EDL Emulsion Spill in Dickey Lake

The community grapevine has been in full swing about the chemical spill in Dickey Lake on Tuesday, August 25th. With chemical spills, the major questions are “What was it?” and “How much?”

The rule of thumb in toxicology is “The dose makes the poison”. Even everyday common substances can be deadly, given a sufficiently high dose. So, the answer to our first question: “What is it?” will determine the meaning of the second question: “How much?”

I contacted Montana’s Department of Environmental Quality (DEQ) and asked that first question. I received a very prompt response: EDL Emulsion, a dust suppressant.

From there, the next visit is to the safety sheet, which is available online and fairly easy to find. This sheet offers details about what exactly EDL Emulsion is – a mixture of asphalt fume, water, fuel oil number 2 and two emulsifiers. The majority of EDL Emulsion is the asphalt fume. It has a black color and often a smell of rotten eggs associated with the presence of hydrogen sulfide.

The safety sheet includes direct exposure information, and EDL Emulsion is definitely not something one wants to have direct, up close personal contact with. It’s an eye and skin irritant that comes with a host of nasty side-effects when inhaled. Details on this can be found in Section 11: Toxicological Information – It may help to know that LD50 refers to the dose at which half of the animals it was tested on died.

But, the dose makes the poison and the more pressing question, since it has been dispersed through a large body of water, is about the ecotoxicology. How dangerous is it for the environment? The safety sheet does describe it as a marine pollutant, but without any further details.

Since toxicology information is available for two of the components of EDL Emulsion: asphalt fume and fuel oil number 2, those are the next to examine. The safety data sheet for Fuel Oil Number 2 (also Number 2 Fuel Oil) can be found here. Section 12 Ecological Information outlines the potential toxicology to aquatic life for the various chemicals that make up Fuel Oil Number 2.

The asphalt fume is specifically a Bitumen fume; Bitumens are petrolium products, often called asphalt cement. While most of my initial findings were about occupational exposure of the many people who work with Bitumens, I did manage to find a Canadian study that addressed the impacts of mixtures including Bitumens on fish (deadly under some circumstances).

The rule in toxicology is that the dose makes the poison. We don’t know how much of Fuel Oil Number 2 (5-20% of EDL Emulsion) or asphalt fume (30-70%) entered Dickey Lake as part of the EDL Emulsion that was released. What we do know is that some of the materials included in EDL Emulsion are marine pollutants, with potential to harm aquatic life.

Whether the dose will be high enough to be harmful is a question that must consider the amount that entered the water, the dispersal rate, the solubility, currents, etc. It’s a complex problem and we’re looking forward to seeing what DEQ concludes.

Contact information for MT DEQ can be found here. If you need to report a chemical spill or make a complaint, the form is available on DEQ’s website.

2 thoughts on “EDL Emulsion Spill in Dickey Lake”

  1. This was a wonderful article. It addresses toxicology very well. I would like to add that there is both a moral and legal issue involved, here. It’s not legal to dump things in our waterways – especially by commercial enterprises – without permission. If the company that did this did not have permission then I very strongly believe a fine is appropriate. I hope that is levied if this was not an action that was sanctioned. Also, we do not need a precedent set that would allow others to disregard their legal and moral obligations. This happens far too often these days when folks are allowed off the hook with just a “warning” that rarely does any good in preventing further wrong doing. Thank you.


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