The NeuroScope system was used by scientist to discover that sheep dips damages brain at low levels
-May 29, 2000
-By environment correspondent Alex Kirby
UK researchers have found evidence that chemicals used by many farmers can damage the nervous system after years of apparently innocent use.
The chemicals are organophosphates (OPs), used for treating sheep against parasites.
Most government testing for OP poisoning has been on patients who had suffered acute exposure.
The researchers say they have found that significant damage occurs after long-term low-level exposure to the chemicals.
Their work is reported on BBC Radio 4's programme Farming Today, which says one crucial factor is the discovery that chronic OP poisoning leaves a unique "fingerprint".
OPs, thought by some to cause brain damage, skin disorders and premature death, were withdrawn last December until containers became available which would minimise exposure to the chemicals.
But there is pressure for them to be put on sale again as soon as possible.
Farming Today interviewed Dr Peter Julu, senior research fellow in neurophysiology at Imperial College, London.
He has seen more than 60 patients with OP poisoning, and has analysed the results from 40 of them. His special concern is the autonomic nervous system, the nerves that control the heart, lungs, brain and skin.
The programme says Dr Julu has found a pattern of damage to nerves that affect the blood supply, and nerve damage to the major blood vessels which regulate heartbeat.
Lack of blood
He told Farming Today: "The patients lack the capacity to increase or decrease their heart rate according to demand.
"Therefore they feel fatigued. They are not receiving enough blood to meet the demands they are making.
"I examined one farmer who had stopped using OPs more than five years ago, and he still showed this distinctive pattern of damage."
The programme also spoke to Dr Sarah MacKenzie-Ross, a clinical neuropsychologist at University College, London.
She has examined 20 patients diagnosed with OP poisoning, most of them farmers but some who were truck drivers delivering the chemicals, or chemical factory workers.
She said: "All bar one of the people I've seen have a significant verbal memory impairment. This means they have difficulty learning new information when it is verbal as opposed to visual in nature.
"They have really quite significant memory difficulties, and these problems are not only distressing for them but are actually making it difficult for them to carry on working."
Memory problems missed
Problems Dr MacKenzie-Ross found included reading, reduced mental flexibility, difficulties in processing information, and severe mood swings.
She said all were consistent with damage to the sub-cortical region of the brain, something she believed had not been identified in earlier research.
And she expressed concern that memory problems had not been identified earlier as a common feature of long-term OP exposure.
"The previous studies which looked at people with chronic low-level exposure had not found evidence of particularly significant memory impairment. I wasn't anticipating finding it."
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