Air Quality in the Barnett Shale - Part 11: Is there a real concern for DISH, Texas?

So what do we know so far regarding the real health concerns for the citizens of the Town of DISH, Texas?:

• Benzene and other chemicals were found in the seven samples collected during one 24 hour sampling event conducted by Wolf Eagle Environmental.
• The TCEQ has sampled the air in the Town of DISH, Texas and reports hourly values below the short-termAir Monitoring Comparison Values (AMCV)  
• The TCEQ has sampled the air in the Town of DISH, Texas and reports hourly values below the short-termAir Monitoring Comparison Values (AMCV)  

Here is what I gathered from the TCEQ website for air monitoring at DISH, Texas:

Note: Report generated on Dec 16, 2010.  Monthly and Yearly data reported for BTEX.

As you can see, the amount of BTEX (Benzene, Toluene, Ethylbenzene, and Xylene) is under the AMCV for each chemical.  That's a good sign.  But lets make the assumption that the 24 hour results reported by Wolf Eagle Environmental are what the citizens of DISH, Texas are being exposed to on a regular basis.  Would there be a health concern?

That's a difficult one to make a call on.  In fact it is so uncertain that even Wolf Eagle Environmental and Wilma Subra in any of their reports do not make any claim what-so-ever as to these levels creating a undo health risk.  All that is said is that they exceed the ESL for some of the chemicals found.

The TCEQ, on the other hand, does state:

"24-hour air monitors in the Barnett Shale area are showing no levels of concern for any chemicals." and "there are no immediate health concerns from air quality in the area" and "that when they are properly managed and maintained, oil and gas operations do not cause harmful excess air emissions.”

Now I know better than to rest my case on one set of data.  However, I have at my disposal - and anyone clicking the links I cite does as well - a whole bunch of data or 'n'.  This gives me more confidence to agree with the statement TCEQ has issued above.

There is one more issue in play that leads me to conclude that the air is safe and that the folks in the Town of DISH, Texas are not going to experience " health concerns from air quality in the area."

Exposure is but one step of the K.C.Donnelly Risk Paradigm I discussed in Part 2.

What needs to happen after exposure to a chemical takes place is uptake.  That is, the chemical has to enter into the body where the dose, time, and pharmacokinetics now come into play.

The question becomes, OK, if they are exposed, how much are they actually getting into their system?  In order for a health effect to manifest, uptake must take place.  And if uptake has taken place, we can measure the actual concentration of the chemical in the blood stream or tissue.

And wouldn't you know it, that has been done.

Much of the concern about natural gas operations has been centered in DISH, so in early 2009, the Texas Department of State Health Services performed blood tests on 28 DISH residents (representing about 13 percent of the town’s population).

Test results showed that the exposure of DISH residents to VOCs was similar to that of the general U.S. population, and that exposure to certain contaminants was no higher than that of the general U.S. population.

The study further found that the only residents who had higher levels of benzene in their blood were smokers. Cigarette smoke contains benzene, so finding this in smokers’ blood is not unusual, the department noted. (1)

So now what do we know?

• We know that we have detected chemicals contaminants in the 24 hour samples collected by Wolf Eagle Environmental
• We can assume exposure has taken place.
• We can show - through blood tests - that exposed citizens have levels of contaminants no higher than those of the general US population.

So what can we conclude from all this?  That excluding odor, noise, and catastrophic events, the TCEQ is correct in asserting "that when they are properly managed and maintained, oil and gas operations do not cause harmful excess air emissions.”


Next Post: Air Quality in the Barnett Shale - Part 12: Oil & Gas, it's better if you go green!

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Air Quality in the Barnett Shale - Part 10: How not to describe Toluene

So here I am on my 10th rant...err, I mean post.  What started all of this was a simple Google search looking for information on air quality and oil & gas exploration/production involving frac'ing in Texas.  What I found mentioned over and over again mentioned sampling performed in the Town of DISH, Texas by Wolf Eagle Environmental.  Reading their report, written by an MPH named Alisa Rich, I come across a number of descriptions as to the hazards posed by the contaminants detected in the seven samples they took in the Town of DISH, Texas back in September of 2009.

The one on Toluene was what started these posts.  Nothing makes me madder than when someone who is in the know reports faulty, misleading or incorrect information to the general public.  As an MPH she knows better.  Although what she said was factually true, the context it was put in was misleading:

Lets look at a different chemical to illustrate how misleading a statement like this can be:

Phosphoric Acid - CAS Number 7664-38-2  

Corrosive. Causes skin and eye burns. Harmful if inhaled or swallowed. Irritating to respiratory system. Prolonged exposure may cause chronic effects.  This product is considered hazardous under 29 CFR 1910.1200 (Hazard Communication).  Risk of serious damage to eyes. Do not get this material in contact with eyes.  Causes skin burns. Harmful if inhaled. Inhalation of vapors or mists of the product may be irritating to the respiratory system. Prolonged inhalation may be harmful. Do not breathe dust/fume/gas/mist/vapors/spray.  Harmful if swallowed. Components of the product may be absorbed into the body by ingestion. Ingestion may produce burns to the lips, oral cavity, upper airway, esophagus and  possibly the digestive tract. Circulatory collapse. Unconsciousness, possibly death. Do not ingest. Components of this product are hazardous to aquatic life. May cause long-term adverse effects in the environment. (1)

Pay particular attention to the section in red.  Wow!  That phosphoric acid must be really bad stuff!  Now lets look at a can of Coke, or Pepsi, or Dr. Pepper, or any other carbonated drink.

So will drinking a can of Coke cause you to suffer "Circulatory collapse. Unconsciousness, possibly death?"  

No.

Is Coke, which contains phosphoric acid, "Harmful if swallowed?"

No.

Does ingestion of this product "produce burns to the lips, oral cavity, upper airway, esophagus and  possibly the digestive tract?"

No.

And the reason?  The dose!  In other words, there is a "safe amount" of phosphoric acid that a person can be exposed to.  Carbonated drinks contain that "safe amount."

So were the citizens of DISH, Texas exposed to an amount of Toluene that would/could present any of the hazards described in Wolf Eagle Environmental's report?

No. (2)(3)

And yet both Alisa Rich and Wilma Subra presented to the Town of DISH, Texas reports that imply that the amount of contaminants detected in the seven samples exposed the citizens to "a neurotoxin." (4)

If we go back to looking at chemical exposure in terms of exposure to a dog, in DISH, Texas a dog was indeed found to be present.  Even if we assume worst-case as the TCEQ did in their memo - increasing the amount of chemicals detected in a 24 hour sample to 24 times the levels detected - what was detected at the Town of DISH, Texas by Wolf Eagle Environmental, was a dog that looks like this:

But the way their report was worded, it describes a dog that looks like this:

So as Wilma Subra concludes in her report:

The data from the report should be used to educate community members living in the area with the highest concentrations of chemicals and chemicals in excess of TCEQ ESLs in the air they are being exposed to.

Well you now have the data and the correct context to help make a proper determination as to the risk posed by the oil & gas production that is taking place.


Next post: Air Quality in the Barnett Shale - Part 11:  Is there a real concern for DISH, Texas?


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Air Quality in the Barnett Shale - Part 9: Dose and Dogs

So now back to TCEQ and their statement:

“In response to these concerns, the TCEQ has committed a tremendous amount of time and resources to the issue of Barnett Shale air quality, and we will continue to do so.  After several months of operation, state-of-the-art, 24-hour air monitors in the Barnett Shale area are showing no levels of concern for any chemicals. This reinforces our conclusion that there are no immediate health concerns from air quality in the area, and that when they are properly managed and maintained, oil and gas operations do not cause harmful excess air emissions.”

How can this statement be made when contradictory statements from Wolf Eagle Environmental and Wilma Subra contend:

• Laboratory results confirmed the presence of multiple Recognized and Suspected Human Carcinogens in fugitive air emissions present on several locations tested in the Town of DISH. (1)
• Xylenes (m & p), a neorotoxin, was present in the highest concentration of all stations sampled and exceeded the Long-term ESL by 2 times. (2)
• Benzene, a know human cancer causing agent, was present in the highest concentration of all stations sampled. (2)

It all comes back to the dose.

Lets say that you wanted to know the possible health effects of human contact with different types of mammals.  The first thing you would do is group them.

1. Cats
2. Dogs
3. Hamsters
4. Pigs
5. Goats

Then you would look at each one to see what health effects occur.  For the sake of simpleness, lets pretend the only health hazards we are concerned with are bites, bone breaks, rabies, and death.

Now through research - some good and some poor - we find that not all bites are the same, so we break them down into small bites, medium bites, and large bites.

So our concern with human exposure to mammals has to do with the following health effects:

1. Small bites
2. Medium bites
3. Large bites
4. Bone breaks
5. Rabies
6. Death

The next thing one would do is look to see what type of exposure to one of the five mammal groups causes any of these health effects.  Through research we find that these health effects are dependent on the size of mammal (dose) and the amount of time in contact with the mammal (duration).

As a rule, we find that the bigger the mammal the larger the bite; the more time spent with the mammal the higher the chance of rabies; and in cases where a large number of mammals is encountered at one time, death may occur.

We also find that in most cases nothing happens.  Also, some large mammals can just nip and some small mammals can bite, although the size of the mammal does impact the size of the bite.  Additionally, any one single contact may have the ability to transmit rabies.

So looking at dogs, for example:

Now we need to determine what a safe level of dog exposure is.  For other than rabies, we look to see if there is a non-linear dose-response relationship, which means it has an effects threshold - an amount of dog for which human exposure is not expected to result in any adverse health effects.

We also find that within a human population, some people are much more prone to have negative health effects when exposed to dogs.  So when determining this safe level, it will need to be based on the most sensitive population (children, elderly) and adjusted for uncertainty and variability.

In toxicological assessments, this safe value is usually based on a determination of no-observed-adverse-effect-level - or - NOAEL.  The NOAEL is than divided by an uncertainty factor.  

For example, benzene - which is not a dog but a chemical - has a BMDL (which is similar in scope to the NOAEL) of 1.2 mg/kg/day is divided by an uncertainty factor of 300 for a reference dose (RfD) of 0.004 mg/kg/day.  The reference dose is the safe level one can be exposed to without any adverse health effects.

This uncertainty makes the safe level of benzene 300 times lower than the amount determined to be at the no-observed-adverse-effect-level (NOAEL).  In other words, at 1.2 mg/kg/day we don't expect anything, so at 0.004 mg/kg/day we are pretty dang sure nothing will happen.  Aint science fun!

It is because of this uncertainty that TCEQ can say:

"If predicted airborne levels of a constituent do not exceed the screening level, adverse health or welfare effects are not expected.  If predicted ambient levels of constituents in air exceed the screening levels, it does not necessarily indicate a problem but rather triggers a review in more depth."

So what would be the safe level of dog?  One that would show consistently a no-observed-adverse-effect-level.   That would probably be a puppy.

And because of uncertainty, not just any puppy, but a really young puppy:

So that's basically how dose and this "safe level" of ESL, RfD, and AMCV works.  Exposure to any of the dogs pictured - as well as encountering a pack of dogs - does not necessarily mean you will get bit or harmed.  And the chance of rabies?  Slim.  Yet these health effects - including rabies - are possible any time you are exposed to a dog.

Next post: Air Quality in the Barnett Shale - Part 10:  How not to describe Toluene

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Air Quality in the Barnett Shale - Part 8: Benzene is like a bull...

So those last two posts were a bit on the scientific side.  However, if I am going to be critical on someone else's report lacking credibility and good science, I need to be ably to show why.  So with cheesy graphics, let me see if I can 'splain it a little bit better.

Let's deal with Benzene first, since it is recognized as a human carcinogen.

Lets say I lived in a house that boarders a very large pasture.  Surrounding this pasture are three other neighbors.  My neighbors and I walk along a well traveled path through the field to the town hall, where we all like to meet nightly to socialize and whittle sticks into pointy spears.

One day this well-dressed out-of-towner shows up at our town hall and offers us a bunch of money if we would lease him part of our pasture.  Liking money, we all say "yes" except neighbor three.

"I heard about him" neighbor 3 says, "He sets up on our town and lets loose bulls and rams in our pasture!  I think we need to do a little bit more research before we say yes to this offer."

"Well I just looked it up on the Google," neighbor 2 yells excitedly.  "Says on the Internet that living near bulls and rams can bring all sorts of harm.  In fact, bulls are known to gouge which can become infected causing death!  I have two small children that walk in that pasture!  I'm going to have to say 'no' now"

"Hold on a minute!" neighbor 1 says a bit perturbed.  "I've been around bulls and rams all my life, and nothing has ever happened to me!  I don't know what y'all are afraid of, look at the money we would all be getting?  So what if they add some bulls and rams to our pasture.  It's worth it in my opinion."

"I have a suggestion" I say.  "Why don't we contact one of those Bullologists from the local University and see what an expert has to say."

The next day, a man looking just like a college professor, shows up at our town hall and tells us his name is Professor Paracelsus.  "Call me Dr. P" he says with a smile.

"So the concern is over the bulls and rams that this out-of-town fellow will be adding to your pasture," Dr. P says.  "I can see you have been researching this on the Internet and have little doubt why some of you are now very afraid.  Let's look at the rams first shall we."

"We look at exposure to rams and bulls..." Dr. P continued, "...based on their acute (short-term) and chronic (long-term) adverse effects.  We then determine the number of bulls and rams a person can be exposed to - called a dose - and the health effect that will result - called the response."

"Because rams have horns that bend inward they are unable to gouge you if you come in contact with one.  No gouging means no infection.  Now rams can still cause harm, but you need a bunch of them.  One can knock you over, but the only way you can be seriously hurt is if a bunch trample over you.

"Now the number we determine will cause harm is dependent on the population that will be exposed.  Young children, older folks, and those that are sick are most vulnerable to being trampled so we set the "safe" amount of rams you can be around daily based on this.  This dose-response level is called a threshold or Reference Value (ReV) -  a dose below which no effect is observed. In scientific terms, we call this a non-linear nonlinear dose-response relationships."

"Acute ReVs are the number of non-gouging animals a person can be exposed to and are typically derived for a 1-hour exposure time with that animal.   Chronic ReVs are are derived for a lifetime exposure duration to non-gouging animals and assume that constant exposure that causes bruising, sprains and broken bone may cause arthritis or amputations in a person's later years."

"So being exposed periodically to rams will allow for a much higher number than if you were to constantly be exposed to them throughout a lifetime.  ReVs are designed to protect the most sensitive individuals in a population by inclusion of  uncertainty/variability factors (UFs). UFs account for differences between the test populations we study, variability within the human species (football players take less damage than ballerinas), and uncertainties related to the applicability and completeness of the available data. Since UFs are incorporated to address these data gaps, variability, and other uncertainties, exceeding the ReV does not automatically indicate that an adverse health effect would occur."

"So how many rams could my children and I be exposed to?" neighbor 2 asks.

"Well, based on what data is available, your short-term level is 14 rams and the long-term level is 9 rams.  So your kids should be safe as long as the number of rams they are exposed to periodically is below 14.  And as long as it does not go above 9 rams each and every day, there should not be any short or long term health effects at all."

"Well that's all well and good for rams," neighbor 3 says.  "But what about them bulls!  All it takes is one to gouge you and you could get an infection and die!"

"Well...in a round about way," Dr. P. responds.  "Gouging is a bit harder to give a "safe" number for the animal since all it takes is one.  That's why with animals that can gouge we use the term relative risk as the safe level."

"Oh, you mean that one in a hundred-thousand infection nonsense? neighbor 2 pipes in.  "Yeah...safe huh?  How would you like your child to be that "one" that does get the infection and dies?"

"Er...yeah, that's what it sounds like, but that's not how it works," Dr. P. says.  "What we do is use mathematical models which are based on human and animal studies to estimate the probability of a person developing infection from being gouged while exposed to a specified number of that particular gouging animal. A range is then calculated for the increase in the lifetime risk of an individual who is continuously exposed to that particular number each and every day over their lifetime."

"So the Center for Horn Gouging has estimated that continuously walking in a pasture with 7 to 9 bulls would result in not greater than a one-in-a-hundred thousand increased chance of getting an infection.  Now remember, that's an increase chance, it is not a given.  And even if you were to get an infection, it can often times be cured or is very slow in developing."

"Still, I don't like it!" neighbor 3 says adamantly.  "This out-of-town fellow is going to be bringing rams and bulls into our pasture.   If we say "no" we will not be exposed to any bulls or rams."

"Not so fast," neighbor 1 says.  "You have been walking in this pasture for a long time now.  We have bulls and rams living there and - up till now - you have never paid them any attention or concern!  Every pasture you walk through is going to have some type of animal that can cause you harm."

"That's correct," Dr. P. interjected.  "You cannot escape exposure to gouging and non-gouging animals.  They are everywhere you go and are part of your everyday existence.  As long as this out-of-town fellow uses proper bull and ram reproductive prevention devices, living with this increased exposure will present no immediate health concerns from their presence in your pasture."

"Well I still don't like it," neighbor 3 says.

"That's understandable" Dr. P. reassured her. "But until we find a better way to do without them, these types of risk will always be with us.  My job is to present you with factual information.  Your job is to weigh the pros and cons and to make sure that out-of-town fellow does everything he possibly can to minimize your risk.  You can say "yes" and be safe, but that fellow has got to do his part in making sure his bulls and rams stay well confined and in small enough numbers so that you are not harmed."

"Oh, and stop reading stuff on the Internet unless you know it's from a reliable and reputable source.  There are a lot of people out there with an agenda that will mislead you to believe what they want you to believe."

Next post: Air Quality in the Barnett Shale - Part 9: Dose and Dogs

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Air Quality in the Barnett Shale - Part 7: Benzene Exposure and the No Significant Risk Level.

Carcinogens are a bit trickier to deal with in terms of determining a safe level.  This is because there is no concentration other than zero that one can say will present no chance of getting cancer from exposure to it.  Instead of a threshold dose, we look at a exposure level determined to present "no significant risk."

This level is defined as the level which is calculated to result in not more than one excess case of cancer in 100,000 individuals exposed over a 70-year lifetime. In other words, if you are exposed to the chemical in question at this level every day for 70 years, theoretically it will increase your chances of getting cancer by no more than 1 case in 100,000 individuals so exposed. (5)

What it does not mean is that one person per 100,000 individuals will get cancer.  This is the same concept behind rolling a six sided die.  You expect to see a "one" show up every six rolls, but you could roll it 50 times without ever rolling a one.

Basically, the ESL and AMCV are calculated the same way:

• (chronic)ESL = 0.00001 / URF
• (chronic)AMCV = 0.00001 / URF

The URF or "Unit Risk Factor" for carcinogens do not have a threshold dose at which below that concentration no cancer would take place. What this means is that any exposure has the chance to cause cancer and that the more exposures the more chances for cancer to manifest itself result.  This makes exposure to "Benzene, a know human cancer causing agent" a scary thing to read over and over again in a report (7).  This is where context and explanation are critical components to any report involving a complex formula, a number, and the words "know human cancer causing agent."  This is also where Alisa Rich, who - need I remind you again - has a Master in Public Health, failed to convey the risk properly.

Why did Alisa Rich and Wilma Subra fail to put this information in context?  Maybe it's because they lack a basic understanding of how the "no significant risk" is calculated and how to compare the 24 hour values with this risk.  It is quite possible that we receive a much better education in our MPH program at Texas A&M's School of Rural Public Health than one receives at the University of  North Texas, but I know that is not the case here.  So instead I will assume that both of  these experts just don't fully understand the topic they sell themselves as knowledgeable in.

Here is how TCEQ explains it in their 2006 document called "Guidelines to Develop Effects Screening Levels, Reference Values, and Unit Risk Factors" in 1.5.2:

For adverse effects associated with a linear dose-response [such as carcinogens], it is assumed that an effects threshold does not exist. Therefore, a linear extrapolation from the POD [point of departure] to the origin of the inhalation dose-response curve is performed to estimate excess lifetime risk at lower doses. The slope of the line from this linear extrapolation is the inhalation URF, which is defined as the upper-bound excess risk estimated to result from continuous lifetime exposure to an agent at a concentration of 1 μg/m3 in air (i.e., risk estimate per μg/m3). 

Confusing?  Lets look at this in terms of Benzene: (8)

• EPA uses mathematical models, based on human and animal studies, to estimate the probability of a person developing cancer from breathing air containing a specified concentration of a chemical. EPA calculated a range of 2.2 x 10-6 to 7.8 x 10-6 as the increase in the lifetime risk of an individual who is continuously exposed to 1 µg/m3 of benzene in the air over their lifetime.  
• EPA estimates that, if an individual were to continuously breathe air containing benzene at an average of 0.13 to 0.45 µg/m3 over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of continuously breathing air containing this chemical.
• Similarly, EPA estimates that continuously breathing air containing 1.3 to 4.5 µg/m3 would result in not greater than a one-in-a-hundred thousand increased chance of developing cancer, and air containing 13 to 45 µg/m3 would result in not greater than a one-in-ten thousand increased chance of developing cancer.

So the Benzene values obtained from a single 24 hour sampling event performed by Wolf Eagle Environmental were

Now on first glance, one might think "I'm going to get cancer because of Samples 2, 3,and 4."  But that is not the case.  There are two things necessary for one to develop cancer from breathing this particular air.  The first is you would need to breath that air - at the concentration - for 70 years.  Secondly, your body would have to have develop a cancer from the uptake of that particular contaminant.  

It's a lot like flipping a coin.  If you have a 50% chance of the coin landing on tails - when you flip the coin - either heads or tails can come up.  So if I told you you had a 1 in 2 increased chance in developing cancer, you might not want to be exposed.  Now lets change that coin for a single die with six sides.  If you exceed that level over a lifetime, you roll the die and if the number "one" shows up you get cancer.  That would be a one in six increased lifetime chance.  Now lets change out that 6-sided die for one of those funky die they use when playing Dungeons and  Dragons, only in this case, it will have 100,000 sides to it with the numbers 1 to 100,000.  Now if you continuously breath air containing 1.3 to 4.5 µg/m3 of Benzene for a lifetime, you would roll this 100,000 sided die and if the number "1" came up you would get cancer.

For samples 2, 3, and 4, the benzene level is higher than the amount deemed no significant risk.  In this case, the risk - if one were to be exposed at that level in sample 4 constantly over a 70 year lifetime-  would be between:

• 247.9 x  0.0000022 = 0.0005   and    247.9 x 0.0000078 =  0.002

Or an added - or excess - lifetime risk between 1 in 500 and 1 in 2000.  At these elevated levels, the cancer risk has increased, but that is only if the exposure remains at 247.9 ug/m3 and the body fails to repair itself and develops a cancer.  Obviously the levels of benzene detected are too high and additional investigation should be done to determine the cause and fix the problem.  But even at these levels, cancer from benzene is not inevitable.

So looking at this in context, exposure to benzene has the potential to cause cancer but unless the levels are high and sustained over a lifetime, the risk of cancer is not significant.  You may be the unlucky person that rolls the "1".  This is where evaluating risk comes into play and the concept of accepted risk and risk that is forced upon you.  One may reasonably conclude that any risk is a risk too many.  But is eliminating the potential for a one in 100,000 possibility at something negative happening worth the benefits obtained from having it?  I can't make this decision for someone who is potentially impacted by the risk coming from those benefits.  What I can do is try and put it in perspective.   Because even if you eliminated every gas well and drilling rig from the area, exposure to Benzene will still take place and cancer - from lots of other sources - will still manifest itself.

There are a lot of factors in place for citizens in and around gas production activities.  The fact that we find chemicals in the air on one particular day does not mean that exposure at that level will take place the other 364.  And even if there is exposure at that level, we still do not know if the second to final step in the K. C. Donnelly Risk Paradigm - uptake - takes place.  And even if uptake does happen, the body is very good at dealing with contaminants through a process called pharmacokinetics.  And even if we end up with a negative health effect we have very good medical procedures to treat this.

And even if the die rolls a one, we are still unable to pinpoint the culprit, for we have no background data on what levels of these contaminants were present before the gas operation began.  All of this must be taken into consideration befor you say "yes" or "no" to assuming the risk.

Now lest you think I am giving the oil and gas industry a free ride here, I am not.  I will deal with their issues at the conclusion.  What I am writing about in these posts is how Wolf Eagle Environmental and Wilma Subra have painted a picture that does not represent fully and accurately the reality the citizens of the Town of DISH Texas are facing.  That is unfair to them, unfair to the Oil & Gas industry, and unfair and damaging to my profession which is dedicated to protecting the environmental and public health.

Next post: Air Quality in the Barnett Shale - Part 8: Benzene is like a bull...

Note: 2/16/11 A bio found on the internet lead me to incorrectly assume that Alisa Rich received her MPH and was working on her Ph.D from UT.  An email I received from Barnett Shale News included a Deposition from her stating she got her MPH from UNT's Health Science Center and is working on her Ph.D at UT Arlington.
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Air Quality in the Barnett Shale - Part 6: Cumulative Risk & ESL Development

In my last post, I wrote that the TCEQ, makes a rather unambiguous statement regarding the health concerns in the Barnett Shale stating explicitly:

"[T]here are no immediate health concerns from air quality in the area."

Now you can read into that what you will.  You can ignore it, you can disagree with it, you can doubt it, or you can follow up with, 'but what about long-term health concerns?' For which the TCEQ addresses by stating:

"[T]hat when they are properly managed and maintained, oil and gas operations do not cause harmful excess air emissions.”

There are two issues I am trying to address with these posts.  The first is Wolf Eagle Environmental assertion that the chemicals present pose an acute and/or physical hazard:

While atmospheric Methane concentrations recorded over the past year in the Town of Dish do not exceed TCEQ ESLs, the intrinsic quality of Methane to be an asphyxiant should not be overlooked.  In addition, Methanes is highly flammable and can form explosive mixtures in high concntrations in air." (1)

"In addition, several locations confirmed exceedences in a chemical identified by TCEQ with the capability for 'disaster potential'," (2)

The second asks the question does exposure to these chemicals at the levels detected in the one hour and annual averaging - as well as the levels reported by Wolf Eagle Environmental pose a chronic health concern?  That's the $64k question, since some adverse health effects take decades to manifest themselves.  So what toxicologists and health officials do is try to determine a "safe" level.  Unfortunately we are exposed to many chemicals at different concentrations throughout the day and over our lifetime.  Because two or more chemicals can interact synergistically, additively, antagonistically, or be potentiating, a cumulative risk approach is adopted.

In the process of determining risk and/or a 'safe' level, the culprit releasing the chemical of concern is not important.  So when ambient air monitoring is performed it takes a snapshot of all the different chemicals that were present in the air at the one location in time.  What has been shown is that single chemical contaminants can be detected intermittently over time and a single chemical detected at that one location may come from multiple sources. (3)

TCEQs ESLs are "intended to be comparison levels used in the TCEQ’s air permitting process to help ensure that authorized emissions of air contaminants do not cause or contribute to a condition of air pollution."  ESLs are used for air permitting whereas the “air monitoring comparison values” or AMCVs are used for comparing air monitoring results.  ESLs are chemical specific concentrations modeled on a worst-case ground-level air concentration of a single chemical exposure and the potential for an adverse effect due to operation of the facility.  ESLs are very conservative in how they are calculated so when a measured concentration is above the ESL, a review of the actual toxicity data on that chemical may conclude that health effects would not be likely to occur at that level. ((AMCV Document))

Say what?!?  Yeah...which is why the TCEQ goes on to say:

"This broad conservative application of the ESLs has resulted in misunderstandings among the public because the ESLs did not represent the predictive toxicity of the chemical. ESLs continue to be useful screening values for air permitting, but more realistic, predictive values are needed for use in the review of ambient air monitoring data."

Why would they do this?  Why would the purposely develop a method that - for the most part - says - It is a health problem if it exceeds the level unless it isn't a health problem.  That's what Dr. Robin Autenrieth meant when she said "the people demand a number."

Because chemicals do not follow the same drummer, coming up with a uniform way to categorize their toxicological health risk - the "number" we can compare to - creates situations where on one hand it exceeds the level that indicates a health risk but on the other hand there is no data showing a health risk at that level.

And we wonder why the public can be confused, and - in the case of data presented by two experts - misled to believe there are problems because of the number of times a contaminant exceeded this level.  And if I have not beat this dead horse enough, it is inexcusable for Alisa Rich - who holds a Master in Public Health from the University of Texas - to not have understood this and addressed it accordingly in her reports to the good people in the Town of DISH, Texas.

But I digress.  So if the people demand a number, how is this number derived?  Well it basically boils down to this - "the no significant risk level for an individual chemical" defined as:

• the concentration associated with a hazard quotient (HQ) of 1, and...
• the concentration associated with a theoretical excess lifetime cancer risk of one in 100,000 (1 x 10-5).

This where the math that is needed to derive the number comes into play.  Mathematics follow very hard and fast rules.  Two plus two always equals four.  But in toxicology, there are very few hard and fast rules.  Almost everyone has heard stories of someone who drinks like a fish and/or smokes like a chimney and lives to be 90!

So to level the playing field as to what is 'safe' the HQ is used for concentrations of non-cancer chemicals and the theoretical excess lifetime cancer risk of one in 100,000 is used for cancer causing chemicals.  Because there is both cumulative and aggregate exposure to chemicals, the TCEQ uses an HQ of 0.3 to calculate Short-term and Long-term ESLs for the bulk of chemicals.  This is why an ESL is described as "70% lower than the reference value" itself. (6)  In most risk assessments, the HQ is set at "1" which is how the AMCV is calculated.

Why the difference for air permitting and air monitoring?  I am not quite sure, what I suspect is that air monitoring assumes a baseline amount - that is - there is nothing that can be done about that concentration we are exposed to.  When a business wants to start up an operation that will produce and potentially add those chemicals into the mix, the cumulative and aggregate exposure may result in an increase in health concerns that would not bee seen if we were only addressing that particular contaminate by itself.  So, to be extra protective, the level (number) applicable to air permitting is derived using an HQ of 0.3.  This is why the TCEQ states:

ESLs are used in the air permitting process to assess the protectiveness of substance-specific emission rate limits for facilities undergoing air permit reviews. Evaluations of modeled worst-case ground-level air concentrations are conducted to determine the potential for adverse effects to occur due to the operation of a proposed facility. They are comparison levels, not ambient air standards. If predicted airborne levels of a chemical exceed its ESL, adverse health or welfare effects would not necessarily be expected to result, but a more in-depth review would be triggered. (7)

AMCVs and ESLs  that are derived from a HQ are for non-cancer causing chemicals.  Air contaminants that are known or suspected carcinogens receive a comparison value derived from a mathematical formula that assumes that at that value there will be no significant risk for cancer.

For a chemical that is listed as a carcinogen, the "no significant risk" level is defined as the level which is calculated to result in not more than one excess case of cancer in 100,000 individuals exposed over a 70-year lifetime. In other words, if you are exposed to the chemical in question at this level every day for 70 years, theoretically it will increase your chances of getting cancer by no more than 1 case in 100,000 individuals so exposed. (5)

For non-cancer causing chemicals and chemicals that show a nonlinear effect, the formula:

• (acute)ESL = 0.3 x (acute)ReV
• (chronic)ESL = 0.3 x (chronic)ReV
• (acute)AMCV = (acute)ReV
• (chronic)AMCV = (chronic)ReV

Both the ESL and the Reference Value (ReV) must be expressed in the same units (micro-grams/cubic meter)  and represent the same exposure period.  This means that if you are going to compare your sample data to an ESL or AMCV, the units and exposure period must be the same.  When Wolf-Environmental and Wilma Subra report 16 volatile organic chemicals exceeded the TCEQ ESLs they used data from a sampling exposure period that was 24 times to long for the short-term and was not averaged over a one year period for the long-term.

This would be like trying to run a restaurant knowing that one coffee pot can effectively serve enough coffee for 100 people per hour. So you hire Wolf Eagle Environmental and Wilma Subra to find out how many coffee pots you need.  They monitor the store for 24 hours and report 800 people.  They then tell you that this exceeded the manufacture's stated value of 100 people by over 8 times!

OK...OK...they were they screwed up when they compared a 24 hour sample to a one hour level.  But were not talking about coffee here.  Even if they had taken the sample for an hour, it appears that they detected Benzene.  And Benzene, according to their reports is a known cancer causing contaminant!  I read on the internets that there is no safe level for a cancer causing compound.  That any exposure increases the risk of cancer.  If there is Benzene in their samples and I am exposed to that, will I get cancer?

Probably not.


Probably?? Is that the best answer you can give?


Well...that's the only answer anyone really can give.  Although - for most chemicals -I can say  with with a very high degree of certainty 'if you stay below this value, you will have no adverse health effects', carcinogens require me to say there is 'no significant risk' if you stay below this level.

Next post:  Air Quality in the Barnett Shale - Part 7: Benzene Exposure and the No Significant Risk Level.

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Air Quality in the Barnett Shale - Part 5: 'n' is for sample size.

To be honest, it has been difficult to write these posts without wanting to completely tear apart everything Wolf Eagle Environmental did for the Town of DISH, Texas.  I'll save my "feelings" on this for my last post.  I am critical - and believe it is warranted - because the author of the reports - Alisa Rich, holds a Master in Public Health (MPH).  I hold one too, so I know she had to have exposure (pun intended) to the concept of "sample size" or 'n' in a number of her classes - particularly statistics and Epi..

I am also fairly certain that she was informed in her pursuit of her MPH about sampling and analytical bias, particularly bias caused through operator error - which is why we like lots and lots of 'n' as well as replicate samples.  As a Ph.D. candidate (PhDc), she should have had more exposure to this concept than us regular ol' MPHs.  So it is a bit difficult to defend her sampling plan and methodology which she and Wilma Subra used to formulate their conclusion which was submitted to the citizens of the Town of DISH, Texas.

So here I am, once again, having to ignore all of that potential error and bias (scientific) and make an assumption as to its validity.  The TCEQ had to acknowledge the same thing in their memo regarding Wolf Eagle Environmental's sampling results.  So, as it stands, I must assume that the data obtained on August 17, 2009, is an accurate representation of what a citizen of DISH, Texas is exposed to.

Because a comparison of these collected values were made against values established by the TCEQ as 'safe' (ESL), and the reporting by both Ms. Rich and Ms. Subra that there were 45 incidents where the values obtained from analysis of seven different sample locations exceeded these safe values, the confidence in the data they collected and analyzed is paramount.  Unfortunately, it is not,  Still, it is all we have, and the cat has been let out of the bag regarding the potential health impact that could come about because of these values reported along with how this information was laid out in their conclusions.

So how does one work through this?  What should have taken place on August 17, 2009. were seven "instantaneous" samples collected at least twice during the day. Analysis costs money, so the fewer the samples the less the cost.  But, this also brings in bias, which is why researchers always want more data.   Had instantaneous samples been collected instead of leaving the valve open for 24 hours, a more clear comparison to a "safe" value could have been made because ESLs and AMCVs are based on one hour sample collections in terms of impact from exposure.

Instead we are presented with analytical results that show contaminant ppb concentrations that were collected over a 24 hour period.  Although I am perfectly within my right to take this 24 hour value and divide it by 24, by doing so, I will dilute any spikes that may have happened.  This is why the TCEQ monitors these contaminants on an hourly basis.  Because you may exceed a threshold during one hour period which would be diluted by all the other hours collected.  Averaging is important, but so is knowledge of when - or if - thresholds are being exceeded during certain times of the day.

The seven samples - had they been instantaneous - would have been a snapshot of that particular time and day.  Even had they purposely biased the sample by choosing the most ideal conditions, it would have been of more use than a sample collected over a 24 hour period when trying to look at potential risk for a one hour period.  To counter this problem with Wolf Eagle Environmental's methodology, the TCEQ in their memo made the assumption that the 24 hour values obtained reflected a one hour sampling event that was diluted by 23 hours of air that contained no contaminants.  Why?  Because instantaneous samples are a snapshot, 24 hours are an average.  It is just as possible that this scenario happened as it was that the levels were uniform throughout the day at which case they could have been divided by 24 (my way).

To determine the potential 1-hour maximum concentrations of all reported chemicals, the reported 24-hour concentration was multiplied by 24. This calculation conservatively assumes that the chemical had a maximum concentration for one hour and was not detected for the remaining 23 hours.

And therein lies the problem with how we determine risk.  We make assumptions most always on the side of 'worst case' or upper bound limits just to be on the safe side.  This compounded conservatism gives us values that are extremely low so that we health and safety types can reasonably tell you "it's safe."

If you read Wolf Eagle Environmental's final report as well as Wilma Subra's summary report they never state explicitly that there is a health concern.  The TCEQ, however, does make a statement on health concerns in the Barnett Shale stating explicitly "there are no immediate health concerns from air quality in the area."  What you need to realize here is that we public health types cannot say, for certain, that there are, or will never be, a health concern.  Why?  Because we lack data on humans.  So we use available data on animals and models, and subjective health questionnaires to help us make a reasonable guess as to the level of concern.

And it is because of this guessing, and the need to be 'sure,' that levels are set so low.  And it is also because of this guessing that those who have an agenda or see anecdotal evidence of cause and effect, feel free to guess as well.  And all of this leads to confusion, concern, and fear for the people that are downwind from the event.

But there is a difference between guessing using scientific principles and methods and the reliance on anecdotal evidence, incorrect sampling, improper comparisons, conjecture, and implausibility.  In other words, public health safety guessing is not just guessing. There is a method behind the madness, and it has to do with accepting a model that is built around a a flawed premise and compounded conservatism.  It's all about the reference value (ReV) and the fact - as my Risk Assessment Professor - Dr. Robin Autenrieth - so succinctly informed me "the people demand a number."

Next Post: Air Quality in the Barnett Shale - Part 6: Cumulative Risk & ESL Development


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Air Quality in the Barnett Shale - Part 4: Exceeding TCEQs Short-term ESLs

So what do we know so far:

1. Wolf Eagle Environmental and Wilma Subra used sample results collected from one 24 hour sampling event to compare against Long-term ESLs that are used to evaluate modeled 1-year concentrations.
2. For the seven sample locations, there were a total of 13 times where a chemical detected exceeded the TCEQ's Short-term ESL.
3. TCEQ states that exceeding the ESL "does not necessarily indicate a problem but rather triggers a review in more depth."
4. TCEQ states that “[a]fter several months of operation, state-of-the-art, 24-hour air monitors in the Barnett Shale area are showing no levels of concern for any chemicals. This reinforces our conclusion that there are no immediate health concerns from air quality in the area[.]"

Lets assume that the values obtained from this single 24-hour sampling event represent the amount the citizens of DISH are exposed to, day in, day out.  Because this was a sample collected over a 24 hour period, the 1 hour concentration is equal to 1/24 of the concentration detected and reported.  So, if the highest concentration of benzene reported by Wolf Eagle Environmental was 77.7 ppb (Airfield @1:29) the one hour concentration would be 77.7 / 24 =  3.24 ppb.


Note 2/14/11: I looked at it as an average concentration,  The way TCEQ looked at it, was that there was a single one hour level which was diluted with 23 hours of "clean air."  In re-looking at this, because we are comparing a sample concentration to a one hour ESL (the amount that would be the highest concentration in an hour whereby no adverse health effects would be found) the TCEQ assumption fits better than my averaging assumption.

The reason we divide by 24 is because the sample canister was left on for 24 hours. The Short-term ESLs used by the TCEQ are based on the concentration that would be present in a one hour block of time.  Because we use ppb - or parts of contaminant per billion parts of air - to make comparisons, leaving the canister open for more than one hour would take in more parts of contaminant but the total volume of air would remain the same.  

Canister Sampling is  method of taking a sample of air that uses a stainless steel canister that has been scrupulously cleaned and is under a vacuum. The operator opens the valve on the canister, allowing the air sample to rush into the canister to fill the vacuum. When the canister is opened all at once allowing the air to be sampled over the span of a few seconds, [TCEQ] terms this an instantaneous sample.  A controller can be put on the canister sampler controlling (slowing) the flow of air into the canister over a prescribed time, i.e. 30 minutes, 1 hour, or 24 hours. The samples in the canister are then analyzed on another instrument, typically a gas chromatograph (GC).

TCEQ also recognized this flaw in Wolf Eagle Environmental's reporting but gave them the added benefit of conservatively assuming "that the chemical had a maximum concentration for one hour and was not detected for the remaining 23 hours."  In their memo dated October 29, 2009, TCEQ, in order to compare Wolf Eagle Environmental's 24-hour concentrations with a 1 hour value, multiplied them by 24.  In this manner, the TCEQ compared reported concentrations of the ambient air at the Town of DISH that were 24 times higher than actually detected!  They did, however, note: "This may or may not represent actual conditions."

So now we can add one more to the list of what we know so far

5. Sampling and analysis reported 24 hour concentrations which were compared to ESL values that represent the concentration collected in a one hour period of time.

 Ready for another one?  Yes, there is a number 6.  One more error in their reporting of certain chemicals exceeding TCEQ's ESLs.  The ESLs they used to compare with in their "Revised Air Study Documents" were the wrong type of values to use.


According to the TCEQs AMCV document called "Uses of Effects Screening Levels (ESLs) and Air Monitoring Comparison Values (AMCVs) Revised (May 2010)" Although the same Short-term and Long-term were used for both air permitting and air monitoring, air concentrations of chemicals collected in air monitoring samples represent emissions from multiple chemicals and from different facilities and sources.  For review of air monitoring data, the health-based ReV is appropriate.

ReVs [reference values] are designed to protect the most sensitive individuals in a population by inclusion of uncertainty/variability factors (UFs). UFs account for differences between study animal and human species, variability within the human species, and uncertainties related to the applicability and completeness of the available data. Since UFs are incorporated to address data gaps, variability, and other uncertainties, exceeding the ReV does not automatically indicate that an adverse health effect would occur.

For air permit applications, site-wide modeled concentrations for one chemical at a time are evaluated.  Therefore, for air permitting, an additional buffer is applied to the acute or chronic ReV to calculate the acute and chronic ESLs. The final acute and chronic ESLs developed using the Guidelines are 70% lower than the respective acute and chronic ReV.
  

Because there are "significant differences between performing health effect reviews of air permits and the various forms of ambient air monitoring data," the [TCEQ] has begun using the term “air monitoring comparison values” (AMCVs) in evaluations of air monitoring data.  

AMCVs are chemical-specific air concentrations set to protect human health and welfare. Exposure to an air concentration at or below the AMCVs is not likely to cause adverse health effects in the general public, including sensitive subgroups such as children, the elderly, pregnant women, and people with preexisting health conditions. AMCVs are a collective term that refer to all values used by [TCEQ] staff to review ambient air monitoring data.

The use of different values and different terminology is appropriate because the air monitoring and air permitting programs perform different functions in the protection of human health and welfare."

• The short-term AMCV, based on acute exposure health and welfare data, is compared to monitored concentrations that can be instantaneous or up to 1-hour, which represent a point in time for a specific location.
• The short-term ESL, based on acute exposure health and welfare data, is compared to the modeled 1-hour Maximum Ground Level Concentration (GLCmax).
• The long-term AMCV, based on chronic health and welfare data, is used to evaluate annual averaged monitored concentrations or annual concentrations averaged over multiple years (if available), which represent multiple points in time for a specific locations.
• The long-term ESL, based on chronic or lifetime exposure health and welfare data, is compared to the worst-case annual GLCmax.

So basically, the work performed by Wolf Eagle Environmental looked at the contaminants detected and reported them as if they were being addressed for an air permit.  Lets assume that the values obtained did represent the concentration in air that a citizen of the Town of DISH was going to be exposed to.  What then?

Getting back to benzene and xylene (m & p), how many times was there an exceedence?  And by how much?

Now remember, there are two things in play here.  1st, the ppbv results shown are for 24 hours worth of sampling and could be 24 times higher than what you would have seen if the sample was collected for just one hour.  And 2nd, the ESLs are 70% lower than the reference values.  So, because none of these values exceed the AMCV, we can safely say that exposure to an air concentration at or below the AMCV is not likely to cause an adverse health effect in the general public, including sensitive subgroups such as children, the elderly, pregnant women, and people with preexisting health conditions.

Ignoring the incorrect sampling...ignoring the incorrect comparison, and assuming that these values represent the amount a citizen of the Town of DISH is exposed to, will there be any negative health concerns from these contaminants?

Here is what the TCEQ states in their memo:

The highest potential 1-hour maximum benzene concentration [actual x 24] is below the health effects level observed in short-term animal and human studies; however, it is possible that adverse health effects could occur from exposure to this concentration. It was not possible to determine if residents were exposed to this concentration of benzene based on the information provided.

Here is what I say - and I am not going to far out on a limb: Not likely - because even if you multiplied the contaminate concentrations by 24 like the TCEQ, and even if they exceeded the ESL and the AMCV, there is a margin of safety - uncertainty - built into these comparison values.  It all comes down to how we calculate risk and the value we use in the calculation for the ESL and AMCV.  It's all about the reference value - the ReV.

Air Quality in the Barnett Shale - Part 5:  'n' is for sample size.

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Air Quality in the Barnett Shale - Part 3: TCEQs Effects Screening Levels.

According to Wilma Subra's summary report based on the Wolf Eagle Environmental's final report, the following values for Benzene and Xylene (m & p) were given for each of the sample locations where an exceedance was noted:

• Benzene exceeded the Long-term  ESL by 8.7 times the standard.
• Xylene (m & p) exceeded the Long-term ESL by a factor of 1.1 times.
• Benzene in the air exceeded the Short-term ESL by 1.45 times and the Long-term ESL by 55 times.
• Xylenes (m & p) exceeded the Long-term ESL by 2 times.
• Benzene in the air exceeded the Long-term ESL by a factor of 7.6 times.
• Three sample locations exceeded TCEQ ESLs [for Benzene]
• Two sample locations exceeded TCEQ ESLs [for Xylene (m & p)].

The Wolf Eagle Environmental's final report makes the following statement (using bold type):

(I'll discuss the use of the term 'disaster potential' in an upcoming blog)

So what is an ESL that these two environmental professionals keep referencing as having been exceeded?  Lets look at the TCEQ definition (emphasis mine):

Effects Screening Levels [are] used to evaluate the potential for effects to occur as a result of exposure to concentrations of constituents in the air. ESLs are based on data concerning health effects, the potential for odors to be a nuisance, and effects on vegetation.

If predicted airborne levels of a constituent do not exceed the screening level, adverse health or welfare effects are not expected.  If predicted ambient levels of constituents in air exceed the screening levels, it does not necessarily indicate a problem but rather triggers a review in more depth.

ESLs [are] expressed in terms of microgram per cubic meter (µg/m3) or parts per billion by volume (ppbv) in air.  

If you recall, here is what the TCEQ has said about the air quality in this area:

“After several months of operation, state-of-the-art, 24-hour air monitors in the Barnett Shale area are showing no levels of concern for any chemicals. This reinforces our conclusion that there are no immediate health concerns from air quality in the area, and that when they are properly managed and maintained, oil and gas operations do not cause harmful excess air emissions.”

So if the test results of Wolf Eagle Environmental are correct, how can all these samples that exceeded the ESLs be dismissed by the TCEQ?  I mean, what gives?

Well - and I hate to say this about two of my fellow environmental professionals - they obviously either do not understand how to use the ESLs, or - and I hope this is not the case - they are using them to show the appearance of a risk that is necessary to further a particular agenda.

Now I am only addressing Benzene and Xylene (m & p) in this post - not to cover anything up about the rest of the chemicals found, but to make this post a bit more readable.  I will address all the chemicals that exceeded the ESLs in an upcoming post.  According to the TCEQ in their document titled ESL List June2010.xls:

“Short-term” generally indicates a one-hour averaging period. Exceptions are noted parenthetically after a constituent name [for reproductive/developmental effects]. “Long-term” indicates an annual averaging period.  Both short- and long-term ESLs are listed on the ESL List.

 The reason that there are two values has to do with effects that are 'acute' or 'chronic.'  Acute effects are what we expect to see with a one time short duration exposure.  Chronic effects are what results when one is exposed constantly over a very long period - usually calculated as 70 years of exposure at that particular concentration.  The sampling performed has a different duration when looking at Short-term ESLs or Long-term ESLs.  According to the TCEQ:

The exposure duration generally associated with short-term ESLs is 1 h, although exposure may occur on an intermittent basis.  Long-term ESLs are are used to evaluate modeled 1-year average concentrations.

What this means is that you cannot use sampling data that was collected during a single 24 hour period and use it to compare against ESLs that have been established for sampling data averaged over one year.  Unless you want to infer that a one time sampling event will represent what would be seen each day for 365 days, regardless of wind direction, humidity, temperature, rain, and snow, you cannot do this.  Well at least I would never make such a bold assertion, especially knowing that one of my peers might come across my report....

But besides all that, if you are going to make a statement that the Long-Term ESLs were exceeded, and you are going to use that bit of information to assert excess exposure to known human carcinogens, then you need to use them as they were intended.  You cannot compare Long-term ESLs with sampling results collected from a one time sampling event.  This would be similar to looking at my bank account on the first of the month (payday) and making the statement that I have that much money in my account everyday.

So based on this, for all the chemicals analyzed, there were a total of thirteen that exceeded the short-term ESL (the only ESL that can be compared against) and of these, only Benzene was found to exceed the Short-term ESL once.

OK, so if we ignore the Long-term comparison because they only took one single 24 hour hour sample, there were still thirteen times one or more chemicals exceeded the Short-term ESL.  And one of those chemicals - Benzene - a known human carcinogen - was found to have exceeded the Short-ESL.  Shouldn't that cause concern?

No, not really.  Remember what the TCEQ says about exceeding the ESL:

If predicted ambient levels of constituents in air exceed the screening levels, it does not necessarily indicate a problem but rather triggers a review in more depth.

Next post: Air Quality in the Barnett Shale - Part 4:  Exceeding TCEQs Short-term ESLs


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Air Quality in the Barnett Shale - Part 2: Exposure to a toxic chemical

Did you know that the average five year old child is exposed - on a daily basis in most cases - to over 44 times the lethal dose (LD50) that has been established for the chemical dihydrogen oxide (CAS# 7732-18-5) with the molecular Weight: of 18.02?

Sounds pretty scary doesn't it?  It's all true too.  And if you were to read this in a scientific report written by experts who tout their purpose as helping "ordinary citizens understand, cope with and combat environmental issues" you might have reason for concern, especially if your kid was, in deed, being exposed.

No one wants to have themselves or their family - especially children - forced into a situation where there is "exposure" to a chemical that has scientific data indicating that it is "lethal" or a "neorotoxin" or a "known human cancer causing agent."

So when the citizens of the Town of DISH Texas read a report located on their city's webpage titled "Evaluation of Town of DISH, Texas Ambient Air Monitoring Analysis written by someone who was "Vice-Chair of the EnvironmentalProtection Agency National Advisory Council for Environmental Policy and Technology (NACEPT)" they could not be faulted for coming to the conclusion that the development of the Barnett Shale gas industry in a residential area could lead to immediate or long-term health concerns due to the production of harmful excess air emissions.

Now it is not my intention to say the that there is, or is not, a health concern posed by this operation.  The TCEQ indicates that their monitoring "after several months of operation....reinforces [their] conclusion that there are no immediate health concerns from air quality in the area."  The sampling performed by Wolf Eagle Environmental indicates concentrations above the TCEQs established short-term and long-term ESLs

Assuming that the Wolf Eagle Environmental data used for the conclusion in the report is correct; does exposure exceeding by "2 times" the ESL for meta- or para-xylene put the citizens of the Town of DISH at risk for "neurological effects" or "kidney injury and renal carcinomas?"

In other words, if a chemical is known to cause a health effect, will exposure to it result in that negative health effect happening?  What if the exposure is twice the amount deemed to be a safe level?  This concern - valid in my opinion - becomes particularly disconcerting when you talk about exposure to a chemical that is described as a "known human carcinogen" since cancers do not show up until many years later.

It is at this point that a little bit of background information on toxicity and exposure is necessary.  For the general public at large - misinformed by those with an agenda or fed information that is misleading, incomplete, or out of context - potential exposure - not of one's own choosing - to a chemical is almost always perceived as one that will or has caused a health effect.

But it is much more complex than that, and both Ms. Subra and Dr. Rich (with an MPH no less!) should have understood this paradigm.  At SRPH, we are drilled over and over on what we were told was called the "EPA Risk Paradigm."  Unfortunately, the promoter of this paradigm - Dr. K.C. Donnelly - passed away two years ago from pancreatic cancer and was never able to tell us why he called it that.  The EPA Risk Paradigm used by the EPA has a much different format and context.  The EPA's does not have the elegance of the one Dr. Donnelly taught us.  The original author is not know, so in hopes that he/she will not mind, I will henceforth refer to this as the K.C. Donnelly Risk Paradigm:

In a nutshell, just because a chemical is there, or could be generated, does not mean it will result in an adverse health effect.  Not only does it need to be released into the environment, it has to travel to the receptor, the receptor has to be exposed to it, and the chemical then has to enter into the body.  Even then there is no automatic negative health effect guaranteed since the body does a really good job of ridding these nasty chemicals as well as fixing the problems - including damage to DNA that could result in cancer - even if uptake does occur.

For air contaminants, the first five are easily met.  So looking at toluene for example; it is present as a constituent of fuel and petroleum products, so the chemical is present.  It is released into the air through exhaust or leaks, it is transported in the air, and if a person is in that path, exposure can take place.  Once exposed, the receptor - through breathing - can uptake the chemical through the lungs and into the blood stream.  All that is left is to see if the chemical now in the system will produce a negative health effect.

So lets look at our dihydrogen oxide example discussed at the start of this blog.  It is a chemical - having a Chemical Abstract Services number (CAS) of  7732-18-5.  It is intentionally released by the parent when the faucet is turned on to fill up the bathtub.  It is transported through the water system pipes into the bath tub where the child is exposed to it when they are placed into the bathtub.  The dihydrogen oxide enters into the child through breathing of vapors - especially if the bath is hot.  It is also sometimes consumed orally by the child as well as absorbed through the skin and through cuts and abrasions on the surface of the skin.  So uptake does, in deed, take place.  So will this exposure and uptake result in an adverse health effect?

This depends on one important criteria for all chemical health effects:  the dose.

Now dihydrogen oxide has a median lethal dose (LD50) of  >90 ml per Kg of body weight.  What this means is that a five year old weighing 20 kilograms (Kg) would need to have an uptake (dose) of 20 x 90 = 1800 ml or 1.8 liters to have a 50/50 chance of the negative health effect of death.  1.8 liters is a little less than drinking a two liter bottle of coke all at one time.  Now if the child sits in a bathtub full of this chemical, the amount exposed to (80 liters) is over 44 times the amount needed to cause death!  How could you let this happen to little Billy?

Now if you have not figured it out by now, dihydrogen oxide is a fancy chemistry way of saying water.  And yes, water has a toxic effect, just like any other chemical out there.  Drinking too much water can cause death if the amount consumed is over the LD50 of 90 ml/Kg.  This toxic effect is called water intoxication.

So you can see in this example that it is possible to kill a five year old in a bath tub from something other than drowning.  In this case, like in the Town of DISH, exposure to a chemical has taken place.  But the dose needed to illicit a negative health effect - death - from the uptake of water is quite high, making death by water from other than drowning possible, but not probable.

In the case of a child exposed to water we know two things.  One, the safe amount of water that can be consumed (threshold) and two, the amount that will cause a negative health effect - death.  Water, is also one of those special chemicals that can cause a toxic effect if two little is consumed as well as too much.

In the Town of DISH, all we know - according to the findings by Wolf Eagle Environmental - is that there are chemicals present in the ambient air and that their concentrations are above TCEQs ESL which are "chemical-specific air concentrations set to protect human health and welfare."

What we need to figure out - and this is where the two reports failed (in my opinion) - is what type of health effects would be possible at the concentrations reported?

If you read the conclusion in both reports, emphasis on the fact that "high concentrations of carcinogenic and neurotoxin compounds in ambient air near and/or on residential property" was found, and "many of the compounds in the air exceeded the Short-term and Long-term Effects Screening Levels (ESLs) according to [TCEQ] regulations." is stressed over and over again  This appears to imply that the health effects possible (cancer, neurological) are plausible because of the concentrations exceeding the safe level (threshold) established by the TCEQ in the form of an ESL.

What's in play here is really no different than that of water.  the effects may be different as well as the threshold  needed to be exceeded, but the basics of exposure - dose - is exactly the same.

Next post: Air Quality in the Barnett Shale - Part 3:  TCEQs Effects Screening Levels.

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