Time to ban organophosphate pesticides?

How would you react if your neighbour told you he was going to spray his garden with a neurotoxin used in WW2? "Oh don't worry!" he assures you, "it's only a low dose!"
"A neurotoxin?" you ask incredulously "Are you crazy?"
"It's very effective!" he asserts.
"How does it work?" you ask.
"It stops the pests' brains working" he asserts with a smile.  "Everyone uses it."
"But..."

Campaigners in the USA hope that with Scott Pruitt’s resignation, and with a new administrator Andrew Wheeler at the helm of the Environmental Protection Agency (EPA), this presents another chance to apply pressure and achieve a national ban in the United States on the organophosphate pesticide chlorpyrifos once and for all.

Photo by Elle Dunn


Organophosphate insecticides, such as diazinon, chlorpyrifos, disulfoton, azinphos-methyl, and fonofos, have been used widely in agriculture and in household applications as pesticides since the 1960s, despite growing evidence for its risks to human health and its indiscriminate impact on wildlife.

A strong agrochemical lobby

Just when we think we might make some progress in banning the use of organophosphate pesticides, we seem to take another step back.  The agrochemical lobby is strong.  It is big business, as also is the intensive crop farming it supports.

Last year,  the US Environmental Protection Agency (EPA) refused a petition to revoke chlorpyrifos registrations saying there was insufficient evidence to ban it.

The Agency concluded that the science linking its effects on neurodevelopment remains "unresolved".

Indeed, the former EPA Administrator Scott Pruitt said it was “crucial to U.S. agriculture” and to “ensuring an abundant and affordable food supply for this nation and for the world.” 



Let's look at the nature of these pesticides. 

How they work

The German military developed these substances as neurotoxins in World War Two.  They act by interfering with signalling in the brain, and in particular by disrupting the signalling chemical (transmitter), Acetylcholine (Ach). 

Acetylcholine (Ach) is a transmitter involved in the function of millions of neurones (nerve cells) in our brains. It mediates the signals that control our muscles. It also slows our heart rate and controls contraction strength.

When signals are passed between nerve cells, tiny packets of the transmitter are released. The transmitter then acts on receptors in the muscle to cause contraction, or on another neurone to produce nerve signals. This is essentially how cell signalling works in our brains.

The neurones also produce an enzyme that breaks down the transmitter once released, thus controlling the duration of its effect. This enzyme (cholinesterase) is what is targeted by the organophosphates.  They stop the enzyme working.

Accumulation of acetylcholine at the neuromuscular junction causes persistent dysfunction of skeletal muscle, resulting in weakness and fasciculations,  whilst in the brain neural transmission is disrupted.

So, this is how organophosphates can affect our nervous systems, and it is the major reason it is so effective in killing 'pests'.  Such pesticides don't distinguish our brains from those of the pests.  They act indiscriminately on all insects,  'good bugs' as wells as 'bad', and are just as likely to affect other animals.




Little surprise then, with the extensive use of these pesticides, about 20,000 cases of organophosphate intoxication are reported yearly in the USA.

A joint report by the UK Royal College of Physicians and Psychiatrists concluded that a wide range of often-severe symptoms such as excessive fatigue, poor concentration, and suicidal thoughts are reported more frequently in populations exposed repeatedly.

Evidence of harm to health

There is a growing body of evidence documenting adverse effects of organophosphate exposure in general, and chlorpyrifos in particular, especially with low-level exposure in pregnancy and effects on the developing fetal brain.

There is also abundant clinical evidence for the special risk that these substances pose for children. Chlorpyrifos (Dursban) was involved in a negotiated phaseout in June 2000.  We have now gone backwards. The phaseout resulted from recognition of the special risk that these substances posed for children. 

Four percent of patients presenting to poison control centres in the US are the result of pesticide exposure. Of those patients, 34% are children younger than 6 years.

As recently argued in the The Lancet, the precautionary principle of proving chemicals are safe rather than proving their harm might be more beneficial.  A group of experts, on behalf of WHO and the UN Environment Programme (UNEP), published a  report documenting substantial laboratory and human evidence supporting a causative role of  endocrine disrupting chemicals in disease and dysfunction across the human lifespan, including organophosphates.  

Worse in Europe

As much as this article has focused on the USA, the situation is worse in Europe. For pesticides and their use in food crops, US regulations have been more stringent than those in Europe. In particular, the US Food Quality Protection Act of 1996  requires additional safety considerations for children before pesticide use in agriculture is approved, but no such  regulation exists in the European Union, even for pesticides that induce toxic neurodevelopmental effects.

Chlorpyrifos is banned for agricultural use in Sweden, and was effectively banned in the United Kingdom in 2016 following a change in EU regulations.









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