Margin-of-exposure

The MOE approach is often used to determine the acceptability of acute risks for single chemicals and MOEs of 100 or 10 are usually considered acceptable when derived from toxicological data from animal and human studies, respectively. The US-EPA favors this concept for performing aggregate and cumulative risk assessments (Whalan and Pettigrew 1997). 

The combined MOE (MOEj) is the reciprocal of the MOEs of each compound in the mixture. 

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NOAEL (no-observed-adverse-effect level) is defined as the highest dose at which no adverse effects are observed in the most susceptible animal species. The NOAEL is used as a basis for setting human safety standards for acceptable daily intakes (ADIs), taking into account uncertainty factors for extrapolation from animals to humans and inter-individual variabilities of humans. The adequacy of any margin of safety or margin of exposure must consider the nature and quality of the available hazard identification and dose-response data and the reliability and relevance of the exposure estimations. In some cases, no adverse endpoint can be identified such as for many naturally occurring compounds that are widespread in foods. In that case, an ADI Not Specified is assigned. ... 

To calculate the safe re-entry interval (REI), the margin of exposure (MOE) must be considered. Worker risk is measured as a margin of exposure and is related to how closely the occupational exposure comes to the no observed adverse effect level (NOAEL, for oxamyl 50 mg kg day ). MOE is defined as... 

Using the nonlinear model substituting 0.915 p.gcm (the DFR value from the model 1 day after application) into Equation (6) yields a dose of 1.05 mgkg day" and an MOL from Equation (5) of 47, below the required value of 100 for margin of exposure. Performing the same calculation on the day 2 data gives a dose of 0.344 mg kg day and an MOE of 145, which is above the level of 100 required to establish a safe re-entry level. Therefore, a 2-day period is adequate to ensure worker safety. The observed values of 0.936 and 0.234 qg cm for days 1 and 2 match closely the values predicted by the model. 

Assessments of risks associated with the use of chlorpyrifos insecticide products for workers have been made. The assessments are based on the results of field studies conducted in citrus groves, a Christmas tree farm, cauliflower and tomato fields, and greenhouses that utilized both passive dosimetry and biomonitoring techniques to determine exposure. The biomonitoring results likely provide the best estimate of absorbed dose of chlorpyrifos, and these have been compared to the acute and chronic no observed effect levels (NOELs) for chlorpyrifos. Standard margin-of-exposure (MOE) calculations using the geometric mean of the data are performed however, probability (Student s f-test) and distributional (Monte Carlo simulation) analyses are deemed to provide more realistic evaluations of exposure and risk to the exposed population. 

The most commonly used approach, and most conservative, for assessing risks to humans is to compare tire exposure results directly to the appropriate toxicological endpoint by calculating the margin of exposure (MOE margin of safety in many countries), which is given by ... 

Table 3 Estimated Margins of Exposure for Chlorpyrifos from Biomonitoring Data Using Geometric Means (Single-Point Approach)3...

Belt-conveyor scales, 26 244—245 Belt filter press, 25 913 Belt saponification, in vinyl alcohol polymerization, 25 609-610 Benard instability, 11 764 Benazepril hydrochloride, molecular formula and structure, 5 149t Benchmark dose and margin-of-exposure method, 25 244... 

Margaric acid, physical properties, 5 29t Marginal failure, 26 982 Marginal regeneration process, 12 13 Margin of exposure, 25 244 Margin of safety determination, 25 234-235... 

For some experts the margin of safety has the same meaning as the margin of exposure, while for others, the margin of safety means the margin between the reference dose and the acmal exposure dose or concentration. 

A margin of exposure of 2 has been selected as a basis for distinguishing scenarios that are of concern from those which are unlikely to be of concern. Consequently, for inhalation of solids, the GEVs are corresponding to an intake of 25, 500, and 5000 pg/person/day for high, medium, and low hazard category, respectively, based on a respiratory volume of lOm /day. 

MOE (Margin of Exposure) approach is formally similar to the MOS (Margin of Safety) approach for threshold effects (see Section 8.3.3 for MOS approach). 

The Margin of Exposure (MOE) in the context of the assessment of compounds that are both genotoxic and carcinogenic, as defined in EFSA (2005), is different from the OECD/IPCS definition given above The Margin of Exposure (MOE) is the ratio between a defined point on the dose-response curve (reference point) for the adverse effect of the compound in the animal carcinogenicity study and the estimated human intake of the compound. ... 

Risk characterization for non-threshold effects, e.g., for chemicals that are both genotoxic and carcinogenic, generally proceeds by comparing the acceptable risk level (Section 6.2.4) with the actual or estimated total daily intake. An alternative, new approach is the margin of exposure approach (Section 6.4). 

The direct comparison of a POD (DNEL) with the estimated exposure (E) leads to the establishment of a ratio (DNEL/E), often denoted as the margin of safety (MOS) or margin of exposure (MOE). 

Margin of Exposure is Ratio of the no-observed-adverse-effect level (NOAEL) for the critical effect to the theoretical, predicted or estimated exposure dose or concentration. ... 

The approaches discussed are the hazard index (HI) (Section 10.5.1.1) and the weight-of-evidence (WOE) modification to the HI (Section 10.5.1.2), the point of departure index (PODl) (Section 10.5.1.3), toxicity equivalency factors (TEFs) (Section 10.5.1.4), the margin of exposure (MOE) procedures (Section 10.5.1.5), and the cumulative risk index (CRl) method (Section 10.5.1.6). 

Whalan J.E. and H.M. Pettigrew. 1997. Inhalation risk assessments and the combining of margins of exposure. Washington, DC U.S. Environmental Protection Agency, Office of Pesticide Programs. 

The third descriptor that is sometimes used to characterize risk is the margin of exposure ( ). The is the ratio of the NOAEL (or BMD) from the most appropriate or sensitive species to the estimated level of human exposure from all potential sources. 

Margin of exposure. The ratio of the NOAEL to the estimated exposure dose. 

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