Results for the health effects of Mercury and Taiji-cho Residents

Results for the health effects of Mercury and Taiji-cho Residents
National Institute for Minamata Disease
May 9th, 2010

(Background)
An investigation into the Methyl Mercury concentration levels in hair samples was performed at the request of Taiji-cho, Higashimuro-Gun, Wakayama.

(Subject of Investigation and Method)
1. Inquiry to the consumption of methyl mercury
Of the Taiji residents (population 3,536; 1,600 males, 1926 females, as of July 2009), in the summer study between June=Aug. 2009, 1017 residents, and in the winter study in Feb. 2010, 372 residents had hair samples tested for mercury concentrations. (252 overlapping subjects, for a total of 1137 residents tested) Subjects tested were asked to complete a voluntary survey with respect to the amount of and kinds of fish consumed.

2. Study on the effects on Health
Of the subjects studied in the summer study, 182 who had relatively high mercury concentrations (105 males, 77 females), were administered a standard two-point discrimination test and upper limb functionality exercise tests by neurological specialists between July and November 2009 and in January 2010.

Results
1. Methyl Mercury Concentration Study
1) Summer study results of mercury concentration in hair samples of subjects (from smallest to largest) was on average 11.0ppm for males (0.74ppm~139ppm), and 6.63ppm for females (0.61ppm~79.9ppm), compared to 14 other regions of Japan, the average was (from smallest to largest, 2.47ppm in males (0.10ppm~40.6ppm), and 1.64ppm for women (0.01ppm~25.8ppm).
2) Summer study results showed 3.1%, 32 subjects (26 male, 6 female) whose mercury levels exceeded WHO’s 50ppm lower limit for neurological symptoms.
3) Winter study results of mercury concentration averages showed males at 11.2ppm, females at 6.46ppm, an insignificant difference compared to the summer study. Both the summer and winter studies combined, subjects with over 50ppm equaled 3.8%, for a total of 43 subjects. Some subjects in the winter report overlapped in the summer study and it can be said that there was an increase in the mercury concentrations in the hair samples.
4) There is a correlation between eating some types of whale meat and mercury concentration in hair samples.
2) Study on Health Effects
1) In this study, it could not be proven that there was a case for mercury poisoning.
2) From the analysis of upper limb functional movement, “upper limb involuntary functionality” (tremors) which had been recognized in many Taiji residents who took the test, has low possibility of being a pathological condition.
3) In neurological testing, a correlation is recognized between the decline or loss of the Achilles tendon reflex and mercury concentrations in hair samples. Compared to the residents from K cho, Ooshima-gun, Kagoshima Prefecture, there was an insignificant possibility of the effects of mercury on the tested Taiji-cho residents as the decline or loss of the Achilles tendon reflex was low .

(Further Investigation)
While the results from this study did not show the health affects of methyl mercury in Taiji residents, because of the extremely high concentrations of mercury in hairs samples, further testing is necessary. From 2010 on, in addition to further mercury concentration hair samples and neurological tests, testing on the effects on children and circulatory systems will be carried out by the National Institute for Minamata Disease. Also, for objective assessment for sensory disorders, the possibility of the use of magnetoencephalo meteres will be recommended. This data was collected for the continuing research for Taiji-cho Residents.

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