You Can't Get There From Here

Yet again...another MPH tries to compare a contaminant concentration to the incorrect threshold.  Only this time the MPH is Dr. Volz, an Assistant Professor of Environmental & Occupational Health (EOH) at the Graduate School of Public Health (GSPH) and Director for GSPH's Environmental Health Risk Assessment Certificate Program.

Seems Dr. Volz got himself into some hot water regarding a report on the water being discharged from a brine treatment facility that accepts frac water.

Well if you have read any of my past posts, you know I read the reports that people take offense to and/or reference.  Sometimes folks misconstrue what the author was stating.  Even if the writer is an advocate, I can overlook bias if the data has been gathered correctly and the hypothesis is plausible.

When I got to this part:

Barium had a mean concentration in effluent of 27.3 ppm (maximum of 37 ppm); this is approximately 14 times the United States Environmental Protection Agency (EPA) maximum concentration limit (MCL) of Ba in drinking water of 2 ppm.

I said to myself "oh no, he didn't....."  But alas, yes...yes he did.

So lets look at this from the beginning of his report, what were his objectives?.

This report contains results from sampling and analysis of wastewater effluent entering Blacklick Creek, Indiana County Pennsylvania from the Pennsylvania Brine Treatment (PBT) Josephine Facility.  The PBT-Josephine Facility accepts only wastewater from the oil and gas industry, including flowback water from Marcellus Shale gas extraction operations.

OK...

This report describes the concentrations of selected analyzed contaminants in the effluent water and compares the contaminant effluent concentrations to standards, guidelines and criteria set by federal and state regulatory and investigative agencies for the protection of human and aquatic health. 

OK...nothing wrong with that...

In particular and where applicable, it compares effluent concentrations to Agency for Toxic Substance and Disease Registry (ATSDR) minimal risk levels (MRL). MRL’s are screening levels used as an estimate of “daily human exposure to a hazardous substance that is not likely to pose an appreciable risk of adverse noncancerous health effects.”

Hmm...OK...MRLs..that seems appropriated.  Here is what I know about MRLs:

• An MRL is an estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse noncancer health effects over a specified duration of exposure.

• ATSDR uses the no observed adverse effect level/uncertainty factor (NOAEL/UF) approach to derive MRLs for hazardous substances. 

• They are set below levels that, based on current information, might cause adverse health effects in the people most sensitive to such substance induced effects. MRLs are derived for acute (1-14 days), intermediate (>14-364 days), and chronic (365 days and longer) exposure durations, and for the oral and inhalation routes of exposure.

I wrote about No Observable Adverse Effect Levels (NOAELs) and Uncertainty Factors (UF) in a previous post.  To summarize:  The MRL is set lower than the highest concentration found to cause no observable effects.  That value is then divided by an uncertainty value based on the number of studies and data available.  In this way, because animals do not always represent how a human would manifest the effect, we can be assumed "safe" at that level.

What Dr. Volz is attempting to do in this report is look at the hazardous substance concentrations in the treated water effluent being discharged under an NPDES permit to see if that concentration exceeds the MRL.  That assumption, therefore, would also mean that if the treated water has a chemical substance below the MRL, it would "likely be without appreciable risk of adverse noncancer health effects over a specified duration of exposure."

What this does not mean is that a concentration above that level will result in a risk.  However, the higher the contaminant level - and the longer the exposure duration to that level - the greater the risk of a health effect showing up (Barium = Increase in Blood Pressure [EPA]).

Dose response, exposure duration, receptor, and pharmacokinetics are what we environmental MPHs live and breath and we look to to determine the possible risk caused by a hazardous substance.  The fact that it is there - and exposure has taken place - does not mean there will be an "appreciable risk of adverse noncancer health effects."  You need a specific concentration and a specific duration to bring forth an "appreciable risk" if the contaminant follows a normal dose response curve.

Now the reason I keep quoting "appreciable risk" is to make it quite well understood that there is always a risk when there is exposure.  In environmental public health we look at the risk to the population as a whole, focusing on the most vulnerable.  We then use statistics and the knowledge that there is no such thing as zero risk when a chemical with a dose response is present.  This is why we say "likely to be without appreciable risk of adverse noncancer health effects over a specified duration of exposure" when the concentration is below a threshold.

As an environmental MPH, we make the assumption that below a specified value there is minimal - or likely to be without - risk.  This means that the concentration we find in our sample, when compared to "standards, guidelines and criteria set by federal and state regulatory and investigative agencies for the protection of human and aquatic health" will give us an idea of how much risk there is.

That's how it is done.  So why then does Dr. Votz say this in his report?

Barium had a mean concentration in effluent of 27.3 ppm [and] is approximately 14 times the  (EPA) maximum concentration limit (MCL) of Ba in drinking water of 2 ppm.

Why is.he is comparing effluent concentrations to drinking water MCLs?  Surely he must know how an MCL is derived?  I mean, he is the Director for GSPH's Environmental Health Risk Assessment Certificate Program for Pete's sake.  MCLs are based on the consumption of 2 liters of water at the MCL level for a lifetime...

• For chemicals that can cause adverse non-cancer health effects, the MCLG (G = Goal) is based on the reference dose. A reference dose (RfD) is an estimate of the amount of a chemical that a person can be exposed to on a daily basis that is not anticipated to cause adverse health effects over a person's lifetime. In RfD calculations, sensitive subgroups are included, and uncertainty may span an order of magnitude. (EPA)

• Reference Dose (RfD): An estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. It can be derived from a NOAEL, LOAEL, or benchmark dose, with uncertainty factors generally applied to reflect limitations of the data used. Generally used in EPA's noncancer health assessments. [Durations include acute, short-term, subchronic, and chronic and are defined individually in this glossary]. (EPA-IRIS)

• A "lifetime is calculated as 70 years (EPA)

What Dr. Volz is implying is, that had you stuck your head into the pipe coming from the treatment facility and consumed 2 liters of effluent, you would be consuming 14 times the safe level of Barium.  The only problem here is that the water body into which this brine treatment effluent is discharged into is not used as a drinking water source.  And, as it makes its way downstream and mixes with other waters, when that water is used as a drinking water source, it is treated so that the barium and other contaminants - natural and man-made - are BELOW the MCL when offered to the consumer.

Comparing this effluent's Barium concentration to an MCL is like telling a wine drinker that there is 5 times the alcohol in that bottle of vodka sitting on the shelf.  Unless you are going to drink the same amount of vodka as the wine you have been drinking - it does not matter.  It means nothing in terms of a risk to you unless you decide to drink a wine glass full of vodka continuously for a lifetime (assuming a "safe" threshold of wine is one glass per day).

And that is why you can't get there from here.


Next post: Swimming and eating stuff from the water downstream.

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