Scientists say there is no acceptable dose to avoid brain damage. Its use is banned in several European countries. Yet its residues are found in fruit baskets, on dinner plates, and in human urine samples from all over Europe. Now producers are pushing for a renewed EU approval – perhaps in vain.
The name is chlorpyrifos. Here is why the chemical and its risks are almost unknown to the public.
Chlorpyrifos kills insects on growing vegetables and fruit.
Thomas Backhaus, professor for ecotoxicology and environmental science at the University of Gothenburg, says that the substance took a long time to be recognised as one of the “nasty” ones.
“In comparison with glyphosate, the active substance in Roundup, chlorpyrifos has been flying under the radar. When we talk of herbicides like glyphosate that kill weed humans can cope because we don’t have chlorophyll and don’t get directly affected. When we talk about insecticides, you have the problem that they affect all developing animals, including humans,” he says.
Backhaus’ concerns are well known in academic circles and shared by other researchers.
Philippe Grandjean, professor in environmental medicine at the University of Southern Denmark and Harvard School of Public Health in the US, notes that brain damage connected to chlorpyrifos have been found at the lowest detectable dose.
“That means by definition that you can’t define a dose tolerable for consumption – that dose must be zero,” he says.
The poisonous effect of chlorpyrifos on insects is not disputed.
The unresolved question is to what extent the usage of chlorpyrifos is dangerous to all living organisms like fish in nearby waters or farm workers in the fields, or to anybody eating the treated products.
Tests of food samples in all EU countries in 2016 show chlorpyrifos and chlorpyrifos-methyl in 5.5 percent of the 76,200 samples, as recorded by EU institution EFSA (European Food Safety Agency).
If we look only at randomly-sampled unprocessed plant based food products in EU, the percentage is 6.2 according to Pesticide Action Network Europe.
In the samples recorded by the EFSA, 847 contained chlorpyrifos or chlorpyrifos-methyl above the Maixmal Residue Limit (MRL).
However environmental scientists believe residue levels for chlorpyrifos should be zero.
In countries where the use of chlorpyrifos is banned the pesticide nevertheless reaches consumers through the free movement of goods in the internal market.
In 2013, Swedish researchers reported findings of chlorpyrifos and other pesticides in urine from middle-aged women, a group with a high intake of fruits and vegetables.
Chlorpyrifos has never been registered for agricultural use in Sweden.
In 2016, studies for the Danish ministry of environment found chlorpyrifos in the urine from nine out of ten children and their mothers.
The researchers suggested a possible connection between chlorpyrifos and development of ADHD (Attention Deficit Hyperactivity Disorder).
In Wallonia, the French-speaking part of Belgium, the Public Service Scientific Institute in 2018 found residues of chlorpyrifos in 100 percent of urine samples from 258 schoolchildren aged 9-12.
A recent study in California connect autism and early brain damage in children with prenatal and infant exposure of chlorpyrifos.
A child’s risk of brain damage increases if its mother had been exposed to the pesticide by living nearby sprayed fields, the study found.
The Californian study published in March 2019 has triggered a ban of chlorpyrifos in the US’s largest agricultural state. Five other US states; Hawaii, Oregon, New York, Connecticut and New Jersey have announced or decided similar bans.
On a federal level a ban on chlorpyrifos has been blocked by the Trump administration since 2017.
In April 2019, a court ordered the US Environmental Protection Agency to decide by mid-July if it will permanently ban the chemical.
The European confusion
In Europe the scientific debate over chlorpyrifos is hardly known outside expert circles and the decision process about allowing or banning pesticides is difficult to track and to follow.
EU countries follow common decisions on whether to approve a substance like chlorpyrifos or not.
Chlorpyrifos has been approved on an EU-level since 2006 while decisions to allow products with the active substance, and the use of them, are up to the member states.
Eight member states have banned, or never authorised the use of chlorpyrifos products: Denmark, Finland, Germany, Ireland, Latvia, Lithuania, Slovenia and Sweden.
The United Kingdom banned the use of chlorpyrifos, with one exception, in 2016. Chlorpyrios is not authorised in Norway, nor in Iceland. The Swiss government decided to withdraw permissions for 12 chlorpyrifos and chlorpyrifos-methyl products 12 June, according to newspaper Tagblatt.
As goods within the EU are supposed to move freely across national borders, treated food thus gets spread around. That’s why consumers might find vegetables and fruit treated with chlorpyrifos in their grocery stores even if such treatment has never been allowed in the country.
A pan-European alert system has been set up for national authorities to notify other authorities on findings of hazardous food. These alerts often come after suspicious products have been sold – and consumed.
How companies have a say
Evaluation of possible health and environmental hazards are primarily based on studies paid for by the producers.
In the case of chlorpyrifos the main producer has been Dow Chemicals, now Corteva Agriscience, the agricultural division of DowDuPont. Corteva Agriscience turned into a standalone company on 1 June 2019.
“The producers’ role is obvious and well known to the scientific community. The present EU assessment of chlorpyrifos is to a large extent based on hundreds of studies financed and submitted by Dow,” says Axel Mie, associate professor at the Karolinska Institute, Department of Clinical Science and Education, Stockholm.
With colleagues Christina Ruden and Philippe Grandjean, Mie has initiated a scientific debate.
The three environmental scientists claim that data from Dow Chemicals’ own research back in 2000 actually showed that chlorpyrifos has an impact of the development of cerebellum (‘little brain’) in rats. These findings had however not been recorded in the conclusions filed to the EU authorities.
The scientists behind the criticised studies reject these claims. They argue the loss of brain weight in rats can be explained by the brains’ fixation in formaldehyde before being measured, and that no pesticide control product has been more thoroughly evaluated.
In the debate published by scientific journal Environmental Health, where Grandjean is one of the editors-in-chief, the defenders of chlorpyrifos first stated they had no competing interests.
In a correction posted in May 2019, they declared that at the time of their submission to the journal, they were employed by Dow Chemicals, the primary registrant and manufacturer of chlorpyrifos.