Chemist: Oysters contain 1.25% (12,500 ppm) hydrocarbons near MS River Delta

First fundamental flaw: In your calculation of the amount that the reported concentration exceeds the EPA/FDA advisory level you use the 12,500 mg/kg for total hydrocarbons and divide that by the 5 ppb (µg/kg) advisory level for total PAHs. The reported concentration of total PAHs in the snippet of the article that you copy above is actually 0.063 mg/kg (or 63 µg/kg). Thus, following your approach, the calculation should be 63/5 - showing that the lab results indicate that the exceedance is only about 12 times, not 250,000 times. But - there's a problem with this approach, too. Keep reading.

Second fundamental flaw: Note that the units of the EPA/FDA advisory level (concentration) is in "BaPE", or Benzo(a)pyrene Equivalents - not in units of ppm of total PAHs. Please read this to see how BaPEs correspond to concentrations of individual PAHs. You may also want to read this (a pdf file). Table 1 in the first report I ask you to read shows that the advisory levels for individual carcinogenic PAHs range from 0.143 to 143 ppm. The advisory levels for individual non-carcinogenic PAHs range from 133 to 2000 ppm. The concentration of total PAHs reported in the article you seeded is 0.063 ppm. Thus, the concentration of any individual PAH cannot exceed its advisory level. Therefore, the analytical results reported by LEAN support the EPA/NOAA evaluations and show that the oysters contain PAHs at concentrations well below the EPA/FDA advisory levels, and are thus safe to eat.

This result, perhaps, addresses your statement in Comment #1.1 that the MSM is not reporting this. They are, in fact, reporting this - but you won't believe it.

Nyghtshayde -

I just did some fiddling around with some of the data that you told us about on one of your other articles. I was going to put all this over there - but I figured 'what the heck' - let's not clutter that article since what I'm going to write below has more to do with this article.

We go to http://bostonchemicaldata.com/LEAN/ and click on the "BCD Data" link to pull up a spreadsheet of analytical data. We look at Row 135 of http://bostonchemicaldata.com/LEAN/Data/DWH/LabReports/LabLEAN124to136.pdf
to find the results of the oyster sampling on 8/2/2010 reported in the LEAN article. The spreadsheet indicates that an oyster sample was designated by LEAN as L917222-11, and subsequently designated as DWH0134B by the lab, and that it was analyzed by USEPA Methods 8015 mod ext, 6010, 7471 and 8260. So far, so good.

We pull up the lab report to find:

• Of the PAHs analyzed, C4 Phenanthrenes/Anthracenes is present at 0.042 mg/kg and Phenanthrene is present at 0.021 mg/kg - this is consistent with the 0.063 mg/kg value reported in the LEAN article, but it does raise the question of 'double counting'. Is phenanthrene reported twice? Should the 'real' total concentration of PAHs really be only 0.042 mg/kg. But - there's really no big difference, so rather than get hung up on this, let's move on.
• Page 7 of 13 reports 12,500 mg/kg of "Hydrocarbons C11-C60 GC/FID Scan (mg/kg)" for L917222-11/DWH0134B 5-1 - which, again, is consistent with the value reported in the LEAN article. I note that there are no data flags.

Something nags the back of our mind, though, when we recall that the USEPA does not have a method for determining C11-C60 organics, but Canada does - and the ALS Laboratory Group (who did the analyses) is a Canadian firm. Also - the laboratory methods listed on page 12 of 13 (EPA 3580/8000-GC-FID) do not correspond with what the spreadsheet gave as as those that were used. But - we won't worry about this now either since we recall that Method 3580 is a dilution procedure, Method 6010 is a procedure for analyzing metals, Method 7471 is for mercury, and Method 8260 is GC/MS analysis of volatile organics, so they don't apply. Further, Method 8000 is a 'general' procedure that could refer us to 8015 and thus could be relevant, so, we'll move on.

We note the note on page 13 of 13 describing the PAH-ALK-ED analysis of Biota. It says, "The following PAH parameter results are determined via a semi-quantitative method. To be used for reserch purposes only." - and we see "C4 Phenanthrenes/Anthracenes" - one of the categories reported for our oyster sample - among those on the list. Oh well, moving on.

We also note on that page that all of the laboratories owned by the ALS Laboratory Group are in Canada. That really doesn't worry us too much since Canadian labs are also very good. But we make a mental note to do some more research into the methods that were used - if for no other reason than to be able to better interpret the results.

We read on page 15 (of the pdf file) that the lab analyzed our oyster sample using a Soxhlet extraction. Hummm. EPA Method 8015 is a semi-quantitative method for GRO and DRO compounds, and can be used with a Soxhlet extraction prep procedure (e.g., Method 3540). It's curious why this procedure isn't mentioned by anyone - but who cares? Let's move on.

We wade into the results, which begin on page 15 (of the pdf file), and look for things having to do with Sample L917222-11. We find:

• "Figure 25 shows a GC/MS-SIM plot for m/z 85 (L917222-10 and -11) consistent with the presence of hydrocarbons. A source plot (L911700-3) is shown for comparison. No evidence of hydrocarbon consistent with the source is evident."
• "GC/MS-SIM plots for m/z 191, 217, 218, 231 and 242, consistent with the presence of terpanes, steranes, triaromatic steranes and methyl chrysenes were generated for samples L917222-10 and L917222-11. These plots were compared to the source plots obtained for sample L911700-3. No evidence of exposure to this source was observed for these samples."
• "Figure 26 shows a source cross-plot for all the samples received. Although all the samples show ratios consistent with the presence of source oil, caution should be used in interpretation. Samples L917222-1, -9, -10, and -11 had observed PAH values below reporting limits."

What is this 'source'? There is no description of a Sample L911700-3, but it sounds like they're comparing the fingerprint of the contamination found on the oyster with the BP Oil Spill oil - and they're not seeing any similarities.

OK - we're down to the "Conclusions" now. What do they say about L917222-11?

• "For samples L917222-10 [a mussel] and -11: There is no biomarker evidence to suggest contamination with source oil although the PAH source data does support such contamination the PAH values are below reporting limits."

We clearly see some diesel oil contamination in (or on) our oyster, but the fingerprint of the contamination shows that it is not from BP oil. What gives?

So - the oyster data that got you so worked up actually shows: 1) PAH concentrations not 250,000 times the advisory levels, but in fact, they are below (about 1/2) the advisory levels, and 2) the total petroleum contamination is from diesel fuel, and not from the BP oil spill.

Interpretation of all the data and reading the fine print is a @!$%#, isn't it?

Thanks both of you-- I've read it twice and almost understand it... I will rely on your greater expertise than mine!

Thanks very much for the article, nyghtshade and the breakdown, rls8r!