Scientific Uncertainty is the Root Cause of the RBOEL Controversy

Uncertainty drives us; indeed, the reality is that we do not understand what changes are or are not occurring at the tissue level in human beings as a result of their exposure at current OELs. 

 

Using the traditional OEL-setting method of toxicological point of departure (POD) divided by a modifying (safety, uncertainty, adjustment) factor, experts can say that from the available toxicological data their best opinion is that “nearly all” exposed worked are or will be protected at this specific level of exposure (i.e., the OEL).   Those of us who advocate risk based OELs (RBOELs) can say that by using a model or models with stated assumptions there is a range of quantitative risk estimated at the OEL.  

In the current method (POD/SF) the quantitative level of uncertainty is essentially unaddressed, with RBOELs it is out in the open and explicitly indicated.   Indeed, this distinction may lie at the heart of why RBOELs (particularly for non-carcinogens) have not gained any traction within our profession.

It does not take a genius to predict that, using most currently available data, an RBOEL at a target risk of 1 in 1000 at will have a large error band; that is, a large range of risk exists around that 1 in 1000 prediction.   Even more potentially troubling, the risk range predicted using this methodology with many, if not most, of the data associated with current OEL values will be quite high when viewing the top of any reasonably constructed error band.

So what might be done to fix this admitted difficult situation?   I have always thought that the solution to large error bands was confident scientific knowledge.   In this case it would be knowledge of what is actually happening at the human tissue level in target organs during exposure at the OEL.   My sense is that this will only happen when we apply the science of molecular/genetic biology to the questions at hand.  In the past 10 years there has been an explosion of this type of research; unfortunately, I do not know of any specific application of this type of research to our questions today regarding OELs.    Indeed, these scientists in general do not come to our conferences around exposure assessment and even toxicolgoy and, as far as I can tell, there is little relevant interdisciplinary activity in this area.

The bottom line today is that we are all people of good faith working in the trenches to do the best we can with the data we have.  In general, we are forced to deal with this situation without the power to feed the process what it needs most; namely, research resources (spelled M-O-N-E-Y) and data.  The individuals with the real power to allocate or otherwise control the resources to be applied to the entire problem do not have the specific task of setting OELs.   They appear to have a lot on their plate and one of their primary motivations seems to be cost control.  Perhaps, we have simply failed to sell it or indeed, we ourselves also may not realize there is a problem.

For the most part these decision makers are probably satisfied with the current system; however, I personally am not.  In my opinion, using the current system we are most likely adequately controlling most of the risk to worker health from exposure.   The fact remains, however, that we are being surprised at a fairly predictable rate with dangers we failed to address as we were with popcorn fragrance.   Over the years we have been repeatedly “surprised” as the vast majority of OEL changes have been in the direction of significant reduction.  

 

When problems relative to any OEL being too high find us, it is too late for those adversely effected and we as risk assessor or risk manager have failed.    Given this history, I am convinced that there are exposures around current OELs that are ultimately causing adverse health effects in workers.   How much danger is out there and how important it might be to proactively address it is a matter of personal perspective.    I believe that there is currently enough danger and opportunity to avoid adverse health effects to spur us to do better.

The use of RBOELs could be seen as the first step in improving the system.   My sense is that exposing the uncertainty around the estimated quantitative risk at OEL (RBOELs) will drive getting more data as the stakeholders in the process first see these numbers and then confront this scientific and political reality by addressing the uncertainty with more resources and data.