Signs and symptoms of methylmercury contamination in a First Nations community in Northwestern Ontario, Canada

• Published in: The Science of the total environment Vol. 468-469; pp. 950 - 957
• Main Authors: Takaoka, Shigeru, Fujino, Tadashi, Hotta, Nobuyuki, Ueda, Keishi, Hanada, Masanobu, Tajiri, Masami, Inoue, Yukari
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.01.2014
• Subjects: Adolescent; Adult; Aged; Complaints; Environmental Exposure - analysis; Humans; Indians, North American - statistics & numerical data; Japan - epidemiology; Mercury Poisoning - complications; Mercury Poisoning - epidemiology; Methylmercury; Methylmercury Compounds - analysis; Methylmercury Compounds - toxicity; Middle Aged; Neurological findings; Ontario - epidemiology; Prevalence; Quantitative somatosensory measurements; Sensory disturbance; Somatosensory Disorders - chemically induced; Somatosensory Disorders - epidemiology; Somatosensory Disorders - pathology; Ontario; Japan; Canada, Ontario, Grassy Narrows; Canada, Ontario; Complaints; Sensory disturbance; Quantitative somatosensory measurements; Neurological findings; Methylmercury
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2013.09.015

In 1970, fish caught in the English–Wabigoon River system in northwestern Ontario, Canada, were found to be contaminated with mercury coming from a chlor-alkali plant in the province. In the 1970s, patients exhibiting some of the symptoms of the Hunter–Russell syndrome (e.g. paresthesias, visual field constriction, ataxia, impaired hearing, and speech impairment) were reported by some researchers. However attempts to diagnose the patients as suffering from methylmercury poisoning proved to be controversial. In order to research the presence of methylmercury contamination, and show that the patients, through eating contaminated fish, were suffering from methylmercury poisoning, we studied the results of subjective complaints, neurological findings, and quantitative somatosensory measurements gathered in Grassy Narrows Indian Reservation, Ontario, in March, 2010. At that time, the population of the Grassy Narrows settlement was around 900. Ninety-one residents volunteered to be examined. From them, we selected 80 people who were older than 15years old, and divided them into two groups. Canadian Younger (CY): 36 residents who were from 16 to 45years old. Canadian Older (CO): 44 residents who were from 46 to 76years old. We compared them to Japanese Exposed (JE): 88 methylmercury exposed residents from the Minamata district in Japan, and Japanese Control (JC): 164 control residents from non-polluted areas in Japan. Complaints and abnormal neurological findings were more prevalent and quantitative sensory measurements were worse in the two Canadian groups and the Japanese Exposed group than in the Japanese Control group. Complaints, neurological findings and quantitative sensory measurements were similar in Canadian Older and Japanese Exposed. The results for Canadian Younger fell between those of Canadian Older and Japanese Control. These findings indicate that the clinical signs and symptoms of the residents of Grassy Narrows are almost the same as those recorded for Minamata disease in Japan. •Similarities between the prevalence of complaints in Minamata and Grassy Narrows•Similarities in neurological findings were also found.•Quantitative sensory measurements gave similar results for impairments.•Younger Canadians were less severely affected than older ones.•Results suggest that subjects from Grassy Narrows had methylmercury poisoning.