Researchers in Britain have discovered that high levels of exposure to some pesticides may be bad for peoples' health.
A team at Aberdeen University say exposure to pesticides could lead to an increased risk of contracting Parkinson's disease by as much as 39% and even low levels of pesticides raised it by 9%.
In Britain one person in every 500 is likely to develop the incurable degenerative brain disease, or a similar illness; the symptoms can include unsteadiness and tremor in the hands or arms, along with difficulties with speech or movement.
In the United States, it is estimated that 60,000 new cases are diagnosed each year, and 1.5 million Americans are currently afflicted by the disease.
The condition usually develops around age 58-65, but 15% of those diagnosed are under 50; it is principally a disease of the elderly and occurs in all parts of the world.
It appears to be more common in people of European ancestry and in rural rather than urban areas; men are affected more often than women.
Other studies too have suggested that exposure to pesticides has been a suspect in some cases, with agricultural workers showing higher rates of the illness.
The Scottish study involved 959 cases of Parkinsonism, a term used to describe people with diagnoses of Parkinson's disease, and other, similar conditions.
All the participants were questioned about their lifetime occupational and recreational exposure to a variety of chemicals, including solvents, pesticides, iron, copper and manganese.
As there have also been suspicions that the head injuries involved in boxing could be linked to Parkinson's, the patients were also asked whether they had ever been knocked unconscious.
The study also included general questions about family health history and tobacco use.
The responses were then compared to those from a group of people of similar age and sex who had not been diagnosed with Parkinson's and it was found that though having a family history of Parkinson's was the clearest risk factor for developing the disease, exposure to pesticides also indicated a clear increase.
People who had been exposed to low levels of pesticides were found to be 1.13 times as likely to have Parkinson's disease compared with those who had never been exposed; those who had been exposed to high levels of pesticides were 1.41 times as likely to be affected.
The researchers also found that people who had been knocked out once were 35% more at risk, while being knocked out on more than one occasion appeared to increase the risk by two-and-a-half times.
The researchers do say however that it was impossible to tell from the results whether the patients had been knocked out after falling as a result of their Parkinson's.
Lead researcher Dr. Finlay Dick, says the study shows that exposure to pesticides, raises the risk of Parkinson's disease and while it does not prove that pesticides cause Parkinson's disease, it does add to the increasing body of evidence that there may be a link.
However the researchers do add that the overall risk of developing the disease is nevertheless relatively small.
The study was funded by the European Commission and is published in the journal Occupational and Environmental Medicine.