"[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
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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