Toxicity threshold levels

CA 86, 51210 (1977) [The toxic effect of PVC combstn products on the human organism was evaluated and the Toxic Threshold Level is reported as 0.3g of PVC products/M3 of air] 2) M. Bert et al, Reduction of Smoke Generation in Poly (Vinyl Chloride) Combustion , FireRes (4-5), 301-11 (1978) CA 90,72796 (1979) [The authors report that the most efficient (toxic) smoke suppressors for PVC are those which show catalytic activity in oxidation reactions, such as Cu, Fe, or V compds. These suppressors cause incandescence and complete combstn of the solid residue without excessive smoke prodn. They conclude that their efficiency is not very dependent on the anion bound to the metal, but may depend on the temp] 3) E A. Harrison, Toxicity of Vinyl... 

According to Sax (Ref 5) the toxic threshold level of the trisulfide vap, which is primarily H2S, is 15mg/m3 of air. Exposure to 800— lOOOppm of the vap in 30 mins may be fatal. Exposure to a v high concn of the vap (H2S) results in immediate death. The vap is av strong irritant to the mucous membranes (Ref 3). The liq trisulfide forms a caustic (Na2S) when in contact with the skin because of the alkali present in moist skin. This explains the strong irritant action of both the liq and vap (Refs 2,... 

Remember that decontamination is a physical process, the purpose of which is to remove the contaminant from the patient in the shortest possible time and thus reduce the concentration of any toxic material to below toxic threshold levels. Two old time nursing principles are true of decontamination. First, separate the puddle from the patient. Second, the solution to pollution is dilution. Multiple different protocols may be devised to accomplish this goal, each having its own advantages and disadvantages. The important thing is that everyone be familiar with their particular protocol and then execute that protocol faultlessly. A particular order of decontamination is appropriate ... 

On the basis of these results, researchers suggest 4 mg Buvinol /kg/day as the subacute toxic threshold level (ADI). This value is larger by several orders of magnitude than the normal application and consumption level. 

The 1990 Clean Air Act Amendments Hst 189 hazardous air pollutants (HAPs) that the EPA must regulate to enforce maximum achievable control technology (MACT) to standards which are to be set by the year 2000. The 33/50 project calls for reduction of emissions of 17 specified solvents to predetermined levels by 1995. The SARA statute provides a mechanism by which the community can be informed of the existence, quantities, and releases of toxic chemicals, and requires that anyone releasing specific toxic chemicals above a threshold level to annually submit a toxic chemical release form to the EPA. The status of various ketones under these regulations is shown in Table 4. 

Chronic Toxicity Studies. With the exception of tumorigenesis, most types of repeated exposure toxicity are detected by subchronic exposure conditions. Therefore, chronic exposure conditions are usually conducted for the following reasons if there is a need to investigate the tumorigenic potential of a material if it is necessary to determine a no-effects or threshold level of toxicity for lifetime exposure to a material and if there is reason to suspect that particular forms of toxicity are exhibited only under chronic exposure conditions. 

Toxicity and Hazards. The odor cf ozone can be detected in concn as low as several parts per hundred million by vol (pphm). The threshold limit value (TLV) is O.lppmor 0.2mg/m3 its toxic dose level (TDL), 50% kill concn is 2ppm (Ref 6) Pure 100% liq ozone may be kept safely at 90°K (cooled by liq oxygen) for indefinite periods of time, but the smallest provocation, such as a spark or fast warming, even only up to bp (161°K), causes detonation. The evapn of liq ozone, for example, in the process of the prepn of pure gaseous ozone is, therefore, a dangerous procedure (Ref 3, p 224)... 

The latter problems are of particular interest to chemists, who should devise appropriate methods for resolving the complexity of chemicals, properly identifying them and finally determining their exact composition and makeup. The participation of chemists is needed to verify the concept of allelopathy as a concentration-dependent phenomenon. They should help to reconstitute the chemical composition as it was found in the original and isolated plant samples. This systematic approach leads to verification of the concept as well as to proper assessment of the initial observation with crude extracts, and to final application to the field situation. Once the concept is proven, same simulation experiments need to be performed to maximize the allelopathic effect (toxin action). The concentration of the toxic chemicals is varied to where the threshold levels of chemicals prove to be involved in the exhibition of allelopathy under field conditions. 

As we ve seen above, there are really only two basic ways in which toxic chemicals can affect body tissues and cells. There are, however, different ways this happens. A chemical, once in the body, can exert an immediate effect and then be eliminated, or it can be allowed to accumulate to a particular threshold level before it takes further action, or it can be changed in form to a less toxic state. 

LOAEL), and the highest dose at which no effects are observed, the no adverse effect level (NOAEL). In the interest of prudence, the NOAEL is generally considered as a conservative estimate of the toxicity threshold. 

For these reasons, TDM can serve several roles when using clomipramine. First, it can be used to determine whether clomipramine or its demethlylated metabolite constitutes the majority of the circulating drug. Second, TDM can be used to guide dose adjustment to ensure plasma concentrations equivalent to those seen in adults whose OCD is successfully treated. This approach also ensures that concentration levels do not approach or exceed the toxic threshold for TCAs (i.e., greater than 450 ng/mL). Like adults, children and adolescents demonstrate a wide variability in their capacity to metabolize TCAs. As mentioned earlier, children are usually faster metabolizers of these drugs than adults, so they typically need doses of approximately 2.5 to 3.5 mg/kg. Once puberty has been reached, the required doses can be reduced by as much as 50%. 

People can suffer from a variety of inborn metabolic errors that can result in various amino acids exhibiting toxic effects if ingested above certain threshold levels. Specialty products, intended to be absent these amino acids, must be rigorously tested for verification that threshold levels are not exceeded. Examples of this situation include phenylketoneuria (intolerance of phenylalanine) and maple syrup urine disease (intolerance for leucine, isoleucine, and valine). 

One principle that is central to the understanding of toxicology is the dose-response relationship, which implies that there is a threshold level below which no toxic effects are observed. This level can be approximated in studies in which animals are dosed with the pesticide the maximum dose tested at which there are no detectable differences between treated and untreated control animals is called the no observed effect level (NOEL). The dosage slightly in excess of the NOEL at which toxic effects are observed is referred to as the lowest observed effect level (LOEL). These two dosages should be relatively close together in order to clearly define the threshold level. 

For instance, an extrapolated water TBT concentration (0.21 5.9 ngL-1) based on concentrations of TBT and its bioconcentration factors (5000 10,400 for TBT in mussel and 9400-11,000 in marine fish) (Sudaryanto et al., 2005d) were also close to or above the threshold levels of toxic implications, such as imposex in mollusks and immunotoxicity in mussel (St-Jean et al., 2002). The levels were also near to the criteria established by US-EPA (2003) to protect saltwater aquatic life from chronic toxic effects of TBT (0.0074 pg L-1). Indeed, high incidence of imposex in gastropods has been shown to occur in Indonesia, such as the Ambon coastal area (Ellis and Pattisina, 1990). An evidence of ecotox-icological impact of TBT, imposex incidence is also a usual phenomenon in gastropods in coastal waters of some other Asian countries... 

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