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*                        INFORMATION ALERT                          *  
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*  Produced by:  Saskatchewan Human Resources,                      *  
*                Labour and Employment                              *  
*  Provided by:  Canadian Centre for Occupational Health and Safety *  
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MEDICAL MONITORING OF WORKERS EXPOSED TO ORGANOPHOSPHORUS PESTICIDES  
  
  
*** MODE OF ACTION:  ***  
  
  Organophosphorus pesticides kill target insects, ticks, and mites by  
  inhibiting the activity of the enzyme acetylcholinesterase.  This  
  results in death by asphyxiation.  Unfortunately, these insecticides  
  can have a similar effect on warm blooded animals, including man.  
  They are readily absorbed through breathing of vapour, ingestion, or  
  skin contact.  
  
  
*** REGULATION:  ***  
  
  Section 67 of 'The Occupational Health and Safety Regulations'  
  requires the employer to take all practicable steps to prevent harm  
  to workers as a result of exposure to a substance.  Biological  
  monitoring is the only means of ensuring that the exposure to an  
  organophosphorus pesticide is not excessive.  The following  
  recommendations are intended to assist in the monitoring of exposure  
  and identification of harmful effects.  
  
  
***  SYMPTOMS:  ***  
  
  The continuing daily absorption of organophosphorus pesticides at  
  intermediate dosage may cause an influenza-like illness characterized  
  by weakness, anorexia and malaise.  Headache, dizziness, weakness,  
  incoordination, muscle twitching, tremor, nausea, abdominal cramps,  
  diarrhoea and sweating are common early symptoms.  
  
  Blurred or dark vision, confusion, tightness in the chest, wheezing,  
  productive cough and pulmonary edema may occur.  Incontinence,  
  unconsiousness and convulsions indicate very severe poisoning.  Slow  
  heartbeat, salivation and tearing are common syptoms of severe  
  poisoning.  Toxic psychosis, with manic or bizarre behaviour, has led  
  to a misdiagnosis of acute alcoholism.  
  
  
*** BIOLOGICAL MONITORING:  ***  
  
  Changes in cholinesterase levels can provide an estimation of  
  exposure.  Both plasma (pseudo) cholinsterase and erythrocyte (true)  
  cholinesterase activities are affected.  There is, however, a large  
  variation in normal levels from one individual to another.  It is  
  essential then, that workers who are to be monitored have at least one  
  pre-exposure estimation of both plasma and erythrocyte cholinesterase  
  activities.  This will provide a baseline against which future  
  estimations can be compared.  
  
        RECOMMENDATIONS FOR A MONITORING PROGRAM  
  
        Workers who have only sporadic exposure (a day or two at a time  
        several times a year) should not require routine monitoring of  
        cholinesterase.  
  
        Workers who will have continuous exposure should have plasma  
        (pseudo) cholinsterase determinations monthly.  It could be  
        useful, however, to test more frequently (every ten days) at  
        the beginning of a new operation in order to evaluate the  
        soundnesss of the work procedures followed.  
  
        A reduction of 25% or more in pseudocholinesterase levels is  
        strong evidence of excessive absorption.  If a medical  
        examination reveals other signs and syptoms of overxposure, a  
        physican may decide to temporarily remove the worker from  
        exposure.  A reduction of 50%  from base line is usually  
        accompanied by syptoms and is indication for immediate removal  
        from exposure.  
  
        Weekly checks of the enzyme level should be made until the  
        cholinesterase activity returns to at least 75% of normal.  This  
        level in the absence of other signs and symptoms would permit  
        a person to resume working with the pesticide.  It is of course  
        important to examine the work procedures of that person to  
        eliminate the causes of exposure.  
  
        Depression of pseudocholinesterase levels usually persist for  
        several days to a few weeks.  The erythrocyte ezyme activity  
        remains depressed longer, sometimes 1-3 months and would be an  
        appropriate measurement following severe illness.  Plasma  
        cholinsterase levels can also be suppressed by some medications  
        and by liver disease.  
  
  
*** HOW CAN TESTING BE DONE:  ***  
  
  5 ml of heparinized whole blood is requried per sample.  Arrangements  
  should be made with the Provincial Laboratory (Dr. H.E. Robertson  
  Laboratories) in Regina for the analysis of samples and the reporting  
  of results back to a physician.  
  
  
Bulletin TU 17, July 1990  
  
  
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