Harpenden researchers warn about toxic metals found in household goods

Tiny metal particles increasingly used in sunscreens, cosmetics and clothes may be toxic to plants and soil microorganisms, researchers in Harpenden have warned.

A team of international scientists, including experts from Rothamsted Research, have found that treated sewage sludge containing nanoparticles – tiny man-made metal particles – pose a risk to the environment.

Nanoparticles of silver, titanium dioxide and zinc oxide are being used more and more in common industrial and consumer products.

But there are fears they could end up in sewage treatment plants, where they are removed from wastewater and reside in sewage sludge as nanomaterials.

Professor Steve McGrath, head of Rothamsted’s department of sustainable soil and grassland systems, warned: “Manufactured nanoparticles containing metals are being increasingly released into the environment.”

Researchers have been examining, for the first time, the environmental effects after the tiny metal particles have been processed through full treatment works, and then mixed with soil.

Tests found that the treated sewage sludge containing nanomaterials had an impact on plants, which suffered stunted growth and took up far more zinc compared to sewage sludge containing typical forms of the metals.

The make-up of microbial communities in the soil was also changed.

During treatment of sewage, contaminants are removed from wastewater to produce clean wastewater.

But a by-product of such treatment is a semi-solid slurry, called sewage sludge, which undergoes further treatment before being spread on agricultural land.

For many decades this has been used successfully as a fertiliser, as it can provide much needed nutrients and organic matter to the soil.

However, until recently, manufactured nanomaterials have not been present in sewage sludge.