On a wet weight basis (nanograms per gram of tissue), concentrations of TCDD, PeCDD, 4-PeCDF, and PCB-126 were higher in the liver than in adipose tissue [see Supplemental Material, Table S3 (http:////)]. In contrast, concentrations of the mono -ortho PCBs 156 and 118, and the non-dioxin-like PCB-153 were lower in liver than in adipose tissue. These differences were even more pronounced when concentrations were expressed as percent of dose per gram of tissue. Thus, the more potent DLCs had a higher liver affinity than the less potent PCBs 118 and 156. Therefore, we determined the ratio between liver and adipose tissue concentrations to study congener-specific hepatic sequestration. Diliberto et al. (1997) previously suggested that a liver:adipose ratio > reflects congener-specific hepatic sequestration. In our study, we observed liver:adipose ratios > for TCDD, PeCDD, 4-PeCDF, and PCB-126 but liver:adipose ratios < for PCBs 118, 156, and 153 ( Table 1 ). Hepatic sequestration was dose dependent for TCDD and PCB-126 (as shown by increasing liver:adipose ratios at higher dose levels) but not for PeCDD and 4-PeCDF.
Emission factors based on useful energy delivered have denominators with units of megajoules delivered (MJ d ), and those based on fuel energy used have denominators with units of megajoules thermal (MJ th ). Energy efficiency is the ratio of useful-energy delivered to fuel energy used (MJ d /MJ th ). We calculated pollutant and mutagenicity emission factors in a variety of units, and emission factors based on useful cooking energy (MJ d ) enabled comparisons among all cookstove/fuel combinations. For example, we estimated for mutagenicity emission factors the number of revertants (rev) per MJ d as: rev/MJ d = (rev/mg PM ) × (mg PM /MJ d ).
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