Residue tolerance

Of course, the number of acyclic residues tolerated in 2.5-helical peptides will vary as a function of the peptide length. For example, CD measurements performed on an amphiphilic 17-mer peptide with ACPC and APC residues and containing six / -Hleu residues, shows the expected signature in water with a mean-... 

Several aspects of the problem of herbicides being contaminated with nitrosamines, and the resulting inadvertent introduction of nitrosamines into the environment, will be discussed in other papers in this symposium. Unrecognized until less than five years ago, the situation has inspired intense debate and prompted several of the environmental chemistry studies mentioned in this paper. Like the presumed threat from the in vivo nitros-ation of pesticide residues, discussions sometimes lack the type of anticipated dose and effect calculations just mentioned. Unlike the active ingredients, whose benefits can justify residue tolerances and acceptable daily intakes, nitrosamine contaminents afford no known benefits, and the desirability of minimizing their levels is undisputed. 

By definition, the determinative procedure must be able to quantify the concentration of the marker residue. For compounds with a tolerance, it is critical that the analysis be able to determine accurately if the concentration of the marker residue is above or below the tolerance in the target tissue. The CVM guidelines for determinative procedures call for an average recovery >80% with a coefficient of variation (CV) of <10% for marker residue tolerances of lOOpgkg or greater and an average recovery of >60% with a CV of <20% for marker residues with a tolerance below 100 ppb. 

The MRL is the EU equivalent of the US tolerance. Since in addition to consumption figures the relative distribution of residues between edible tissues is considered in the calculation of the MRL, practical withdrawal periods can be set for products containing the active substances concerned. This is an important point that differentiates the approach used to set MRLs in the Europe from the approach used by the United States to set residue tolerances. At least two tissues, one on the carcass and one organ meat, have to be designated as target tissues. 

The same situation applies to testosterone and progesterone. Unlike the naturally occurring hormones, there is no daily production rate for the synthetic compounds trenbolone acetate and zeranol. Therefore, the FDA requires toxicological testing in animals to determine a safe level in meat for these compounds. When FDA approved zeranol and trenbolone, it determined that residues were well below a safe concentration and therefore no residue tolerance was required (25). Due to consumer concerns, testing procedures for zeranol were put into place in the early 1980s but were discontinued in the late 1980s because no residue violations were found. 

The long-term treatment studies also include hydroponic studies (Hilton et al, 1974, 1976), as well as preemergence studies (Robinson et al, 1970 Gronberg et al, 1971 Church and Flint, 1973 Morgan, 1974 Fenz et al, 1987) and postemergence studies (Morgan, 1972,1973 Stanley and Flint, 1974 Maun and McLoed, 1978 Schocken et al, 1987) involving analysis of mature plants. The duration of these studies was usually measured in terms of weeks or months, and their purpose was to determine the nature of the terminal residues in crops in order to set pesticide residue tolerances. 

This is a point on which I do not agree. The Environmental Protection Agency has indicated that there are no known human health hazards associated with the use of most Bt toxins. Nor do Bt toxins have any known effect on wildlife such as mammals, birds, and fish. In fact, the EPA has found Bt toxins to be of such low risk that it has exempted them from food residue tolerances, groundwater restrictions, endangered species labeling, and special review requirements—one of the reasons organic farmers... 

FAO/WHO. 1975. Food and Agricultural Organization of the United Nations/World Health Organization. Pesticides residue tolerances for foodgrains. Pesticides 9 33-34. 

For a certain drug, the total residue is determined from a radioisotope study, and the marker concentration is determined by the approved regulatory method. Once the Rm value is known, a marker residue tolerance is established. This value is then used in field monitoring programs to ensure that no edible tissues containing drug residue above the safe concentration will reach the consumer. For albendazole, the Rm value for the 2-aminosulfone metabolite in 0.20 or 20% of the total residue. Since the safe concentration for albendazole residues in liver is 1.2 ppm (0.6 ppm in meat x 2 (food factor)), the marker tolerance has been established at 240 ppb. 

The difference in the maximum drop of body temperature, the greater blood flow, and the higher incidence of vomiting in non-addicts can be interpreted as evidence of residual tolerance to morphine in post-addicts. It is also possible that addicts are different physiologically in their responses to morphine as either a hereditary or an acquired characteristic. Customary therapeutic doses of 8-15 mg. of morphine sulfate suffice for the relief of post-operative pain in former morphine addicts just as they do in nonaddicts. Changes in pupil size, pulse rate, respiratory rate, and blood pressure after 20 mg. of morphine were. similar in addicts and post-addicts (55). 

Sodium silicate and sodium metasilicate are exempt from the requirement of a residue tolerance in pesticide formulations applied to growing crops or to raw agricultural commodities after harvest (33). 

Worldwide Usually <0.3 mg/kg FW, but residue tolerances vary between 0.02 and 0.5 mg/kg FW, based on the sum of ds-chlordane, trans-chlordane, and oxychlordane... 

---