出版社：Korean Society of Environmental Health and Toxicology
摘要：It has been observed that the linear relationship between the logarithm of biococentration factor (log BCF) of highly hydrophobic chemicals and their log Kom breaks when log Kom becomes greater than 6.0. Consequently,super hydrophobic chemicals were not thought to cause baseline toxicity as a single compound. Researchers often call this phenomenon as "*hydrophobicity cutoff meaning that bioconcentration or corresponding baseline toxicity has a certain cutoff at high log Kow value of hydrophobie organic pollutants. The underlying assumption is that the increased molecular size with increasing hydrophobicity prohibis highly hydrophobic compounds from crossing biological membranes. However,there are debates among scientists about mechanisms and at which log Kou this phenomenon occurs. This paper reviews three hypotheses to explain observed "cutoffr": steric efects,kinetic or physiological limitations. and chemical activity cutoff. Although the eritical molecular size that makes biological membranes not permeable to hydrophobic organic chemicals is uncerain,size ffects in combination with kinetic limitation would explain observed non-linearity between log BCF and log Kxw. Chemical activity of hydrophobic chemicals generally decreases with increasing melting point a their aquecous solubility. Thus,there may be a chemical activity cutoff of baseline toxicity if there is a critical chemical activity over which baseline efects can be observed.
