1. IntroductionArtisanal and small-scale gold mining (ASGM) directly and indirectly employs more than 100 million people in over 70 countries around the world [1,2]. An estimated 10–15 million people work directly on ASGM activities worldwide, out of which 4–5 million are women and children [3,4,5] and this is increasing in Latin America every year. ASGM produces 12 to 15% of the gold in the world,, yet it uses more than 1400 tons/year of elemental mercury (Hg) which is released in the air, water, sediments, land and food [3]. Elemental mercury released into bodies of water after ASGM activities can be oxidized into soluble species (Hg2+), which can then be deposited in the sediments and converted by natural process into methylmercury (MeHg), the most toxic of the Hg species. The MeHg can be bioaccumulated and biomagnified in fish via the food web, and then eaten by the human population [4,5,6].ASGM is characterized as an informal job that requires limited technical skills and few resources, but requires the use of hazardous substances, such as elemental Hg for gold amalgamation. Mercury contamination has frequently been associated to a set of adverse health effects and environment impacts with social consequences [7,8]. These ASGM miners do not normally use any required personal protective equipment (including masks, gloves, helmets or boots). People in the areas near mining sites, including children, pregnant women and the elderly, are also exposed. Pathways to mercury exposure for ASGM miners include dermal contact and the inhalation of vapor during the amalgamation, inhalation after amalgam smelting to isolate the gold, as well as eating contaminated fish [9,10,11].Recent studies have show that mercury is a powerful neurotoxic and induces serious health effects, such as irreversible neurological disorders, damage to the bone system, teratogenicity, oxidative stress, hormonal alterations, kidney injury, hearing loss, endocrine effects, infertility, menstrual alterations, spontaneous abortions, and other adverse health conditions [9,11,12,13,14,15,16,17]. Additionally, elemental Hg and its inorganic salts are corrosive to the skin, eyes, and gastrointestinal tract by ingestion [18]. Over the last decade, we have increased our understanding of the critical processes involved in the global cycle of Hg and how this element moves in the environment. ASGM is one of the largest emitters of Hg in freshwater globally, releasing approximately 880 tons every year [19]. In many places, the use of mercury may be restricted and its use in ASGM is illegal. Releasing Mercury from an ASGM is considered a risk that affects the health of miners, their communities, and the environment. Therefore, mercury pollution is expected to be reduced in the future in anthropogenic activities responsible for global emissions with the implementation of the international agreement of the Minamata Convention on Mercury, adopted by 140 countries [20].In some countries, the precious metal in ASGM is extracted from ores containing gold, in which rocks are finely pulverized (i.e., sinkholes) by hand with hammers and later using ball mills. The material reduced to powder is mixed with elemental Hg forming an amalgam (a gold–Hg alloy) [19]. During the rock pulverization process, dust emissions producing particulate matter (PM) can be dispersed in the air. Exposure to PM is associated with lung function impairment, depending on PM size and its composition. The vast majority of PM from mining activities are formed from particles greater than PM 10, generated from mechanical activities on the rock and dispersed by the wind and suspended in the air. Exposure to airborne aerosols as small (PM2.5 and PM10) or larger particles (more than PM10) can lead over time to be absorbed through the lungs and associated with respiratory diseases that can affect the health of workers, including symptoms such as coughing, increasing breathlessness, and respiratory pathologies such as asbestosis, mesotheliomas, pneumoconiosis, tuberculosis, or lung cancer [21]. Colombia reported between 268 and 418 thousand people working as ASGM miners, who lost a combined total of 23–52 thousand years of life [22]. In San Martin de Loba (Bolivar), a small municipality in Colombia, sinkhole ASGM has been carried out since the pre-Hispanic era [23]. Approximately 70% of the 17,295 inhabitants of San Martin de Loba depend on ASGM activities for income [8,24]. Several studies on ASGM in Latin America have shown Hg levels in air, food, and biological samples that exceed the critical threshold of the Agency for the Registration of Toxic Substances and Diseases of the Centers for Disease Control and Prevention of the United States [24,25] but few studies have focused on lung function impairments associated with gold mining [26]. The main routes of mercury poisoning are metal vapors, yet the exposure by inhalation of particles containing species of this element is very low. The threshold limit for T-Hg in whole blood according to the World Health Organization is 10 μg/L, whereas it is 5 μg/L for the Environmental Protection Agency [27,28,29].Miners working in ASGM in San Martin de Loba (Bolivar, Colombia) are exposed to mercury through the extraction of gold from excavations of sinkhole mines which are linked to health hazards related to lung function impairment, chronic lung disease, and cognitive dysfunction, in terms of neurological effects. Therefore, the aim of this study was to determine lung function, total Hg levels in whole blood, neurotoxicity (Q16) and quality of life (SF-36) in ASGM miners and non-miners from this municipality [30,31]. 4. DiscussionRecent studies in Latin America on ASGM workplaces have shown high mercury concentrations in biological samples (hair, blood, and urine) taken from miners, due to the use of mercury [26,34,35,36,37,38,39,40,41,42] (Table 6). Several studies have shown a significant impact of the use of Hg on the environment and the health of miners and people living in the vicinity of ASM miners [8,25,36]. Reported concentrations of Hg in the environment increase in ASGM sites. Most of these studies were published in Colombia, Peru, Ecuador and Mexico, displaying the rise of ASGM in Latin America and the lack of knowledge regarding Hg management in extractive processes. Although women are part of this practice, the number of women surveyed is generally low in these recent studies (Table 6). Our results concurred with the findings of previous studies. Mean concentrations of T-Hg in blood samples of the miners from San Martin de Loba were similar or greater to values from miners or communities near ASGM in other studies in Colombia [43,44,45,46], yet lower than those reported by Cruz-Esquivel et al., 2019 [26] and Calao-Ramos et al., 2021 [45] (Table 6). In general, mean concentrations of T-Hg in blood samples taken from female miners in this study were greater than those from male miners, although there were no significant statistical differences between them. The lack of statistical difference between T-Hg concentrations of males and females may be due to the small sample size in this study. This result was similar to other studies carried out in Colombia [26,43,45] (Table 6). The results for quality of life (SF-36) were adjusted at low and high T-Hg concentrations; therefore, statistical differences were found between females and males in 7 of the 8 evaluated parameters (Table 4). The largest concentration of Hg in whole blood was found in ASGM in departments such as Choco [41], a poor region in this country, similar to San Martin de Loba (the present study). These socioeconomic inequalities are correlated with ASGM [4,39] and have the potential to interact with Hg by reducing the opportunity for health care for the consequences of toxicity, with lower education levels. In addition, some of these settings are more susceptible to illegal mercury trade, and violence is used to control the territory. These three factors—Hg toxicity, poverty, and violence—are synergically interacting with each other and increasing the adverse effects of Hg on these populations and the environment [47,48]. The ASGMs have been considered hazardous working places for miners because they involve rudimentary and semi-automatic tools, and miners are usually associated with poor health without following the safety standards such as wearing personal protection elements (PPE) that could include gloves, safety glasses, shoes, earplugs, hats, respirators, or body suits, etc. Miners from ASGMs in San Martin de Loba do not wear PPE or they have poor PPE compliance, greatly increasing the risk of mercury exposure. Therefore, these miners had high mercury concentrations in blood samples because they have been directly exposed to mercury vapor produced during the amalgamation and the burning processes, as well as eating fish that has been contaminated with methylmercury. Previous studies report that the exposure of miners to mercury in order to extract gold can cause immune, sensory, neurological, motor, and behavioral dysfunctions similar to neuronal diseases [32,33]. In a systematic review of recent studies reporting Hg concentrations in male and female miners from ASGMs in Latin America, Colombia is the country with the most publications, followed by Mexico, Ecuador, and Peru (Table 5).The results of this study showed that the male miners with a normal spirometry had a better quality of life than miners with an abnormal spirometry, specifically in physical function and physical role [1]. These results suggested that the miners from San Martin de Loba have worked in ASGMs and performed activities in tunnels extracting rocks containing gold-rich ores and later used hammers and ball mills to reduce the mineral to a fine powder. In addition, the miners use excavation techniques such as explosives, pneumatic, manual excavation tools, and work in poorly ventilated environments with low ventilation which are associated with dust or PM (Figure 4). Airborne PM has a strong association with lung capacity, reduced lung function, and pneumoconiosis (Figure 4). However, lung function may have a long impact if the miners are exposed to dust or PM with an aerodynamic diameter ≤ 2.5 μm (PM 2.5) [49,50].

In this study, 60% of the miners from San Martin de Loba had neurotoxic abnormalities (≥6) according to the Q16 neurological toxicity test. In addition, miners had 8.9 times more neurotoxic abnormalities (≥6) than non-miners. Therefore, miners with neurotoxic abnormalities (≥6) should be referred to higher levels of health care. These results were significant and were also found in adjusted analyses, including our small sample size. The present analysis also shows significant increases of some neurological parameters in miners, such as loss of understanding of TV/radio, problems with usual activities, fatigue, oppression in chest, painful tingling, loss of strength in arms, legs, loss of sensitivity in arms, legs and having more than 6 abnormalities, which guides us to advance with more specific neurological studies.

In Latin America, ASGM activities play an important role in affecting the quality of life of many communities. Dysfunctional households end up being a burden for women in these settings [8]. In San Martin de Loba, ASGM mining is the main economic activity, starting at an early age. It may cause school dropouts and increase addiction in the young population. Diet is also a relevant factor that depends on the consumption of fish from the Magdalena basin, adjacent to this town [4]. This body of water receives mercury contamination from ASGM activities and the nearby communities are affected by methylmercury-fish consumption. An earlier study in the San Martin de Loba showed that 90% of the participants eat fish approximately three to five times a week [24], potentially increasing the amount of Hg ingested in these mining sites. Based on the results of this study, further research is needed to evaluate how ASGM impacts lung function by measuring airborne particles such as PM2.5 and PM10 with a larger sample size and more detailed surveys to assess multiple stressors on respiratory health. Additionally, studies with larger sample sizes studies are needed to evaluate the health impact in miners as well as the impact on their communities.