Cholinesterase ChE Monitoring in Washington State

1
Cholinesterase (ChE) Monitoring inWashington
State

• John Furman, Ph.D., MSN, COHN-S
• 
  
• 
  Thank you to Dr.
  Matthew Keifer

2
Biology of Cholinesterase

• An enzyme
• Produced in tissues and blood
• Hydrolyses acetylcholine
• Present in the autonomic, central and peripheral
  nervous systems
• Excellent web page on the enzyme
  http//www.weizmann.ac.il/Structural_Biology/Pages
  /Sussman/webpage2/kurt/che.html

3
Two Kinds of ChE in the Body

• Different enzymes with some behaviors in common
• Plasma Cholinesterase
• Butyrylcholinesterase, pseudocholinesterase,
  PChE, or just cholinesterase and ChE
• RBC Cholinesterase
• True cholinesterase, acetylcholinesterase, or AChE

4
Pesticides That Inhibit Cholinesterase

• Organophosphates
• Inhibit irreversibly
• aging of complex
• ChE must be replaced by the body
• N-methyl-Carbamates
• Inhibit temporarily
• No aging
• Reversal is rapid and level related
• ChE reactivates and is ready to go

5
Toxicity of ChE Inhibitors

• Mild cases
• tiredness, weakness, dizziness, nausea and
  blurred vision
• Moderate cases
• headache, sweating, tearing, drooling, vomiting,
  tunnel vision, and twitching
• Severe cases
• abdominal cramps, urinating, diarrhea, muscular
  tremors, staggering gait, pinpoint pupils,
  hypotension (abnormally low blood pressure), slow
  heartbeat, breathing difficulty, and possibly
  death
• Extoxnet http//ace.ace.orst.edu/info/extoxnet/

6
Why is ChE Testing Useful?

• ChE reflects the toxicant on its target
• Integrates exposure over time
• The test is widely available
• A blood sample all that is needed
• BUT!
• Baseline is needed
• Good lab methods needed
• Interpretation and timing important
• Sample handling important

7
What ChE monitoring accomplishes ?

• Identifies hazardous conditions/practices
• Increases worker/employer hazard awareness
• Assists in medical return to work
• Avoids problems from chronic exposure
• Influences economic decisions
• - Increases costs of production
• - May influence choice of pesticide

8
Regulatory Background

• 1993 - ChE monitoring recommendation
• 1995 - Tag report
• 2002 - Rios decision
• 2003 - Rule adoption, chapter 296-307-148 WAC

9
When to Test?

• Class I and II Carbamates Organophosphates
• DANGER or WARNING
• LD 50 of lt 50 mg oral or 100 dermal
• LD 50 of gt50 lt500 oral or lt1000 dermal
• Threshold 50 hrs in 30 days

10
Baselines

• Obtain before exposure
• 30 days since last handling
• Maintain records for future comparison
• If its abnormally low
• Recheck, average or discard
• More tests are better than less

11
How Often to Test?

• Retest with the same laboratory, same methods
• Department of Health (DOH) laboratory doing all
  testing through 2005
• Ellman method
• Retesting every 30 days of reaching exposure
  threshold

12
How to Interpret Results

• Large difference between upper and lower range of
  normal
• 20 depression- Significant
• 30 AChE- Removal
• 50 AChE- Poisoning
• 40 PChE- Removal
• 60 PChE- Poisoning
• California, WHO and ACGIH recommendations on
  removal thresholds

13
What Response to Depressed Results

• Act promptly
• Youre already late
• Evaluate for false positives
• Communicate with worker and with employer
• Assure removal if meets threshold
• Be sure the workplace is evaluated

14
False Positives

• Plasma Cholinesterase
• Drugs therapeutic and recreational
• BCPs, metaclopramide, cocaine? INH
• Liver Disease-alcoholism
• Congenital Deficiency (3)
• Pregnancy
• Nephrotic syndrome
• Carbon disulfide, organic mercury
• RBC Cholinesterase
• Drugs and Reticulocytosis

15
Medical Removal

• Remove from all exposure to class I II OPS and
  CBs
• Medical removal protection benefits
• Up to 3 months for each occurrence
• Return to handling when ChE levels return to
  within 20 of baseline

16
Industrial Insurance

• No effect on industrial insurance system
• Associated symptomology must be present
• Pesticide illness reporting

17
Surveillance

• DOH conducting all testing
• Cholinesterase Monitoring data System (CMDS)
• Data Sharing agreement with LI

18
Program Status as of 5/3/04

• Employers
• Employees 2600
• Periodic tests 345
• Significant depressions
• Employees 82
• Employers
  27
• Work removal 20

19
Rule Evaluation

• Stakeholder committee
• Scientific team
• Legislative requirements
• Annual reports
• Correlation of handling hours with test results
• Reimbursement of clinical costs
• Data gathering

20
Challenges

• Medical provider resources
• Consistent laboratory methodology
• Test validity
• Greater than expected affected population
• Timely reporting
• Surveillance
• False positives

21
Questions ?

• John Furman
• Department of Labor Industries
• WISHA Services
• 360-902-5666
• furk235_at_lni.wa.gov