Helena Horton – The Guardian April 11, 2025

Almost 200 pesticides have been found by a study examining dust in homes around Europe, as scientists say regulators need to take “toxic cocktails” of chemicals into account when banning or restricting the use of pesticides.

Scientists say their research supports the idea that regulators should assess the risks posed by pesticides when they react with other chemicals, as well as individually. They say this should apply to substances already in use, as well as those yet to be approved.

In preliminary findings from the largest study of its kind, scientists examining household dust from homes in 10 European countries in 2021 detected 197 pesticides in total.

More than 40% of the pesticides found in the dust have been linked to highly toxic effects, including cancer and disruption of the hormonal system in humans.

The number of pesticides in each home ranged between 25 and 121, and levels of pesticides tended to be higher in the homes of farmers.

Prof Paul Scheepers, of the Radboud Institute for Biological and Environmental Sciences, said: “We have many epidemiological studies showing that diseases are associated with mixtures of pesticides.”

He said the pesticides in dust found their way into people’s homes via shoes, as well as cats and dogs. “If we don’t take off the shoes at the doorstep, then we take in a lot of dirt from outside. Pets are also a source,” Scheepers said.

“There are many studies indicating that animals collect certain contaminations, also including pesticides, from outdoors. Another group are the consumer products that we bring into our homes … any pesticides that we buy in the shop for certain reasons, and an important source is flea and tick treatments for pets.”

Though the concentrations of each pesticide in the dust were small, the mixtures of dozens of chemicals could have an impact on health, as well as increasing exposure to pesticides when they were also often encountered in higher concentrations on fruit, vegetables and flowers.

The study found that DDT remained in the environment despite the pesticide having been banned in some countries in 1972.

Scheepers said those authorising the use of products should take environmental persistence into account, and that even if products such as Pfas were banned now, they would probably remain in the environment.

Pfas are known as “forever chemicals” because they do not break down in the environment. They are used in a wide range of consumer products and industrial processes, and some have been linked to serious diseases in humans and animals, including cancers.

Scheepers said: “Products like DDT that have been banned for a long time are so persistent that they accumulate in the environment, so they are constantly circulating … Now we have also the problem with Pfas that’s exactly a repeat of this.

“Maybe regulators can consider the persistence of chemicals – let’s say chemical stability means persistence in the environment and also accumulation in the food chain, we are likely in the future to discover similar problems with other persistent chemicals.”

The researchers said their study revealed which mixtures of pesticides had been found in the environment, so regulators could test these as well as the combinations produced for commercial use that they already tested.

The discovery of DDT also meant risk assessments of newer pesticides might need to consider interactions with older ones, they said.

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