Related health risk assessment of exposure to arsenic and some heavy metals in gold mines in Banmauk Township, Myanmar Exposure to heavy metals in mining activities is a health issue among miners. This study was carried out at three small-scale gold mining sites situated in Banmauk Township, Myanmar and aims to assess the occupational health risks of small-scale gold miners who are exposed to arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) in the soil through the dermal route. Soil samples were analyzed through atomic absorption spectroscopy (AAS). The concentrations of the heavy metals in soils found As, ranged 1.04 mg/kg to 22.17 mg/kg, 0.13 mg/kg to 3.07 mg/kg for Cd, 0.15 mg/kg to 77.44 mg/kg for Hg, and 7.67 mg/kg to 210.00 mg/kg for Pb. In this study, 79% of the participants did not use any form of personal protective equipment (PPE) while working in gold mining processes. Regarding noncancer risk assessment, the results found all hazard quotient were lower than acceptable level (HQ < 1). In addition, all hazard index (HI) was lover than 1, the highest HI was found as 5.66 × 10−1 in the amalgamation process. On the other hand, the result found cancer risk ranged from 8.02 × 10−8 to 1.75 × 10−6, and the estimated cancer risks for 9 years ranged from 4.78 × 10−7 to 1.04 × 10−5. Therefore, the cancer risks of the miners were greater than the United State Environmental Protection Agency (U.S. EPA) acceptable cancer risk level, 1 × 10−6, and the miners may be at risk of developing carcinogenic diseases. The suggestion is to educate miners about the health risks of heavy metals and to encourage the use of proper PPE all the time while working in gold mine. Artisanal and small-scale mining (ASM) activities are widely conducted in many developing countries such as Central and South America, Asia, Africa and Oceania as these mining activities provide approximately three to five times more income than other rural-based small-scale agriculture, forestry and fishery activities95 . Gold mining is the most popular activity among the ASM activities96 . Although artisanal and small-scale gold mining (ASGM) activities are normally conducted under unsafe conditions, twenty to thirty percent of the total world gold supply is provided by ASGM1. These mining activities generally use simple tools and methods to extract gold from ore deposits 96. In these gold mining processes, mercury (Hg) is commonly used to capture gold; as a result, mercury can enter the environment in the soil, water, and atmosphere2,3,4,5. Therefore, ASGM has been identified as the world's largest source of anthropogenic Hg released into the environment6. Furthermore, these mining activities can lead to increase the concentrations of heavy metals, such as arsenic (As), cadmium (Cd), Hg, lead (Pb), copper (Cu), and Zinc (Zn) which occur naturally in the Earth's crust7,8,9,10,11,12,13,14. As a result, these increased concentrations of heavy metals can cause sediment, soil and water contamination, and many studies have reported carcinogenic and noncarnogenic diseases in humans because of exposure to heavy metals via inhalation, ingestion and dermal contact15,16,17,18,19,20,21,22.Among the heavy metals, As, Cd, Hg, and Pb are classified as the heavy metals most toxic to humans and animals because of their elemental impurities, carcinogenicity and likelihood of occurrence23,24,25,26. Regarding the adverse health effects, the heavy metals can accumulate into target organs and tissues by carrying them through bloodstream, once it is taken up into the body and then can result serious health problems depending on lifestyle, demographic factors, duration, and magnitude of exposure. Exposure to As can cause a wide range of health problem ranging from gastrointestinal disturbance to development of neoplasms, anorexia, fever, fluid loss, goiter, hair loss, headache, herpes, impaired healing, muscle spasms, sore throat, weakness, especially liver, kidney and lymphatic cancer. Even low-level exposure to As can result abnormal heartbeat, blood vessels damage, abdominal pain, nausea and vomiting, and pricking sensations in the hands and legs in short term exposure, and long term exposure can leads to skin lesion, diabetes mellitus, pulmonary disease and cardiovascular disease, peripheral vascular disease, neurological problem, and certain type of cancers27,28. In case of exposure to Cd, health problem can range from aching pain in back and limb, muscular pain, chills, sweating, weakness, fever, and cancer. Long term exposure to Cd can cause fragile bone, lung damage, cardiovascular disease, diabetes, especially kidney and liver disease. It can also affects to brain, central nervous system, skeletal system, lung, stomach, heart, placenta, and female reproductive system27,29. Hg, which is non-essential and very toxic to human body, is mainly released from the anthropogenic activities like mining. Long term exposure to Hg can lead to serious effect on kidney and nervous system, and health problems can also hair loss, blisters on skin, rashes, nausea, diarrhea, joint pain, irritability and damaging stomach and intestines30,31. Regarding exposure to Pb, the sensitive targets are hematological and cardiovascular system, nervous system, and kidney. Long term exposure to Pb can result vomiting, forgetfulness, poor attention, coma, and death. Especially, it can cause serious health effect such as behavioral problem, learning disability, and death on young children27,32,33.Furthermore, many studies have reported high concentrations of As, Cd, Hg and Pb in the soil and tailings of gold mining areas of Ghana34,35, Tanzania36, Iran37, Kenya38,39, Thailand11,40,41 and Oman42. Additionally, the main exposure pathway to these heavy metals from tailings and the soil to humans was reported to be the dermal route43. Exposure to these heavy metals can cause many serious health problems such as kidney and liver cancers, dermal keratosis44, damage to the central nervous system, heart disease29, joint pain, shyness, irritability30, vomiting, poor attention span, and headache32,33. Therefore, previous studies have conducted noncancer and cancer risk assessments of dermal exposure to these heavy metals in gold mining areas in Nigeria45, Ghana46, South Africa47,48, and China43,49, and unacceptable noncancer and cancer risks have been reported.Gold mining activities have been conducted all over the country in Myanmar, especially in the Kachin, Sagaing, Mandalay, and Bago regions of Myanmar50. Therefore, Myanmar gold production was recorded as 1692 kg in 2015 and 1700 kg in 2016, and ASGM is the main sector of Myanmar's gold production51. The ASGM activities also provide the great likelihoods to the local people for their socio-economy. Although gold mining activities are being widely conducted throughout in the country, a limited number of scientific papers exist regarding the human health risks of these gold mining activities. Few reports contain valuable information on small-scale gold mining in Kachin State of Myanmar but not including scientific data, were reported by Images Asia and Pan Kachin Development Society52 and Images Asia and Kachin Development Networking Group53. Earth Right International and Karen Environmental and Social Action Network additionally reported important information about gold mining in Shwekyin, Bago Region of Myanmar54, but it was not scientifically information. Though, Osawa & Hatsukawa50 published a scientific paper mentioned that environment of Myanmar might be contaminated with Hg released from ASGM. Kawakami et al.55 reported a high concentration of Hg in the atmosphere of ASGM area in Thabeikkyin Township, Mandalay Division of Myanmar. None of these previous studies conducted proper health risk assessments for miners. However, a recent research paper conducting health risk assessment by analyzing hair samples of the miners in the Thabeikkyin Township reported that neurological signs and symptoms of chronic Hg intoxication was investigated in 3 out of 18 miners56.As mentioned, Myanmar still has limited information on gold mining impacts on miners especially in local small-scale mine. In addition, there is lack of information on health risk assessment that is conducting for specific exposure routes and environmental exposure such as air, water, and soil in terms of occupational health risks on miners. To fill these gaps, this study attempted to identify the local small-scale gold mining processes that might have adverse health effects on miners. And then, this study aims to assess carcinogenic and noncarcinogenic risks on both male and female miners who were exposed to the toxic metals such as As, Cd, Hg and Pb from their works.This paper is the first health risk assessment report that is conducting on a specific exposure pathway to heavy metals existing in the environmental medium in terms of occupational health risk on miners in gold mine in Myanmar. This paper provides information on small-scale gold mining process, skin surface area of the miners and their job responsibilities, use of PPE of the miners, and conditions on carcinogenic and noncarcinogenic risks of miners.In Myanmar, the small-scale gold mining method involves the main steps of extraction of material, ore processing, concentration: sluicing and panning, amalgamation, and burning of the amalgam3,50,57.In the extraction of the material, ore is excavated with backhoes after removing the topsoil that covers the ore deposits. Then, in the ore processing step, water is added into the excavated ore to form a slurry to separate gold and other material. The separated gold ore is then concentrated through gravity methods called sluicing and panning to further liberate the gold from other materials. The sluicing step uses the waterproof carpets that are placed over the surface of the wooden sluices to recover gold from the gold ore. Then, gold from the gold ore is further recovered by using a pan in the panning step. Then, Hg is mixed with the gold ore in a pan to obtain gold-Hg amalgam that is then squeezed by hand in a cloth bag. Then, the gold-Hg amalgam is heated to recover gold by evaporating Hg3,4. Finally, ore residues that have high amounts of Hg are removed, however, these Hg-rich ore residues are reprocessed again and again through the cyanide leaching method to further recover gold at some mining sites.Among these gold mining steps, the extraction of the material step widely uses machines instead of human workers to remove the topsoil and to mine the ore, and human workers are mainly used in the other gold mining steps. However, at the step of burning the amalgam, miners can only be exposed to Hg vapor via the inhalation route, as this step is carried out in a particular place. As a result, among the gold mining steps, ore processing, sluicing, panning and amalgamation steps use mainly manual labor, and these gold mining steps are likely to include exposure to heavy metals in the soil on the body parts of the laborer through the dermal route. Therefore, these aforementioned four small-scale gold mining steps are the focus of occupational health risk assessments of miners in this study.The small-scale gold mining sites, namely, Sites A, B and C, near Nar Nant Htun Village in Banmauk Township, Sagaing Region, Myanmar, were the sites selected for this study. The areas permitted by the Government of Myanmar for Sites A, B and C are 0.081 km2, 0.081 km2 and 0.055 km2, respectively. In the permitted areas, the actual working area for Site A is 0.032 km2, Site B is 0.028 km2, and Site C is 0.016 km2. Normally, these mining sites are permitted by the government to conduct gold mining activities at their respective mining sites for one year. Therefore, after every year of gold mining, the site owners have to request a permit for the extension of their mining activities at the same sites for another year from the government. In this way, gold mining activities have been conducted at the same sites year by year. Therefore, at the same gold mining sites, Site A has been working for approximately five years, Site B has been working for approximately three years, and Site C has been working for approximately three years. These mining sites are situated approximately 46.7 km away from northeastern Banmauk town. Banmauk Township is one of the main gold mining areas in the Sagaing Region of Myanmar, and both legal and illegal gold mining activities can be widely found in Banmauk Township because of the wide occurrence of placer deposits in this area. However, research papers regarding the impacts of mining activities in this area are very limited. Placer deposits, which are very common for ASGM miners due to their ease of access and extraction of placer gold, can also be widely found in the vicinity of the study area.Data collectionThis study was a cross-sectional study. Questionnaires and soil samples were collected in this study to investigate the occupational health risks of both male and female miners. This study has already been approved by The Ethics Review Committee for Research Involving Human Research Subjects, Health Science Group, Chulalongkorn University with certificate of approval—COA No. 002/2019 (Date of approval: 3 January 2019). Both the questionnaires and soil samples were collected in January 2019.Questionnaire survey and analysisThe targeted population in this study was both male and female small-scale gold miners within the age range of 18–60 years. Furthermore, miners were considered the targeted population only if they were working in the aforementioned gold mining steps and had a high potential for exposure to heavy metals in soil for at least 12 months. After recruiting the participants, a total of 53 participants (19 participants from site A, 17 participants from site B, and 17 participants from site C) were clearly explained the purpose of the study before the questions were asked. Continuously, information sheets that were written in English and Myanmar separately, including informed consent forms, were provided to the participants, and then they were asked to sign informed consent forms with full understanding and willingness. Then, face-to-face questions regarding the personal information of the miners such as height, weight, job responsibilities and personal protective equipment (PPE) use behavior were asked of the participants to prevent misunderstanding of the questionnaire, thereby obtaining information on the working behaviors of the miners in the gold mining steps.Soil samples collectionThree soil samples were collected from each gold mining step of ore processing, sluicing, panning, and amalgamation in each gold mining site in the study area. Therefore, a total of 36 soil samples were collected from 3 mining sites by using a steel trowel at a depth of 0–10 cm. To obtain a homogeneous soil sample, a 2 m × 2 m plot was created at each sampling point, and then five replicate soil samples were collected at the corners and center of each plot. Then, a 50-g homogeneous soil sample was finally collected from the bucket58. The collected soil samples were then put into polyethylene plastic bags that were thoroughly prewashed in 10% nitric acid and distilled water before use59,60. After collecting all samples, these samples were stored in an icebox and sent to the laboratory to analyze the concentrations of the aforementioned heavy metals and soil pH as soon as possible.Soil sample analysisThe collected soil samples were analyzed at the laboratory of the Department of Agriculture, Ministry of Agriculture, Livestock and Irrigation, Myanmar. To obtain a homogeneous sample, the soil samples were air dried first for two to three days and then sieved via a 2-mm nylon mesh. Then, each of the 5-g dry weight fine powder soil samples and 21-ml concentrated hydrochloric acid were mixed in a 2
https://www.nature.com/articles/s41598-021-02171-9
Related health risk assessment of exposure to arsenic and some heavy metals in gold mines in Banmauk Township, Myanmar
