This is part 2 of the blog series on the 5 outlooks of Environmental Forensics.
Environmental forensics investigations are many times instigated after the fact. Data may have been collected years prior to the client suggesting or determining that an environmental forensics investigation is needed. In these cases, the environmental forensics scientist must work with the data they have. In a more idealized situation, it would be much better if those collecting the data realized that the data might some day be used in litigation to determine source.
Example: Analysis of PCDD/Fs
Being limited by data is very frustrating when conducting environmental forensics investigations – especially when more data could have very easily been collected, sometimes without much extra cost.
The first example I used in my talk was the analysis of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). The history of PCDD/Fs was summarized to when PCDD/Fs were first being analyzed and the research that was being done at that time.
In the early 1970s, researchers were frantically trying to identify these unknown organic chemicals that were killing horses and birds in Times Beach, Missouri. Researchers were able to synthesize the chemicals one by one to identify them as fast as possible. The process of identifying ALL the PCDD/F congeners in the samples started.
One compound in particular, 2,3,7,8-tetrachlorodibenzo-p-dioxin seemed to be particularly toxic and started to get a lot of focus from the toxicologists trying to figure out how the toxicity mode of action worked. Ten years later, researchers had identified the Ah receptor binding as the first step in 2378-TCDD’s toxicity and developed the toxicity equivalency factors for the 17 congeners that had the requisite structure to bind with high affinity to the receptor.
From this point on, PCDD/F environmental measurements focused on the 17 2378 substituted congeners, almost ignoring the other 193 potential congeners in this family of compounds.
Environmental forensic chemists would love to have access to this historical data now so the subtle patterns that were present in these signatures could be untangled and used to distinguish the source of PCDD/Fs at litigious sites around the world. The 17 congeners provides but a glimpse of the fingerprint that may be present in the sample and is only partial fingerprint to what could be done if all congener concentrations would have been reported.
Example: Analysis of PAHs
The second example I used was the analysis of polycyclic aromatic hydrocarbons (PAHs). Environmental studies have consistently measured 16 PAHs.
I asked the audience at the conference if they knew when these 16 PAHs had been decided upon and the answer really surprised them. The 16 PAHs were selected in 1976. These 16 PAHs were the most abundant and most easily separated PAHs at that time and have lasted ever since. It was not a wrong decision at the time but 40 years later, we know a lot more and can do a lot more.
We now know that there are 1000s of PAHs in the environment and these other PAHs can be used to determine the source of where the PAHs originated from. In addition, there are hundreds of studies that show that some of these other identified PAHs have potential toxicity making them important to monitor.
The 16 PAH method needs to be updated to include these extra PAHs and alkylated PAHs that are so commonly used in PAH fingerprinting. This has been pointed out by Andersson and Achten in 2015.
Outlooks of Environmental Forensics
So, the second point of my talk at the INEF conference was: 2. Environmental forensics investigations should not be limited to regulatory compounds.
Next week, I’ll cover the third of the 5 outlooks of environmental forensics: Knowing the fundamental principles behind graphs and diagnostic ratios. If you missed part 1 of this blog series, you can catch up and learn about the use and origin of environmental forensics, and it’s use in litigious matters in my last blog.