Sunday, November 2, 2014

Looking for lost keys under a street-light

This statement sums up what a lot of us fall prey to; namely, seeking solutions where the looking is easy rather than striking off into the darkness for the true answers.

A real-world example in the world of Industrial Hygiene might be the situation where there is a continual occurrence of workers with symptoms of chemical overexposure.   The “street-light” approach here would be to determine what chemicals are present within the workplace and then monitor the breathing zone of the workers for the chemical.   In many, perhaps most, cases an overexposure is detected and then controlled and the problem solved.   The “easy” and obvious approached worked.

To stretch the analogy further, street-lights are positioned with a purpose.   They are designed to illuminate spaces that we need to see.  Thus, looking under street-lights for solutions is a good place to start.

In some cases, however, the solution does not reveal itself so readily.   You monitor and monitor, compare the results to all your OELs and nothing presents itself as (to steal another phrase) a “smoking gun.”   In this situation, the easy “street-light” approach has failed you and you need to strike out into the dark.   What to do?

It is now time to bring out the scientific method
  1.        State the problem
  2.        Form a hypothesis as to cause
  3.        Experiment and Observe
  4.        Interpret the Data
  5.        Draw Conclusions and Make Predictions

IF 5 does not work out, THEN you need to go back to step 2.

You can do this on a number of levels.   Perhaps the simplest level you can do it is as a thought experiment.   That is, form a hypothesis and run it through the Hill Criteria of Causation that was the subject of a previous blog.  Just go to:  and expand the “September” link to the right and then click on “The Hill Criteria of Causation” to see a detailed discussion of this important tool.   When you do this consider all of the available data and circumstance to see how good the fit is of your hypothesis to reality.   If it does not fit very well go to step 2 and form another hypothesis.    Just “rinse and repeat” until a coherent picture starts to emerge.

Giving the above problem a number of hypotheses are possible.  Here are a few that I thought of but there are almost certainly others:

   1.   You are measuring the wrong agent:
Perhaps a chemical you did not consider or perhaps it is a biological agent that is causing the problem.  It could be an agent, not directly associated with the operations, occurring in the ambient environment of the workers.

2    You are measuring air and dermal is the primary route of exposure:

    High MW, high Kow compounds will not be in the air as much as they might enter the body unmeasured through the skin.

3.  You are measuring to an 8 hour time-weighted average exposure and very short acute exposures are causing the problem which are not showing up as an over-exposure to an 8 hour OEL.

4.  The workers are lying or "faking it" to get out of work

5.  The effected workers are extremely sensitive; that is, “hypersusceptible” and will react to very low concentrations of chemicals in their workplace environment

On the face of it and without data, any of these could be true, it is up to you to figure out which one is the best fit to the facts at hand and then get as much data as you can or do some experiments to prove it.   Indeed, it is incumbent upon you as the IH to sort through the various hypotheses in a concerted effort to really nail down the cause of the adverse health effects of workers in your charge. 

What you do not want to do is “fall in love” with any particular paradigm designed to evaluate the risk of chemical exposures in the workplace.   You do not want to insist that you have done everything you can to find the answer and that there really is no problem because you cannot find it.  You owe it to your workers and yourself to really look into what they say is happening to them relative to adverse health effects at work.  I have found most workers to be honest witnesses to what is happening to them and their coworkers.   You need to listen carefully to what they are telling you and, unless you are sure that #4 is occurring in this situation, you need to give credence to their accounts.

 If you fail to do the above, if you continue to turn the handle on a paradigm that is not showing you what is happening, you may be guilty of futilely “looking for your lost keys under a street-light”.

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