ERF of methyl mercury on intelligence quotient
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Scope
ERF of methyl mercury on intelligence quotient describes the quantitative relationship between exposure to (prenatal) methyl mercury exposure and intelligence quotient (IQ) score (in children).
Definition
Causality
Data
Actual content
Prenatal MeHg exposure sufficient to increase the concentration of mercury in maternal hair at parturition by 1 ug/g decreases IQ by 0.7 points (min and max 0 and 1.5, respectively).
Narrative description
Every 1 ug/g of methylmercury in mothers hair decreases IQ of a child by 0.7 points. Study by Cohen et al[1] finds that prenatal MeHg exposure sufficient to increase the concentration of mercury in maternal hair at parturition by 1 ug/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.[1]
A triangular distribution with parameters: min = 0, mode = 0.7 and max = 1.5 was created. Distribution by author judgement. D↷
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 ug/l is related to the average daily dietary intake (d) in ug 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.[2] D↷
Formula
Analytica_id:
<Anacode>triangular(-1.5,-0.7,0)*Blood_to_hair</Anacode>
Unit
IQ points / 1 ug/g increase in maternal hair
Result
0.7333