Threshold exposure

AEGLs represent threshold exposure limits (exposure levels below which adverse health effects are not likely to occur) for the general public and are applicable to emergency exposures ranging from 10 min to 8 h. Three levels—... 

Ethylene and D2O were formed only above a threshold exposure of the surface to ethanol. Figure 27 shows that acetaldehyde was first formed this was the result of the reactions... 

The physico-chemical characterization of processed flat photoresist layers showed that the properties of the photoresist change significantly if it is processed with the threshold exposure dose that makes the photoresist soluble in the developer. Caused by a deprotection reaction, the photoresist becomes acidic and more hydrophilic. It was postulated that the thin residual photoresist layers processed with the threshold dose are appropriate model surfaces for the sidewalls of the photoresist structures in the photolithographic process. 

Interspecies and intraspecies UFs have been used in the development of safe or threshold exposure levels for chronic, noncancer toxicity by health organizations throughout the world. Examples include the acceptable daily intake (ADI) (Lu 1988 Truhaut 1991 Lu and Sielken 1991), the tolerable daily intake (TDI) or tolerable concentration (TC) (Meek et al. 1994 IPCS 1994), the minimal risk level (MRL) (Pohl and Abadin 1995), the reference dose (RfD) (Barnes and Dourson 1988 Dourson 1996), and the reference concentration (RfC) (EPA 1994 Jarabek et al. 1990). The importance of using distribution-based analyses to assess the degree of variability and uncertainty in risk assessments has been emphasized in recent trends in risk analysis. This will enable risk managers to make more informed decisions and... 

No inhalation MRLs were derived for exposures to hydrazines for acute or chronic durations. Although data from animal studies indicate that inhalation exposures to hydrazines produce adverse effects on the liver and central nervous system following acute (Rinehart et al. 1960) and chronic exposures (Vemot et al. 1985), these studies do not define the threshold exposure level for these effects with confidence. 

It can be derived from this model that the reciprocal of k2 (l/fcj) equals a threshold exposure (AUCX) required for complete suppression of tumor growth. This AUCX equals a threshold concentration (Cx) multiplied by the mean tumor growth time, thus it represents a total AUC for the length of mean tumor growth time. For example, 1 lk2 (AUCX) represents a total AUC for four days, when = 0.25 day1. 

Two models of radiation damage, illustrated in Fig. 19.17, have been proposed the linear model and the threshold model. The linear model postulates that damage from radiation is proportional to the dose, even at low levels of exposure. Thus any exposure is dangerous. The threshold model, on the other hand, assumes that no significant damage occurs below a certain exposure, called the threshold exposure. Note that if the linear model is correct, radiation exposure should be limited to a bare minimum (ideally at the natural levels). If the threshold model is correct, a certain level of radiation exposure beyond natural levels can be tolerated. Most scientists feel that since there is little evidence available to evaluate these models, it is safest to assume that the linear hypothesis is correct and to minimize radiation exposure. 

Agent Threshold Exposure Concentration (mg/m ) Threshold Exposure Response Time Maximum(s) Relative Humidity (% RH) Range Temperature Range (°C)... 

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