The Village of DePue: I'll take information for $200, Alex - Part 4

According to the "Contamination Map" on the "Clean Up DePue" web page, the two samples collected at the baseball field show:

Contaminants above MCL for drinking water : Iron, Manganese, Sulfate, pH

Clicking on the little red question mark tells the reader that an MCL stands for Maximum Contaminant Level and is the EPA's "level of a contaminant in drinking water below which there is no known or expected risk to health."  The reader is then told that "EPA standards for human health risk in soil are relatively close to those set for drinking water."

No...no they are not.  Why they state that is...well..perplexing, because at the end of the paragraph they write:

Please note: There are no known soil "standards" on a state or federal level; there are only objectives or screening criteria and those vary with the source. EPA drinking water MCLs exist, however they may not be compared directly to the soil concentrations listed on this website.

So what is the reason for posting the data in the first place?  What is the information that the reader - particularly a DePue resident - supposed to think when they read:

• "Contaminants above MCL for drinking water : Iron, Manganese, Sulfate, pH"
• "EPA standards for human health risk in soil are relatively close to those set for drinking water.

C'mon, they - Northwestern University's Environmental Advocacy Center - know exactly what message they want the reader - particularly a DePue resident - to come away with.  And if they - Northwestern University's Environmental Advocacy Center - do not understand how data can be misinterpreted then perhaps they should not be the ones to be relied on for their expertise on evaluating the remediation plan.

I know, I know, "they put a note there at the bottom," you might be thinking.  That's the giveaway for me.  They do understand that the secondary MCL has nothing to do with evaluating the risk at the baseball park.  They needed to show something above a threshold, so they choose Iron, Manganese, Sulfate, and pH

And therein lies the problem, it distorts the thinking of the folks who live in DePue:

ExxonMobil and CBS are continuing to minimize the risks to human health and the environment and to set the groundwork for leaving the contaminated waste where it is,” said Nancy Loeb, director of the Environmental Advocacy Clinic at Northwestern University School of Law’s Bluhm Legal Clinic and pro-bono counsel for the Village of DePue. 

With Northwestern University School of Law’s Bluhm Legal Clinic telling the the village of 1,800 residents that the actual risk has been minimized, you can see how easy it is for those citizens to tell the Chicago Tribune:

"All the complaining we've done, we've learned that there's good reason for us to be worried about the type of cleanup we get here."

..and be quoted in the Press Release stating:

“The consent order required the responsible parties to come up with the plan, supervised by the Illinois EPA. I don’t know how to respond to that plan. It’s not even close to what’s needed.” 

What they are being told may - or may not - be a factual/sound representation of risk.  So how can we go about evaluating that risk with the information we do have?  If all we have is groundwater samples and we are told that "EPA drinking water MCLs exist, however they may not be compared directly to the soil concentrations listed on this website," what can we look at to give us an idea if, as per the Press Release:

Contaminated debris blows onto public and private property throughout the village and surrounding natural areas, exposing residents -- more than a quarter of whom are children under the age of 16 -- and local wildlife to arsenic and heavy metals such as lead, mercury and cadmium. 

Let's focus on that concern.  That the contaminants are blowing onto public and private property.  If that statement is true, then we would expect to see these contaminants outside of the fence line.  And, if they are outside of the fence line, they must be in a concentration high enough to cause a health effect.

We can assume that any amount outside of the fence line that falls below a health/environmental threshold is not a concern.  This is how the EPA looks at contaminated property.  This graphic comes from the EPA from the data that the Cleanup DePue website cites:

Source

So you see from the graphic that somewhere between "zero" concentration and this thing called a "screening level" no further study is necessary.  In other words, below the screening level for that contaminant we will consider the site to not present a health concern for the activity that will commence on it.  For the citizens of DePue we will consider the activity to be "residential" use.

So what the heck is a "screening level" and can it be used to determine if the conditions found today are "jeopardizing the health and well-being of the children, families and wildlife in DePue?”

when the reader is incorrectly told by Cleanup DePue that  "EPA standards for human health risk in soil are relatively close to those set for drinking water," that statement is attributed to a document cited as "[2, PDF]."  That EPA publication is called the "Soil Screening Guidance: Technical Background Document."  Now where in that EPA document - I checked - does it imply or state that risk in soil are relatively close to an MCL.

What it does say, in relationship to an MCL, is this:

SSLs are backcalculated for migration to ground water pathways using ground water concentration limits [nonzero maximum contaminant level goals (MCLGs), maximum contaminant levels (MCLs), or health-based limits (HBLs) (10-6 cancer risk or a HQ of 1) where MCLs are not available]. (Page 5)

What that means is the contribution to groundwater contamination through leaching - which is the primary health concern if the groundwater is used for drinking - is considered when establish the Soil Screening Level (SSL).  Even if little Sally will not come in contact with that soil through contact and/or ingestion, the impact on the drinking water that little Sally will drink is considered in setting that SSL.

So once more, what the heck is a soil "screening level?"

SSLs are risk-based concentrations derived from standardized equations combining exposure information assumptions with EPA toxicity data. (1)

So...there is an equation that is used to make this determination of risk.  Cool.  And I know that Mr. "Keith Garcia, a science teacher at DePue High School [had] his class sample soil and water to document unsafe concentrations of pollutants."  And those soil sample results are available on the Cleanup DePue website:

Source

Now that I know the contaminants of concern, I can look to see what the Soil Screening Levels are for those compounds that have been calculated based on residential use of the property.

You know what really cool about being a researcher in the 21st century.  The internet, google and the availability of mathematical formulas to calculate just about anything.  you provide the data and they provide the calculation.  How cool is that!

The EPA just so happens to have a really cool calculator for doing this.  This is based on the methodology put forth in the "Soil Screening Guidance: Technical Background Document" the Cleanup DePue's website cites.

Source

So...I asked it to calculate the Soil Screening Levels (SSLs) for the 12 metals that Mr. Garcia, a science teacher at DePue High School had his class sample for at the baseball field.  Here is what the calculations look like:

Wow, that's a lot of numbers.  A lot of scientifically looking stuff.  A lot of data.  Yeppers, that's what we have here.  A lot of data and no information.  So if you are still reading this...let's get to understanding what it all means.

First, if you recall the definition of a SSL:

SSLs are risk-based concentrations derived from standardized equations combining exposure information assumptions with EPA toxicity data. (1)

...then we need to accept those calculations as sound.  If you have a better way of calculating the concentration that is of concern, then you need to support that method and tell me why it is better than this one.  I am going to assume - warts and all - that the value and parameters used in these calculations is conservative enough to be an indicator of the risk if those levels are exceeded.

That's how we do it.  We public health scientists have agreed to these formulas and parameters.  So the number it spits out; "Screening Level (mg/kg)," is how we will make a determination of potential risk to a resident at this site.  And yes, they take into account exposure of children in these calculations.

With that in place, if the quantity of any of these 12 compounds Mr. Garcia' class sampled at the baseball field exceed the Screening Level, we can assume that a value below that is protective of human health.

At this point - I am writing this as I do the research - I do not know if the 12 compounds at the baseball field exceed the SSLs establish for a resident.  Lets put this data in a more user friendly format to find out:

In looking at the Screening Levels that were calculated for chronic exposure to these 12 contaminants, none of the concentrations found by Mr. Garcia's class in the soil at the baseball field are exceeded.  That's just as I suspected when I looked at them on the website.

This means, that based on one sample collected, assuming that it is representative of the baseball field where children play, the level of contaminants found are low enough to be protective of public health.  Magnesium and Manganese are not public health concerns in soil which is why they are not calculated.

This soil sample, along with the two groundwater samples that were collected, does not support the conclusion of the press release:

Contaminated debris blows onto public and private property throughout the village and surrounding natural areas, exposing residents -- more than a quarter of whom are children under the age of 16 -- and local wildlife to arsenic and heavy metals such as lead, mercury and cadmium. Visit www.CleanUpDePue.org to see an interactive map that details the way-above-normal concentrations of pollutants at hundreds of contaminated sites.

...at least for the baseball field.  I guess we need to look at Mr. Garcia's samples for the other stops on the virtual tour.  If the baseball field does not have concentrations "way-above-normal", maybe somewhere else does.

Next Post: The Village of DePue: Where are they way-above-normal? - Part 5

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