Peter said:

* The point of the article was to show that 2,4-D not only contains traces of dioxins but it can break down to them when exposed to sunlight. Additionally to warn that the use of these products could result in significant environmental damage from dioxin by products. 

Hello Peter,
   I took a look at that paper and I think the only conclusion one can come to is that there can be low levels perhaps on the order of 10-100 ppb of dioxin percursors in any given 2,4-D formulation that might be very quickly (they say 30mins in the paper) converted into PCDD/Fs(dioxins) and when they are used up the levels remain constant.  There appears to be another class of dioxins that can form from 2,4-D TCDDs but they only increase from from 0.1-2 to 1-3 ppb if you compare the controls.  I don't think there is any justification for the absolute environmental exposure numbers they state in the paper or even extrapolation of any of the percent increases due to photo chemical processes since they don't even bother to use their own controls as baselines.  They should be reporting a 1200% increase as compared to the control sample rather than the 3000% number based on the initial concentration in the samples.  Otherwise, why have a "control" sample in the first place.

The only absolutes that I take away from that paper is that formulations of 2,4-D and PCNBs have low levels of impurities (<150ppb) and that they can undergo photochemistry and that it is possible for 2,4-D to undergo photochemical reactions as well, but when you are trying to compare 0.8 ppb in your control versus 4ppb in your experiment things like measurement error and reproducibility start to become problematic.  I think they are serious about doing good science but perhaps a little extravagant in their statements and conclusions.  But I am not familiar with the work or the specifically the GCMS detection methods used, which can be extremely accurate, so I'll pass you the salt, please take a few grains with my comments.  Mark

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