CONCENTRATIONS OF COPROSTANOL THAT CORRESPOND TO EXISTING BACTERIAL INDICATOR GUIDELINE LIMITS

Coprostanol is a faecal sterol that has been proposed as an alternativ e measure of faecal pollution. While the technique has been used succe ssfully to trace sewage-derived organic matter in a range of environme nts, it has not been embraced for use as a water quality indicator. Th is is mostly because of a lack of epidemiological evidence relating co prostanol abundance to any health risk. However, there is a valuable r eason why the concentration of coprostanol should be related as quanti tatively as possible to the abundance of bacterial indicators currentl y used to measure faecal pollution. The measurement of coprostanol (an d concurrently other faecal sterols) offers many diagnostic and quanti tative advantages over traditional techniques for detecting human sewa ge pollution versus faecal contamination from animal sources. Knowing the amount of coprostanol expected given a certain amount of human sew age pollution would provide a measure against which water managers cou ld quantitatively assess faecal pollution as a whole and relate that a ssessment to variables with which they are more familiar. This study d etermines the relationships between coprostanol concentrations and ind icator bacterial counts and synthesises the results from several envir onments to propose coprostanol concentrations broadly equivalent to ex isting bacterial standards. Our data suggest that 60 and 400 ng L(-1) of coprostanol correspond to currently defined primary and secondary c ontact limits for bacteria measured as thermotolerant coliforms (commo nly referred to as faecal coliforms) or enterococci. Copyright (C) 199 6 Elsevier Science Ltd.