Power, toxic laboratories

Laboratories designed for the handling of toxic materials normally maintain reduced pressures in the rooms and hallways, relative to the pressure outside the buildings. Hoods should therefore be fitted with antibackflow valves to avoid sucking the contents of the ductwork into the laboratory in the event of a power failure. Backup power provided in 15 seconds does not prevent this phenomenon, even if the hoods and airhandlers are designed to restart automatically. 

PCP (PHENCYCLIDINE) Also known as angel dust, a powerful and toxic synthetic chemical developed in home laboratories. 

In addition to its powerful synergistic action with alcohol by the inhibition of aldehyde dehydrogenase, Disulfiram exerts an equally strong synergistic toxic effect in the presence of ethylene dibromide (EDB, ref. 179) Laboratory rats exposed to 20 ppm EDB (inhalation)... 

One major deviation from the typical toxicity test methodologies was that field replicates were used for toxicity testing in lieu of the standard laboratory replication (z. e., one replicate per station rather than 5). This modification was made a priori in order to maximize the number of stations at the expense of statistical power within the available project resources. 

The larger concern about nitro-aromatic compounds is that environmental exposure to these molecules can cause cancer in humans and in other living organisms. Nitro-aromatic compounds are acutely toxic, mutagenic, and carcinogenic in laboratory mammals and in vitro test systems [6, 8]. Despite the potential negative impact of nitro-aromatic compounds on human health, they continue to be emitted into ambient air from municipal incinerators [9], motor vehicles (particularly from diesel exhausts) [10, 11], industrial power plants [12], and other sources. Evidence... 

In the early days of flame AAS, the use of nitrous oxide also occasionally resulted in problems for the analyst. One was that the fumes were appreciably more toxic, so an efficient extraction hood over the flame became much more important. The nitrous oxide-acetylene flame was both hotter and taller than the air-acetylene flame, and the unwary occasionally managed to underestimate the temperature of the exhaust gases at the fan, resulting in distorted fan blades. Plastic fan blades are best avoided It is important to use an appropriate extraction rate. The author knows of one small company which installed such a powerful extractor that the laboratory doors flew open whenever the fan was switched on. On one occasion, even with the laboratory doors open, a passing sparrow was sucked in through the window which also needed to be kept open. 

Extraction hoods serve a number of useful purposes. These include removal of carbon dioxide and steam (the commonest combustion products) and of other, less desirable combustion products, such as sulfur dioxide and other acidic gases from some sample solutions, and of whatever elements were present in the samples. They also remove soot from excessively fuel-rich flames, which otherwise can make a real mess in the laboratory. It is unwise to run instruments for extended periods without fume extraction, even if there is nothing obviously toxic in the sample solutions. This is especially true for the nitrous oxide-acetylene flame. It is well worth considering interfacing the fume extraction switch with the instrument power supply, because it is easy to forget to turn on the extractor when everything else is automated. 

Toxicity and health effects Laboratory rats exposed to 2-nitropropane in high concentrations (207 ppm) developed adverse liver changes like hepatocellular hypertrophy, hyperplasia, necrosis, and liver carcinoma. It has been reported that prolonged exposure to concentrations of 20-45 ppm of 2-nitropropane caused nausea, vomiting, diarrhea, anorexia, and severe headaches among workers. Industrial workers handling 2-nitropropane for the application of epoxy resins to the walls of a nuclear power plant developed toxic hepatitis. - ... 

Clearly, hypothesis-testing using data from currently used toxicity test protocols cannot detect effects well at low concentrations. This is due in part to the lack of statistical power, given the number of replicates and the intrinsic laboratory and organismal variability within the experiments. Current assumptions that NOELs are a no-effect or at a safe level are also not warranted. The above studies also indicate that the level of effect that the NOEL represents is highly variable. LOELs are similarly uninformative. 

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