Levels of Arsenic in Drinking-Water and Cutaneous Lesions in Inner Mongolia

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INTRODUCTION

Arsenic is an ubiquitous element in nature. Contamination of water can occur naturally when arsenic-rich ores leach into ground and surface water (1). Chronic ingestion of water with high concentrations of arsenic cause adverse health effects to human beings. Keratosis, hyperpigmentation, and depigmentation are the most common cutaneous lesions and play important roles in the diagnosis of arsenic poisoning (2-5). Furthermore, cutaneous lesions are often viewed as useful precursors of severe diseases such as skin cancer (6).

Some epidemiological studies have estimated the relationship between levels of arsenic and cutaneous lesions (7,8). Tondel reported that, among people in Bangladesh with cutaneous lesions, the mean concentration of arsenic in drinking-water was 640 [micro]g/L, while for those without any cutaneous lesions the mean concentration of arsenic was only 21 [micro]g/L (range 0-740 [micro]g/L) (9). In addition, Valentine et al. surveyed groups of 20-57 residents in six cities of the United States where concentrations of arsenic in drinking-water ranged from 0.5 to 395 [micro]g/L. No significant differences in the prevalence of dermal or neurological symptoms were detected among any groups studied (10).

Since 1990, there have been some wells with high levels of arsenic in some areas in Inner Mongolia, China. One of our surveys in 1996 indicated that up to 26% of wells or other water sources in the Hetao plain area of Inner Mongolia had arsenic concentrations that were equal to or higher than 50 [micro]g/L with the highest arsenic level being 1,354 [micro]g/L. Moreover, the prevalence of cutaneous lesions was 44% (11). Some patients had the symptoms of keratosis, while others had both keratosis and pigment disorder (hyperpigmentation and depigmentation). However, there have not been sufficient epidemiological studies clarifying the relationship between the level of arsenic exposure in drinking-water and cutaneous lesions in the area. The main objective of the present study was to determine whether the prevalence of various cutaneous lesions was associated with levels of arsenic exposure.

MATERIALS AND METHODS

Study population

As part of the Asia Arsenic Network's (AAN) Investigation and Strategy of Inner Mongolia Arsenic-contaminated Program 1996-2000, a preliminary survey was conducted between 1996 and 1998 in Wuyuan county of Inner Mongolia. In this survey, 66 of the 679 villages were found to be affected by arsenic (levels of arsenic in drinking-water >50 [micro]g/L), while the permitted standard of arsenic in drinking-water is 50 Hg/L in China. One of the 66 arsenic-affected villages was selected as the study area due to cooperation from the local government and the heterogeneity in exposure, enabling the investigators to collect exposure-response data. The village's main source of income comes from agricultural employment, and there are no other industries or mining activities around the village. Until the 1970s, four public open-shallow wells (depth approximately 3-5 m) were used for drinking-water. From the 1980s onwards, the villagers turned to private tubule-type wells (depth approximately 15-30 m) due to reasons relating to hygiene. The concentrations of arsenic in water in the village ranged from non-detectable doses to a dose of 1,354 [micro]g/L.

According to the registered records of the local government office of Wuyuan county, the total number of inhabitants in the village was 662,589 (89%) of the total number of residents who were in the arsenic-affected village at the time they participated in our study. Most of them were engaged in agricultural work. After the officials from the local government explained the purpose of the study, residents were asked to participate. All subjects signed an informed consent form before being interviewed.

Interviews and cutaneous examination

All participants were given standardized sets of questionnaire during face-to-face interviews in their homes. …