# Presentation: 108590

## Exposure to Organophosphate & Carbamate Insecticides

*Monitoring for Over Exposure*

## 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”*

## 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

## 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

## 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)

## 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

## 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

## 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”

## Cholinesterase Biological Monitoring for OP/Carb Exposure

- 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)?

- No

- Yes

-  **Stop!**

**Cholinesterase Biological Monitoring for OP/Carb Exposure**
- 	        **Clinical Component****	****	****Safety/ Industrial Hygiene ****	****	****	****        Component**

## Cholinesterase Biological Monitoring for OP/Carb Exposure

**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?

- 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.

- 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**

## ACUTE EXPOSURE INCIDENT OCCURS:

**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

## Conclusions

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

## 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