From: Ken Kretchman <kwkretch**At_Symbol_Here**ncsu.edu>
Subject: Re: [DCHAS-L] Validity of the risk matrix
Date: Thu, 17 Oct 2019 16:21:24 -0400
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Message-ID: CAOYSQ48FEk6pd46t+JhiS0mZkm7e_msv1jCXMw6OJxo8cYgEUg**At_Symbol_Here**mail.gmail.com
In-Reply-To <372a948087c041619f6d79420064be7f**At_Symbol_Here**usw.org>


I echo Mike Wrights comments. One does not have to get hung up in true probability, or severity for that matter. I think one might focus attention toward
prevention of a medium severity problem that could be caused and affect any of 5000 persons than something of seemingly similar severity potentially caused and affecting only a few.
I don't know the true probability but expect a single incident would be more likely for the former.

Then one can consider the dollars spent vs benefit derived to really dial in where to spend resources (which references severity and probability).

Using the matrix as a starting point for further discussion on priorities rather than the end all is certainly valuable.

Ken

Ken Kretchman, CIH, CSP Director, Environmental Health and Safety
NC State University / Box 8007 / 2620 Wolf Village Way / Raleigh North Carolina 27695-8007
Email: Ken_Kretchman**At_Symbol_Here**ncsu.edu / Phone: (919).515.6860 / Fax: (919).515.6307


On Thu, Oct 17, 2019 at 12:09 PM Wright, Mike <mwright**At_Symbol_Here**usw.org> wrote:

We use and teach the matrix in our occupational safety and health classes all the time. But we don't try to plug numbers into the cells. And we stress that it should be used to prioritize items, not to decide whether to address them at all. We also build in another variable, although we don't try to construct a 3-dimensional matrix. That variable is the ease of correcting the problem. If we can address two hazards in a particular cell of the matrix for the price in effort and expense of one, that's what we try to accomplish first.

Our problem isn't so much deciding which decision logic to use to prioritize problems - it's convincing the employer to address them at all.

I can see using the Bayesian approach in the kind of cybersecurity situation the author is familiar with, or in a PSM situation with a highly sophisticated corporate safety department. However, thinking back a couple of decades, I remember trying to explain to a few plant managers how the total quality management ideas of Deming and Juran could be applied to their safety program (or lack thereof). It didn't go well. Not sure I want to try with Bayesian statistics.

Mike Wright

Michael J. Wright

Director of Health, Safety and Environment

United Steelworkers

412-562-2580 office

412-370-0105 cell

"My friends, love is better than anger. Hope is better than fear. Optimism is better than despair. So let us be loving, hopeful and optimistic. And we'll change the world."

Jack Layton

From: ACS Division of Chemical Health and Safety [mailto:DCHAS-L**At_Symbol_Here**PRINCETON.EDU] On Behalf Of Monona Rossol
Sent: Thursday, October 17, 2019 11:07 AM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: Re: [DCHAS-L] Validity of the risk matrix

David, Aw shucks, and I just hit the button on an email telling someone to use the matrix. But let me tell you one of the good things about the matrix. In order to use it, you have to have data on the severity of the risk.

So this person was emailing about a job involving Q-tip surface cleaning of a very large, complex surface area by a number of workers on a large object (one that will remain nameless because it may identify the project). More than one person would be involved and while the surface just looked like there was schmutz on it, it became clear on a literature search that this schmutz probably was lead salts with cadmium, chrome VI and a bunch of toxic metals thrown in for laughs. To save money, they didn't want to identify the schmutz and just use good universal precautions. But the matrix requires a number indicating the severity of the potential hazard, ergo: analyze the schmutz and give it a number.

This is also the ethical thing to do because the client whose cleaned massive object will be returned to them certainly should be informed about what is likely to be released at the surface again over time to protect their own maintenance people.

Score one for the matrix.

Monona

-----Original Message-----
From: David C. Finster <dfinster**At_Symbol_Here**WITTENBERG.EDU>
To: DCHAS-L <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Sent: Thu, Oct 17, 2019 10:01 am
Subject: [DCHAS-L] Validity of the risk matrix

While stumbling around the web with regard to thinking about the risk matrix, I came upon an article that questioned its value:

The essence of the argument, I think, is that estimates of probability are very unreliable. I'd appreciate the wisdom of the list regarding this essay and its conclusion.

Dave

David C. Finster
Professor Emeritus, Department of Chemistry
Wittenberg University

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