Saturday, May 30, 2015

Risk Assessment and the American Industrial Hygiene Association

The American Industrial Hygiene Association has made great strides in the realm of human health exposure and risk assessment in the last 20 years or so.   I had frankly not thought of it in this manner but it became obvious to me when a friend and colleague, Dr. Jack Hamilton (Bostik, Inc) mentioned this happy fact during a recent visit I made to his workplace.

Jack is a toxicologist with a strong technical background in risk assessment.  When I started explaining the various tools for Industrial Hygienists that have been developed by AIHA volunteer groups, he made what is now an obvious but dramatic point; specifically, the AIHA has made substantial and dramatic advances in the practical development of human health exposure assessment.

The annual American Industrial Hygiene Conference and Exposition is happening this week in Salt Lake City.  Given Jack’s comment and my new found appreciation, I thought I would outline what I see as the highlights of these offerings.   The following is a partial cut and paste from the Exposure Assessment Strategies Committee web site:

TOOLS (For the Practicing Industrial Hygienist)


The following software tools provide the practicing industrial hygienist with quick and easy access to the information necessary to evaluate exposure profiles and determine if the exposures are acceptable, not acceptable or if more data is needed to make the determination of acceptability. The tools are all free and are regularly updated. Several are available in multiple languages.   
·         New IHSTAT /  IHSTAT Macro Free Version: Excel applications that calculate a variety of exposure statistitics, performs goodness of fit tests and graphs exposure data. Multiple languages available.  
The links below will show you how to adjust the macros settings in your version of Excel, if needed  
  •  IH MOD: Includes mathematical models for estimating occupational exposures. Multiple  Languages   Click on this link for IH MOD General Help 
  • IH SkinPerm: Excel application for estimating dermal exposures. Factors in evaporation and
    absorption. The manual for IH SkinPerm is available separately.    


These free software products represent literally thousands of volunteer hours of technical effort by some of the top workers in the field.

They come associated with perhaps the best and most authoritative books available on the subject of occupational exposure assessment:

A Strategy for Assessing and Managing Occupational Exposures, 3rd edition
Edited by Joselito S. Ignacio and William H. Bullock (NOTE: THE 4TH EDITION IS COMING VERY SOON!)

Mathematical Models for Estimating Occupational Exposure to Chemicals, 2nd Edition
Edited by Charles B. Keil, Catherine E. Simmons, and T. Renee Anthony

This is probably a good place to mention a book we published in 2000 that I believe still has some value:

Risk Assessment Principles for the Industrial Hygienist, M.A. Jayjock, J.R. Lynch and D.I. Nelson
You can view this entire book on or buy it in either pdf or hardcopy at:

In all, the body of work put out by the AIHA volunteers especially over the last 20 years has indeed been remarkable but it is not finished.  As mentioned above, the 4th Edition of the basic strategies book is due out any day now.  Revisions to the modeling software are constantly being made.

If you want to become a part of this movement, the AIHA and the various committees would welcome you!  Indeed, if you are going to Salt Lake City next week please consider coming to the meetings of the Exposure Strategies Committee, the Risk Assessment Committee, The Toxicology Committee or any other committee that might strike your interest.  It is a great place to learn and grow.

Sunday, May 24, 2015

Risk of Eating (or NOT Eating) Fish

If your mother was like mine, eating fish was a good thing.   She called it “brain food” and all we kids wanted to be smart so we would eat fish even if we did not like it.

Things have changed; eating some types of fish can presumably put your brain at risk.  Mercury, a neurotoxin contaminant in fish, comes to mind (no pun intended).   A 2004 FDA web site (still viewable online):  advises us to NOT eat:

·         Shark
·         Swordfish
·         King Mackerel
·         Tilefish

This same web site advises to only eat limited amounts of tuna.

Predatory fish are relatively high on the food chain and toxic contaminants tend to bio-accumulate up the food chain such that these higher-ranked species have higher levels of mercury.   Of course, we all know who is at the top of the food chain!

Then there is the additional risk of cancer, again from eating fish that are relatively high on the food chain for the same reason; that is, accumulation of potentially cancer causing toxicants in the fish.
So what is a person to do?  If you hate fish, it is good excuse for avoiding it but that avoidance is not rational. 
I found an excellent web site that puts a lot of this into context:
I found the following quote from this site:
“Again and again, research shows that people eating diets with a moderate amount of seafood have lower risk of cancer and other chronic diseases and longer lives.”

It goes into some detail as to why this is the case but it makes the excellent general point:  Almost all risk as attended with some benefit.    Often the benefit clearly outweighs the risk.

Black and white thinking is generally not useful and this is particularly so in the realm of risk assessment and risk management.   If exposure and risk to unacceptable levels of a substance is occurring then clearly some risk management action needs to occur to reduce or eliminate that exposure.  If it is not practical to reduce the exposure then exposure to that substance should be eliminated.   Elimination should only happen when there is no other reasonable alternative. 

We all need to remember that the risk of death in this life for everyone is 10or ONE.  Something is going to get each and every one of us.  Our job as rational beings is to pick and choose what risks we are willing to accept along with the benefits they provide.   That means doing the best job we can at risk assessment.

In conclusion, eat your fish!

Sunday, May 17, 2015

Is Human Health Risk Assessment the Best Tool to Make Decisions?

Human health risk assessment has a bad reputation in some minds. Dr. Peter Montague is an intelligent and articulate thinker, he also pretty much disparages Human Health Risk Assessment, especially the quantitative aspects of it.    The following quote from his writing more than a few years ago struck me the hardest, as I believe it was designed to do:
“Risk assessors are now in the position of the conductors and engineers who kept the trains running on time to the death camps in Nazi Germany to minimize discomfort to their passengers -- they are just doing a job, honorably and to the best of their ability, but the final result of every professional risk assessor's work is the destruction of the natural environment, one decision at a time, and the relentless spread of sickness throughout the human and wildlife populations.”  
If you want to check the entire article to determine the complete context of this quote it is available online at:
In another online essay Dr. Montague asserts:
“Risk assessment is one way of making decisions, but it is not the only way, and it is not the best way.[1] Furthermore, risk assessment as usually practised is unethical.” 
The online reference for this complete opinion piece is: 
It would appear that Dr. Montague believes that we ought to abandon risk assessment in favor of what has been known as the “precautionary principle”.   My read of this principle in its more drastic manifestation suggests that chemicals should be banned (without the benefit of rational risk assessment) if they pose a potentially substantial but relatively uncertain probability of harm from their use and subsequent exposure.
A remarkably thoughtful and articulate defense of risk assessment was put forth by my friend and colleague, Dr. Adam Finkel.    In a published debate with Peter Montague, Adam provides all the reasons I might need to continue to view human health risk assessment as the best way forward.  Please forgive my open admiration for this remarkably powerful and intellectual argument in which Adam defends the rational scientific framework provided by risk assessment while admitting that we have a lot of work to do.   The online reference for Adam’s complete treatise is:   I urge you to download it.
I am reminded in all of this of Winston Churchill’s remarks in 1947: 
     "Democracy is the worst form of government, except for all               those other forms that have been tried from time to time."   
This is how I see risk assessment as a process.
As I have written here previously, uncertainty is the bane of the risk assessment process.  Large error bands (displayed or hidden) in our analyses drive controversy depending on which side of the political or ideological fence you reside.  We have demonstrated that we are fully capable of both over and under-regulating chemical exposures presumably based on risk assessment.   The real task is to shrink those error bands to provide more confident knowledge to feed rational decision.  That means committing the resources to develop the science. 
I believe that it FIRST means that we should acknowledge the size of the error bands while informing the best decisions we can with the always imperfect information in hand.
In my opinion, the authorities who set exposure limits are afraid to admit the current level of uncertainty that exists today.  To date, they have summarily dismissed all calls to do quantitative analysis of exposure limits for non-carcinogens, saying that it is either not possible or meaningless. 
I believe that this condition of not fully disclosing uncertainty also exists, but to a substantially lesser degree, in the realm of exposure assessment.
Unless or until we face up to quantitatively disclosing these uncertainties of our risk assessments to the various stakeholders, I believe that progress will continue to be slow and risk assessment will remain a legitimate target of criticism from both the left and the right.   
In any event, I believe that risk assessment will remain the "worst" tool for making decisions about the risks of chemical exposure to human health, except for all the other approaches.



Monday, May 11, 2015

The Rule-of-10 in Occupational Exposure to VOCs

Some individuals are blessed with a rare combination of technical and managerial acumen along with a gift for seeing the big picture.  In the realm of Industrial Hygiene I can think of no one who personifies  these traits better than Mark Stenzl.   During Mark’s long and very productive career he developed the “Rule-of-10” for inhalation exposure to volatile organic substances.  The rule is presented below:

Level of Control
Fraction of Saturation Vapor Concentration (SVC)
Confined Space – Virtually no circulation
1/10th of Saturation
Poor – Limited Circulation
1/ 100th of Saturation
Good – General
  ~ 6 air turnovers/hr.
1/1,000th of Saturation
1/10,000th of Saturation
1/100,000th of Saturation

You may remember that:
Saturation Concentration (ppm v/v) = 
(Vapor Pressure/Atmospheric Pressure)(1,000,000)

Below are some comments Mark sent to me when I asked him if I could write a blog about it.  After he said it was OK to write about it, he provided the following background:

“I have been using the Rule-of-10 for at least 35 years.  It was a basic component of our qualitative exposure assessment process at both Celanese and later at OxyChem.  We sent every exposure scenario through this qualitative process and predicted the likely exposure category (similar to AIHA’s except we had an extra category 0.1 to 0.25 times the OEL and then 0.25 to 0.5 time the OEL). We then established our sample strategy based on this assignment.  If we thought that exposures were above 0.5 times the OEL we collected at least 5 samples evenly over the year.  If our predicted exposure was between 0.25 and 0.50 we collected at least 4 samples and if the predicted exposures were between 0.1 and 0.25 times the OEL we collected 3 samples and for all exposures thought to be less than 0.1 times the OEL, we would randomly pick out 10 SEGs [Similar Exposure Groups] and collect 3 samples.  Usually, on an annual basis, we would analyze all of our data and prepare an interpretive statement for each facility. Part of the analysis was to evaluate how well our qualitative assessment performed.  We did consider several other determinants of exposure in our algorithm beyond the Rule- of-10.  They included the observed level of control, frequency and duration of the exposure scenario, the hazard vapor ratio and the particulate hazard index.  I found that the Rule-of-10 to be amazingly accurate considering how simple it is. I have found the rule to be very beneficial in other applications such as the chemical approval process related to the introduction of new chemicals into the workplace or the change of existing processes; in auditing IH programs; in conducting due diligence related to potential acquisitions; and in inspections.” 

Further information on the implementation of Mark’s Rule-of-10 along with a check-list approach, designed to provide a more detailed analysis, developed by Susan Arnold will be included in the upcoming 4th Edition of the AIHA Exposure Strategies Book.   My sense is that these additions alone will be worth the price of this basic reference that every Industrial Hygienist should have.

In another note to me, Mark makes the following points: 

“In the examples of the application of the Rule-of-10 [in the 4th Edition] …, the IH may only be in the workplace a few minutes and likely does not have access to a “good” basic characterization.  Even in these cases, if the IH only knows what chemicals are present (and approximate composition), have an OEL or at least an estimate of an OEL and know the vapor pressure (information that is readily available) they can use the Rule of 10 as a screen.  That is, they know what type of controls and configurations they should be observing and match that up with what they are observing.  So the end point is not to classify the exposure into the correct exposure category, but rather to use it as a tool to raise “red flags”; where they should ask more questions and where they need to do a more formal exposure assessment.”

The 4th Edition of the Exposure Strategies Book should be out this year.  I heartily recommend you get it.


Sunday, May 3, 2015

OELs: The “HOT” Topic at this year’s AIhce in Salt Lake City

Those of you who read this blog regularly know that I am very interested in exposure limits, especially Occupational Exposure Limits (OELs).   They represent literally half of the risk assessment process done by most Industrial Hygienists when they compare the exposures they measure (EXP) to the OEL in the classic hazard index (HI) = EXP/OEL.     HI >1  L  HI < 1  J

As such, OELs are critical to the IH profession.
The histories of OELs as a whole is that they have almost invariably have come DOWN in value with time.  Indeed, I can only think of a single example where an OEL went UP.   That fact indicates to me that we have not done a particularly good job of understanding and explaining the uncertainty associated with our OELs.

Understanding the uncertainties associated with OELs and communicating the nature and size of the uncertainty as a part of the documentation has been a point I have been trying to make for some time.

In June I get to present some of these ideas again at the 2015 American Industrial Hygiene Conference & Exposition (AIHce) in Salt Lake City May 30 – June 4, 2015.

On Sunday, starting a 8am, I get to teach a Professional Development course with my friend and colleague Dr. Andy Maier (University of Cincinnati) and Dr. Dan Arieta (Chevron Phillips).   These folks are are a rare breed in the ranks of Industrial Hygiene;  namely, they are board certified toxicologists.  For my part,  I am less expert in the realm of toxicology by very enthusiastic about the subject as it relates to OELs.   The title of the PDC is:  The Hierarchy of Occupational Exposure Limits (OELs): A Suite of Tools for Assessing Worker Health Risk  (PDC402).    Some discussion topics with the presenters in this PDC are shown below:
Why the OEL Hierarchy Concept
Concepts of Toxicology for OEL users
The WEELs Keep Turning -  Setting Traditional OELs
To Be a Savvy OEL User – OEL Limitations
Activity - The Great OEL Debate
OEBs and other hazard-based techniques
Risk-Based OELs

On  Monday morning I get to talk about Risk Based OELs and the Risk@OEL during a Science Symposium Session entitled Occupational Exposure Banding (OEBs): The Solution for the Glacial Pace of OELs  from 10:30 am to 12:50 am.   The title of my talk will be:  Risk@OEL: An Approach to Conduct Tier 3 OEBs

My last presentation is Roundtable RT236 "Toxicological Challenges to the Derivation and Application of Occupational Exposure Limits (OELs)".   It will happen on Wednesday afternoon from 1 to 4:30pm.  I will be talking about  Aligning Occupational Exposure Limits (OELs) with Exposures, especially as they relate to bolus exposures.

I will write about the bullet points of these talks and offer the slides from them in future blogs.   In the meantime,  I am looking forward to meeting some of you at these events and hearing from you about what future topics you want to see in this blog and about what aspects of OELs are important to you.