Exposure to Organophosphate

1
Exposure to Organophosphate Carbamate
Insecticides

• Monitoring for Over Exposure

2
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

3
Mechanism of Action
Nerve Ending

• 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

Neuromuscular Junction
4
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

5
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 its not too simple)

6
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

7
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 gt 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

8
Using Cholinesterase Activity to Assess Toxicity

• Correlation between depression of activity and
  health effects
• At gt 25 inhibition, occurrence of adverse
  effects rises quickly - slippery slope

9
Cholinesterase Biological Monitoring for OP/Carb
Exposure Clinical Component Safety/
Industrial Hygiene Component
Does employee have potential for exposure to
organophosphates (OP) or carbamates (CARB)?
Obtain Safety / Industrial Hygiene input before
proceeding. See partial list of commonly used
OPs and CARBs (attached)
No
Yes
Don't Know
Does employee have potential for exposure to
organophosphates (OP) or carbamates (CARB)?
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 gt 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.

No
Yes
Stop!
10
Cholinesterase Biological Monitoring for OP/Carb
Exposure Clinical Component Safety/
Industrial Hygiene Component

• 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 gt 25 baseline?
Notify Safety / IH office to investigate work
site and assess potential for excessive exposure
Yes
No
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.

11
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 to
• Emergency/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
12
Conclusions

• Establish adequate baselines
• RBC and Plasma Levels
• Identify genetically low plasma cholinesterase
  levels
• Use similar lab/methodologies
• Process and Cool Specimen quickly

13
Conclusions (contd)

• Look for gt25 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