Article 18(1b). Some compounds are considered not toxic in relevant concentrations, and no MRLs are applied to those (Annex IV of Regulation 396/2005). All the European MRL values are published by the EU Commission in an online database at http://ec.europa.eu/food/plant/pesticides/eu-pesticides-database/public/?event=pesticide.residue.selection
Food and Agriculture Organization of the United Nations (FAO)
The European definitions are very much in line with the international definitions as used by the FAO, which defines MRLs as follows:
“MRL” is the maximum concentration of a pesticide residue (expressed as mg/kg), recommended by the Codex Alimentarius Commission to be legally permitted in or in food commodities and animal feeds. MRLs are based on GAP data and foods derived from commodities that comply with the respective MRLs are intended to be toxicologically acceptable.
Codex MRLs which are primarily intended to apply in international trade, are derived from estimations made by the JMPR following:
a) toxicological assessment of the pesticide and its residue; and
b) review of residue data from supervised trials and supervised uses including those reflecting national food agricultural practices. Data from supervised trials conducted at the highest nationally recommended, authorised or registered uses are included in the review. In order to accommodate variations in national pest control requirements, Codex MRLs take into account the higher levels shown to arise in such supervised trials, which are considered to represent effective pest control practices.
Consideration of the various dietary residue estimates and determinations both at the national and international level in comparison with the ADI, should indicate that foods complying with Codex MRLs are safe for human consumption.
From FAO (2017).
So, again: consumer safety, i.e. the toxicological evaluation of the pesticide in question in relation to the expectable residues on produced food, takes the front seat. The MRL values for the various combinations of pesticide and food item can be found online here: http://www.fao.org/fao-who-codexalimentarius/standards/pestres/pesticides/en/
US
Of course, the US has to come up with a different nomenclature. Just to make life more interesting, I guess… Anyway, MRLs are called “tolerances” in the jargon of the US EPA (EPA, 2017). Similar to the approaches outlined above for the EU and the FAO, the toxicological safety assessment takes priority:
Before allowing the use of a pesticide on food crops, we set a tolerance, or maximum residue limit, which is the amount of pesticide residue allowed to remain in or on each treated food commodity. […]
In setting the tolerance, we must make a safety finding that the pesticide can be used with “reasonable certainty of no harm.” To make this finding, we consider:
- The toxicity of the pesticide and its break-down products.
- How much of the pesticide is applied and how often.
- How much of the pesticide (i.e., the residue) remains in or on food by the time it is marketed and prepared.
- All possible routes of exposure to that pesticide (residues on each crop use, as well as exposure from drinking water and residential exposure).
We perform dietary risk assessments to ensure that all tolerances established for each pesticide are safe. These assessments account for the fact that the diets of infants and children may be quite different from those of adults and that they consume more food for their size than adults. We address these differences by combining survey information on food consumption by infants and children with data on pesticide residues to estimate their exposure from food. We also estimate exposure of other age groups such as women of reproductive age, ethnic groups and regional populations.
We then combine information about pesticide exposure (from food, drinking water and residential uses) to infants, children and other subgroups with information about toxicity to determine potential risks posed by pesticide residues. If risks are unacceptable, we won’t approve the tolerances.
From EPA (2017a)
Searching for the EPA’s MRLs doesn’t seem to be as straight forward as searching for the European and FAO values. Please check the details here https://www.epa.gov/pesticide-tolerances/how-search-tolerances-pesticide-ingredients-code-federal-regulations. The US EPA is also sponsoring access to the international MRL database at https://www.globalmrl.com/home/, which provides the US MRLs (Haven’t tried it myself yet).
A final comment
This text is just supposed to give an overview of the important definitions, the aims and protection goals for setting MRLs and how the regulatory procedure is set up. I do not comment in this post on whether or not I think that the process works as intended.
References
Food and Agriculture Organization (FAO) (2017): Glossary to the Codex Alimentarius. Available online here: http://www.fao.org/fao-who-codexalimentarius/standards/pestres/glossary/en/ [Nov. 2017]
EU Parliament (2005) Regulation (EC) NO 396/2005 of the European Parliament and of the Council of 23 February 2005 on maximum residue levels of pesticides in or on food and feed of plant and animal origin and amending Council Directive 91/414/EEC OJ L 70, 16.3.2005, p. 1–16 Available online here. The consolidated version with all annexes is available here.
United States Environmental Protection Agency (EPA) (2017): https://www.epa.gov/pesticide-tolerances [Nov. 2017]
United States Environmental Protection Agency (EPA) (2017a): https://www.epa.gov/pesticide-tolerances/setting-tolerances-pesticide-residues-foods [Nov. 2017]