Tailings are the waste materials left over after valuable components of ore are extracted during mining. This residual material is finely ground rock particles mixed with water, forming a slurry. These byproducts pose significant environmental and human health concerns due to their composition and vast quantities.
Hazardous Composition of Tailings
The danger of tailings stems directly from their chemical and physical makeup. After ore processing, tailings retain residual chemicals used in the extraction, such as cyanide, mercury, or various acidic solutions. These processing chemicals are often toxic and can remain active within the waste material for extended periods.
Tailings also contain heavy metals. Elements like arsenic, lead, cadmium, copper, and zinc, once locked within stable rock formations, become exposed and more reactive when the ore is finely ground. This increased surface area allows these toxic metals to interact more readily with air and water.
Environmental Contamination Risks
Tailings threaten natural environments through several pathways. A primary concern is acid mine drainage (AMD), which occurs when sulfide minerals within the tailings react with oxygen and water. This chemical reaction generates sulfuric acid, which then leaches heavy metals from the tailings into surrounding ecosystems.
The acidic, metal-laden water from AMD can contaminate surface water bodies like rivers and lakes, making them toxic for aquatic life. It can also seep into groundwater, rendering water sources unsuitable for consumption by humans or animals. Beyond water, soil contamination is another risk, as hazardous substances from tailings can infiltrate agricultural lands and natural habitats. This contamination can stunt plant growth, reduce biodiversity, and enter the food chain through vegetation. In dry conditions, fine tailing particles can become airborne dust, spreading hazardous materials and contributing to air pollution.
Human Health Impacts
Exposure to tailings can lead to human health issues through multiple routes. Direct contact with contaminated soil or water can cause skin irritation and other dermal problems. Ingestion of contaminated water, or food grown on tainted land, allows toxic substances to enter the body’s systems.
Inhaling dust particles from dry tailings piles is another common exposure pathway, leading to respiratory problems. The heavy metals and chemicals present in tailings, such as lead and arsenic, are neurotoxins that can cause neurological damage, particularly in children. Exposure to cadmium can result in kidney failure, while mercury can affect brain development and function. Some components, like arsenic and some heavy metals, are also carcinogens, increasing the risk of various cancers over long-term exposure.
Physical and Structural Hazards
Beyond their chemical toxicity, tailings storage facilities (TSFs), often called tailings dams, present physical and structural hazards. These structures are designed to hold large quantities of waste, often in a slurry form, behind earthen or rock-fill embankments. However, their stability is not always guaranteed.
Failures can occur due to poor design, inadequate maintenance, or external factors like seismic activity and extreme weather, like heavy rainfall. When a TSF fails, it can release a flood of liquefied tailings, which behaves like a fast-moving mudslide. Such events can rapidly devastate downstream communities, infrastructure, and natural ecosystems, causing immediate loss of life and widespread destruction.