Parkinsonís disease and the environment: Review
Parkinson Disease (PD) is not caused by a specific reason (as poliomyelitis); it is a product of the interaction between aging, genetic factor sensitivity and other environmental causes1.
Parkinson Disease (PD) usually appears around the age of 50, although most doctors believe its age of onset is between 58 and 61 years. Research conducted in the 20's and 30's, shows that 12% of the patients had the disease when they were 50 years old.
PD is rather due to aging, but some scientists believe it is responsible for the acceleration of aging. It has also been proven that the characteristic trauma caused in the brain by PD, induces cell decoloration in the pedicle area (substantia nigra). It is those same cells that produce dopamine (a neurotransmitter, which transfers messages from one brain cell to another). The term "decoloration" has resulted in confusion. It does not mean that single cells lose their pigment or that this pigment cannot be composed. It simply means that there are less stained cells, which remain in those areas. Some of them are dead and their pigment has been removed.
The cause of death of these cells is a mystery that must be solved in PD. In the aging process, more and more pigment, known as neuromelanine (which is decolorated by dopamine), tends to accumulate in the cells of the pedicle cerebral area.
Approximately one million Americans currently suffer from PD. Symptoms include slow movement, tremor during rest and muscle rigidity during walking. It is possible that these symptoms are due to the progressive cell death and most probably of the melena substance followed by the loss of dopamine (neurotransmitter)2.
Exposure to external factors, as well as knowledge of environmental causes of this disease and co-existance of other diseases are all considered necessary. The interaction of all the above together with genetic sensitivity or heredity, can give us important information about the kind of PD.
Scientific research shows that natural toxins found in the environment could play an important role in the development of this brain disorder and the transfer or weakening of cerebral cells. Those toxins are found in pesticides like paraquat3,4.
In addition, heavy metals like lead, copper and iron increase the risk of PD, as it has been shown by research. NIEH scientists found out that exposure to an agricultural mixture (paraquat and maneb) reduced activity, increased dopamine, and reduced other dopamine influence factors at much greater levels than the same chemical substances would have it they were apart and treated as such6.
The experiment carried out by the same scientific society, NIEH, which examined some people who were exposed to heavy metals while at work, proved that the risk of developing PD is much greater in multiple exposure than it is in one5.
In that case, the combined mixtures that created the conditions for the development of PD were the ones of lead, copper and iron.
Interestingly enough, there are some environmental factors like smoking and antioxidant diet that inhibit the appearance of PD and reduce the risk of onset.
To sum up, the expression of PD can be attributed to four main reasons: sensitivity, environmental exposure, the age of the individual and his/her genetic identity.
Key words: Parkinsonís disease, environment, toxicity.