Metal processing plants and smelters are facilities that extract various metals from ore to create more refined metal products. Metals include copper, nickel, lead, zinc, silver, cobalt, gold, cadmium, etc. Smelting specifically involves heating the ore with a reducing agent such as coke, charcoal or other purifying agents. Primary smelting processes mine ore and concentrates, whereas secondary smelting processes recover scrap.
Extractive metallurgical and smelting processes can be highly polluting activities. Some facilities that carry out metal and smelting processes are known to emit high quantities of air pollutants such as hydrogen fluoride, sulfur dioxide, oxides of nitrogen, offensive and noxious smoke fumes, vapors, gases, and other toxins. A variety of heavy metals: lead, arsenic, chromium, cadmium, nickel, copper, and zinc are also released by the facilities.
In addition, pickling and other processes in metalworking use large volumes of sulfuric acid which may also be released. Estimates from a survey conclude that steel production alone accounts for 5 to 6 percent of worldwide, man-made CO2 emissions.1 Metallurgical complexes primarily cause pollution through gaseous and particle release into the environment.
Metals may be released as fine particles or volatile compounds, either via a chimney or as “fugitive” emissions from general operations. Organic vapors and sulfur oxides resulting from secondary smelting roasting operations and fuel combustion can cause smog, containing ozone, fine airborne particles, nitrogen oxides, sulfur dioxide and carbon monoxide.2 In addition, some smelting processes can also produce large quantities of solid waste, known as slag, which usually contain significant amounts of contaminants. Metal-bearing dust particles can travel far distances to pollute the soil and surface waterways. Highly alkaline smelter effluent and tailings also release acid to waterways from waste pits.3
Exposure to Pathways
Humans typically become exposed to metal processing plant and smelter contaminants through inhalation and ingestion.4 Inhalation of pollutants occurs as a consequence of gaseous emissions and fine particulate matter (i.e. dust). Layers of dust can also settle onto nearby agricultural fields, causing crop intake of pollutants and later consumed by humans.
Particulate matter emissions, sewage waters, and solid wastes also enter waterways used for drinking water. Workers in metal processing plants and smelters generally have a higher risk of exposure to toxic pollutants since they can come into direct contact with the pollutants when working with substances containing metal processing and smelting waste.
Exposure to airborne pollutants from metal processing and smelting can lead to various acute and chronic diseases. Initial sudden exposure can lead to an irritation of the eyes, nose and throat. More serious and chronic effects are heart and lung problems, and even premature death. Heavy metals also pose chronic health risks including bioaccumulation of toxic elements in organisms, which can result into birth defects, kidney and liver problems, gastrointestinal tract issues, joint pain, as well as nervous, respiratory and reproductive system damage. In La Oroya, Peru, a lead smelter operating since 1922 is blamed for the high levels of lead, a heavy metal, in the local children. A study from 2002 found that eighty percent of children tested in the area have blood lead levels two and three times greater than accepted levels.5 The study also found that 73% of La Oroya’s children between the ages of 6 months and six years had lead levels between 20 and 44 μg/dL, and 23% were found with levels higher than 45 μg/dL, which is almost quadruple the WHO limit of 10 μg/dL. 6
Some of the sites that have been noted as examples of the problem
La Oroya, Peru
Tuticorin, Tamil Nadu, India
Rudnaya Valley, Russia
What is Being Done
Modern processing plants and smelters can be designed and operated to control releases to very low levels. However, such operations can be relatively costly and many plants, especially where regulations are not applied seriously, do not meet the standards. One key issue therefore is to improve the quality of operations. Older smelters (which can be many decades old) are often very poor in terms of emissions control and while some upgrading can be carried out, major improvements (such as upgraded sulfur recovery) can be very costly. The real opportunities for improvement come when processing plants are upgraded for economic and production reasons. Old smelters also often have a legacy of a highly polluted surrounding area, where metal dust may have spread toxic pollutants over wide areas and years of acid releases can result in serious ecological damage. Remediation of such areas has to be focused on removing or curtailing the source of the problems and then tackling the key pathways that affect the local population, often water and contaminated food.
1 Beauman, Chris. “STEEL: Climate change poses stern challenge.” The Financial Times. October 8, 2007. Available at http://us.ft.com/ftgateway/superpage.ft?news_id=fto100820070416397176
2 “Secondary smelting of nonferrous metals: Impacts, Risks and Regulations.” National Center for Manufacturing Sciences: Environmental Roadmapping Initiative. Last Updated March 27, 2003. Available at ecm.ncms.org/ERI/new/IRRsecsmelt.htm
3 Environmental, Health, and Safety Guidelines: Base Metal Smelting and Refining.” International Finance Corporation. World Bank Group. April 30, 2007. Available at http://www.ifc.org/ifcext/enviro.nsf/AttachmentsByTitle/gui_EHSGuidelines2007_SmeltingandRefining/$FILE/Final+Smelting+and+Refining.pdf
5 Serrano, Fernando. “Environmental Contamination in the Homes of La Oroya and Concepcion and its Effects in the Health of Community Residents.” Division of Environmental and Occupational Health. School of Public Health. Saint Louis University. February 2008. Available at http://www.upr-info.org/IMG/pdf/InternationalAssociationforEnvironmentalDefense_Peru_
Metal processing. Bhiwadi, India. Photo by Blacksmith Institute.
Lax regulation has contributed to the severe pollution of adjescent communites. Peru. Photo by Blackmith Insitute.