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Issue # 4, Regarding dimethyl mercury and fish consumption for pregnant women in Japan December 2005

Food Safety Citizens'Watch was established in April 2003 as a network of experts to monitor developments and make proposals to the government regarding food safety issues from the citizen's point of view.
Regarding dimethyl mercury and fish consumption for pregnant women in Japan

Possibility of effects on the growth of the fetus
On November 2, 2005, Japan's Ministry of Health, Labour and Welfare announced the result of the deliberation of the Pharmaceutical Affairs and Food Sanitation Council, calling for attention about guidelines regarding consumption of 16 types of fish containing dimethyl mercury by pregnant women.

We note that different countries have different standards and guidelines for mercury in fish (including dimethyl mercury). There are also different opinions regarding levels in breast milk, as well as countries with guidelines for young children and adults other than pregnant women, which are important areas of concern.

Leading up to this November 2 announcement there was a risk communication meeting on July 19 of the government's Food Safety Commission. There has also been an opportunity for the public to make comments to the Ministry of Health, Labour and Welfare.
The progress so far
In June, 2003, the Food Safety Commission announced its first advice (based on a risk assessment/evaluation) for pregnant women on fish consumption concerning mercury contamination. They set the safe levels to 3.4 ʂ per kg bodyweight per week (1ʂ is 1/1,000,000 gram).

After this was announced, JECFA, the joint FAO and WHO expert group, also noted concerns reagrding the toxicity associated with mercury. Several other countries then decided to make a re-evaluation of the intake recommendations for pregnant women.

In July 2004, Japan's Ministry of Health, Labour and Welfare asked the Food Safety Commission to begin a Food and Health Effect Assessment.
The Food and Health Effect Assessment of the Food Safety Commission
The special contaminant committee within the Food Safety Commission must generally consider the food culture of Japan, and in this case especially take into account the high intake of fish. It is necessary to look at the epidemiological data of the Japanese citizens at risk as national guidelines are made. But, in this case such data does not exist, so it considered data and human cohort studies from other similar countries, such as the Seychelles and the Faeroe Islands, where much fish is also consumed in the daily diet.
(1) The concept of high risk group: The fetus
It is well known that the fetus is highly sensitive to the influence of mercury. Since dimethyl mercury almost never moves via the breast milk, the infant child is less at risk even if the breast-feeding mother eats fish. In addition, the ingested dimethyl mercury is excreted from the baby at the same rate as in the case of adults. Thus the possibility of an influence on the brain development is the reason the fetus is thought to be a high risk group, which puts the focus on the guidelines on pregnant women and women who may become pregnant.
(2) The level of 2.0ʂ Hg per kg bodyweight as a permitted safe level of intake
The JECFA appraisal was based on calculations using research from hair and blood samples from the Seychelles and Faeroe islands (measuring the ratio of mercury concentration in hair and blood) as well as data on excretory ratios.
From the contents of Japan's reevaluation
The Food Safety Commission's Health Effect Assessment and risk communication, after accepting the public comments, said there was a decision:

"to increase the number of fish on the list of species that should be restricted to 16 types, including maguro (tuna), for pregnant women and women who may become pregnant."
Summary

In brief, it appears that there are still many unclear points, and a deplorable lack of data. The Ministry of Health, Labour and Welfare has expressed that "this data is not final. As we get more information, we will continue to update the guideline".

Dimethyl mercury has the most toxic effect among the substances known as organic mercury. In food, most of the dimethyl mercury exposure (84.2%) is estimated to come from consumption of fish. Certain species of older and larger fish, as well as carnivorous fish and swordfish, contain relatively high levels of dimethyl mercury.

In our opinion, it is essential that the government make more and more use of the precautionary principle to protect citizens, and we will continue to call for further
research to get more data regarding this issue.
(Copyright FSCW August 2005)

Address:
Food Safety Citizens' Watch
c/o Consumers Union of Japan
Nikken Bldg.
75 Waseda-machi, Shinjuku-ku
Tokyo 162-0042, Japan
URL: http://www1.jca.org/foodsafety
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