Minimal toxic concentration

The demands and design of a local ventilation system (not only local ex hausts) should naturally start with the demanded target levels and the toxicity of the air contaminants (see Chapters 5 and 6). For best performance the exhaust should be close to the source and preferably enclose the source, there should be no disturbances of the flow, and at the same time it should have a low flow rate and be able to minimize the concentration of even quite dangerous air contaminants in the working zone. 

Toxicity Monitor and assess for adverse effects and evaluate antimicrobial serum concentrations when appropriate to minimize toxicity and improve outcomes... 

The AEGL-3 values were derived based upon the 1-h LC50 value of 82 ppm reported for squirrel monkeys (Haun et al. 1970). As previously noted, there appears to be a critical and narrow threshold between an exposure that induces only minimal toxicity and one that causes death. For squirrel monkeys, 1-h exposure to a mean concentration of 82 ppm (range, 70-95 ppm) killed two of four animals. For derivation of the AEGL-3, the lethality threshold for squirrel monkeys was estimated by a 3-fold reduction of the LC50 (82 ppm) to obtain a value of 27.3 ppm. This estimate can be justified by the known steep exposure-response relationship for the toxic effects of monomethylhydrazine, and the fact that the resulting 27.3-ppm value represents an exposure concentration that does not produce overt toxicity in test animals. 

High concentrations of acetone were required to produce death in animals the 4-hour inhalation LCso value is 32,OOOppm for rats. Administered in the drinking water for 13 weeks, the minimal toxic doses were 20,000ppm for male rats and mice and... 

Infiltration (i.e., the injection of local anesthetics under the skin) of the surgical site provides adequate anesthesia if contiguous structures are not stimulated. Since the onset of local anesthesia is rapid, the surgical procedures can proceed with little delay. Minimally effective concentrations should be used, especially in extensive procedures, to avoid toxicity from overdosage. 

Despite the need to know how nanotubes may affect or cause toxicity for live organisms, only a small number of studies have been dedicated to this problem. Furthermore, results of these studies have been inconsistent and not fully understood. The data obtained show that crude nanotubes possess a certain level of toxicity (in both in vivo and in vitro studies) associated mainly with the presence of metals, which are used as catalysts in nanotube synthesis. For purified nanotubes minimal toxic effects were seen even at high concentrations, and chemically functionalized nanotubes used for drug delivery did not show any toxic effects. However, the ability of nanotubes to form aggregates requires further research in this area. 

The selective use of drug concentrations to enhance efficacy and minimize toxicity... 

The 7-azabenzisoselenazol-3(27/)-ones (169) (Fig. 12), substituted at the 2-position with phenyl or alkyl groups, and the methiodides (170) were found in the antiviral assay to be strong inhibitors of cytopathic activity of herpes simplex type 1 virus (HSV-1) and encephalomyocarditis virus (EMCV), more potent than ebselen. The minimal inhibitory concentration (MIC) values were in the range 0.4-6.0 pg mL 1, substantially lower than those when toxicity was observed. The vesicular stomatis virus (VSV) remained resistant toward tested compounds, except moderately active methiodide (171) [51, 271],... 

Topical antibiotics may be considered to be advantageous over their systemic counterparts because they deliver a higher concentration of medication directly to the desired area and are less frequently implicated in causing bacterial resistance. An ideal topical antimicrobial has a broad spectrum of activity, persistent antibacterial effects, and minimal toxicity or incidence of allergy. 

Heavy metals, like lead and mercury, have been recognized as toxic poisons for centuries. Further, toxic concentrations of mercury, for example, can trigger several effects like autoimmune diseases, infections, unexplained chronic fatigue, depression, nerve impairment, memory problems, decreased mental clarity, and bowel disorders. For several decades, mercury vapor exposure has caused severe health problems among chloralkali workers. This is only an example. It may be repeated that education can effectively minimize exposure to hazardous metals. Basic information and training for proper handling of toxic chemicals will reduce potential adverse health effects. 

Semibatch Reactors Some of the reactants are loaded into the reactor, and the rest of the reactants are fed gradually. Alternatively, one reactant is loaded into the reactor, and the other reactant is fed continuously. Once the reactor is full, it may be operated in a batch mode to complete the reaction. Semibatch reactors are especially favored when there are large heat effects and heat-transfer capability is limited. Exothermic reactions may be slowed down and endothermic reactions controlled by limiting reactant concentration. In bioreactors, the reactant concentration may be limited to minimize toxicity. Other situations that may call for semibatch reactors include control of undesirable by-products or when one of the reactants is a gas of limited solubility that is fed continuously at the dissolution rate. 

Exposure to acutely toxic concentrations of nerve agents can result in excessive bronchial, salivary, ocular and intestinal secretions, sweating, miosis, bronchospasm, intestinal hypermotility, bradycardia, muscle fasciculations, twitching, weakness, paralysis, loss of consciousness, convulsions, depression of the central respiratory drive, and death (Grob and Harvey, 1953 Grob, 1956 Marrs, 2007 Sidell, 1997 Yanagisawa et al, 2006 many others). Minimal effects observed at low vapor concentrations... 

The kinetics of theophylline transfer into breast-milk have been studied in three lactating women given theophylline intravenously (SEDA-6, 2). The data suggested that theophylline accumulation to toxic concentrations should not occur in most breast-fed infants, but that serum theophylline concentrations in the mother should be kept as low as possible and transfer will be minimal if infants are nursed just before the mother takes the theophylline. 

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