The hazards to public health due to sewage in the river Thames
River users are exposed to extreme levels of gastrointestinal bacteria, giardia & cryptosporidium parasites and other hazardous pathogens for up to 120 days per year. Some suffer extreme stomach upsets, poisoning, eye and wound infections, from water-borne parasites, viruses and bacteria associated with the sewage (Norovirus, Campylobacter, Giardia, Salmonella, E.Coli - even Cholera has been found - see History).
The Environment Agency monitor oxygen content as an indicator of water quality. They tell Thames Water when to employ the two 'Thames Bubbler' aeration vessels when conditions become very poor, to try to reduce the impact on the river ecosystem.
The Corporation of London have recently become more concerned as they believe health hazards are becoming worse, and are running a survey of their own with the Health Protection Agency (TREC). Many Thames workers and river users are picking up water-borne parasites and illnesses associated with sewage. If you get ill, possibly as a result of contact with river water, please fill out their self reported illness questionnaire to help them with the survey (HPA thames study).
Port of London Health Authority