Tracing faecal pollution Pollution from human and animal waste is one of the main causes of water quality deteriorating and nutrient loads increasing in coastal and inland waterways. Local councils and State environment protection authorities have long believed, and had circumstantial evidence, that domestic pets, farm animals, and native birds and mammals are also a large source of bacterial contamination of lakes and creeks, particularly after heavy rain. Sewage contamination has traditionally been determined by counting the faecal coliform bacteria in a water sample. This test is the standard measure referred to in environmental legislation. However, none of the currently used bacterial indicators, on their own, are specific enough to distinguish different sources of faecal matter, although identifying the source is essential to solving the problem.
Faecal sterols are source- specific.
This is caused by a combination of three factors. Animals are broadly omnivorous, carnivorous or herbivorous, and each diet contains different sterols in different amounts, giving a distinctive and unique profile on an analyser. Secondly, many animals naturally produce sterols. Finally, and most importantly, anaerobic bacteria in the digestive tract of some animals converts sterols to stanols. It is the combination of these three factors that determines the sterol fingerprint.