Toxic cocktail: Study finds almost 200 pesticides in households

In a study, which examined dust in European households, almost 200 pesticides were found.

Scientists say that regulators must take into account “toxic cocktails” of chemicals when banning or restricting the use of pesticides.

The scientists say their research supports the idea that regulators should assess the risks of pesticides when they interact with other chemicals, but also when used individually. This should apply both to substances already in use and to those yet to be approved.

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

More than 40% of the pesticides found in the dust were associated with highly toxic effects, including cancer and disruption of the human hormonal system.

The number of pesticides in individual homes ranged from 25 to 121, with pesticide levels in the homes of farmers tending to be higher.

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

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

"There are many studies indicating that animals pick up certain contaminants, including pesticides, from outdoors. Another group is the consumer products we bring into our homes … all the pesticides we buy in shops for various reasons, and an important source is flea and tick treatments for pets."

Although the concentrations of individual pesticides in dust were low, the mixtures of dozens of chemicals could affect health and increase exposure to pesticides, particularly when these are also frequently found in higher concentrations on fruit, vegetables and flowers.

The study found that DDT persists in the environment, even though the pesticide was banned in some countries as early as 1972.

Scheepers said that those approving the use of products should take environmental persistence into account, and that products such as PFAS, even if banned now, would likely 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 variety of consumer goods and industrial processes, and some have been linked to serious diseases in humans and animals, including cancer.

Scheepers said: "Products like DDT, which have long been banned, are so persistent that they accumulate in the environment, meaning they are constantly in circulation … now we also have the problem with PFAS, which is exactly a repetition of that."

"Perhaps regulators can take the persistence of chemicals into account — let us say chemical stability means persistence in the environment and also accumulation in the food chain — then we will likely discover similar problems with other persistent chemicals in the future."

The researchers explained that their study shed light on which pesticide mixtures have been found in the environment, enabling regulators to examine these as well as the combinations produced for commercial use that they have already tested.

The discovery of DDT also meant that risk assessments for newer pesticides would need to take into account interactions with older pesticides, the researchers said.

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