Russel
I don't think anyone is disputing the toxicity of BaP.
What I take issue with is the methodology to go from LOEL/NOAEL to
TDI/ID....which is then coupled with a process using a set of pathway
algorithms (many of which are painfully simple) to end up at a soil level
completely at odds with natural background levels of a substance we see
country wide.
To top it all, we then often get a blind application/enforcement of the GAC.
The brownfield community need to pick apart the CLEA model output pathway
by pathway and look objectively at how the model arrives at the lowest
pathway outputs and then decide the reasonableness/robustness of it all.
Like I said, my initial guess that the new indoor air Killer Dust Pathway (calling
it a pathway is somewhat generous given the simplicity of the calculation) is
leading to a lower BaP number than it really should be (whatever ever 'really
should be' means.
....and I live in a high radon and high natural lead area: do I worry about
either - NO! (and I did a radiation protection masters and did my dissertation
on radon). And I've no doubt that BaP in my garden is >1 mg/kg.
And I am quite sure in my mind that "It ain't high enough to be workable, guv."
IS A sound and scientific reason for dismissal of 0.8 mg/kg if this level is
clearly below levels found in gardens and imported topsoil that are so obviously
not "contaminated" by brownfield activities relating to substances containing
BaP (I'm not talking about a bit of ash/coal).
The Agency has already used a similar line of logic for setting the Tox for
benzene, where the inhalation tox data (which would have given a lower ID)
was put to one side in favour of an ID back calculated from the UK air quality
guideline.
Thinking about it, we could use the CLEA model to back-calculate BaP IDs
based on background soil levels in UK.......now there's a thought....wouldn't
take long
|