(Bloomberg) -- England’s rivers and lakes are at risk of contamination from human excrement, its chief medical officer warned, asking the government and utility companies to improve both infrastructure and monitoring.

A report commissioned by Chris Whitty warned that sewage treatment works continue pumping fecal organisms into rivers, seas and lakes. The concentrations are likely higher in dry weather when the water levels are low and less able to dilute the contaminants. That is also when most people enjoy being in the water.

“In particularly hot dry periods of the year — which tends to be when people are most likely to swim, paddle, children bathe — this is likely to be a bigger part of the problem,” Whitty said at a briefing ahead of the report’s publication on Tuesday.

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The report by the Royal Academy of Engineering and the National Engineering Policy Centre, seeks to raise awareness of the public health dangers of sewage entering the water causing illnesses and antimicrobial resistance. 

While it largely addresses the contamination of public waterways, especially from human fecal matter, it comes as residents in Devon, in southwest England, face an outbreak of cryptosporidiosis, after a parasite got in the local drinking water supply, causing hundreds of people to become ill. 

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Tuesday’s report sets out a series of recommendations, including water companies prioritizing investment in new and existing assets, and for the government to expand water quality monitoring to analyze the microbiological quality of treated effluents. It also called for the Department for Environment, Food and Rural Affairs to review the designation and protection of bathing waters.

“We are categorical that the scale of sewage discharge into our waterways is completely unacceptable,” a Defra spokesperson said. “We will not hesitate to act if water companies do not clean up their act fast, including through criminal prosecution and unlimited fines where companies are failing to prevent these shameful spills.”

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