Problems and Limits of Occupational Exposure Limits (OELs) and

Threshold Limit Values ( TLVs)

Even though most workplaces are in compliance with current OEL’s, this does not mean there are little or no hazards due to the exposures among Ontario workers. First of all, not all workers will be protected by complying with OEL’s. In fact if one follows the history of OEL’s one will notice a gradual decline in most OEL’s over the years as more evidence of workers experience symptoms and diseases are established. What is to say that an exposure which may be legal now may in the future be considered associated with an occupational disease once the evidence (i.e. affected workers) has been collected and assessed. This has been the pattern in the past and there is little reason to suspect it will not continue. 

The Ministry of Labour has instituted a policy which recognizes that just because exposure assessments demonstrate compliance is no reason to ignore workers symptoms and health problems associated with such exposures. 

The standard of evidence for the basis of some OEL’s is extremely poor by general scientific standards; some merely suggesting limits by analogy or based on animal toxicity experiments despite that fact that thousands of workers are exposed daily to such chemicals.

The limits to OELs and TLVs are explored in depth in a presentation made by OHCOW to Workers Health and Safety (WHSC) instructors. View presentation

New OELs enacted - changes to styrene and formaldehyde.  View ontario regulation 607/05