Perchloroethylene , estimating

Exposure Assessment. Since perchloroethylene is used as a dry cleaning solvent and PCE vapor is easily monitored, estimates of PCE exposure are relatively straightforward to make from existing data in the literature. Table II summarizes the results. Based on NIOSH data (17), machine operators are exposed to an average of about 30 ppm of PCE vapor during the working day, equivalent to a... 

In a 1995 treatability study conducted for the U.S. Department of Energy (DOE) Savannah River facility, a cost estimate was prepared for an FTO system with a flow rate of 400 standard cubic feet per minute (scfm) using natural gas to maintain process temperatures. Costs were estimated at 0.72/lb. For the purposes of this estimate, the inlet concentration was assumed to be 400 ppm of trichloroethylene (TCE), perchloroethylene (PCE), and 1,1,1-trichloroethane (TCA). Capital costs were estimated at 160,000. Capital costs were amortized over 10 years, not over the time required to remediate the site. This cost estimate found FTO to be more cost effective than thermal catalytic technologies due to lower operating and maintenance costs (D125122, p. 10). 

A limited number of sink effect studies have been conducted in full-sized environments. Tichenor et al. [20] showed the effect of sinks on indoor concentrations of total VOCs in a test house from the use of a wood stain. Sparks et al. [50] reported on test house studies of several indoor VOC sources (i.e., p-dichlorobenzene moth cakes, clothes dry-cleaned with perchloroethylene, and aerosol perchloroethylene spot remover) and they were compared with computer model simulations. These test house studies indicated that small-chamber-derived sink parameters and kj) may not be applicable to full-scale, complex environments. The re-emission rate (kj) appeared to be much slower in the test house. This result was also reported by other investigators in a later study [51]. New estimates of and were provided,including estimates of fca (or deposition velocity) based on the diffusivity of the VOC molecule [50]. In a test house study reported by Guo et al. [52], ethylbenzene vapor was injected at a constant rate for 72 h to load the sinks. Re-emissions from the sinks were determined over a 50-day period using a mass-balance approach. When compared with concentrations that would have occurred by simple dilution without sinks, the indoor concentrations of ethylbenzene were almost 300 times higher after 2 days and 7 times higher after 50 days. Studies of building bake-out have also included sink evaluations. Offermann et al. [53] reported that formaldehyde and VOC levels were reduced only temporarily by bake-out. They hypothesized that the sinks were depleted by the bake-out and then returned to equilibrium after the post-bake-out ventilation period. Finally, a test house study of latex paint emissions and sink effects again showed that... 

JP has been calciflated for 16 current-use pesticides [8], the surfactant nonylphenol polyethoxylate (NPnEO), and the solvent perchloroethylene [5], based on a thorough compilation of experimental data on compound properties and transformation schemes (if such data are not available, they have to be estimated as described in Sect. 4.2). hi Fig. 2, the JP results for the 18 compounds are displayed. 

Many rapid methods are now available for estimation of fat content. The Foss-Let fat analysis system determines the fat content as a function of relative density of a perchloroethylene extract of the sample. It was designed for analysis of oilseeds, but is also applicable to other foods. The method is very rapid and its accuracy is comparable to other standard methods. Nuclear magnetic resonance (NMR) spectrometry is a rapid, nondestructive method also suitable for determining the fat content of oilseeds. The NMR value is related to the total hydrogen content of the lipid, with actual lipid content calculated from calibration tables. 

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