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| − | [[Category:Exposure-response functions]]
| + | #REDIRECT [[ERF of methylmercury]] |
| − | [[Category:Heavy metals]]
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| − | {{Variable|moderator=Olli}}
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| − | == Scope ==
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| − | What is the exposure-response function '''([[ERF]]) of methyl mercury on intelligence quotient''' between exposure to prenatal methyl mercury and intelligence quotient (IQ) score in children?
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| − | == Definition ==
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| − | === Data ===
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| − | Study by Cohen et al<ref name="cohenMMVa">Methyl mercury: Cohen et al 2005a</ref> finds that prenatal MeHg exposure sufficient to increase the concentration of mercury in maternal hair at parturition by 1 µg/g decreases IQ by 0.7 points. The paper identifies important sources of uncertainty influencing this estimate, concluding that the plausible range of values for this loss is 0 to 1.5 IQ points.
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| − | A triangular distribution with parameters: min = 0, mode = 0.7 and max = 1.5 was created. Distribution by author judgement <ref>[[User:Jouni]] 9 Feb 2008</ref>. {{disclink|Author judgement about the chosen distribution}}
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| − | '''Conversion 1:
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| − | This variable includes conversion from mercury intake to mercury concentration in hair. Firstly, WHO(1990) suggests the use of a single-compartment model, through which the steady-state Hg concentration in blood (C) in µg/l is related to the average daily dietary intake (d) in µg of Hg, as follows: C = 0.95 * d. Secondly, blood mercury was converted to total hair mercury using a 1:250 ratio (New Zealand and Seychilles Island studies) and an assumption of equivalent maternal and cord levels.<ref>Methyl mercury: Bidone et al. (2004)</ref> {{disclink|Toxicologicy of methylmercury}}
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| − | '''Conversion 2:
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| − | Another conversion from MeHg hair concentration into dietary MeHg intake is proposed by EPA <ref name="EPA"> EPA (IRIS), 2001. http://www.epa.gov/iris/subst/0073.htm </ref>. This conversion is used in the Bayesian Belief Network (BBN) model developed for the fish case study in Beneris project. Assuming that the concentration of MeHg in blood is at a steady-state the daily dietary intake of MeHg from fish corresponding to a given hair MeHg concentration can be estimated as
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| − | were:
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| − | * Concentration_MeHg_Hair is the hair MeHg concentration,
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| − | * b is the elimination rate from blood (assumed 0.014<ref name ="EPA" />),
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| − | * V is the blood volume (assumed 5 L<ref name ="EPA" />),
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| − | * f is the fraction of absorbed MeHg that is distributed to the blood (assumed 0.059<ref name ="EPA" />),
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| − | * A is the fraction of ingested MeHg that is absorbed from GI tract (assumed 0.95<ref name ="EPA" />),
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| − | * BW is the body weight of pregnant woman,
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| − | * a is the proportion of daily dietary intake of MeHg by pregnant women that comes from fish (assumed 1=100%),
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| − | * 250 is the hair-to-blood Hg concentration ratio.
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| − | As a result, the [[ERF]] of MeHg exposure from fish for the child's IQ can be calculated as a product of ERF of MeHg hair concentration for child's IQ and (A*f*BW*250*0.001)/(b*V).
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| − | ===Dependencies===
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| − | List of parent variables:
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| − | *[[Body weight in Finland]]
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| − | == Unit ==
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| − | ;Conversion 1: IQ points / 1 µg/g increase in maternal hair
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| − | ;Conversion 2: IQ points/(µg/(kg bw*day))
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| − | === Formula ===
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| − | ;Conversion 1 (Analytica): <Anacode>triangular(-1.5,-0.7,0)*Blood_to_hair</Anacode>
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| − | ;Conversion 2: triangular(-1.5,-0.7,0)*(0.8007*BW*250*0.001)
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| − | == Result ==
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| − | NOTE! Conversion 2 was used for the current results.
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| − | {{resultlink}}
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| − | [[image:ERF of methyl mercury on intelligence quotient.png]]
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| − | ==References==
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| − | <references/>
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