Quantitative Application of Fecal Sterols Using Gas Chromatography−Mass Spectrometry To Investigate Fecal Pollution in Tropical Waters:  Western Malaysia and Mekong Delta, Vietnam

Abstract

This is the first report on fecal pollution using molecular markers in Southeast Asia where serious sewage pollution has occurred. A simple and sensitive analytical method using gas chromatography-mass spectrometry for 10 sterols in various environmental samples was developed to monitor extensive areas of tropical Asia. First, the method was applied to wastewater to confirm that >95% of sterols existed in the particulate phase. Then the approach was applied to a tropical Asian region, Malaysia and Vietnam, with a selection of 59 sampling stations in total. River water and sediment samples were collected and analyzed for chemical markers (coprostanol and other sterols) and microbiological markers (fecal coliforms and fecal streptococci). Particulate coprostanol concentrations ranged from <0.0001 to 13.47 microg/L in tropical river and estuarine waters, indicating severe fecal pollution in populous areas. Coprostanol concentrations in the sediments ranged from 0.005 to 15.5 microg/g-dry. The sedimentary coprostanol concentrations were lower than those reported in some urban areas of industrialized countries. This is probably because frequent heavy rain induces intensive input of eroded soil, which dilutes fecal material in river sediments. The relationship between the concentrations of fecal sterols and bacterial indicators was examined in an attempt to develop public health criteria for coprostanol levels applicable to the tropical region. Coprostanol concentrations of 30-100 ng/L or percent coprostanol levels of 2% corresponded to approximately 1000 fecal coliforms per 100 mL, which is set for secondary contact limit in many countries. These coprostanol concentrations were lower than those proposed as criteria in temperate countries, probably owing to greater survival of bacteria in warmer tropical waters. On the basis of these criteria, extensive monitoring of sediments suggests that poor sanitary conditions exist in most of the urbanized area of Malaysia and in several urban and rural sites in Vietnam.

Recent Advances in the Use of Chemical Markers for Tracing Wastewater Contamination in Aquatic Environment: A Review

“…Isobe et al [68] studied the fecal pollution using SSs in tropical countries where serious sewage pollution had occurred. A total of 59 sampling stations were investigated and analyzed for chemical markers (SSs) and microbiological markers (fecal coliforms and fecal streptococci).…”

A comparison between faecal sterols and coliform counts in the investigation of sewage contamination in sediments

“…According to Isobe et al (2002), in tropical areas the limit for primary contact of ~1000 faecal coliforms per 100 ml (commonly adopted in several countries, including Brazil) corresponds to 30-100 ng L -1 of coprostanol.…”

“…However, the use of bacteria as markers is controversial, because environmental factors such as salinity, temperature, rain, and effluent characteristics (chlorination, presence of other contaminants, etc) affect their survival. Consequently, their effectiveness as indicators of the presence of pathogenic organisms that might pose a threat to human health is greatly compromised (Isobe et al, 2002;Isobe et al, 2004;Noblet et al, 2004).…”

“…Several studies conducted in temperate and cold areas based on water samples have shown a good correlation between counts of faecal indicator bacteria and coprostanol concentration Isobe et al, 2002;Noblet et al, 2004 and references therein). On the other hand, significant deviations between the two markers have been observed in tropical regions due to specific environmental conditions (Isobe et al, 2004).…”

Sterols as Indicators of Fecal Pollution in Sediments from Shellfish Farming Areas (Yeoja Bay and Gangjin Bay) of Korea

“…coprostanol , 50-80%( 3.4 mg/g-dry) 5 (Leeming et al, 1996). Isobe et al (2002) coprostanol ( , Escherichia coli.) .…”