BIOGEOCHEMICAL, HEALTH, AND ECOTOXICOLOGICAL PERSPECTIVES ON GOLD AND GOLD MINING - CHAPTER 16 (end) doc

333 CHAPTER 16 Concluding Remarks Despite all evidence to the contrary and for reasons that seem neither logical nor rational, it is probable that society will continue to value gold as a commodity in the forseeable future and to provide continued employment to about 30 million individuals worldwide who derive a significant portion of their income from the mining, refining, and sale of raw and finished gold. Jewelry, coins, and bullion will doubtless continue to account for the great majority of all new gold mined — about 2000 tons annually — although new gold and gold products are constantly being developed for use in electronics, medicine, and other disciplines. As is true for other commodities, it is expected that the price of gold will continue to fluctuate over time based on demand and supply. As demand for gold decreases, the price for raw gold will decrease and marginally productive mines will be closed or abandoned, often with little or no regard for the environmental consequences. Gold miners and refiners will continue to suffer from increased illnesses and death rates when compared with the general population, although this is expected to lessen on exposure of miners to additional training and education, implementation of existing safety regulations, and installation of adequate mine safety equipment. Environmental degradation associ- ated with the extraction of gold will continue or increase in developing nations, and at a reduced rate among nations with strong and enforceable environmental laws. New mining technologies now under development to produce gold from very low- grade ores are expected to be both cost-effective and environmentally friendly. Additional research efforts and information on various aspects of gold and gold mining are merited. Some of the more pressing needs are listed below. 1. Reliable production data Major producers of gold include the Republic of South Africa, the United States, the former Soviet Union, Canada, Australia, the Peoples’s Republic of China, and Brazil. However, official gold production data from many localities and nations are unreliable and are usually underreported. Accurate reporting of gold production is needed in order to establish a realistic price for this commodity. 2898_book.fm Page 333 Monday, July 26, 2004 12:14 PM 334 PERSPECTIVES ON GOLD AND GOLD MINING 2. Geologic characterization of gold deposits Geologic characteristics of commercial gold-bearing strata are not known with certainty, although many deposits are related to proximity to volcanic settings, granitic magmas and fluids, pyrites of iron and other metals, and potassium-con- taining igneous rocks. Cost-effective technologies need to be developed to locate gold and other valuable mineral ore deposits. 3. Gold properties database Gold is a complex and reactive element, with unique chemical, physical, and biochemical properties. Additional research is strongly recommended on expansion of knowledge concerning properties of gold and its salts, and to centralize all findings in a single accessible database. 4. Significance of gold concentrations in abiotic materials and living organisms Gold concentrations are unusually high in certain abiotic materials, such as sewage sludge from a gold mining community (4.5 mg Au/kg DW), polymetallic sulfides from the ocean floor (28.7 mg/kg DW), and freshwater sediments near a gold mine tailings pile (256.0 mg/kg DW), suggesting that gold recovery is com- mercially feasible from these materials. A similar situation exists for gold accumu- lator plants, which may contain as much as 100.0 mg Au/kg DW. However, the significance of gold concentrations in various organisms and materials and mecha- nisms governing its uptake and retention are relatively unknown when compared with most metals. To more fully evaluate the role of gold in the environment, systematic monitoring of gold concentrations is recommended in abiotic materials and organisms comprising complex food chains; samples should also be analyzed for selected metals, metalloids, and other compounds known to modify gold uptake and retention. 5. Expanded use of gold and gold salts The unique properties of gold have led to increasing use of the metal and its salts in the disciplines of electronics, dentistry, physiology, immunology, electron microscopy, and human medicine. Additional applications need to be explored. 6. Gold effects on biota Recommended areas of research emphasis include: sublethal effects of Au +3 species to aquatic organisms because concentrations as low as 98 µ g Au +3 /L adversely affect algal growth; mechanisms of accumulation of Au 0 , Au + , and Au +3 by microorganisms and algae; and effects of injected colloidal gold Au 0 and mono- valent gold drugs (Au + ) in mammals on temperature regulation, brain chemistry, carcinogenicity, teratogenicity, and nephrotoxicity, with potential application to human medicine. 2898_book.fm Page 334 Monday, July 26, 2004 12:14 PM CONCLUDING REMARKS 335 7. Biorecovery of gold Gold recovery technologies based on bacteria, fungi, and other organisms are now commercially available; additional research is recommended on biorecovery of gold under different physicochemical conditions. 8. Health protection of gold miners To protect the health of underground workers, continued intensive monitoring of atmospheric dust levels is recommended for conformance with safe occupational levels, implementation of regular and frequent medical examinations with emphasis on early detection and treatment of disease states, and continuation of educational programs on hazards of risky behaviors outside the mine environment. Miners who use elemental mercury to extract gold need to control mercury emissions in confined environments and limit consumption of larger carnivorous fishes. Intensive moni- toring by physicians and toxicologists of populations at high risk for mercury poisoning is recommended in order to provide adherence to existing mercury criteria, as is critical examination of current mercury criteria to protect human health. 9. Gold sensitivity to humans There is increasing documentation of allergic contact dermatitis and other effects to metallic gold from jewelry, dental restorations, and occupational exposure; these effects are most frequent in females wearing body-piercing gold objects. Research is needed to determine the extent of sensitivity (one estimate lists gold allergy at 13% worldwide), the mechanisms of action, and whether nursing infants are at risk. Similar studies are recommended for gold salts. 10. Gold drugs in medicine Gold and gold drugs have been used in human medicine for centuries, and certain gold drugs have been used routinely for more than 75 years to treat rheumatoid arthritis. However, anti-inflammatory properties of gold metabolites and other mech- anisms of action of gold drugs are not known with certainty and merit additional research, as does development of gold drugs with minimal side effects, alternate routes of gold drug administration for maximum efficacy, evaluation of gold drugs in combination with other drugs to enhance relief, and development of more sensitive and uniform indicators for evaluation of gold drug therapy. 11. Gold mine wastes Acidic metal-rich water and tailings wastes from active gold mines devastate receiving aquatic ecosystems. More research is needed on prediction of extent of acid mine drainage and its prevention through physical, chemical, and biological remediation technologies, and on appropriate storage of tailings wastes. 2898_book.fm Page 335 Monday, July 26, 2004 12:14 PM 336 PERSPECTIVES ON GOLD AND GOLD MINING 12. Amalgamation contaminant problems The use of mercury to recover gold has resulted in wholesale and persistent contamination of the biosphere, with direct — and frequently fatal — consequences to all members of the immediate biosphere, including humans. The use of mercury for this purpose must be abandoned, and improved remediation methodologies developed for mercury-contaminated environments using physical, chemical, and biological technologies. 13. Cyanide extraction and water management issues The use of cyanide to extract gold from low-grade ores by major mine operators has caused a variety of lethal and significant sublethal effects on wildlife, especially in desert-like arid areas. But this situation has been steadily improving as wildlife are shielded from cyanide-containing solutions and new habitat has been created from waste rock, overburden, and tailings piles. Pit lakes, however, resulting from surface mining technologies, including cyanidation, may create a variety of prob- lems, as yet poorly documented, to wildlife and human health. Additional research is merited on ecotoxicology of pit lakes. 14. Arsenic wastes Because arsenic interferes with gold extraction and most gold-containing ores contain significant quantities of arsenic, these ores are roasted to remove the arsenic, with resultant arsenic contamination of air, water, and soil ecosystems. Cost-effective methods to remove the arsenic without release to the surrounding environment need to be refined, especially those involving microorganisms. 15. Disposition of abandoned underground mine sites Abandoned underground gold mines are known habitats for species of concern, including threatened and endangered species of bats. Abandoned mine use by ver- tebrates needs to be quantified through monitoring, and their entrances structurally modified for greater protection of these species. Acid mine drainage from abandoned mines is one of the more environmentally devastating by-products of gold mining; additional research is needed to predict and control acidity and metals contamination from this source. 16. Mining legislation All mining laws should be reexamined, especially the Surface Mining Act of 1872, in order to provide economic and other safeguards against environmental damage caused by current gold extraction practices. 2898_book.fm Page 336 Monday, July 26, 2004 12:14 PM . devastating by-products of gold mining; additional research is needed to predict and control acidity and metals contamination from this source. 16. Mining legislation All mining laws should be. 2898_book.fm Page 333 Monday, July 26, 2004 12:14 PM 334 PERSPECTIVES ON GOLD AND GOLD MINING 2. Geologic characterization of gold deposits Geologic characteristics of commercial gold- bearing strata. gold need to control mercury emissions in confined environments and limit consumption of larger carnivorous fishes. Intensive moni- toring by physicians and toxicologists of populations at high risk