Hidroarsenisismo crónico regional endémico: un desafío diagnóstico y de prevención / Chronic endemic regional hydroarsenicism: a challenge for diagnosis and prevention

El arsénico (As) es un semi-metal, ampliamente distribuido en la naturaleza en aguas y suelos. La contaminación de los cursos de agua, tanto superficiales como profundos, constituye el principal problema ambiental generado por este elemento. La intoxicación con As se denomina hidroarsenicismo crónico regional endémico (HACRE). Su importancia de la intoxicación crónica con As en la infancia está dada por los conocidos efectos asociados a la exposición acumulada desde el período prenatal en bajas concentraciones. El HACRE se desarrolla progresivamente, comprometiendo diversos órganos y sistemas, principalmente la piel. Una de las complicaciones más importantes del HACRE es el desarrollo de neoplasias, principalmente tumores cutáneos. El HACRE es una enfermedad prevenible. La salud ambiental infantil representa un desafío del nuevo milenio y los profesionales de la salud cumplen un rol fundamental frente a las amenazas ambientales como las que presentala intoxicación crónica con arsenico.

Arsenic (As) is a semimetal that is widely distributed in nature, in water and soil. In Argentine, the contamination of both waterways and groundwater represents the main environmental problem caused by this element. Chronic As poisoning is known as Chronic endemic regional hydroarsenicism (C.E.R.HA.). Long-term exposure to low concentrations of the element from the prenatal period onward results in the well-known symptoms of chronic As poisoning. CERHA develops progressively, compromising different organs and systems, most importantly the skin. One of the most important complications of CERHA is de development of neoplasias, mainly skin tumors. Childhood environmental health is a challenge in the new millennium and health care professionals play a fundamental role in the protection against environmental hazards such as chronic arsenic poisoning.

Systemic manifestations in chronic arsenic toxicity in absence of skin lesions in West Bengal.

BACKGROUND & OBJECTIVE: Pigmentation and keratosis are the prerequisites to diagnose arsenicosis. However, many systemic manifestations occur in association with pigmentation and keratosis in people exposed to chronic drinking of arsenic contaminated water. The present study aim to find out whether systemic manifestations occur in significant number of cases in arsenic exposed people in the absence of skin lesions in an affected district in West Bengal, India. METHODS: A cross-sectional study was carried out in South 24 Parganas, an arsenic affected district of West Bengal, India. Both dermatological and systemic manifestations were recorded and water samples collected for arsenic analysis from 7683 participants. A correlation of systemic manifestations in relation to arsenic exposure was carried out in subjects having no arsenical skin lesion. Prevalence odds ratio (POR) was calculated for each outcome comparing those with high arsenic exposure with those with lowest exposure. RESULTS: The frequency of occurrence of various clinical manifestations like weakness, anaemia, diarrhoea, hepatomegaly and lung disease was found to be significantly higher among participants drinking water having arsenic concentration > or = 50 microg/l in comparison to those taking water with arsenic content below this level. Further, there was increased occurrence of these manifestations with increasing concentration of arsenic level in drinking water, and this followed a dose-response relationship. INTERPRETATION & CONCLUSION: It appears that it is worthwhile to include people with systemic manifestations in absence of skin lesions with evidence of arsenic exposure as suspected cases of arsenicosis for case detection and in surveillance programme.

Arsenic exposure and its health effects and risk of cancer in developing countries: micronutrients as host defence.

Arsenic (As) is a ubiquitous metalloid found in several forms in food and the environment, such as the soil, air and water. The predominant form is inorganic arsenic in drinking water, which is both highly toxic and carcinogenic and rapidly bioavailable. As is currently one of the most important environmental global contaminants and toxicants, particularly in the developing countries. For decades, very large populations have been and are currently still exposed to inorganic As through geogenically contaminated drinking water. An increased incidence of disease mediated by this toxicant is the consequence of long-term exposure. In humans, chronic ingestion of inorganic arsenic (> 500 mg/L As) has been associated with cardiovascular, nervous, hepatic and renal diseases and diabetes mellitus as well as cancer of the skin, bladder, lung, liver and prostate. Contrary to the earlier view that methylated compounds are innocuous, the methylated metabolites are now recognized to be both toxic and carcinogenic, possibly due to genotoxicity, inhibition of antioxidative enzyme functions, or other mechanisms. As inhibits indirectly sulfhydryl containing enzymes and interferes with cellular metabolism. Effects involve such phenomena as cytotoxicity, genotoxicity and inhibition of enzymes with antioxidant function. These are all related to nutritional factors directly or indirectly. Nutritional studies both in experimental and epidemiological studies provide convincing evidence that nutritional intervention, including chemoprevention, offers a pragmatic approach to mitigate the health effects of arsenic exposure, particularly cancer, in the relatively resource-poor developing countries. Nutritional intervention, especially with micronutrients, many of which are antioxidants and share the same pathway with As, appears a host defence against the health effects of arsenic contamination in developing countries and should be embraced as it is pragmatic and inexpensive.

Access to drinking-water and arsenicosis in Bangladesh.

The discovery of arsenic contamination in groundwater has challenged efforts to provide safe drinking-water to households in rural Bangladesh. Two nationally-representative surveys in 2000 and 2002 investigated water-usage patterns, water-testing, knowledge of arsenic poisoning, and behavioural responses to arsenic contamination. Knowledge of arsenicosis rose between the two surveys among women from 42% to 64% but awareness of consequences of arsenic remained limited; only 13% knew that it could lead to death. Behavioural responses to arsenic have been limited, probably in part because of the lack of concern but also because households are uncertain of how best to respond and have a strong preference for tubewell water even when wells are known to be contaminated. Further work conducted by the survey team highlighted the difficulties in providing alternative sources of water, with many households switching back to their original sources of water.

Arsenic contamination in groundwater: a global perspective with emphasis on the Asian scenario.

The incidence of high concentrations of arsenic in drinking-water has emerged as a major public-health problem. With newer-affected sites discovered during the last decade, a significant change has been observed in the global scenario of arsenic contamination, especially in Asian countries. This communication presents an overview of the current scenario of arsenic contamination in countries across the globe with an emphasis on Asia. Along with the present situation in severely-affected countries in Asia, such as Bangladesh, India, and China, recent instances from Pakistan, Myanmar, Afghanistan, Cambodia, etc. are presented.

Arsenic exposure in pregnancy: a population-based study in Matlab, Bangladesh.

This study assessed the exposure of pregnant women to arsenic in Matlab, Bangladesh, an area with highly-elevated concentrations of arsenic in tubewells, by measuring concentrations of arsenic in urine. In a defined administrative area, all new pregnancies were identified by urine test in gestational week 6-8, and women were asked to participate in the assessment of arsenic exposure. Urine for analysis of arsenic was collected immediately and in gestational week 30. In total, 3,426 pregnant women provided urine samples during January 2002-March 2003. There was a considerable variation in urinary concentrations of arsenic (total range 1-1,470 microg/L, adjusted to specific gravity 1.012 g/mL), with an overall median concentration of 80 microg/L (25th and 75th percentiles were 37 and 208 microg/L respectively). Similar concentrations were found in gestational week 30, indicating no trend of decreasing exposure, despite the initiation of mitigation activities in the area. Arsenic exposure was negatively associated with socioeconomic classes and achieved educational level. There were marked geographical variations in exposure. The results emphasize the urgent need for efficient mitigation activities and investigations of arsenic-related reproductive effects.

Prevalence of arsenicosis in terai, Nepal.

This paper summarizes the findings of surveys on arsenicosis cases conducted during 2001-2004 in terai, Nepal, by governmental and non-governmental organizations in their respective project areas and by some national and international institutes. Studies were conducted in six arsenic-contaminated districts of terai, namely Nawalparasi, Bara, Parsa, Rautahat, Rupandehi, and Kapilvastu. In these districts, arsenic contamination in tubewells varied from 2.1% to 25.7%. The prevalence of arsenicosis was, on average, 2.2% and varied from 0.7% in Kapilavastu district to 3.6% in Nawalparasi district. In the community-based study, the highest prevalence (18.6%) of arsenicosis was found in Patkhouli village of Nawalparasi, where 95.8% of tubewells were contaminated with arsenic. The prevalence of arsenicosis was higher in older age-groups (>50 years) of both the sexes. Males suffered more from arsenicosis than females (odds ratio: 2.50, 95% confidence interval 1.80-3.47). Skin manifestations, such as melanosis and keratosis, were the common symptoms of arsenicosis. Most patients were identified in the early or mild stage of the disease. They are expected to recover if further exposure to arsenic could be avoided by providing arsenic-safe drinking-water through intervention measures.

Arsenic exposure and its impact on health in Chile.

The problem of arsenic in Chile was reviewed. In Chile, the population is exposed to arsenic naturally via drinking-water and by air pollution resulted from mining activities. The sources of arsenic were identified to estimate the exposure of population to arsenic through air, water, and food. Health effects, particularly early effects, observed in children and adults, such as vascular diseases (premature cardiac infarct), respiratory illnesses (bronchiectasis), and skin lesions have been described. Chronic effects, such as lung and bladder cancers, were reported 20 years after peak exposure and persisted 27 years after mitigation measures for removing arsenic from drinking surface water were initiated. Although the effects of arsenic are similar in different ethnic and cultural groups (e.g. Japanese, Chinese, Indian, Bangladeshi, American, and Taiwanese), variations could be explained by age at exposure, the dose received, smoking, and nutrition. Since health effects were observed at arsenic levels of 50 microg/L in drinking-water, it is advised that Chile follows the World Health Organization's recommendation of 10 microg/L. The Chilean experience in removal of arsenic suggests that it is feasible to reach this level using the conventional coagulation process.

Current research problems of chronic arsenicosis in China.

Chronic arsenicosis is a newly-emerged public-health issue in China and many other Asian countries. Over 200 million people are estimated to be at the risk of high arsenic exposure from drinking-water in the Asian region. To protect people from the hazards of chronic arsenic poisoning, the Chinese Government has been providing low-arsenic drinking-water to some seriously-affected rural areas, such as Inner Mongolia autonomous province. Results of follow-up studies showed that both the average values of arsenic, including inorganic arsenic (iAs), monomethylated arsenic, dimethylated arsenic and trimethylated arsenic, and 8-hydroxydeoxyguanine in urine, decreased significantly after drinking low-arsenic water for one year, and arsenic-specific skin lesions also improved to some extent. However, a five-year follow-up study showed no more significant improvement of skin lesions, while the potential risk of arsenic-induced cancers after cutting off high-arsenic exposure was still uncertain and indefinite. The susceptibility of children compared to adults to chronic arsenic exposure and the need to re-evaluate the appropriate standard of arsenic in drinking-water were also discussed in this paper.

Socio-economic status of chronic arsenicosis patients in Bangladesh.

The study showed that the maximum number of arsenicosis patients (71%) belonged to low income group and 29% belong to middle class income group but none was found in high income group and all these patients were from rural areas of the country. Majority of all these patients was related with the traditional occupation of the country like cultivation (53%) in addition to lower level of educational background (81.5%). Most of the patients of chronic arsenicosis were suffering from malnutrition (91%). The present study which reflects that the vast majority of patients of chronic arsenicosis in the country belonged to low income group, but also to low educational background and individuals, who had been suffering from malnutrition, needs a special consideration in the management of the problem. Emphasis has been given to have access to arsenic-free water and protein rich diet to people of arsenic affected areas.

Study on lead and arsenic poisoning status of workers at Thai Nguyen Color Metal Company

A description and analysis were realized to determine the intoxication of lead and arsenic in workers who were exposed to various enviromental factors in Thai Nguyen colored metallurgy factories. These workers had > 5 years old professional age in the field of exploiting and processing the metal. Study showed a high level of intoxication. The mean value of urine ALA oscillated in the range from 7.15 – 7.8 mg/l. There were 20-51 cases with pathological manifestation of lead and arsenic intoxication in the years 1998-2000.

Magnitude of arsenic toxicity in tube-well drinking water in Bangladesh and its adverse effects on human health including cancer: evidence from a review of the literature.

Only after a decade from 1993, arsenic contamination of groundwater in Bangladesh has been reported as the biggest arsenic catastrophe in the world. It is a burning public health issue in this country. More than 50 percent of the total population is estimated at risk of contamination. Already thousands of people have been affected by the disease arsenicosis. Many more may be on the way to manifest lesions in future. We conducted a review of previous studies and published articles including MEDLINE database on this issue. We found that 59 districts out of 64 have been already affected by arsenic in underground drinking water, where this particular source of drinking water is the main source for 97 percent of the rural people. The water is unfortunately now a great threat for the human being due to high level of arsenic. Continuous arsenic exposure can lead people to develop arsenicosis, which in turn elevates the risk of cancer. Skin lesions are the most common manifestations in arsenicosis patients. Relatively poor rural people and other socio-economically disadvantaged groups are more affected by this exposure. Until now cancer patients have been relatively limited in Bangladesh. One of the reasons may be that several years are needed to show cancer manifestations from the beginning of arsenic exposure. But it is suspected that after some years a large number of patients will appear with cancer in different sites for arsenic exposure in drinking water. Various studies have been conducted in arsenic affected countries - notably in Argentina, Chile, China, Japan, and Taiwan -to find the potential of arsenic exposure to cause development of cancer. Among the arsenic related cancers, liver, lung, skin, bladder and kidney cancers are reported to be prevalent in these countries. Unfortunately no scientific study has been yet conducted in Bangladesh to find the relationship between arsenic exposure and cancers in different sites of the body. So our aim is to conduct an ecological as well as a case-control study in the country in the future.

Follow up of water use in a tin mining area affected with arsenic poisoning.

Ron Phibun district in southern Thailand has been known as an endemic area for arsenic contamination. The government has been trying to improve the situation by encouraging the use of rainwater and piped water. This study aimed to document the change of water use and to identify factors associated with safe water use in 1997 compared to that in 1994. Home visits and face-to-face questionnaire interviews were undertaken. Information on water use for drinking, cooking, washing food and washing utensils in 1994 and 1997 was obtained. Among 3,849 households from which data could be obtained (estimated 79% of total households), the percentages of using safe water (including water from bottled rain water, piped and artesian well water) for drinking and cooking rose from 72.5 and 57.9 in 1994 to 93.6 and 80.9 in 1997, respectively. The percentages for washing foods and for washing utensils rose from 28.6 and 20.5 to 59.1 and 53.8, respectively. In 1997, percentage of households using piped water for drinking and cooking was still low (3.6 and 12.3) compared to those using piped water for washing food and utensils (39.1 and 43.6). Multivariate analysis shows that independent factors of the household predicting safe water use are: high arsenic area, near main road and having piped water installed. The influence of these factors (as judged by the level of odds ratio) operates more or less equally on water use for all purposes, except that installation of piped water has more influence on washing water than drinking and cooking water. We conclude that safe water supply in the area is still inadequate. Even if piped water is installed, it is often not used for drinking and cooking. The reasons for not using piped water for drinking and cooking need to be identified.