Mine Tailings

 

What are mine tailings?

Mine tailings are large piles of crushed rock that are left over after the minerals of interest such us lead, zinc, copper, silver, gold, etc., have been extracted from the rocks that con- tained them.

The extraction process is only partially efficient and, as a result, a percentage of the desired minerals are left behind in the mine tailings. The extraction process may also concentrate unwanted minerals in the tailings. As a result of the crushing and grinding (milling) processes, the large pieces of rocks are turned into small tailings particles. These fine tailings particles (silty sand-like material) can now easily become suspended into the atmosphere by wind and dispersed throughout the environ- ment as dust particles, which might contain high concentrations of potentially toxic material. 

 

What is dust?

Dust is a generic term used to describe dry particulate matter (PM) suspended in the atmosphere. Dust is formed when fine particles are taken up into the atmosphere by wind or other physical disturbances.   
 
                                                     
  
 
                                           
 

 

 

 

 
 
 
 
 
 
 
 
 
Aside from wind blowing on mine tailings there are many other mining activities that can also generate dust such as the removal of vegetation and topsoil, onsite blasting and drilling operations, use of crushing and screening equipment, construction activities and the driving of vehicles on access and haul roads. Dust levels are significantly influenced by climatic factors such as rainfall, temperature, and wind. Hot and dry environmental condi- tions generally result in more dust. Dust is typically classified according to its particle size: 

• PM10 refers to particles 0.01 micrometers (μm) in size or less (coarse particles).

• PM2.5 refers to particles 0.0025 μm in size or less (fine particles). 

 

 

Particle size is an important factor influencing the dispersion and transport of dust in the atmosphere and the effects of dust on human health. 

 

 

 

 

 

 

 

 

 

How can dust from mine tailings affect your health?

Dust from mine tailings can affect human health due to its physical characteristics (e.g., small particles are more efficiently inhaled and deposited into the lungs) and because it might contain a number of potentially hazard- ous substances. Certain contaminants are more soluble in human fluids and available for absorption by the body (bioavailable) and have a greater potential to be a health con cern. 

People may be exposed to contaminants in the mine tailings through:

• skin contact (dermal exposure) • ingestion (swallowing)
• inhalation (breathing) 

Skin contact with the contaminants could occur through activities such as playing or gardening in areas with contaminated surface soil or mine tailings. However, only an insig- nificant fraction of most of the contaminants in mine tailings can be absorbed through the skin. 

Dust ingestion can occur via hand to mouth contact or through food ingestion (e.g. con- sumption of food from outdoors vendors, or consumption of home grown produce). A portion of the contaminants in mine tailings dust could potentially be absorbed through the intestinal tract. Absorption from the gut depends on several factors including solubility of the contaminant and dietary habits of an individual. Poor nutritional status can lead to enhanced absorption. 

Dust inhalation is probably the most likely pathway of exposure to the contaminants in mine tailings. Small dust particles 10 μm in diameter (PM10) or less are likely to pose the greatest health problems because those particles are inhaled and are most efficiently deposited in the respiratory system. 

The U.S. Environmental Protection Agency (US EPA) regulates only the particles 10 μm in diameter ( PM10) or less. The EPA has deter- mined that fine particles can pose a risk to human health if they become lodged deep in the lungs. The hazard associated with dust exposure depends on the amount and type of dust inhaled, duration of exposure, and the overall health condition of the person exposed. Over short periods of time, these fine particles do not pose a serious human health concern. However, individuals exposed to fine particles for long periods of time can develop respiratory disease and sustain lung damage.

Depending on the nature of the ore and min- eral processing, dust from mine tailings could contain a number of substances that may pose a health hazard (e.g., lead, arsenic, cad- mium, zinc, selenium, mercury, manganese, boron, etc.).

Lead can have an adverse health impact particularly to the nervous system of children and the unborn. Exposure to arsenic has been proven to increase the risk of developing cancer and other blood and nerve disorders. Low cadmium levels over long periods of time can accumulate in the body and cause kidney disease. At high levels, cadmium can damage the lungs. Too much zinc in a short period of time can cause stomach cramps, nausea, and vomiting. Long-term exposure to zinc can cause anemia, pancreas damage, and other health problems. 

Inhalation of airborne dust containing selenium may cause damage to the respiratory tract, gastrointestinal and cardiovascular effects, and irritation of the skin and eyes. 

What can you do to reduce your exposure to dust from mine tailings?

• Restrict public access to the mine tailings to reduce entry and use of the mine site for recreational purposes (bicycles, motorcycles and ATVs).

• Implement dust control measures to reduce emissions from mine tailings through:

 

• watering

• chemical stabilization 

• synthetic covers

• vegetative covers

• phytostabilization*

• wind breaks, etc. 

 

*Phytostabilization is the use of plants to immobilize contaminants like metals in the soil. 

 

People living in the vicinity of the mine tailings can also follow dust control measures. For example, using wet mops instead of brooms to clean floors and using a damp cloth for dusting. They should wash their hands after contacting dust (especially children after play- ing outdoors). People should also avoid direct contact with tailings. 

Want more information? 

Arizona Department of Environmental Quality 

Agency for Toxic substances and Disease Registry

US Environmental Protection Agency

National Institute of Environmental Health Sciences Superfund Research Program

Research Priorities for Airborne Particulate Matter: IV. Continuing Research Prgoress.  Committee on Research Priorities for Airborne Particulate Matter, National Research Council 

 

 

 

For more information, please contact:

Denise Moreno, Program Coordinator

1703 East Mabel Street

Tucson, Arizona 85721-0207

Telefono: 520.429.1428, Fax: 520.626.2466

dmoreno@pharmacy.arizona.edu