text: Since 5β-coprostanol is formed from cholesterol in the vertebrate gut, the ratio of the product over reactant can be used to indicate the degree of faecal matter in samples. Raw untreated sewage typically has a 5β-coprostanol / cholesterol ratio of ~10 which decreases through a sewage treatment plant (STP) such that in the discharged liquid wastewaters the ratio is ~2. Undiluted STP wastewaters may be identified by this high ratio. As the faecal matter is dispersed in the environment, the ratio will decrease as more (non-faecal) cholesterol from animals is encountered. Grimalt & Albaiges () have suggested that samples with a 5β-coprostanol / cholesterol greater than 0.2 may be considered as contaminated by faecal material.