The society’s report, Sustainable Water: Chemical Science Priorities, is calling for urgent research to determine the scale of the threat.

Dr Jeff Hardy, the RSC’s environment and energy manager, said: "While many people might not be interested in what happens to their nice-smelling shower gel after it has disappeared down the drain, chemists and employees of the water industry most certainly are."

Wastewater treatment works are unable to prevent chemicals used in many household products escaping into the environment. The report, due to be published today, raises concern over the growing number of chemicals that are now being picked up. Their effects on the environment, including human health, are unclear and need to be investigated.

"An understanding of the inputs, fate and subsequent exposure of aquatic systems to chemical contaminants is essential in determining and controlling the risks of the contamination to the environment and human health," it says.

One of the chemicals which causes environmentalists most concern is triclosan. An estimated 90 tonnes of the antibacterial agent goes into domestic products such as washing-up liquids, plastic kitchen utensils, toothpastes, deodorants and soaps every year. Triclosan builds up in the environment and is toxic to aquatic life. It has been found in the bodies of fish and in human breast milk.

Another are phthalates, a family of some 120 industrial chemicals used in shampoos, moisturisers and perfumes. They have been linked to reproductive problems in wildlife, and can build up in animals’ bodies.

The Scottish Environment Protection Agency last night echoed the report’s call for more research: "We are concerned about the collective impact of such products and how they could potentially harm the environment."

Jason Rose, spokesman for Scottish Water, said: "Our treatment works were not designed to filter these chemicals out.

He added: "What do we do about them? The short answer is they shouldn’t be going down the plughole in the first place. People can buy plant-based, eco-friendly alternatives for many products."