Are Fecal Sterols a Possible Alternative Indicator of Human Waste Contamination in Hawaiian Recreational Waters?

Many of Hawaii’s recreational streams and beaches contain high fecal indicator bacteria levels that are not indicative of sewage pollution. Instead, this pollution is due to environmental sources of fecal bacteria which reside and multiply in tropical soils. Current EPA fecal indicator bacteria are no longer representative of human fecal contamination in tropical waters. Fecal sterols have been used as chemical indicators of fecal pollution in many parts of the world. The primary sterol found in human feces is coprostanol. Detection and quantification of coprostanol and related sterols using GCMS analysis provides a fingerprint that can be used to characterize fecal contamination. The objective of this study was to assay for fecal sterols as an independent method to determine whether streams in Hawaii are contaminated with sewage. This method was applied to ambient streams, a stream recently contaminated by a sewage spill, and a stream suspected to be affected by a sewage line leak. The results of this study showed that some ambient streams in Hawaii contain high levels of fecal indicator bacteria, but low concentrations of coprostanol (1000 ng/L) when fecal indicators were also high, confirming a possible sewage line leak. This study demonstrated that coprostanol is a useful and independent measurement of sewage pollution. It is best used in conjunction with other fecal indicators and human fecal markers if confirmation of human fecal pollution is sought