NEW DEVELOPMENTS IN 2003
provisional tolerable weekly intake (PTWI) for methylmercury of 3.3 g/kg body weight per
week was revised by the sixty-first meeting of the Joint FAO/WHO Expert
Committee On Food Additives (JECFA), Rome, 10-19 June 2003 as follows:.
other toxicological recommendations
tolerable weekly intake (PTWI) of 1.6 µg/kg bw
The Committee considered this PTWI to be sufficient to
protect the developing fetus, the most sensitive subgroup of the
population. The Committee also reaffirmed its position that fish are
an important part of a balanced nutritious diet and that this has to be
appropriately considered in public health decisions when setting limits
for methylmercury concentrations in fish.
NEW DEVELOPMENTS IN 2006
JECFA, during its sixty-seventh meeting in
Rome, 20-29 June 2006 made some additional considerations relating to the provisional tolerable weekly intake
(PTWI) for methylmercury as follows:
The Committee made it clear that the
previous PTWI of 3.3 µg/kg bw had, in fact, been withdrawn in 2003. The
Committee confirmed the existing PTWI of 1.6 µg/kg bw, set in
2003, based on the most sensitive toxicological end-point (developmental
neurotoxicity) in the most susceptible species (humans). However, the
Committee noted that life-stages other than the embryo and fetus may be
less sensitive to the adverse effects of methyl mercury.
In the case of adults, the Committee
considered that intakes of up to about two times higher than the existing
PTWI of 1.6 µg/kg bw would not pose any risk of neurotoxicity in adults,
although in the case of women of childbearing age, it should be borne in
mind that intake should not exceed the PTWI, in order to protect the
embryo and fetus.
Concerning infants and children aged up to
about 17 years, the data do not allow firm conclusions to be drawn
regarding their sensitivity compared to that of adults. While it is clear
that they are not more sensitive than the embryo or fetus, they may be
more sensitive than adults because significant development of the brain
continues in infancy and childhood. Therefore, the Committee could not
identify a level of intake higher than the existing PTWI that would not
pose a risk of developmental neurotoxicity for infants and children.
The Committee has previously noted that
fish makes an important contribution to nutrition, especially in certain
regional and ethnic diets. The present Committee recommends that the known
benefits of fish consumption need to be taken into consideration in any
advice aimed at different subpopulations. Risk managers may wish to
consider whether specific advice should be given concerning children and
adults, after weighing the potential risks and benefits.
The Committee concluded that the setting of
guideline levels for methyl mercury in fish may not be an effective way of
reducing exposure for the general population. The Committee noted that
advice targeted at population subgroups that may be at risk from methyl
mercury exposure may provide an effective method for lowering the number
of individuals with exposures greater than the PTWI.
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