ERF of methylmercury
|Moderator:Olli (see all)|
What is the exposure-response function (ERF) of methyl mercury on several health endpoints such as intelligence quotient and lifetime risk of myocardial infarction after prenatal or long-term adult exposure, respectively?
#: . Please note that the following new pieces of information have not been considered when writing the page:
- Seychell study: omega-3 blocks the effects of mercury
- EFSA benefit-risk assessment about omega-3 and mercury, press release
- EFSA benefit-risk assessment about omega-3 and mercury --Jouni (talk) 11:51, 26 January 2015 (UTC) (type: truth; paradigms: science: relevant attack)
Exposure-response of MeHg intake for MI risk in adults is indexed by variable age. It applies to the last two age categories.
|Obs||Exposure agent||Response||Exposure||Exposure unit||ER function||Scaling||Threshold||ERF||Description|
|1||MeHg||Loss in child's IQ points||Through placenta as maternal MeHg concentration in hair||ug /g||ERS||None||0||0.7 (0 - 1.5)|
|2||MeHg||Loss in child's IQ points||Maternal ingested intake||µg /kg /d||ERS||BW||0||6.533 (0 - 14)||Converted from the row above assuming linearity|
- ERF publications
|Exposure agent||Trait||Response metric||Exposure route||Exposure metric||Exposure unit||ERF parameter||Threshold||ERF||Description|
|MeHg||Childhood intelligence||IQ change||Placenta||Maternal MeHg concentration in hair||ug /g||ERS||0||-1.5;-0.7;0|
Study by Cohen et al 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, and they use triangular distribution. R↻
According to Health Canada, 14 ppm in the hair corresponds to 1.5 µg/kg/d intake of methylmercury. Assuming linearity, the ERF can be converted to
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. R↻
Another conversion from MeHg hair concentration into dietary MeHg intake is proposed by the U.S.EPA . 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
- Concentration_MeHg_Hair is the hair MeHg concentration,
- b is the elimination rate from blood (assumed 0.014),
- V is the blood volume (assumed 5 L),
- f is the fraction of absorbed MeHg that is distributed to the blood (assumed 0.059),
- A is the fraction of ingested MeHg that is absorbed from GI tract (assumed 0.95),
- BW is the body weight of pregnant woman,
- a is the proportion of daily dietary intake of MeHg by pregnant women that comes from fish (assumed 1=100%),
- 250 is the hair-to-blood Hg concentration ratio.
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).
Jyrki K. Virtanen, Tiina H. Rissanen, Sari Voutilainen, Tomi-Pekka Tuomainen. Mercury as a risk factor for cardiovascular diseases. Journal of Nutritional Biochemistry 18 (2007) 75–85. Beneris:media:Virtanen_JNutrBiochem_2007_HgandCVD.pdf
- Conversion 1
- IQ points / 1 µg/g increase in maternal hair
- Conversion 2
- IQ points/(µg/(kg bw*day))
library(OpasnetUtils) d <- opbase.data("Op_en5825") d$Obs <- NULL colnames(d) <- gsub(" ", "_", colnames(d)) d$Result <- ifelse(d$Result == "", "0", as.character(d$Result)) ERF_mehg <- Ovariable("ERF_mehg", data = d[d$Observation == "ERF", colnames(d) != "Observation"]) threshold_mehg <- Ovariable("threshold_mehg", data = d[d$Observation == "Threshold", colnames(d) != "Observation"]) objects.store(ERF_mehg, threshold_mehg) cat("Ovariables ERF, threshold stored.\n")
- Conversion 1 (Analytica)
- Conversion 2
- Cohen JT, Bellinger DC, Shaywitz BA. A quantitative analysis of prenatal methyl mercury exposure and cognitive development. Am J Prev Med. 2005 Nov;29(4):353-65. 
- Olli Leino: Fish consumption: human health effects and decision making. National Institute for Health and Welfare, Research 120/2014. Dissertation.
- Methyl mercury: Bidone et al. (2004)
- EPA (IRIS), 2001. http://www.epa.gov/iris/subst/0073.htm