The New Straits Times, March 18, 2001
By Professor Dzulkifli Abdul Razak
LAST June, the Parkinson Foundation of Malaysia did a road show to explain about the disease to the lay public. Poison Control wholeheartedly supported the effort to make more people aware of the disease and take informed initiatives to retard its onslaught.
Moreover, Parkinson’s disease is highly treatable, and heightened public awareness and participation could make a difference in controlling its spread.
In the column then, a link between Parkinson’s and the use of pesticides were mentioned in a study done by researchers in Stanford University (Poison Control, NST, June 18, 2000). To what extent pesticides are implicated as a possible cause is still questionable.
Since then, in the last six months, at least two independent studies have reported further linkages between pesticides and Parkinson’s disease, albeit these studies involved animals.
They, do, however sound sufficient warning of the potential hazards of pesticides beyond what is already known. One study appeared in the Journal of Neuroscience, and another in Nature Neuroscience.
In view of this, the recent announcement by the Ministry of Health that vegetables sold in the country have reduced pesticides contaminants must come as a relief to every Malaysian.
This is because for a long time Malaysians have been reading reports that locally grown vegetables can’t be exported allegedly due to high levels of pesticides.
This invariably raises some doubts as to the safety of vegetables sold locally. This doubt is even more justified now, given the two recent studies linking certain pesticides to Parkinson’s disease, a condition in which a special brain chemical called dopamine falls to an extremely low level.
This could be traced to the loss of dopamine-containing cells found in certain parts of the brain. It is a degenerative disease that could be due to various factors, and pesticide is suggestive as one of them.
This degenerative disease strikes about one per cent of all people over 65, including celebrities like Muhammad Ali and Michael J. Fox.
It is characterised by trembling of the hands, muscular immobility, leading to lack of co-ordination and difficulty of movement including speaking and swallowing.
The disease is also known to develop in animal species like mice, rats and monkeys when treated with certain chemicals, for example MPTP. This chemical disrupts some processes in brain cells, producing Parkinson’s-like signs and symptoms.
Similarly, the studies that appeared in the Journal of Neuroscience reported that in mice injected with a herbicide, Paraquat, and a fungicide, Maneb, showed brain damage identical to humans suffering from Parkinson’s.
The finding reinforces the link between pesticides and Parkinson’s. It seems exposure to a mix of two crop-treating chemicals used in farming can cause the disease, as revealed by researchers from the University of Rochester.
In addition, an agricultural map in the US shows a good correlation between places where these chemicals are spread on crops and areas where people are more likely to die of Parkinson’s.
The study found that farmers, rural dwellers, and people who drink well water were also more likely to have the disease than people who do not.
In the other study that appeared in Nature Neuroscience, scientists from Emory University in Atlanta reported that degeneration occurred in dopamine-containing nerve cells in the brain area called substantia nigra when pesticides are used.
This time laboratory rats injected with a pesticide, Rotenone (a plant-based insecticide) developed Parkinson’s-like signs and symptoms and even brain damage. Like many other pesticides, Rotenone is said to inhibit some cellular enzyme(s), to exert an effect that mirrors Parkinson’s in humans.
The rats developed clumpy proteins, called Lewy bodies, in the brain area and also suffered some of the characteristics Parkinson’s symptoms.
"The results indicate that chronic exposure to a common pesticide can reproduce the anatomical, neurochemical, behavioural and neuropathological features" of the disease claimed the researchers.
Though there are still many questions remain unanswered, researchers are worried about the implications of the study especially with respect to misuse or abuse of pesticides.
As one of the researchers remarked: "In the real world, we’re exposed to mixtures of chemicals everyday. There are thousands upon thousands of combinations; I think what we have found is the tip of the ice-berg."
For Malaysia where the use of pesticides are widespread and at times controversial, it is time to take stock of the situation before the nation is immobilised by Parkinson’s.
Like the vegetables, people must also undergo periodic health checks so that they themselves do not turn into vegetables when their brains are damaged by Parkison’s, linked to the use (and misuse) of pesticides, namely Paraquat.
