Site-specific target levels

Tier 2 produces site-specific target levels (SSTLs) that are protective of human health and the environment, but utilizes more site-specific data than Tier 1. This level of sophistication should address 70-80% of the sites. This more site-specific assessment involves the assumption of reasonable use exposure assumptions, considers actual beneficial uses of resources, and provides a tool for determining points of compliance. 

To identify necessary response actions, each complete exposure pathway can be analyzed on a site-specific basis to evaluate the potential for exposure in excess of safe levels. For the purpose of this evaluation, Site-Specific Target Levels (SSTLs) can be derived for relevant exposure pathways, receptors, and constituents of concern and compared to measured source media concentrations. Source media exceeding these target levels will require remedial action in a timeframe necessary to control exposure. 

Site-Specific Target Level For a given exposure pathway and contaminant, the SSTL represents a concentration in the affected source medium (soil, groundwater, surface water, or sediment) that is protective of a human or ecological receptor located at a relevant point of exposure (POE). For example, for the human health soil-to-air exposure pathway, the SSTL is the mean concentration in the affected surface soil zone that will prevent unsafe human exposures via vapour or particulate release to air. For each... 

Figure 8.9 The targeted HX-ETD strategy to determine site-specific deuterium levels. Following HX, quench, and enzymatic cleavage, only peptides exhibiting differential deuterium uptake in states A and B (regions marked with yellow and pink) are selected for ETD fragmentation. The time points with the maximal difference in the deuterium uptake are selected for fragmentation (See insert for color representation of the figure.)...

The effects of toxins are, generally, proportional to dosage. Well-controlled dosage, as in these cell systems, provides the best opportunity for relating carcinogenicity to levels of exposure. In live animal experiments, the amount administered is usually defined as the exposure. However, not all fibrous particles will ultimately reach a specific target tissue. Measurement of the fiber load at the tissue site and the pathologic response are tedious but necessary procedures to evaluate this aspect of the problem. 

In landfarming, a layer of contaminated soil is spread out on a specifically constructed site. Microbiological degradation is stimulated by soil tilling, irrigation, and addition of nutrients (nitrogen, phosphorus) and a specialized inoculum, if necessary. When the pollutant concentration is reduced to the target level, a new layer of polluted soil is spread and treated. 

Nrg1tmlFej Targeted mutation 1, Frank E Jones The endogenous locus was modified to contain a stop codon in exon 9 and single loxP sites flanking exons 9,10, and 11. The mutation was designed to specifically target the a-isoform, which encoded by exon 9. RT-PCR analysis showed reduced levels of mRNA, putatively due to nonsense mediated decay... 

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