Abstract
Chronic arsenic intoxication is known to cause multisystem impairment and is still a major threat to public health in many countries. In Toroku, a small village in Japan, arsenic mines operated from 1920 to 1962, and residents suffered serious sequelae of arsenic intoxication. We have performed annual medical examinations of these residents since 1974, allowing us to characterize participants’ long-term health following their last exposure to arsenic. The participants could not be described as having “chronic arsenic intoxication,” because their blood arsenic levels were not measured. In this study, we defined them as having “probable arsenic intoxication.” Symptoms frequently involved the sensory nervous system, skin, and upper respiratory system (89.1–97.8%). In an analysis of neurological findings, sensory neuropathy was common, and more than half of the participants complained of hearing impairment. Longitudinal assessment with neurological examinations and nerve conduction studies revealed that sensory dysfunction gradually worsened, even after exposure cessation. However, we could not conclude that arsenic caused the long-term decline of sensory function due to a lack of comparisons with age-matched healthy controls. This is the first study to characterize the longitudinal sequelae after probable arsenic exposure. Our study will be helpful to assess the prognosis of patients worldwide who still suffer from chronic arsenic intoxication.
Highlights
Arsenic is a heavy metal that causes various adverse effects on human health
To clarify the long-term medical history of patients with arsenic intoxication after exposure cessation, we conducted the following investigations in Toroku residents with probable arsenic intoxication: (1) a descriptive analysis of symptoms, comorbidities, and neurological findings; (2) an observational analysis of sex differences in participants with probable arsenic intoxication during both adulthood and during infancy and early childhood; and (3) a longitudinal analysis of sensory dysfunction based on physical and neurophysiological examinations
This study protocol was approved by the Ethics Committee of the University of Miyazaki, with a waiver of written, informed consent obtained from participants with chronic arsenic exposure, and was performed in accordance with the Declaration of Helsinki
Summary
Arsenic is a heavy metal that causes various adverse effects on human health. It accumulates in the body and generates reactive oxygen species, resulting in oxidative damage to vital organs (Abdul et al 2015). In the residents of Toroku, high arsenic concentrations were detected in the hair (average concentration, 1.52 mg/kg; n = 29), fingernails (10.83 mg/ kg; n = 31), and urine (0.58 mg/L; n = 38) (Miyazaki prefecture 1972; Hotta et al 1979), presumably because many residents had continued to drink the contaminated water from Toroku River after air exposure had ceased. To clarify the long-term medical history of patients with arsenic intoxication after exposure cessation, we conducted the following investigations in Toroku residents with probable arsenic intoxication: (1) a descriptive analysis of symptoms, comorbidities, and neurological findings; (2) an observational analysis of sex differences in participants with probable arsenic intoxication during both adulthood and during infancy and early childhood; and (3) a longitudinal analysis of sensory dysfunction based on physical and neurophysiological examinations
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