Maximum residue levels/limits

Maximum residue level (MRL) Comparable to a U.S. tolerance level, the maximum residue level is the enforceable limit on food pesticide levels in some countries. Levels are set by the Codex Alimentarius Commission, a United Nations agency managed and funded jointly by the World Health Organization and the Food and Agriculture Organization. 

A maximum residue level was proposed at the limit of determination for pesticides in which all residues were non-detectable, even if the minimum sample requirements (59) were not met for satisfying the specified probability (> 95th percentile) and confidence (95%) limits for any of the sub-groups. 

TheFood Sanitary Law in Japan, which is regulated by theMinistry of Health, Labor and Welfare (MHLW), has established maximum residue limits (MRLs) and monitors the residue levels in food commodities in the market, including both domestic and... 

Today, when a pesticide with no detectable residues is registered for use, a Tolerance or maximum residue limit (MRL) is established at the lowest concentration level at which the method was validated. However, for risk assessment purposes it would be wrong to use this number in calculating the risk posed to humans by exposure to the pesticide from the consumption of the food product. This would be assuming that the amount of the pesticide present in all food products treated with the pesticide and for which no detectable residues were found is just less than the lowest level of method validation (LLMV). The assumption is wrong, but there is no better way of performing a risk assessment calculation unless the limit of detection (LOD) and limit of quantification (LOQ) of the method were clearly defined in a uniformly acceptable manner. 

Sulfonylurea herbicides are generally applied to crops as an early post-emergent herbicide. Crops that are tolerant to these herbicides quickly metabolize them to innocuous compounds. At maturity, residues of the parent compound in food and feed commodities are nondetectable. Metabolites are not considered to be of concern, and their levels are usually nondetectable also. For this reason, the residue definition only includes the parent compound. Tolerances [or maximum residue limits (MRLs)] are based on the LOQ of the method submitted for enforcement purposes and usually range from 0.01 to 0.05 mg kg (ppm) for food items and up to O.lmgkg" for feed items. There is no practical need for residue methods for animal tissues or animal-derived products such as milk, meat, and eggs. Sulfonylurea herbicides are not found in animal feed items, as mentioned above. Furthermore, sulfonylurea herbicides intentionally dosed to rats and goats are mostly excreted in the urine and feces, and the traces that are absorbed are rapidly metabolized to nontoxic compounds. For this reason, no descriptions of methods for animal-derived matrices are given here. 

Quantitative immunoassays have also been used as screening devices to determine whether drug residues exceed established maximum residue limits (MRLs) or tolerances in edible tissues. " For these applications, a cut-off value is set at the tolerance or MRL samples detected above this level are positive , and samples below this level are negative. ... 

Table 3 Examples of therapeutic agent maximum residue limits (MRLs) (mg kg ) from EU and tolerance levels (TLs) (mgkg- )fromUSEDA ...

While all nations of the world possess the sovereign right to establish their own acceptable levels for pesticide residues in foods, many lack the resources to develop their own regulatory programs and instead rely upon a set of international standards developed by the Codex Alimentarius Commission, frequently referred to as Codex. The Codex international standards are termed maximum residue limits (MRLs) and, like U.S. tolerances, are established primarily as enforcement tools for determining whether pesticide applications are made according to established directions. While many countries have adopted Codex MRLs, others, such as the U.S. and several Asian countries, rely on their own standards. Thus, there is no uniformity among the world with respect to allowable levels of pesticides on foods. A pesticide-commodity... 

Examples of standard settings developed by the WHO include air quality guidelines (Section 9.2.1.1) and drinking water guidelines (Section 9.2.1.2), and (in collaboration with the FAO) maximum residue limits (MRLs) for pesticides and veterinary drugs and maximum levels for food additives (Section 9.2.1.3). 

OSHA regulates the level of chlorine dioxide in workplace air. The occupational exposure limit for an 8-hour workday, 40-hour workweek is 0.1 parts per million (0.28 milligrams per cubic meter [mg/m ]). The EPA has set a maximum contaminant level of 1 milligram per liter (mg/L) for chlorite in drinking water and a goal of 0.8 mg/L for both the maximum residual disinfectant level for chlorine dioxide and the maximum contaminant level for chlorite in drinking water treated with chlorine dioxide as a disinfectant. 

To undertake a risk assessment on the consumption of food, the first step is to compare the levels with the maximum residue limits (MRLs). MRLs for POPs in Singapore (Government of Singapore, 1990) and the United States (USFDA, 2001) are presented in Table 16.6. Samples were lower than respective MRLs for all POPs. 

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