Peripheral neuropathy induced by drinking water contaminated with low-dose arsenic in Myanmar

Hitoshi Mochizuki,Kyaw Zin Thant,Masugi Maruyama,Yuka Yamamoto,Moe Zaw Myint,Yoshitaka Hishikawa,Win Min Thit,Yasunori Yano,Myo Nanda Aung,Yoshiki Kuroda,Phyo Wai Zin,Khin Phyu Phyu

doi:10.1186/s12199-019-0781-0

Abstract

BackgroundMore than 140 million people drink arsenic-contaminated groundwater. It is unknown how much arsenic exposure is necessary to cause neurological impairment. Here, we evaluate the relationship between neurological impairments and the arsenic concentration in drinking water (ACDW).Participants and methodsA cross-sectional study design was employed. We performed medical examinations of 1867 residents in seven villages in the Thabaung township in Myanmar. Medical examinations consisted of interviews regarding subjective neurological symptoms and objective neurological examinations of sensory disturbances. For subjective neurological symptoms, we ascertained the presence or absence of defects in smell, vision, taste, and hearing; the feeling of weakness; and chronic numbness or pain. For objective sensory disturbances, we examined defects in pain sensation, vibration sensation, and two-point discrimination. We analyzed the relationship between the subjective symptoms, objective sensory disturbances, and ACDW.ResultsResidents with ACDW ≥ 10 parts per billion (ppb) had experienced a “feeling of weakness” and “chronic numbness or pain” significantly more often than those with ACDW < 10 ppb. Residents with ACDW ≥ 50 ppb had three types of sensory disturbances significantly more often than those with ACDW < 50 ppb. In children, there was no significant association between symptoms or signs and ACDW.ConclusionSubjective symptoms, probably due to peripheral neuropathy, occurred at very low ACDW (around 10 ppb). Objective peripheral nerve disturbances of both small and large fibers occurred at low ACDW (> 50 ppb). These data suggest a threshold for the occurrence of peripheral neuropathy due to arsenic exposure, and indicate that the arsenic concentration in drinking water should be less than 10 ppb to ensure human health.

Highlights

Heavy metals are naturally present in earth’s crust, but human activities have dramatically altered their geochemical cycles [1]
We investigated whether neurological symptoms and findings were related to the arsenic concentration of drinking water (ACDW)
We investigated whether two reference arsenic concentration in drinking water (ACDW) values of 10 ppb and 50 ppb were associated with the presence of subjective neurological symptoms and/or objective sensory disturbances

Summary

Introduction

Heavy metals are naturally present in earth’s crust, but human activities have dramatically altered their geochemical cycles [1]. As the human population continues to increase, increasing numbers of people consume groundwater contaminated by arsenic [2]. At least 140 million people in more than 50 countries are exposed to arsenic-contaminated drinking water [3]. In regard to the peripheral nervous system, a considerable number of patients who experience chronic arsenic exposure report subjective complaints of numbness or tingling [7, 10], but nerve conduction studies reveal no abnormal findings [11]. As for the central nervous system, the central sensory conduction time of patients with chronic arsenic exposure is longer than that in age-matched normal controls [6]. More than 140 million people drink arsenic-contaminated groundwater. It is unknown how much arsenic exposure is necessary to cause neurological impairment. We evaluate the relationship between neurological impairments and the arsenic concentration in drinking water (ACDW)

Methods

Results

Discussion

Conclusion