Tuesday, June 11, 2019

Want to Learn Industrial Hygiene? Check this out.

By any measure I am in the latter stages of my career.  I have been around a long time and have seen quite a bit of positive change in the Industrial Hygiene profession.   We are evolving from a “pump jockey” mentality into a much more rigorous scientifically based vocation.   The refinement and enhancement of the science of sampling statistics by Jerry Lynch, John Mulhausen and others along with the pioneering efforts to use Bayesian statistics by Paul Hewitt and others are prime examples. 

At the AIHA conference in Minnesota last month I attended a presentation by Dr. Jerome Lavoue on a freely available statistical analysis tool: expostat.  This effort was new to me and it looked like a great tool.   I sent a note to my friend Tom Armstrong about it.  He responded that he was well aware of this tool and sends me a remarkable slide deck on statistical analysis that he is working on.   

Tom starts off with a 10,000 meter view of IH statistics and rapidly zooms into providing useful, spot-on guidance and details on the current state of the science and where to get more info.  Like I said, it is a remarkable set of 30 or so slides which Tom has agreed to allow me to send to you if you request it:

Another highlight of the conference for me was a visit to Dr. Susan Arnold’s laboratory at the University of Minnesota.   It is a great lab with a lot of salient instruments and a chamber that allows her and her students to conduct some controlled exposure studies.  She also told me something about her IH curriculum which is very heavy in modeling and science.  I am aware of a few other programs along these lines but I was particularly happy to see Susan doing this.  If I were a young person interested in a top-notched program with opportunity for hands-on research I would consider moving to Minnesota weather notwithstanding.

Tuesday, April 23, 2019

Dr. Thomas Armstrong National Treasure

I have written about Tom previously in this blog but his latest contribution to the realm of exposure modeling is really quite extraordinary.   It is 111 slides in a PDF file that contains the following gifts for anyone willing to view and study them:
  •     Worked examples annotated with Tom’s wonderful insight and guidance.
  •      Clear explanation of ALL  the basic elements of inhalation exposure modeling.
  •      Specific guidance to the importance of using                 thermodynamic activity coefficients (ACs).
  •          Where to get the tools for the determination of ACs
  •          Worked example of using ACs
  •     Use of EASTMAN Chemical's nominal evaporation rate scale to provide estimates of quantitative evaporation rates in mass/time.
  •     Numerous excellent referenced tables for Random Air Movement Indoors and the Eddy Diffusion Coefficient (Dt).
  •     Numerous references and links to get what you need to actually do exposure modeling.
  •     A wonderful annotated primer for IH MOD 2.

It is easily equivalent a multi-day course on the general subject but presented in a way such that it is relatively easy to follow.  This is especially true if you have some background in modeling or you are willing to delve into the AIHA Modeling text:  Methematical Models for Estimating Occupational Exposure to Chemicals, 2nd Ed. as a companion resource.

I will send the PDF file to anyone who requests it:

Tom would also love to hear from you.    He has been hospitalised twice recently with a serious illness.  The good news is that he is on the mend and will be out of the hospital soon.  The bad news is that he will miss this year’s AIHA Conference because he needs to undergo further treatment for his condition.  We have been corresponding while he was in the hospital and I recently wrote to him: 
"Tell your caretakers that you are a National Treasure and to get on with it!"   He wrote back that this brought a smile to his face.   The truth is that in the realm of IH he truly is a treasure. 

He is very regularly on email at:

Thursday, March 7, 2019

Are the Exposure Models Used for REACh Wrong?

Dr Joonas Koivisto and 16 others, including this writer, have recently authored what I believe is a very important paper:  Source specific exposure and risk assessment for indoor aerosols.    It sounds a bit like a paper focused on aerosol assessment but it is actually a comprehensive look at inhalation exposure models and the quality of these models to make decisions relative to chemical regulation and risk assessment.   The reality is that aerosols represent the most challenging scenarios for modeling because of their added properties compared to gases.  If one can accurately model aerosols then gases are relatively simple to model.  

The publication outlines the current state of the science and available models.  It also makes a developing case for the use of first principle mathematical mass balance models versus other types of models (knowledge-based models, and statistical models of exposure determinants) especially for regulatory decisions such as those mandated by REACh.

The Europeans are much more advanced than the US in the application of exposure models because they have to be.   The REACh regulation requires a risk assessment for literally thousands of chemicals and a risk assessment requires an exposure assessment.  There is not nearly enough measured exposure data available, so they have turned to models.   It is clearly evident that the inputs to and data bases for the mathematical mass balance models have not been sufficiently developed so the European Regulators have turned to knowledge-based and statistical models of exposure determinants.  These models are more easily applied because the inputs are relatively simple.   The paper implies that these models are not performing up to the task and that there is a real need to develop the input data necessary to feed the more competent first principle mathematical mass balance models.  

The paper points to an earlier paper I did with Tom Armstrong and Mike Taylor in which we challenged the mass balance 2 zone Near-field/Far-field (NF/FF) model to the Daubert legal criteria which is widely used by the Courts to assess whether expert witnesses scientific testimony is methodologically valid.   In that paper we concluded the NF/FF model fulfils the Daubert criteria and when it is used within its stated limitations, it adequately estimates the exposure as applied to legal decisions.  The implication is that the models currently used for making decisions for REACh would, most likely, not pass the Daubert criteria, which requires that these models:

1) Are applicable and have been tested.
2) Have been subjected to peer-review and are generally accepted.
3) The rate of error is known and acceptable.
4) have maintenance of standards and controls concerning their operation.
5) Are generally accepted in the relevant scientific community.

This Daubert paper is:  Jayjock, M.A., Armstrong, T., Taylor, M., 2011. The Daubert Standard as applied to exposure assessment modeling using the two zone (NF/FF) model estimation of indoor air breathing zone concentration as an example. J. Occup. Environ. Hyg. 8, D114–D122.   I will email an electronic copy to anyone requesting it:

What Dr. Koivisto and the other authors are asserting in this paper is somewhat striking; namely, the currently used REACh models need to be explicitly challenged by the Daubert (or similar objective) criteria and, if found wanting, better alternatives should be developed and employed.   This would, most likely, result in something this writer has been advocating for many years; specifically, comprehensive research and compilation of exposure source data bases.

This should be a straightforward objective scientific exercise; that is, a technically competent and empowered group of scientists would set open and objective criteria and test the currently used regulatory sanctioned models to those standards.   The reality, as I see it, is that there are strong vested interests and forces at work in this case that may resist this sort of effort.   Change is never easy but, hopefully, scientific integrity, good judgement and established facts will ultimately work to improve the public health, partisan politics notwithstanding.

The paper was published online this week at as gold open access, which means that the full pdf text is a free download from the publisher Elsevier.