Getting On Our Nerves - Parkinson's Disease

From: Robina Suwol
Date: 20 Jan 2002
Time: 01:01:02
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By Diane Marty, E/The Environmental Magazine,
January 18, 2002

The same herbicides and pesticides many people trust enough to spray on their gardens and crops have been increasingly linked to the onset of Parkinson's Disease (PD), a neurodegenerative disorder that turns the simplest movement into a battle between the brain and the nerves. The first connection was made in the early 1980s, when young people illegally taking an impure form of Demerol (MPTP) exhibited symptoms of an advanced form of this progressive disease. The chemical structure of MPTP resembles that of paraquat, an herbicide. During the past two decades, researchers have continued to explore the associations between pesticides and PD, and some positive correlations have been found. "I was surprised at how accurately rats developed the signs of Parkinson's," said Dr. J. Timothy Greenamyre, a researcher at Emory University.

The rats in the study had been infused with the pesticide rotenone. Because it is often labeled as a "natural" pesticide, many home gardeners feel safe sprinkling rotenone on their tomatoes. Rotenone is also used to kill nuisance fish in lakes and reservoirs and fleas and ticks on pets. In a recent Stanford study, Parkinson's patients were twice as likely to have been exposed to in-home insecticides than those people without the disease. People exposed to herbicides also were more likely to develop PD. A large case-controlled study at the Henry Ford Health System in Detroit, Mich., confirmed that connection. "Contact with herbicides gave people a four times greater chance of developing Parkinson's," said Dr. Jay M. Gorell, head of the Movement Disorders Clinic in the Neurology Department. And people exposed to insecticide were 3.5 times more likely to be diagnosed with Parkinson's disease than people with no history of pesticide exposure.

"The study also searched for a relationship between Parkinson's disease and farming and found it," said Gorell. "Farmers were 2.8 times as likely to have PD as the general population."


More than 1 million Americans have Parkinson's, and every nine minutes another person is diagnosed with the disease. PD is second only to Alzheimer's disease as the most common neurodegenerative disorder in the United States. First described by the English physician James Parkinson in 1817, this condition kills the nerve cells in the brain that release dopamine, a chemical necessary for controlling movements. Normal everyday tasks, such as buttoning a shirt, rising from a chair, or writing a letter, become hardships and eventually impossible. "In order to discover and define cause-and-effect relationships between pesticides and PD, we'll need to be very clever in a couple of ways," said Gorell.

First, coding for genetic variants, analyzing the biochemical actions between pesticides and genes, and calculating the ability of each person's body to metabolize various chemicals will require much more research, innovative models, and precise measurements. "Second, people may or may not be aware of their lifetime history of contact with pesticides," added Gorell. "Experts are searching for ways to quantify past exposures." The weight of heredity is another factor to gauge when studying this disease, although most experts now consider the family tree a significant factor only when studying patients who are 50 years old or younger at the onset of PD. Today, just 10 percent of Parkinson's cases are attributed directly to heredity. Most researchers agree that a sophisticated interrelationship between genetic susceptibility and environmental exposures may hold the key to unlocking the causes of PD. The former remains an illusive quality. But the latter can be measured to some extent.


The Centers for Disease Control and Prevention (CDC) began an ongoing study in 1999 in an effort to calculate the public's exposures to environmental contaminants, including mercury, tobacco smoke, and certain pesticides. By taking blood and urine samples, scientists can monitor the population's contact with chemicals present in the air, water, dust, food, and soil over time. "So far, the results of the initial CDC National Report on Human Exposure to Environmental Chemicals confirm what many people already suspected," said Susan Kegley, staff scientist at Pesticide Action Network North America (PANNA). PANNA works to replace pesticide use with ecologically sound and socially just alternatives. "The general population has contaminant levels exceeding those set by the Environmental Protection Agency (EPA) as safe," she said. Kegley finds the CDC data especially significant because only known ill effects, which usually involve acute poisoning as opposed to chronic exposures, determine EPA guidelines.

The EPA also tests chemicals separately instead of examining combinations of compounds. "The effects of human exposure to more than a single pesticide at one time are not apt to be less harmful," said Kegley. In the meantime, people concerned with limiting their exposure to pesticides should become familiar with both the common and not-so- common ways they come into contact with these chemicals. "Residues on food and home-and-garden insecticides are well-known ways for people to be exposed to pesticides," said Jay Feldman, executive director of Beyond Pesticides (BP), which is committed to pesticide safety and the adoption of alternative pest- management strategies. "But laundry and bathroom products, such as sanitizers and mildew removers, also contain pesticides," said Feldman. "The chemicals commonly used to keep backyard swimming pools clean and clear are laced with pesticides." Institutions and businesses are consumers of these products too. No less than 21 neurotoxins are used in schools. When attempting to calculate their pesticide exposures, people often neglect to consider those elements not in their direct control. "Spraying of nearby agricultural fields or monthly applications by the neighbor's lawn service cause drift that can be a significant source of pesticide exposure," said Kegley.


The irony is that simple and inexpensive strategies can outwit unwelcome intruders. "Sanitation, of course, is always a first course of action," said Feldman. "Maintenance, such as caulking regularly, repairing screens, and eliminating damp spaces, prevents infestations. Outside, flowerpots, leaky gutters, and birdbaths breed mosquitoes and other insects. Removing or repairing these hot spots will reduce resident bugs. And protective clothing circumvents the need for insecticide sprays." "Soap and water discourages many plant pests," said Steve Tvedten, president of Get Set, a company specializing in nontoxic pest control. A quick spray of glass cleaner sends flying insects into a nosedive. Talcum powder obscures ant trails, and razing webs sends spiders scattering. Vacuum cockroaches (for sneak attacks, catch the invaders in a beam of red light) and other bugs. The dust kills them faster than many sprays. In the garden, know your pests and cultivate their enemies.

If those ideas fail, the next step should involve mechanical and low- toxicity products. "Flying insect traps, roach and rodent `motels,' even old-fashioned flypaper, can all lower pesky populations," said Feldman. Bait traps are the next-best method. Diet has a huge effect on the amount of pesticides people ingest. Researchers at the University of Washington in Seattle analyzed the urine of 100 children. "Ninety-nine of the kids had detectable levels of pesticides in their systems," said Kegley. "The only participant with no evidence of exposure ate organic food." She added that if organic foods are not available, take extra care washing those fruits and vegetables known to have higher pesticide residues, including strawberries, pears, grapes, green beans, peaches, winter squash, and leafy green vegetables, especially spinach. "Pesticides have become omnipresent in our rain and air," said Tvedten. "Chemicals used in Africa find their way to Florida in a short amount of time. And our generation has been exposed to more than 500 toxins that our grandparents weren't. Even if pesticides were safe, they're not always effective. If they were, we wouldn't continue to need them. And already, more than one-half of the pests are resistant to poisons." The bad news is we may not be.

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Diane Marty is a Colorado-based freelance writer.
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