title: Methylmercury exposure and neurological outcomes in Taiji residents accustomed to consuming whale meat.
abstract: Methylmercury (MeHg) is a major environmental neurotoxicant that causes damage to the central nervous system. In Japan, industrial emission of MeHg has resulted in MeHg intoxication in Minamata and Niigata, the so-called Minamata disease. Humans are exposed to MeHg derived from natural sources, primarily fish and fish predators. Therefore, MeHg continues to be an environmental risk to human health, particularly in susceptible populations that frequently consume substantial amounts of fish or fish predators such as whale. This study aimed to investigate the health effects of MeHg exposure in adults. The subjects were 194 residents (117 males, 77 females; age 20-85 years) who resided in the coastal town of Taiji, the birthplace of traditional whaling in Japan. We analyzed hair for mercury content and performed detailed neurological examinations and dietary surveys. Audiometry, magnetic resonance imaging, and electromyography were performed to diagnose neurological defects. Whole blood mercury and selenium (Se) levels were measured in 23 subjects. The geometric mean of the hair mercury levels was 14.9 μg/g. Twelve subjects revealed hair mercury levels >50 μg/g (NOAEL) set by WHO. Hair mercury levels significantly correlated with daily whale meat intake. These results suggested that residents in Taiji were highly exposed to MeHg by ingesting MeHg-contaminated whale meat. Multivariate regression analysis demonstrated no significant correlations between hair mercury levels and neurological outcomes, whereas some of the findings significantly correlated with age. A significantly positive correlation between whole blood mercury and Se levels was observed and the whole blood mercury/Se molar ratios of all subjects were <1. These findings suggested that sufficient Se intake might be one of causes of the absence of adverse effects of MeHg exposure in this study.
authors.affiliation: Department of Clinical Medicine, National Institute for Minamata Disease, Minamata, Japan. Electronic address: nakamura@nimd.go.jp.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of International Affairs and Environmental Sciences, National Institute for Minamata Disease, Minamata, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Hachiya
authors.affiliation: Department of Neurology, Wakayama Medical University, Wakayama, Japan.
authors.forename: Ken-ya
authors.initials: KY
authors.lastname: Murata
authors.affiliation: Department of Neurology, Wakayama Medical University, Wakayama, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Nakanishi
authors.affiliation: Department of Neurology, Wakayama Medical University, Wakayama, Japan.
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Kondo
authors.affiliation: Department of Basic Medical Sciences, National Institute for Minamata Disease, Minamata, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Yasutake
authors.affiliation: Department of Clinical Medicine, National Institute for Minamata Disease, Minamata, Japan.
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Miyamoto
authors.affiliation: Department of Human Ecology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Ping Han
authors.initials: PH
authors.lastname: Ser
authors.affiliation: Department of Human Ecology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Sanae
authors.initials: S
authors.lastname: Omi
authors.affiliation: Department of Human Ecology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Hana
authors.initials: H
authors.lastname: Furusawa
authors.affiliation: Department of Human Ecology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Chiho
authors.initials: C
authors.lastname: Watanabe
authors.affiliation: Department of Clinical Medicine, National Institute for Minamata Disease, Minamata, Japan.
authors.forename: Fusako
authors.initials: F
authors.lastname: Usuki
authors.affiliation: Department of International Affairs and Environmental Sciences, National Institute for Minamata Disease, Minamata, Japan.
authors.forename: Mineshi
authors.initials: M
authors.lastname: Sakamoto
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D004032:Diet; D004785:Environmental Pollutants / Q000633:toxicity*; D005260:Female; D005506:Food Contamination / Q000032:analysis; D006197:Hair / Q000737:chemistry; D006319:Hearing Loss, Sensorineural / Q000139:chemically induced / Q000453:epidemiology; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008460:Meat / Q000032:analysis*; D020262:Mercury Poisoning, Nervous System / Q000453:epidemiology; D008767:Methylmercury Compounds / Q000032:analysis / Q000633:toxicity*; D008875:Middle Aged; D009420:Nervous System / Q000187:drug effects*; D012643:Selenium / Q000097:blood; D012678:Sensation Disorders / Q000139:chemically induced / Q000453:epidemiology; D014907:Whales
chemical_list: D004785:Environmental Pollutants; D008767:Methylmercury Compounds; D012643:Selenium
keywords: Methylmercury; Neurological outcomes; Selenium; Taiji; Whale meat