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Biomarker for Neuropathic OP Exposure Found As Neuropathies Skyrocket
(Beyond Pesticides, June 18, 2003) Recent research found a new method to detect human exposure to organophosphate (OP) pesticides. Scientists from the Russian Academy of Sciences released a study, "Biosensor detection of neuropathy target esterase in whole blood as a biomarker of exposure to neuropathic organophosphorus compounds," which appeared in the April 11 2003 edition of the Journal of Toxicology and Environmental Health, that looked at the effectiveness of the newly developed biosensor of OP exposure.

Exposure to organophosphates inhibits a protein in the body called neuropathy target esterase (NTE). Historically, human exposure to OPs could be biomarked by looking at NTE activity in the brain hours after OP exposure. In addition, lymphocyte NTE can be used as a biomarker, although it is more limited. The new biosensor is highly sensitive and can be assayed from whole blood, unlike the other methods. To test its effectiveness, researchers dosed hens with O,O-di1-propyl O-2,2-dichlorvinyl phosphate (PrDChVP). After 24 hours, they measured NTE activity in the brain and lymphocytes, as well as the brain and blood. The NTE inhibition in lymphocyte and blood were both highly correlated to NTE inhibition in the brain, suggesting that "the biosensor NTE assay for whole blood could serve as a biomarker of exposure to neuropathic OP compounds."

The study suggests that the biomarker can predict the onset of OP compound-induced delayed neurotoxicity (OPCIDN), and serve as "an adjunct to its early diagnosis." Neuropathy is a common result of OP poisoning. Symptoms of neuropathy include imbalance, tingling sensations, weakness, and severe pain and/or numbness in the limbs. The disease is widespread. A report released in 2001 from The Neuropathy Association, "The Incidence, Characteristics and Costs of Medicare Beneficiaries with Neuropathy," shows that the disease impacts millions of Americans, costing billions of dollars. The report examined 1999 Medicare records and "revealed 3.4 million Medicare beneficiaries with neuropathy accounted for $3.5 billion in claims."

The problem is that many people who suffer from neuropathy are unaware they have the disease. Neuropathy "appears in many different forms and it is believed that certain toxins and chemicals are among its causes," said Dr. Norman Latov, director of The Neuropathy Center of Weill Cornell Medical College and medical and scientific director of The Neuropathy Association. "Neuropathy may be the most prevalent undiagnosed and often untreatable nerve disease known to medicine today."

Public knowledge of neuropathy, as well as its connection to organophosphate pesticide exposure, is limited. This is detrimental to public health protection, considering the widespread use of OP pesticides. In 1999, EPA's Office Pesticide Programs, Health Effects Division, reported that four OP pesticides, phosmet, proetamphos, chlorpyrifos, and dimethoate, had consistently high rankings in being responsible for symptoms, health care facility visits, hospitalizations, and fatal outcomes in adults and children. These four OP pesticides are responsible for 90% of pesticide exposures reported in children under six to the Poison Control Centers around the country from the 1993-1996. The report also stated that "children, under six exposed to organophosphates, were three times more likely to be hospitalized, five times more likely to be admitted for critical care, and four times more likely to have experienced a major medical outcome or death, than if exposed to some other, non organophosphate, pesticide."