Australasian Science: Australia's authority on science since 1938

A Flood of New Toxins

By Staff

New contaminants that are more toxic than heavy metals are finding their way into the world’s rivers, lakes, groundwater and drinking water, an international expert in environmental chemistry has warned.

The new toxins arise from sources such as artificial sweeteners, nanomaterials, perfumes, medical drugs, hormones, sunscreens, flame retardants, non-stick coatings, pesticide breakdown products, hospital wastes and the by-products of detergents, disinfectants and swimming pool cleansers.

Left undetected and untreated, they can be hazardous to humans, with some already linked to conditions such as cancer, obesity, lower intelligence and infertility, Dr Susan Richardson of the University of South Carolina told the CleanUp 2015 conference in Melbourne.

“The world is no longer dealing with the ‘same old, same old’ contaminants,” she explains. “The list of new ones keeps growing, with ionic liquids and prions being among the most recent.” Ionic liquids are used as “green chemistry” to replace traditional solvents in cleaning products, but their effects are still largely unknown.

Prions – molecules that are highly resistant to disinfection – are known to cause “mad cow disease”, chronic wasting disease in deer and Creutzfeldt-Jakob disease as well as kuru in humans.

“Algal toxins are also an increasing concern,” Richardson says. “An algal bloom in Ohio, US, last year shut down the drinking water system for the whole city. Such blooms are expected to increase as more nitrogen makes its way into our wastewater and rivers.”

Richardson said that many of the new contaminants arise from common household products like cleansers and furnishings, personal care products, food packaging, and the medical as well as recreational drugs we excrete from our bodies. “These products get washed off in the shower or flushed down the toilet and travel to wastewater plants. Some of them become toxic once they react with the chlorine or chloramine with which the water is treated,” she said.

“It’s bad news because our wastewater treatments, which are designed to remove ‘traditional’ waste, cannot treat these toxins efficiently. There is no one-size-fits-all way to clean up all of them.”

One example is the failure to remove NMDA, a carcinogenic disinfection by-product. “Reverse osmosis – the same process that removes salt from water – was used to treat NMDA, but the compound was so small that it passed through the filter. As a result, a half or less of the NMDA is removed.”

Richardson is researching better ways to detect these contaminants. “As some of them are very difficult to treat, it may be more effective to remove the ‘precursor’ molecules before they can react with chlorine or chloramine in wastewater ponds and turn toxic. This means that we need to ‘catch’ them sooner.”