Hi Gareth
I think you've got the wrong end of the stick.
As I said in my long post, I'm not disputing the latest Tox science!
I'm challenging the concept that somehow 40 mg/kg or 200/300 mg/kg calculated using current soil exposure model with robust TOX inputs is the 'safe' soil level.
If that 'were' true, then we'd see elevated blood levels in urban children as the soils they are 'actually' exposed to have levels that are in the range 500 to 1,000+ mg/kg (BGS data).
I live in an mineralised lead area: garden soils in the range 5,000 to 10,000 mg/kg are not unusual (we also have radon & cadmium!). Elevated blood lead in children is not a major concern (Derbyshire Dales have done some blood testing in local schools).
If can use the robust/valid JEFCA TDI value in a soil exposure model to calculate a soil criteria of say 40 mg/kg (based on an intake of 0.3 ug/bw-kg/day), JEFCA's own numbers predict that this intake will give rise to a blood level of 0.44 and 1.34 ug/dl.
If we then actually expose children to an urban NBC of say 810 mg/kg, then by the soil exposure model we used, the predicted blood level (including MDI) measurable in those children would be in the range 10 to 33 ug/dl.
Show me the urban blood level data (post lead in petrol) that matches this prediction. These blood levels are not being exhibited by significant numbers of urban children, therefore our approach to soil exposure model is wrong (even if the Tox data is correct).
Give my previous post another read through.
Paradoxically, if you assume an Index Dose, the risk model outputs will actually go UP as the MDI is not subtracted from the TDI (50% rule applies of course).
Chris Dainton
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