Monday, July 25, 2011

Swimming and eating stuff from the water downstream.

From "This American Life," a show I listen to and like...
The second, Conrad "Dan" Volz, at the University of Pittsburgh, estimated how much toxic crap—chemicals and pollution from gas exploration—might be getting into water supplies. (1)
In my last post, I made the comment that you can't get to the conclusion Dr. Volz presents in his report from his comparison to EPA/ATSDR limits that have been established so that “daily human exposure to a hazardous substance that is not likely to pose an appreciable risk of adverse noncancerous health effects” when the assumption of a "lifetime exposure" will not be met.  In other words, if that water is not going to be consumed at the point where sampling took place, there is also no assumption that someone at 70kg could drink it daily for a 70 year lifetime (MCL).

Comparing the barium concentration in the effluent with an MCL was wrong, and the comment "this is approximately 14 times the [MCL] of Ba in drinking water" is therefore misleading.  But what about Dr. Volz's contention that:
Recreationalists are at high risk of being exposed to outfall contaminants through ingestion, inhalation and through dermal exposure.  [C]hildren wade and swim in the creek during warmer weather... Anglers catching and eating fish from upstream or downstream of the effluent outfall are at risk for exposure to multiple contaminants that were sampled in this study.
What does the term "high risk" convey?  Is it at the level of death?  Should it illicit an OMG! if one comes in contact with the water?  "High risk" of what, exposure?  Dr. Volz reports that I will have a high risk of coming into contact with barium, bromides, strontium, benzene, TSS, and pH if I ingest, inhale or contact the Blacklick Creek Water?  Will that exposure lead to a health effect?  Are we talking about a high risk of exposure to a puppy or a Doberman? (that will make more sense if you read this post).

If we are not going to drink the effluent, will exposure to these chemicals at the concentration found at the point of discharge cause "an appreciable risk of adverse noncancerous health effects?”  Fair question.  What are the concentrations of these chemicals in the water where the children wade and swim?  What are the levels of these contaminants in the fish caught and consumed?  There isn't any of that data presented in Dr. Volz's report.

What the report does is imply that if a chemical - such as barium - is discharged into the creek, it will present an exposure risk to someone who comes in contact with the water downstream "of the effluent outfall ."  In other words, high risk of exposure must translate to "an appreciable risk of adverse noncancerous health effects."

That's not how environmental public health professionals look at a chemical exposure manifesting into a health risk.  You can't get there from here.  You can speculate, imply, assume, insinuate, and wish it to be true, but that's not what an environmental public heath professional is supposed to do.

So once more, with feeling...

To estimate risk we need to know the amount of chemical entering into the receptor (uptake), the length of time the exposure has taken place, the toxicokentics, and compare them to a concentration assumed to present no appreciable risk of adverse noncancerous health effects.

When we know the amount of uptake (how much of the chemical got into the system) from the exposure, we can compare it to a number, such as the MRL.  Keeping with the barium concentration in the effluent reported, Dr. Volz states:
The ATSDR minimum risk levels (MRL) for intermediate and chronic human exposure is .2 mg/L/day; the barium in PBT- Josephine effluent water is approximately 135 times the MRL’s for both intermediate and chronic human exposure.
Lets look at what ASTDR says about barium in it's ToxGuide for Barium:

Notice what Dr. Volz - a DrPH, MPH and (former) Director of the U of Pitt GSPH's Environmental Health Risk Assessment Certificate Program failed to take into account?  That MRL value of 0.2 mg is not per liter, but per kilogram body weight of the receptor.

A 30 kg child would need to consume 0.2 * 30 = 6 mg of barium for 15 - 364 days to potentially have a negative health impact.  To put this in perspective....

If the effluent (discharge end of pipe) contains a maximum of 37 ppm, little Suzy or Billy would have to stand near that pipe and consume about 250 ml of the creek water.  That's the amount of water in the container little Suzy is holding.

Oh, and she would have to do drink that amount for 15 - 364 days.  And even if she did, the ASTDR states:
Exposure to a level above the MRL does not mean that adverse health effects will occur. (2)
The effluent is not 135 times the MRL.  At the end of the pipe - where the samples were collected - it is only 7 times higher than the maximum detected level of barium.  What the barium concentration is downstream where little Suzy and Billy "wade and swim" was not sampled by Dr. Volz.  That's where the sample's should have been taken if risk "of these chemicals in the water where the children wade and swim" was to be evaluated properly.

It is quite possible - as that is the reason for the NPDES permit the treatment facility discharges under - that the water "where the children wade and swim" is below the MRL for barium and all the other chemicals reported.

But heck with the kids!  What about the guys who eat the fish swimming in the "toxic crap?"

Once again we need to know how much barium would be consumed when they eat the fish.  Believe it or not, there is a calculation for that:
And for barium, the amount in the fish that would create concern for the EPA requiring cleanup would be 270 mg of barium per kg of fish.

This is how we look at risk from exposure to a chemical.  The fact that a chemical is present in the environment and we come in contact with it does not mean we will be subject to an appreciable risk of adverse noncancerous health effects.  There is a proper - agreed upon - method to look at estimating elevated, or high risk, when exposed to a chemical.  Dr. Volz must understand that what he present in his report was not a valid indication of the risk to public health and the environment from the water discharged by this frac water treatment facility.

Choosing to ignore the science and objectivity is what led to Dr. Volz no longer being the director of the University of Pittsburgh's Center for Healthy Environments and Communities at Pitt's Graduate School of Public Health.

I am glad that Dr. Volz believes he has a "calling for advocating for public health."  All I ask is that he and others so inclined present and describe the risk properly and objectively.


Thursday, July 21, 2011

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.
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.