So are the metabolic or cellular thresholds breached (which allow synergistic or antagonistic interactions to occur) below a LLTC? Surely if a level is of low toxicological concern and strongly precautionary, then these thresholds are not being breached?
Regards
Christopher Taylor
Enforcement Officer
Regulatory Services
Brent Council
Tel: 020 8937 5159
Fax: 020 8937 5150
www.brent.gov.uk
-----Original Message-----
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Paul Nathanail
Sent: 03 December 2014 18:05
To: [log in to unmask]
Subject: Re: Definition of ‘Margin’ and “MoE”
And if anyone wants the reference to the Committee of TOXICITY report that Gerry is quoting from, it is at:
http://cot.food.gov.uk/sites/default/files/cot/drcotmin14may13.pdf (He is quoting from para 44).
BTW Para 25 is also worth considering where contaminant mixtures are an issue:
"25. The Committee asked whether mixtures of chemicals had been considered.
Mixtures had not been addressed specifically. However, combined effects of pollutants could be taken into account, if relevant data were available."
Whereas SR2 quoting COT(2002):
"Interactive effects may arise due to effects on either toxicokinetics or toxicodynamics and may change at different absolute and relative dose levels of each chemical in the mixture. Prediction of such effects may not be possible based on limited toxicity and mechanistic data. Where there is evidence for chemical interaction, this should be taken into account; when such evidence is not available, each chemical should be assumed to be acting independently. Furthermore, interactions, whether synergistic or antagonistic, often occur only once a metabolic or cellular threshold is breached. Such effects are therefore unlikely at exposures below the HCV (COT, 2002)." (EA 2009, p40)
So assessment criteria based on HCVs (as opposed to the LLTC) can be used where mixtures of contaminants are present.
SR2 is at:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/291011/scho0508bnqy-e-e.pdf
best regards
Paul
-----Original Message-----
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Gerry McGarrity
Sent: 03 December 2014 15:42
To: [log in to unmask]
Subject: Re: Definition of ‘Margin’ and “MoE”
Ah.. i promise i’m not talking to myself!
i’ve been directed to a C4SL presentation by Sarah Bull which says
Margin of exposure -
"PoD(NOAEL/LOAEL/BMD) is compared directly against the estimated exposure MOE=BMDL/Exposure MOE can be compared against bandings suggested by COC during risk management and risk communication MOE approach is useful when HCVs are not available”
and (my take on margins Slide)
margins -
seem to be the separation / function between the POD, exposure scenario and the intake level (mg/kg/day) (LLTC) , with the CoC? saying
“The committee agreed that the use of a chemical-specific margin (CSM) approach, which paralleled the margin of exposure (MOE) approach, was appropriate to derive an LLTC for non-threshold chemicals. However, defining an acceptable margin entailed value judgements, and was not purely scientific.”
“It involved an element of risk management, and careful consideration should be given as to how risk assessment and risk management could be brought together without the possibility of misuse. Specific criteria were needed by which to define the levels of margins, supporting the need for a central discussion rather than ad hoc local decisions.”
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