Decision on the New or Revised Occupational Exposure Limits for 2010

Background:

Each year, the American Conference of Governmental Industrial Hygienists (ACGIH) publishes a list of substances for which they have set new or revised Threshold Limit Values (TLVs). Three categories of TLVs are specified: 8-hour time-weighted average (TWA), short-term exposure limit (STEL), and a ceiling (C).

At their March 2010 meeting, the Board of Directors (“BOD”) approved a new occupational exposure limit (“OEL”) review and adoption procedure.  Under the new procedure, WorkSafeBC reviews the scientific data and the availability of validated sampling methods, and consults with stakeholders on potential implementation issues prior to the adoption of the annual new or revised ACGIH TLVs. Until the BOD makes a decision on which of the annual new or revised ACGIH TLVs are adopted as BC OELs, the existing OELs for these substances continue to be in effect.

Board of Directors' Decision:

At the March 2011 meeting, the BOD provided their decision on the 2010 new and revised ACGIH TLVs for 11 substances.

The BOD decided to adopt the ACGIH TLVs as BC OELs for cotton dust, methyl isobutyl ketone, and thallium and soluble compounds as Tl. Effective June 1, 2011 these three substances will be removed from the Table of OELs for Excluded Substances in Policy R5.48-1, and the ACGIH TLVs will be assigned as BC OELs as follows:

 

Substances WorkSafeBC Occupational Exposure Limit
  8-hour Time-Weighted Average Limit Short-Term Exposure Limit Ceiling Limit
Cotton dust, raw 0.1 mg/m3 (thoracic fraction)    
Methyl isobutyl ketone 20 ppm    

Thallium and soluble compounds as Tl

0.02 mg/m3 (inhalable fraction)  75 ppm  

The BOD decided to maintain the following substances on the Table of OELs for Excluded Substances with no changes to their respective limits:

 

Substances WorkSafeBC Occupational Exposure Limit
  8-hour Time-Weighted Average Limit Short-Term Exposure Limit Ceiling Limit
Citral, inhalable No previous limit No previous limit No previous limit
Dieldrin 0.25 mg/m3    
Thionyl chloride     1 ppm
Cresol, all isomers 10 mg/m3    
Portland cement 10 mg/m3  (E,N);
3 mg/m3  (respirable)
   
alpha-Methyl styrene 50 ppm 75 ppm 100 ppm
Hydrogen sulfide     10 ppm
Oil mist, mineral, mildly refined 0.2 mg/m3    
Oil mist, mineral, severely refined 1 mg/m3    

The reasons for the BOD decision for the above substances are as follows:

  • There are no validated sampling methods for citral, dieldrin, thionyl chloride, and cresol, all isomers. There will be on-going monitoring of the availability of a validated sampling method for each of these substances.
  • Hydrogen sulfide, alpha-Methyl styrene and Portland cement were identified as having both sampling and practicability of implementation concerns. Follow up activities are planned to resolve the implementation issues.
  • The ACGIH TLV for mineral oil excluding metal working fluids was not adopted because the current BC OELs for oil mist, mineral, mildly refined and oil mist, mineral, severely refined are more protective, and include metal working fluids.