Contamination, toleration levels

Table 6-3 Qualitative Tolerance Levels for Individual Contaminants in Isothermal Bench-Scale Carbonate Fuel Cells (46, 47, and 48)... 

The typical fuel gas composition and contaminants from an air-blown gasifier that enter the MCFC at 650°C after hot gas cleanup, and the tolerance level of MCFCs to these contaminants are listed in Table 6-7 (58,71,72). It is apparent from this example that a wide spectrum of contaminants is present in coal-derived fuel gas. The removal of these contaminants can add considerably to the efficiency. A review of various options for gas cleanup is presented by Anderson and Garrigan (70) and Jalan et al. (73). 

In the last few years, a number of factors have led practitioners to abandon the concept of ultraclean processing (reducing the level of contaminants to below the level detectable with state-of-the-art equipment). The approach that seems to have taken hold instead is that of just clean enough, which requires a fundamental understanding of the specific effects of contaminants and as a consequence, the ability to define tolerable levels of contaminants. In the next section we review the characterization tools that can be used in this context. 

The evidence from these tests confirmed that BIT, even at a level of 200 ppm, was unable to control the bacterial contamination based on inoculation and re-inoculation with the resistant/tolerant strains. The results in Figure 2 show that Bronopol was able to control the bacterial contamination at levels down to 50 ppm, even after re-inoculation at the 3-week sample point. The 20 ppm level... 

In the enforcement phase of testing, IDA may also conduct follow-up investigation at the animal producer level to uncover the original source and cause of the contamination problem. This often results to seizure of animal feed or seizure and condemnation of carcasses. In accordance with the federal law, offenders may face prosecution if found guilty of contravening FDA tolerance levels. In addition, farmers harboring violative residues may find future shipments impounded unless they can clearly demonstrate compliance with residue standards. 

Some weeks later FDA investigators and Farm Bureau people found a partly filled bag of Firemaster at the feed mill. Within the month (May 1971 ) action (tolerance) levels were established by the FDA for PBB contamination. The Michigan Department of Agriculture began quarantining contaminated farms—a process that went on until the end of 1975- Another six months saw the original MACs for PBBs further lowered to 0.3 ppm for meats and dairy products, and 0.05 ppm for eggs and feed, as the toxic effects in animals were noted at lesser concentrations, and the routine detection of PBBs at these lower concentrations became feasible. 

The varieties of rice examined in this study show only modest differences in trace element content between the Italian and Asian samples. The slight variations observed can be ascribed to specific characteristics of the botanical varieties, soil composition, and availability for each element, and local environmental contamination. The concentration of potentially toxic elements in rice ascertained in this study raise no specific concerns. On the other hand, the key role played by rice consumption in Asia diets calls for careful evaluation of the average daily intake for elements such as As, Cd, and Pb, which might exceed the established tolerance level. 

Mechanical activation is less expensive alternative to increase sinterability ofTTO, if contamination is suppressed within a tolerable level. 

The microbiological standards applying to drug products are expected to be maintained until time of use by the patient (or healthcare professional) and throughout their shelf-lives. This presents two areas of concern relevant to microbiological control first, that the product should be protected (usually by its packaging) from additional contamination after release to market, and second, that the product should be formulated to prevent proliferation of any microorganisms that may have been present at tolerable levels at the time of release. 

Safety of food is a basic requirement of food quality. Food safety implies absence or acceptable and safe levels of contaminants, adulterants, naturally occurring toxins, or any other substance that may make food injurious to health on an acute or chronic basis. Most countries, therefore, have established official tolerance levels for chemical additives, residues, toxins, and contaminants in food products. Table 30.5 summarizes several CE reports that can be found in the literature that deal with the analysis of toxins, contaminants, pesticides, and residues. A number of reviews appearing... 

Advancements in environmental chemistry are closely tied with developments in other areas, such as analytical chemistry. As particular compounds are found to be toxic at lower and lower levels, it becomes important to be able to detect them at these lower levels (though there are those who contend that being able to detect them at low levels is what causes the legislated tolerance level to drop). Analytical chemistry has pushed its detection limits for some contaminants from... 

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