Mining-Related Heavy Metal Poisoning

Mining-Related Heavy Metal Poisoning

Hazeema (Undergraduate Student at Western University) John Johnson (Medical Student at University of Alberta) Dollyann Santhosh (Medical Student at University of Alberta) Ananda Majumdar (Student at University of Alberta) Austin Mardon (Assistant Adjunct Professor, University of Alberta) Many communities reliant on artisanal mining around the globe, especially in developing nations, are constantly exposed to toxic heavy metals. These naturally occurring heavy metals, usually measured in the environment as part per million or billion, are found in the ores of precious metals and can adversely impact human health at very low concentrations (1,2). One of the most well known mining-related heavy metal poisoning outbreaks occurred in Northern Nigeria in 2010 (3). In the Zamfara state, rural communities relied on illegal subsistence gold mining to meet their financial needs. However, due to lack of training, equipment and proper ore processing protocols, these communities were exposed to toxic levels of lead. Heavy metals like lead are unsafe for humans at all blood levels (4). In fact, research suggests a child’s IQ drops by up to 3 points for every 10 µg/dL increase in the blood lead level (4). Physiologically upon ingestion, heavy metals can compete with other minerals involved in cellular pathways, displacing them and inhibiting important cellular pathways (4). Clinically, heavy metal poisoning can cause twitching, weakness, seizures, blindness, and diarrhea in addition to cognitive impairment (4). As was the case in the lead poisoning outbreak in Northern Nigeria, toxic metals are primarily released during ore processing, a crucial step following ore extraction. During ore processing, the ore is first crushed into smaller pieces and then grinded to extract precious metals. In this process, a significant amount of heavy-metal contaminated dust is released. This dust can be directly inhaled by the miners if Personal Protective Equipment (PPE) is not used and by depositing onto their clothes it can also enter their homes. Additionally, contaminated dust can travel far distances and deposit onto soil surfaces, drinking water bodies and edible plant products resulting in widespread heavy metal toxicity. While the artisanal mining methods rural communities use put them at a high risk for heavy metal poisoning, the extent of heavy metal toxicity also depends on the geology of the ore deposits and the climate conditions of the area (5). In hindsight, the lead poisoning outbreak in Northern Nigeria is a rare event because not all forms of a heavy metal, for example lead, are equally toxic, i.e.,some forms can be more readily absorbed into the bloodstream than others (5). In particular, in Nigeria weathering of gold deposits transformed minimally bioaccessible lead sulfides into highly bioaccessible lead carbonates, resulting in such a large scale lead poisoning outbreak.

Without doubt, the Nigerian lead poisoning outbreak was a devastating event; it resulted in the death of hundreds of children under the age of 5 and left many others with permanent disabilities (5). However, it also provided scientists and stakeholders with a learning opportunity. International stakeholders realized that a complete ban on illegal mining in rural communities is ineffective because these communities living in countries with dysfunctioning economies and corrupt governments are desperately trying to fulfill their financial needs through any means possible. Therefore, to prevent future heavy metal poisoning outbreaks, stakeholders should focus on educating rural communities on the dangers of artisanal mining, implementing safer mining practices, establishing stricter zoning regulations and setting up ore processing sites away from the residential areas (6). Additionally, an interdisciplinary and collaborative effort between geologists, Earth scientists and health scientists may help prevent future lead poisoning outbreaks. By understanding the interactions between geology and climate, Earth scientists and geologists may be able to predict which gold deposits around the world are likely to contain highly bioaccessible forms of lead (5). Then, using this geological data and overlaying it with areas that practice artisanal mining, researchers could identify populations that are most susceptible to heavy metal poisoning. Resultantly, health scientists could direct prevention efforts to the most high-risk population reducing the chances of future heavy metal poisoning outbreaks.

Bibliography
1.Edwards JR, Fossum TW, Nichols KJ, Noah DL, Tarpley RJ, Prozialeck WC. One Health: Children, Waterfowl, and Lead Exposure in Northwestern Nigeria. Journal of Osteopathic Medicine. 2017 Jun 1;117(6):370–6. 2.Piñeiro XF, Ave MT, Mallah N, Caamaño-Isorna F, Jiménez ANG, Vieira DN, et al. Heavy metal contamination in Peru: implications on children’s health. Scientific Reports. 2021 Nov 23;11(1). 3.Lead Poisoning Investigation in Northern Nigeria [Internet]. Centers for Disease Control and Prevention. U.S. Department of Health & Human Services; 2016 [cited 2022 Oct 24]. Available from: https://www.cdc.gov/onehealth/in-action/lead-poisoning.html 4.Rasmussen G. Millions of people being contaminated with toxic mercury used in mines [Internet]. CBC. 2015 [cited 2023 Jan 20]. Available from: https://www.cbc.ca/news/canada/british-columbia/millions-of-people-being-contaminated-with-t oxic-mercury-used-in-mines-1.3375754 5.Avakian M. Scientists Work Together to Reveal Cause of a Lead Poisoning Outbreak in Nigeria [Internet]. National Institute of Environmental Health Sciences. NIH; [cited 2023 Jan 21]. Available from: https://www.niehs.nih.gov/research/programs/geh/geh_newsletter/2013/7/spotlight/scientists_wo rk_together_to_reveal_cause_of_a_lead_poisoning_outbreak_in_nigeria.cfm 6.The United Nations. Lead Pollution and Poisoning Crisis Environmental Emergency Response Mission Zamfara State, Nigeria [Internet]. www.unocha.org. Joint UNEP/OCHA Environment Unit; 2010 [cited 2022 Nov 24]. Available from: https://www.scirp.org/(S(351jmbntvnsjt1aadkposzje))/reference/referencespapers.aspx?reference id=2565859