Hazardous waste isomers

Since endosulfan is a cytochrome P450-dependent monooxygenase inducer, the quantification of specific enzyme activities (e.g., aminopyrine-A -demethylase, aniline hydroxylase) may indicate that exposure to endosulfan has occurred (Agarwal et al. 1978). Because numerous chemicals and drugs found at hazardous waste sites and elsewhere also induce hepatic enzymes, these measurements are nonspecific and are not necessarily an indicator solely of endosulfan exposure. However, these enzyme levels can be useful indicators of exposure, together with the detection of endosulfan isomers or the sulfate metabolite in the tissues or excreta. 

Endosulfan (one or both of its isomers) has been identified in a variety of environmental media (air, surface water, groundwater, soil, and sediment) collected at 164 of the 1,577 NPL hazardous waste sites (HazDat 2000). 

Exposure Levels in Environmental Media. Reliable monitoring data for the levels of di- -octylphthalate in contaminated media at hazardous waste sites are needed so that the information obtained on levels of di-ra-octylphthalate in the environment can be used in combination with the known body burden of di-w-octylphthalate to assess the potential risk of adverse health effects in populations living in the vicinity of hazardous waste sites. Di-u-octylphthalate has been detected in ambient air, rain, surface water, groundwater, and sediment. However, as a result of the confusion about the nomenclature for octylphthalate esters, much of the historical monitoring data available actually pertain to the branched isomer, di(2-ethylhexyl)phthalate (Vista Chemical 1992). Therefore, little current information specific to the /1-octyl isomer is available regarding concentrations of the compound in foods, drinking water, and environmental media, particularly with respect to media at hazardous waste sites. The lack of monitoring data precludes the estimation of human exposure via intake of or contact with contaminated media. 

Exposure Levels in Humans. This information is necessary for assessing the need to conduct health studies on these populations. Di- -oclylphthalatc has historically been reported to have been found in human adipose tissue (EPA 1986d). However, more recent information indicates that the compound detected was actually the branched di(2-ethylhexyl) isomer (EPA 1989b). Additional information on the concentrations of di-n-octylphthalate in human tissues and fluids, particularly for populations living near hazardous waste sites, is needed to assess potential human exposure to the compound. 

Although the production of CDDs during combustion processes are highlighted here, most samples from combustion sources show a complex mixture of isomers and congeners of CDDs and CDFs which vary in their relative concentrations (Kolenda et al. 1994 Nestrick and Lamparski 1983 Vikelsoe et al. 1994). CDDs have been detected in emissions (flue gas and fly ash) from municipal, hazardous waste, and industrial incinerators (Buser 1987 Oppelt 1991 Sedman and Esparza 1991 Schecter 1983). 

In addition to the four classes of hazardous wastes discussed above — ignitable, corrosive, reactive, and toxic wastes—there are 203 individual compounds and salts of some of these compounds as well as soluble cyanide salts that are listed as acute hazardous wastes, and each designated with a RCRA Hazardous Waste Number, starting with the letter P. In addition, there are 455 compounds plus the salts and isomers of some of these compounds, which are designated as toxic wastes. These substances are assigned an RCRA Waste Number, which starts with a U. Because of space limitations. 

The chlorinated phenols, partieularly pentachlorophenol and the trichloro-phenol isomers, are signifieant hazardous wastes. These compounds are biocides that are used to treat wood to prevent rot by fungi and to prevent termite infestation. They are toxic, causing liver malfunction and dermatitis. However, contaminant polychlorinated dibenzodioxins ( dioxin ) may be responsible for some of the observed effects. Pentachlorophenol and other aromatic halides and aromatic hydrocarbons used as wood preservatives are encoimtered at many hazardous-waste sites in wastewaters and sludges. 

---