Pesticides more dangerous than believed

The Asahi Shimbun
March 12, 2004

Recent studies reveal organophosphates in household pesticides and flame retardants used in building materials and home electrical appliances can cause complex neurological and mental disorders that were not recognized before.

Satoshi Ishikawa, a foremost expert on environmental health and director of the Clinical Environmental Health Center at Kitasato Institute Hospital, explained some typical symptoms in a recent interview with Asahi Shimbun staff writer Yomei Tsuji. Excerpts follow:

Q: Do we come into contact with organophosphates in our daily lives?

A: Yes, they are found in common pesticides that are used extensively in public places-shopping malls, restaurants, schools, hospitals and even on trains-to get rid of cockroaches and control infectious diseases.

At home, organophosphates are found in termite control sprays and tick-control sheets placed under tatami mats. They are also major ingredients of outdoor insecticides and herbicides massively used in agricultural areas and in public and private gardens.

The organophosphates vaporize into the atmosphere, which means everyone inhales them without knowing.

Q: What effects do they have on human health?

A: Most pesticides today are modified to prevent convulsions and other severe acute physical reactioins in ordinary use. Until now, it has been believed that even if you did develop such symptoms, you would recover quickly because organophosphates can be easily broken down and eliminated by the human body.

In reality, however, various kinds of mental and neurological disorders can develop later. When the exposures are repeated, even a trace amount of organophosphate may cause these symptoms over a prolonged period of time.

Q: What are some of the symptoms?

A: They vary from patient to patient, but the most common early symptoms include eye problems, such as defocusing and deteriorating vision, and problems with the autonomous nervous system, such as fatigue, muscle pain, headache, nausea and dizziness.

Next-stage symptoms include mental-emotional disorders, such as depression, emotional instability, lapses in memory and the ability to reason, as well as sleeping disorders.

And some pesticides are known to induce hay fever, asthma and multiple chemical sensitivity.

Q: Could you explain why these conditions occur?

A: To put it simply, organophosphates inhibit the working of various enzymes and wreck the natural biorhythm of mind and body mainly by distorting the neurological function of the brain.

If the working of enzymes is repeatedly inhibited, the body starts reacting even to a minute amount of organophosphate, causing the patient's condition to worsen. One notable feature of the toxicity of organophosphates is that unlike cancer, it is not readily visible.

Where enzyme inhibition is concerned, researchers have traditionally focused almost entirely on its neurotoxic effect of organophosphate-induced inhibition of acetylcholinesterase (AchE). But recent studies in America and Europe have confirmed the inhibition of various types of enzymes including fatty acid amide hydrolase (FAAH), which metabolizes the important signaling substances, endogenous cannabinoid, that regulates brain functions directly. These studies have shed considerable light on the toxic nature of organophosphates.

Q: Is anything being done to regulate the use of organophosphates?

A: Europe and the United States are the leaders in the field. In the United States, cases of organophosphate poisoning were noticeable among veterans of the 1991 Persian Gulf War, and pesticides used at U.S. military camps were thought to be the major cause. This prompted the U.S. government to study the subject, and the Environmental Protection Agency launched a review of organophosphate pesticide control in 1994, following the publication of my paper on the neurotoxicity of these substances.

Around 1970, I published a paper on an outbreak of eye diseases in the city of Saku in Nagano Prefecture. I concluded the main cause of the outbreak was an organophosphate pesticide that was being sprayed from the air.

As ``the eye is the window of the brain, various nerves converge at the eye. I theorized at the time that the pesticide must be causing other neurological disorders as well, but hardly any research was being done on chronic poisoning in Japan back then.

I must say the current regulations in Japan are still too lax. And I am concerned about the health of people in China and other parts of Asia where organophosphate pesticides are being used in growing volumes.

Q: What do you think about plasticizers and flame retardants used in building materials and household electric appliances?

A: Compared to the pesticides, these compounds have the same molecular structure around the phosphorous atom. However, only a little research has been done to report their indoor air contamination and their chronic toxicity. We definitely need to study how each compound affects the brain when inhaled repeatedly over a long period.

Q: What precautions would you recommend?

A: Don't go near places sprayed with organophosphate pesticides. Let plenty of fresh air in your home if you are worried about what your home appliances might contain. If ever you suspect poisoning, see a specialist at once.

The extent of enzyme inhibition varies greatly from individual to individual depending on the person's genetic makeup. This means even if you yourself aren't affected, someone else could be damaged by the organophosphates you use. Children in particular need special protection, since the development of their mental and neurological functions of their brains could be affected.

Satoshi Ishikawa, M.D., has been director of the Clinical Environmental Health Center at Kitasato Institute Hospital since 1998. A graduate of Tohoku University, he received the Jonathan Foreman Award from the American Academy of Environmental Medicine in 1996 for his research on the toxicity of organophosphate pesticides.(IHT/Asahi: March 12,2004) (03/12)


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