Residual risk assessment

Improvements in pesticide residue risk assessment practices should improve the scientific basis for managing pesticide residues in foods and the FQPA provides a blueprint for making such improvements. While most of the FQPA provisions are considered in theory to represent improvements in the risk assessment process, the practical adoption of methods to comply with such... 

Process risk management Management of residual risk through hazard identification, risk assessment and reduction, emergency preparedness, and working with suppliers and customers (including carriers) apply... 

The degree of confidence in the final estimation of risk depends on variability, uncertainty, and assumptions identified in all previous steps. The nature of the information available for risk characterization and the associated uncertainties can vary widely, and no single approach is suitable for all hazard and exposure scenarios. In cases in which risk characterization is concluded before human exposure occurs, for example, with food additives that require prior approval, both hazard identification and hazard characterization are largely dependent on animal experiments. And exposure is a theoretical estimate based on predicted uses or residue levels. In contrast, in cases of prior human exposure, hazard identification and hazard characterization may be based on studies in humans and exposure assessment can be based on real-life, actual intake measurements. The influence of estimates and assumptions can be evaluated by using sensitivity and uncertainty analyses. - Risk assessment procedures differ in a range of possible options from relatively unso-... 

Dr Georg Geisler is a product safety expert and modeller working with RCC Ltd, a Contract Research Organisation based in Basel, Switzerland. In this function, he conducts environmental risk assessments of pesticides, biocides and other chemicals, as well as safety assessments for pesticide residues in the food chain. In 2003, Georg Geisler earned his Ph.D. on environmental life-cycle assessment of pesticides at ETH Zurich. In 1999, he had received a Diploma in environmental chemistry at the Friedrich-Schiller University, Jena, Germany. 

Relationship of pesticide residue analysis, regulation, and risk assessment... 

W.G. Fong, Regulatory aspects pesticide registration, risk assessment and tolerance, residue analysis, and monitoring, in Pesticide Residues in Foods Methods, Techniques, and Regulations, ed. W.G. Fong, H.A. Moye, J.N. Seiber, and J.R Toth, WUey, New York, Chapt. 7 (1999). 

Validation should be carried out for each component of the residue definition in each sample matrix used for risk assessment purposes. 

The activities of enforcement laboratories should not be focused on irrelevant problems. Therefore, a clear definition of the relevant residue is needed. In the crops and food sector, procedures are well established to derive the two residue definitions, one for risk assessment and one for monitoring, from metabolism studies. As far as environmental samples are concerned, there is much potential for improvement. There are no clear criteria as to which metabolites should be included in monitoring and control programs. Additionally, the development of criteria for nonpriority pesticides, e.g., naturally occurring compounds or low-risk products, which can be excluded from monitoring exercises would be helpful for laboratories and evaluators. 

The definitions of method detection and quantification limits should be reliable and applicable to a variety of extraction procedures and analytical methods. The issue is of particular importance to the US Environmental Protection Agency (EPA) and also pesticide regulatory and health agencies around the world in risk assessment. The critical question central to risk assessment is assessing the risk posed to a human being from the consumption of foods treated with pesticides, when the amount of the residue present in the food product is reported nondetect (ND) or no detectable residues . 

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. 

If no detectable residues were present, the value used for risk assessment purposes would be 0.05 mg kg This would allow only four uses with no detectable residues and even fewer uses where residues were present. If an appropriate LOD and LOQ had been calculated and reported as follows ... 

The need to develop and use chiral chromatographic techniques to resolve racemates in pesticide residues will be driven by new hazard and risk assessments undertaken using data from differential metabolism studies. The molecular structures of many pesticides incorporate chiral centers and, in some cases, the activity differs between enantiomers. Consequently, in recent years manufacturers have introduced resolved enantiomers to provide pesticides of higher activity per unit mass applied. For example, the fungicide metalaxyl is a racemic mix of R- and 5-enantiomers, both having the same mode of action but differing considerably in effectiveness. The -enantiomer is the most effective and is marketed as a separate product metalaxyl-M. In future, it will not be satisfactory to rely on hazard/risk assessments based on data from metabolism studies of racemic mixes. The metabolism studies will need to be undertaken on one, or more, of the resolved enantiomers. 

It is a regulatory requirement that analytical methods be developed to determine residues of concern in crops, feed, and food commodities as well as environmental samples (air, soil, and water). Methods for crops, feed, and food commodities are required for enforcement purposes but are also needed for a variety of other purposes, such as gathering monitoring data for risk assessment. For nearly any purpose, the methods must be robust, that is, when used by different analysts in several laboratories, they should provide reproducibly similar results. 

In the USA, the passage of the Food Quality Protection Act (FQPA) of 1996 has had a significant impact on the determination of residues in drinking water. FQPA requires that all sources of a pesticide be included in its risk assessment, so the potential exposure from drinking water containing a particular pesticide could be a significant... 

Data collected in drift studies may later be interpreted in risk assessments in conjunction with toxicity data for specific sensitive areas. Eor example, a risk assessment for determination of appropriate mitigation (if necessary) may include field study data on exposure risk from drift, along with information on other routes of exposure (e.g., dislodgable residues, runoff, etc.) and toxicity data from laboratory and/or field study models. The results of such an assessment may be used to estimate whether a given exposure represents a hazard to any specific entity or ecosystem. 

When humans contact a chemical residue such as a pesticide on a treated surface, some of the deposit can be dislodged or transferred to skin or clothing. Ultimately, a portion of the amount transferred may be absorbed and constitute the absorbed daily dose (ADD). The ADD provides the most precise estimate of exposure that can be practically obtained for humans and has become the most useful expression of exposure for risk assessment and risk management. 

Each of these dislodging techniques tries to mimic ways that a person of a certain size or weight could contact the residues applied to turf. This is important because, should one of the techniques provide a more consistent means of dislodging than the others, it would allow risk assessments to be done that would give a good indication of the potential exposure and thus risk to an individual who comes in contact with the treated turf. It would also allow for better estimates to be made as to when the treated turf could be used by a typical homeowner. 

A recent study published by Badema et al. in 2011 describes a combined method to investigate the toxicity of an industrial landfill s leachate which is based on a triad approach including chemical analyses, risk assessment, and in vitro assays [17]. Moreover, to verify the applicability and the robustness of the proposed method, the approach was applied on a real case study a controlled, ISO-14001 certified landfill for nonhazardous industrial waste and residual waste from the treatment of MSW in northern Italy for which data on the presence of leachate contaminants are available from the last 11 years. 

In considering pesticide residues, it was clearly shown that crops from organic production systems contain no or significantly lower levels of pesticide residues than crops from conventional systems (Baker et al., 2002). However, while some scientists are concerned about the potential health impacts from such residues (Porter et al., 1999 Benbrook, 2002), pesticide legislators maintain that current pesticide risk assessments and pesticide registration procedures are adequate and that residues below the current legal limits can not have a negative health impact in humans (e.g. PSD, 2006). 

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