exposure to organophosphate & carbamate insecticides monitoring for over exposure
TRANSCRIPT
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Exposure to Organophosphate & Carbamate Insecticides
Monitoring for Over Exposure
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Principles of Monitoring
Detect organophosphate [OP] or carbamate [Carb] exposures before employees get sick
Based on OP/Carb inhibitory effects of the enzyme- cholinesterase
OPs effects are long term - “irreversible” Carbs effects are shorter term -
“reversible”
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Mechanism of Action
Inhibits Cholinesterase– enzyme responsible for
hydrolyzing acetylcholine to choline
– choline reabsorbed and acetylated ( + = )
Enzyme inhibition leads to excess accumulation of acetylcholine at nerve synapse or neuromuscular receptor
Nerve Ending
Neuromuscular Junction
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Health Effects from Overexposure
Cholinergic stimulation– SST: salivation, sweating, tearing– blurred vision (miosis)– nausea/vomiting, abdominal pains,
diarrhea– chest tightness, wheezing
Nicotinic stimulation– muscle twitching, tremors– weakness– anxiety, irritability
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How is Biological Monitoring Possible? Presence of cholinesterase enzymes in
RBCs and Plasma– reflect what may be happening in nervous
system and muscles Lab methodologies prevalent “Simple” blood test (but it’s not too
simple)
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Factors for Adequate Monitoring
Great variability between individuals & within the same individual
Use two unexposed specimens to average baseline (1-2 weeks apart)
Generally ignore Laboratory “Normal Range”– Individual serves as own baseline b/o great variability
Using same lab, same methodology Cooling down specimens quickly & expeditious
processing– inhibition of enzymes can be reversible, esp. Carbs,
resulting in false negatives
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Plasma vs. RBC Cholinesterase
Plasma Cholinesterase– aka serum, pseudo- or
butyrylcholinesterase
– quick fall and quick recovery after exposure
– 0.03-3.0% genetic deficiency in population
• False “low” reading• can cause panic• not at > risk from
exposure however
RBC Cholinesterase– aka acetylcholinesterase
– slower to fall and recover post-exposure
– no known genetic deficiency
– good for non-acute exposure monitoring
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Using Cholinesterase Activity to Assess Toxicity
Correlation between depression of activity and health effects
At > 25% inhibition, occurrence of adverse effects rises quickly - “slippery slope”
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Does employee have potential for exposure to organophosphates (OP) or carbamates (CARB)?
No Yes Don't Know
Obtain Safety / Industrial Hygiene input before proceeding. See partial list of
commonly used OPs and CARBs (attached)
Stop! Establish Baseline Levels:• Before job assignment or reassignment
to job with potential for exposure• In lieu of this, make sure employee is
free from potential exposure for > 4 weeks
• Obtain first set of RBC and Plasma Cholinesterase levels
• Approximately one week later, obtain second set of RBC and Plasma Cholinesterase levels
• Average both sets – this establishes employees baseline.
• Baseline data should be readily available to employee and supervisory personnel in the event of an acute exposure.
Does employee have potential for exposure to organophosphates (OP) or carbamates (CARB)?
NoYes
Stop!
Cholinesterase Biological Monitoring for OP/Carb Exposure
Clinical Component Safety/ Industrial Hygiene Component
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Monitor Periodically:• Frequency Dependent Upon Exposure (for
example)• Pesticide Applicators – monthly• Seasonally, Biannually or Annually for others• Assessment requires Safety input• For most instances, RBC cholinesterase levels
only need to be obtained• Exceptions: Phosdrin (mevinphos); chlorpyrifos:
require plasma cholinesterase levels
Drop in cholinesterase levels > 25% baseline?
YesNo
Continue monitoring • Remove from Exposure• Notify Safety / IH Office• Repeat levels in 1-2
weeks, under guidance of Occupational Medicine Professional
• Return to duties once employee recovers and Doctor/Safety deems okay.
Notify Safety / IH office to investigate work site and assess potential for excessive exposure
Cholinesterase Biological Monitoring for OP/Carb Exposure
Clinical Component Safety/ Industrial Hygiene Component
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ACUTE EXPOSURE INCIDENT OCCURS:Spill, Leak, Breakdown in Engineering, Personal Protective
Equipment, or other sudden event which leads to unequivocal employee exposure
Does employee have any symptoms or did employee require any decontamination
procedures (shower, partial wash, eye wash, etc.)? [See below for list of symptoms of acute
exposure]
Yes to either No to each
Transport immediately toEmergency/Urgent Care Center:• Evaluation by health
professional• Draw RBC and Plasma
cholinesterase levels• Treatment as needed
Counsel employee to seek medical attention immediately if any symptoms develop (review symptoms with employee)
Arrange for testing for RBC and Plasma cholinesterase levels within 24 hours
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Conclusions
Establish adequate baselines– RBC and Plasma Levels
Identify genetically “low” plasma cholinesterase levels
Use similar lab/methodologies Process and Cool Specimen quickly
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Conclusions (cont’d)
Look for >25% Depression– only when employee works with
organophosphate or carbamate insecticides
– use RBC only, with notable exceptions (mevinphos; chlorpyrifos)
Check plasma cholinesterase under acute exposure circumstances