Sunday, January 12, 2014

IH DIG and the Pump Monkey

The last blog was the confession of a former pump junky; namely, me.  Pump jockey is a somewhat disparaging term but I have heard worst; namely, the very insulting designation "pump monkey".  This week we get to see just how “monkey like” we really can be when we rely just on just our judgment to gauge exposure data.   This opportunity is presented in the form of a free smartphone app:  IH DIG.  

IH DIG is a very cleaver game that presents the player with airborne exposure monitoring data and asks the player to make a judgment about the meaning of that data.   Talk about a situation that is right up our alley!

IH DIG presents the player with 20 sets of air monitoring data one set at a time.   Each set has between 1 and 8 air monitored values and an occupational exposure limit (OEL) for comparison.  It asks you to look at the data and determine whether it indicates an exposure (95%tile) in one of the 4 standard AIHA exposure categories:   

1.      Less than 10% of the OEL
2.       10-50% of the OEL
3.       50-100% of the OEL
4.       Greater than 100% of the OEL
Remember in the last blog we discussed that there is a considerable amount of day-to-day variation in exposure even in the same job done by the same person and that we needed a statistical benchmark that used this variation to determine whether the exposure exceeds the OEL.    Here we (and IH DIG) are using the 95%tile upper bound limit on the exposure to estimate which category the exposure data best fit. 

Just to give you an example, IH DIG presented the following sampling set: 307, 152, 23 mg/m3 with an OEL of 500 mg/m3.  I guessed category 3: (50-100% of the OEL) and was immediately told I was wrong and that it is actually in category 4:  >100 % of the OEL.    IH DIG does this for 19 other data sets and then scores your overall ability to judge exposure when you go forward without the benefit of a sophisticated statistical tool like IH STAT.  If you do very well you are declared to be a "Super IH"; however, if you perform very poorly you could be awarded the unappealling title of "Dart Throwing Monkey"!  

If you play IH DIG enough you will get better at judging which category is correct.   Indeed, I believe it actually makes us more aware of the reality of uncertainty within our data; however, I have never gotten a perfect score and there always seems to be some surprises.    The lesson is clear; we need the benefit of some good statistical analysis software like IH STAT.

I think IH DIG would make a great training tool for new Industrial Hygienists.   It really does present an object lesson and can be very educational if not humbling.

IH DIG is available for I-phone/I-Pad and Android smartphones and tablets.    I think the best way to get it is to fire up the browser/search engine on your smartphone or tablet and put in “IH DIG app”.   The first hit should be the AIHA Exposure Assessment Strategies Committee page with a link half way down the page to the IH DIG app download in either flavor.




  1. A good discussion on a perpetual challenge. Unfortunately many clients only want one sample of each work area.....its hard to develop a UCL with that.

  2. I would suggest you also look at Paul Hewett's research and publications on Bayesian Decision Analysis concerning limited number of samples and results

  3. So....does IH DIG give the standard error of each measurement? I would submit that if you don't know the uncertainty of the measurement, you really don't know what the number means.

  4. Hi Harry, IH DIG does all these calculations in the background but does not disclose them. It does factor in the uncertainty because it uses the 95th percentile for the exposure determination. It is worth checking out...