Exposure to pesticides linked to long-term brain damage

Study draws link between low-level exposure to organophosphate pesticides - the most widely used insecticides in the world - and long-term brain damage.

A long-running campaign to highlight the health impacts of a dangerous chemical, used by farmers around the world, has been vindicated by the conclusions of a major new study.

The findings, confirming a link between use of organophosphate pesticides (OPs) and long-term brain damage, could have global significance, particularly in many developing countries where adequate protective measures are lacking.

Campaigners in the UK have been fighting for more than two decades to raise awareness of the issue. Several hundred farmers in the country are believed to have suffered debilitating health problems from exposure to OPs. A large number of them were sheep farmers, following government orders in the 1980s and 90s to treat their animals with the chemical to protect against the spread of a disease called sheep scab.

Other groups known to have been affected include military veterans from the Gulf War who were exposed to pesticides used to protect them from pests and mosquitoes, and airline pilots and cabin crew, who can be exposed to organophosphates in engine oil.

Derived from World War II nerve gas agents, organophosphate pesticides are the most widely used insecticides in the world. While high-level exposure to the chemicals has long been known to be dangerous, low-levels of exposure of the kind experienced by farmers spraying the chemical or treating animals, was not initially thought to be a hazardous, as governments across the world have promoted a new chemical-dependent era of farming.

However, with growing reports of health problems from the farmers around the UK since the mid-1980s, including more than 600 reports of ill health to an official surveillance scheme, the government has been under pressure to acknowledge that low-level exposure may have caused widespread illness.

Pesticides and brain damage

Now researchers from University College London and the Open University have shown that the type of long-term, low-level exposure many farmers using the chemicals will have experienced produces long-term brain damage.

In the first attempt to review the scientific evidence on the health impacts of OPs, their independent analysis found that 13 out of 16 studies had shown evidence of neurological problems following long-term, low-level exposure to OPs. They included studies from Egypt, India, the UK and US.

The health problems reported included poor memory, reduced reaction time, attention disorders and diminished ability to solve complex problems.

In China, a study funded by the World Health Organization, has also looked at the mental health risks of prolonged exposure to organophosphate pesticides, particularly amongst rural farming communities where suicide rates are 2-5 times higher than those in urban areas.

In the UK, the researchers hope the findings will provide belated recognition to many sufferers still alive today and help others who are unaware their medical condition could be related to the use of organophosphate pesticides.

Peter Dixon, a farmer from the UK, who used OPs throughout the 1980s, 90s and 2000s before suffering worsening health five years ago, said he struggled for many years to work out the reason for his ill health.

"I felt ill, lethargic and weak all the time. My GP couldn’t work out what was wrong with me," he told me.

It was only after visiting a private physician that Peter was told his symptoms were linked to OP poisoning. After detox treatment, he has partially recovered, but believes many farmers may still be suffering without knowing the cause.

For Teresa Layton, whose husband David suffers from multiple sclerosis and relies on her 24-hour care, the findings are scant relief. She claims that proper warnings about the dangers of using OPs were never passed onto farmers like her husband David, who was eventually confirmed as having suffered OP poisoning and which she believes led to his illness.

"Its so frustrating to think of all the things we could have done as a family and with our children which we haven’t now been able to do. And all because of this product that the government and chemical companies knew was dangerous yet let so many peoples lives be ruined.

"Farming is supposed to be such a healthy occupation, outdoors in the lovely countryside and yet there was this dreadful hazard,” she told me. 

In China, the use of pesticides continues to spiral out of control. “If the standard says to use one bottle’s cap’s worth of pesticides then farmers will use three, just to make sure,” Xu Ming, director of the Pollution Prevention Office at the Ministry of Agriculture’s Agro-Environmental Protection Institute, has said.

As well as the environmental impacts of overuse, awareness of the health impact of pesticide exposure is also poor, with Xu Ming pointing out that the certification and monitoring of farmers is badly lacking.

In the UK today, the health and safety procedures are much improved, with farmers required to take a safety course before being allowed to administer the OPs. However, campaigners have long sensed officials have deliberately tried to avoid confirming health impacts for fear of compensation claims from affected farmers.

A former UK farming minister Lord Rooker confirmed as much in a government debate on OPs in 2009 saying, “I do not want to be controversial but ones gets the impression of a natural reluctance of the centre to investigate…Why? Oh, because there are no new cases; because of the issue of compensation; because the science is not quite clear".

Lead-researcher Dr Sarah Mackenzie Ross, from University College London, said she hoped the findings would force the government to reconsider its position.

“This is the first time anyone has analysed the literature concerning the neurotoxicity of organophosphate pesticides, using the statistical technique of meta-analysis.

“The analysis reveals that the majority of well-designed studies undertaken over the last 20 years find a significant association between low-level exposure to organophosphates and impaired cognitive function.”

A UK government spokesperson said they were currently reviewing the evidence on OPs and their link to ill health in humans and could not comment until that review was completed.