Human Mercury Exposure Associated with Small-Scale Gold Mining in Burkina Faso

In many developing countries, governments are yet to formalize or are in the process of formalizing small-scale gold mining and as a result, no substantial guidelines have been implemented to regulate the processes involved in artisanal mining. Therefore, the use of mercury in the extraction process is a cause for concern in terms of environmental toxicity as well as the health repercussions for humans. Tomicic et al. (2011) assessed the mercury exposure and attempted to uncover the factors determining f mercury exposure in various gold mining communities in Burkina Faso. The eight gold mining communities chosen were largely populated with people directly and indirectly affected by mining activity, and all participated in a medical exam which included a questionnaire. Ninety-three directly affected people were categorized as most susceptible to exposure and had their urine tested for mercury.  The researchers found that 69% of the urine samples exceeded the American Conference of Industrial Hygienists biological exposure index and some of the samples were over 10 times the index standard. A third of the susceptible group displayed less than three symptoms associated with mercury exposure while half of the groups suffered from at least five associated symptoms. The authors found that the major determinant in mercury exposure was not the physical handling of mercury but rather the inhalation of mercury vapors during the refining process. The researchers suggest that advice from developed countries would help developing countries establish cleaner small-scale mining processes.—Monkgogi Otlhogile
Tomicic C., Vernez D., Belem T., Berode M., 2011. Human mercury exposure associated with small-scale gold mining in Burkina Faso. International Archives of Occupational and Environmental Health 84, 539–546.

            The artisanal gold mining process usually includes eight steps including the grinding of gold ore into a powder, the washing and sieving of the impure gold ore, the addition of liquid mercury which attracts gold to form an ‘amalgam’, and separates the gold from the impurities in the ore. Finally, the amalgam is placed in an oven and heated until the mercury evaporates and leaves gold behind. Tominic et al. studied the effect of the above-mentioned process on the mining population by examining 1,090 participants in Poushgin, Zinigma, Bouda, Mossobadadougou, Fandojora, Safané and Bagassi for any health effects induced by mercury exposure. Due to the neural, renal, and pulmonary effects of mercury, the medical questionnaire included symptoms such as trembling, chest pains, and dizziness. The susceptible group’s urine samples were tested for albumin and the total urinary mercury concentrations were determined by atomic absorption spectrometry. From the medical questionnaire, the scientists generated exposure determinants which along with the symptoms and total urinary mercury concentrations underwent statistical analysis such as chi-square to prove or disprove their correlation with mercury exposure. Some of the determinants included the gold mine site, which part of the mining process the person took part in, skin contact, and the use of protective equipment.                                                                               The researchers found that after creatinine adjustment, the 93 urine samples ranged from 4.3 to 1, 707 µg/g-Cr with an average of 194.5 µg/g-Cr. Sixty-nine percent of the urine samples exceeded the American Conference of Industrial Hygienists biological exposure index of 35 µg/g-Cr which suggested that excessive mercury exposure is proliferating in the small-scale mining operational sites in Burkina Faso. The authors do assert that their creatinine correction seems to have corrupted a couple of their values but did not exclude them from the study.  From the 93 urine samples, eight of the workers were concerned with the grinding of the gold ore, 33 were involved in ore amalgamation, and 52 were involved in refining the gold. Using the Kruskal-Willis rank test, the researchers saw a significant difference in the urinary mercury levels of all three work groups. The grinding ore workers had the lowest levels of mercury because they had minimal contact with mercury. The amalgamation group exhibited higher levels of mercury because of their direct contact with mercury while the gold refiners exhibited the highest levels of mercury as a result of the inhalation of mercury during the refining process.                                                                         After statistical analysis, the researchers found that six factors were contributing significantly to mercury exposure in Burkina Faso. The factors were age, the occupation of gold refiner, the packaging and heating of mercury, and the Safané and Zinigma sites. The authors found that the heating and inhalation of mercury vapor was a huge factor in the urinary mercury levels which would explain why the gold refiners exhibited the highest levels of mercury in their urine samples. Among the 93 workers who were most susceptible to mercury exposure, headaches, dizziness, chest pain, fatigue, and trembling were the most common mercury associated symptoms. A third of the subgroup displayed less than three mercury defined symptoms while nearly half of the group exhibited five of those symptoms. Among the 779 directly affected participants, the most common symptoms were headaches, dizziness, chest pain, vision disorder and a persistent cough. The researchers found a positive association between ore washers and gold refiners and trembling. They found a positive correlation between heating mercury and chest pain. They also found a positive association between urinary mercury levels and difficulty in grabbing. Even though nearly half of the subgroup had albumin in their urine, there was no association between urinary mercury levels and the presence of albumin.                                                                                                               Though the results of Tomicic et al. suggest that a majority of the gold mine population in Burkina Faso is suffering from mercury-induced health complications, the authors suggest that other external factors may have swayed their data. The lack of a strong association between urinary mercury and symptoms may be caused by the absence of severely sick workers on the sites they surveyed. The researchers suggest that certain health abnormalities such as chest pain and the presence of urinal albumin can also be attributed to dust exposure, other working conditions, and even infectious diseases. They blame this ambiguity on a lack of a control group. However, the authors are confident that their results can be used for the improvement of working conditions in artisanal mining sites in developing countries. The authors believe that strategies such as the recycling of mercury in the amalgamation process and the implementation of international guidelines will reduce the effects of mercury on human health.  

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