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”

Neuromuscular Junction 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

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 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 > 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. Yes No Stop!

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

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