title: Intervention study on cardiac autonomic nervous effects of methylmercury from seafood.
abstract: To scrutinize whether the provisional tolerable weekly intake (PTWI, 3.4 microg/kg body weight/week) of methylmercury in Japan is safe for adults, we conducted an intervention study using heart rate variability (HRV) that has been considered to reflect cardiac events. Fifty-four healthy volunteers were recruited and divided into experimental and control groups. The experimental group was exposed to methylmercury at the PTWI level through consumption of bigeye tuna and swordfish for 14 weeks, and HRV parameters were compared between the two groups. In the experimental group, mean hair mercury levels, determined before and after the dietary methylmercury exposure and after 15-week wash-out period following the cessation of exposure, were 2.30, 8.76 and 4.90 microg/g, respectively. The sympathovagal balance index of HRV was significantly elevated after the exposure, and decreased to the baseline level at the end of this study. Still, such changes in HRV parameters were not found in the control group with a mean hair mercury level of around 2.1 microg/g. In conclusion, the PTWI does not appear to be safe for adult health, because methylmercury exposure from fish consumption induced a temporary sympathodominant state. Rather, long-term exposure to methylmercury may pose a potential risk for cardiac events involving sympathovagal imbalance among fish-consuming populations.
authors.affiliation: Department of Environmental Health Sciences, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Sendai 980-8575, Japan.
authors.forename: Kozue
authors.initials: K
authors.lastname: Yaginuma-Sakurai
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Murata
authors.forename: Miyuki
authors.initials: M
authors.lastname: Shimada
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Nakai
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Kurokawa
authors.forename: Satomi
authors.initials: S
authors.lastname: Kameo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Satoh
mesh_terms: D000328:Adult; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced / Q000209:etiology / Q000503:physiopathology; D001342:Autonomic Nervous System Diseases / Q000139:chemically induced* / Q000503:physiopathology*; D005260:Female; D005526:Food, Formulated / Q000009:adverse effects; D006321:Heart / Q000294:innervation / Q000503:physiopathology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D008628:Mercury / Q000378:metabolism / Q000633:toxicity; D020262:Mercury Poisoning, Nervous System / Q000503:physiopathology*; D008767:Methylmercury Compounds / Q000633:toxicity*; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology; D012307:Risk Factors; D017747:Seafood / Q000506:poisoning*; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology; D013995:Time; D014413:Tuna / Q000378:metabolism; D055815:Young Adult
chemical_list: D008767:Methylmercury Compounds; D008628:Mercury