The impacts of mining in the Philippines

Mining is a top and very controversial environmental issue in the Philippines today. It is increasingly becoming a divisive issue too. The government cites economic benefits as sufficient justification to support and encourage mining. In fact, the Intellasia News Online (http://www.intellasia.net) reported on 08 August 2011 that the Philippines' Mines and Geosciences Bureau (MGB) has announced that about 5 million hectares of potentially mineralized areas across the archipelago are now open to local and foreign investors. On the other hand, environmental and religious groups strongly oppose mining because of its well-known negative environmental and health impacts.

A Fact-Finding Team composed of human rights and environmental experts from the United Kingdom which looked into the impact of mining on the environment and peoples' livelihoods in the Philippines highlighted the occurrence of mining-related human rights abuses affecting local communities especially indigenous people; extrajudicial killings of persons protesting against mining; corruption in the mining sector; political pressure on the judiciary resulting in pro-mining decisions; and environmental impacts.

The team observed that "the record of mining companies with regard to environmental protection, disasters and post-mining clean-up in the Philippines is widely acknowledged, even with the government, to be very poor. As of 2003, there had been at least 16 serious tailing dam failures in the preceding 20 years and about 800 abandoned mine sites have not been cleaned up. Clean-up costs are estimated in billions of dollars and damage will never be fully reversed."

It warned that "water contamination from mining poses one of the top three ecological security threats in the world. Many mining applications in the Philippines are in water catchment areas close to the sea, and pose a major threat to valuable marine resources." The severe pollution of the Taft river system in Eastern Samar as a result of the mining activities in Bagacay is a vivid example (please see related article in this blog).

The report also emphasized the very high geo-hazard risks in the Philippines. "In the Philippines, over half of the active mining concessions and two-thirds of exploratory concessions are located in areas of high seismic risk where earthquakes are likely."

"The Philippines is considered as the hottest hotspot in the world in terms of threats to its mega-diverse biodiversity. Thus there is an urgent need to properly manage its natural resources. It is estimated that 37% of Philippine forests may be exposed to new mining."

Should universities campaign for or against mining?

Some leading state universities in the Philippines are reportedly being pressured by environmental and religious groups to take an “official” anti-mining stand. Universities may take the lead in promoting responsible mining and in fact should conduct relevant scientific investigations to prevent or minimize the impacts of mining on the environment and people. But universities should not take an anti or a pro-mining stand. They should remain neutral and allow their constituents (the researchers and scientists) to evaluate facts and decide for themselves what stand to take about mining. A university should strive to seek the truth. Always.

Reference:

Doyle C, Wicks C, and Nally F. 2007. Mining in the Philippines: Concerns and Conflicts. Report of a Fact-Finding mission to the Philippines. Society of St. Columban, West Midlands, UK, 63pp.

Lead pollution due to vehicular emissions in urban areas in the Philippines

Lead (Pb) has been known to be toxic since ancient times. It is a widespread contaminant in soils and Pb poisoning is one of the most prevalent public health problems in many parts of the world. It was the first metal to be linked with failures in reproduction. It can cross the placenta easily. It also affects the brain, causing hyperactivity and deficiency in the fine motor functions, thus, it results in damage to the brain. The nervous systems of children are especially sensitive to Pb leading to retardation. Pb is cardiotoxic and contributes to cardiomyopathy (disease of the heart muscle leading to the enlargement of the heart).

Pb is released into the environment from the weathering of Pb-containing rocks, the industry, and the combustion of fossil fuels. Emissions from vehicles are thus a major source of environmental contamination by Pb especially in cities. Ona et al. (2006) conducted a study that looked into Pb pollution in selected urban areas in the Philippines with the following objectives: (1) to determine the levels of Pb in soil from selected urbanized cities in central region of the Philippines; (2) to identify areas with soil Pb concentration values that exceed estimated natural concentrations and allow- able limits; and (3) to determine the possible sources that contribute to elevated soil Pb concentration (if any) in the study area.

The study focused on the determination of Pb levels in soils of selected cities in Luzon, Philippines. The sites included: Site 1 – Tarlac City in Tarlac; Site 2 – Cabanatuan City in Nueva Ecija; Site 3 – Malolos City in Bulacan; Site 4 – San Fernando City in Pampanga; Site 5 – Balanga City in Bataan; and Site 6 – Olongapo City in Zambales. Soil samples were collected from areas along major thoroughfares regularly tra- versed by tricycles, passenger jeepneys, cars, vans, trucks, buses, and other motor vehicles. Soil samples were collected from five sampling sites in each of the study areas. Samples from the selected sampling sites were obtained approximately 2 to 3 meters from the road. Analysis of the soil samples for Pb content was conducted using an atomic absorption spectrophotometer.

Findings revealed Pb levels ranging from 1.5 to 251 mg kg–1 in all the soil samples collected from the 30 sampling sites in the six cities. Elevated soil Pb levels i.e.greater than 25 mg kg–1 Pb) were observed in five out of the six cities sampled. Site 4 showed the highest Pb concentration (73.9 ± 94.4 mg kg–1), followed by Site 6 (56.3 ± 17.1 mg kg–1), Site 3 (52.0 ± 33.1 mg kg–1), Site 5 (39.3 ± 19.0 mg kg–1), and Site 2 (38.4 ± 33.2 mg kg–1). Soil Pb level in Site 1 (16.8 ± 12.2 mg kg–1) was within the estimated natural Pb concentration range of 5 to 25 mg kg–1. The study found that the average soil Pb concentration from the six cities studied were below the maximum tolerable limit according to World Health Organization (WHO) standards. The high Pb concentration in Site 4 was attributed by the authors mainly to vehicular emission.

The researchers concluded that "only one (San Juan in Site 4) of the thirty sampling sites showed a Pb concentration above the WHO permissible limit of 100 mg kg–1. San Juan in Site 4 had a Pb concentration of >250 mg kg–1. On the average, elevated Pb concentration was evident in the soil samples from San Fernando, Olongapo, Malolos, Balanga, and Cabanatuan. The average soil Pb concentrations in these cities exceeded the maximum estimated natural soil Pb concentration of 25 mg kg–1. Average soil Pb concentration in Site 1 (16.8 mg kg–1) was well within the estimated natural concentration range of 5 to 25 mg kg–1. Data gathered from the study areas showed that elevated levels of Pb in soil were due primarily to vehicular emissions and partly to igneous activity."

Reference
Ona LF, Alberto AMP, Prudente JA and Sigua GC. 2006. Levels of lead in urban soils from selected cities in a Central Region of the Philippines. Environ Sci & Pollut Res 13 (3) 177 – 183

The problem of high levels of nickel in soils and plants in the ultramafic area in Samar, Philippines

Contributed by Janice P. Susaya, Sejong University, Seoul, Korea


One of the heavy metals that commonly occur in elevated amounts in natural ecosystems is nickel (Ni). Ni is considered an essential micronutrient for plants, humans, and animals. It can exist in trace amounts in air, food, drinking water, and soils. Although Ni plays an important role in the metabolism of humans and animals, its intake in excesssive amounts or over a prolonged period could pose health ricsks. Studies have shown that children living in polluted areas have hypertrophy of tonsils, enlarged lymphatic nodes, and enlarged livers. There is also evidence that soluble Ni particulate is linked to acute lung injury.

High Ni levels in natural ecosystems commonly come from ultramafic rocks (also called ultrabasic rocks). These are intrusive igneous rocks containing less than 45% silica (SiO2) with high concentrations of Ni, Mg, Fe, Cr, and Co. They are found in many places around the world and are common in many places in the Philippine like in Salcedo in the island of Samar.The watershed has a highly weathered soil (Oxisol) derived from the weathering of ultramafic rock. Previous studies conducted in the watershed revealed excessive levels of Ni, Cu, and Cr in the soil. Many farmers also complain of unexplained health problems which may be related to heavy metal toxicity.

In a study conducted in the Salcedo watershed and recently published in the international scientific journal Environmental Monitoring and Assessment, Susaya and co-workers (Susaya et al., 2009) evaluated the degree of Ni contamination in soils and plants in the watershed. The plants sampled included native species (non-food) such as Phyllanthus amarus, Melastoma affine, and Stachytarpeta jamaicensis as well as cultivated food crops like Calocasia esculenta, Citrullus vulgaris, Artocarpus heterophylla, Moringa oleifera, Psidium guajava, Lycopersicon esculentum, and Solanum melongena.

Results of the study showed that the quantity of total Ni in the soil was significantly high with a mean of 1,409 mg kg-1 while the available Ni was low with a mean of 8.66 mg kg-1. As the levels of total Ni greatly exceeded the maximum allowable concentration for agricultural soils, the site is not suitable for agricultural purposes. Available Ni levels were low due to the tight binding between Ni and the soil components. This explains why all plants investigated did not met the criterion for a Ni hyperaccumulator plant. Comparison of Ni levels between the food plants sampled and its recommended daily intake (RDI) suggests that consumption of a particular food plant grown in the study area is unlikely to pose health problems. However, prolonged consumption of a given food plant with high Ni level or combined consumption of different food plants with high Ni levels can induce accumulation of Ni above the RDI and thus could cause health problems.

Reference

Susaya JP, KH Kim, VB Asio, ZS Chen, and IA Navarrete. 2009. Quantifying nickel in soils and plants in the ultramafic area in Philippines. Environmental Monitoring and Assessment (now available online at http://www.springer.com/environment/environmental+toxicology/journal/10661)

A superheavy new element is named "copernicium"

Source: Website of GSI Helmholtz Center for Heavy Ion Research, Darmstadt

Element 112 in the periodic table is named in honor of the great astronomer Nicolaus Copernicus (1473-1543). Copernicus discovered that the Earth orbits the Sun ("heliocentric theory"), thus paving the way for our modern view of the world.

The discovering team of scientists at the GSI Helmholtzzentrum für Schwerionenforschung (Center for Heavy Ion Research) in Darmstadt, Germany, led by Professor Sigurd Hofmann (photo) suggested the name „copernicium“ with the element symbol “Cp” for the new element 112. A few weeks ago, the International Union of Pure and Applied Chemistry, IUPAC, officially confirmed the discovery. In around six months, IUPAC will officially endorse the new element's name. This period is set to allow the scientific community to discuss the suggested name "copernicium" before it is finally accepted by IUPAC.

Copernicus was born 1473 in Torun and died 1543 in Frombork, Poland. His discovery that the planets circle the Sun refuted the then accepted belief that the Earth was the center of the universe (or the "geocentric theory"). This finding was pivotal for the discovery of the gravitational force, which is responsible for the motion of the planets. It also led to the conclusion that the stars are incredibly far away and the universe inconceivably large, as the size and position of the stars does not change even though the Earth is moving. Furthermore, the new world view inspired by Copernicus had an impact on the human self-concept in theology and philosophy: humankind could no longer be seen as the center of the world.

With its planets revolving around the Sun on different orbits, the solar system is also a model for other physical systems. The structure of an atom is like a microcosm: its electrons orbit the atomic nucleus like the planets orbit the Sun. Exactly 112 electrons circle the atomic nucleus in an atom of the new element “copernicium”.

Element 112 is the heaviest element in the periodic table, 277 times heavier than hydrogen. It is produced by a nuclear fusion, when bombarding zinc ions onto a lead target. As the element already decays after a split second, its existence can only be proved with the help of extremely fast and sensitive analysis methods. Twenty-one scientists from Germany, Finland, Russia and Slovakia have been involved in the experiments at GSI that led to the discovery of element 112.

Since 1981, GSI accelerator experiments have yielded the discovery of six chemical elements, which carry the atomic numbers 107 to 112. The discovering teams at GSI already named five of them: element 107 is called bohrium, element 108 hassium, element 109 meitnerium, element 110 darmstadtium, and element 111 is named roentgenium.

The goal of the scientific research conducted at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt (founded in 1969) is to understand the structure and behavior of the world that surrounds us. In addition to broadening our understanding of the world, this knowledge also serves as a basis for technological progress in all areas of our lives.

GSI operates a large, in many aspects worldwide unique accelerator facility for heavy-ion beams. Researchers from around the world use the facility for experiments that help point the way to new and fascinating discoveries in basic research. In addition, the scientists use their findings to continually develop new and impressive applications.

The research program at GSI covers a broad range of activities extending from nuclear and atomic physics to plasma and materials research to biophysics and cancer therapy. Probably the best-known results are the discovery of six new chemical elements and the development of a new type of tumor therapy using ion beams.

Heavy metals in the environment and their health effects

Heavy metals have a density of 6.0 g/cm3 or more (much higher than the average particle density of soils which is 2.65 g/cm3) and occur naturally in rocks but concentrations are frequently elevated as a result of contamination. The most important heavy metals with regard to potential hazards and occurrence in contaminated soils are arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb) and zinc (Zn).

The sources of heavy metal pollutants are metal mining, metal smelting, metallurgical industries, and other metal-using industries, waste disposal, corrosions of metals in use, agriculture and forestry, forestry, fossil fuel combustion, and sports and leisure activities. Heavy metal contamination affects large areas worldwide. Hot spots of heavy metal pollution are located close to industrial sites, around large cities, and in the vicinity of mining and smelting plants. Agriculture in these areas faces major problems due to heavy metal transfer into crops and subsequently into the food chain.

Health effects of selected heavy metals

Arsenic (As). Arsenic is well-known as a poison and a carcinogen. It has an average concentration in the soil of 5 to 6 mg/kg. Its amount in the soil is related to rock type and industrial activity.

Cadmium (Cd). Its toxicity is linked with the reproduction problem because it affects sperm and reduces birth weight. It is a potential carcinogen and seems to be a causal factor in cardiovascular diseases and hypertension. Large concentrations of Cd in the soil are associated with parent material (black slates) and most are manmade (burning of fossil fuels, application of fertilizers, sewage sludge, plastic waste).

Chromium (Cr). It is required for carbohydrate and lipid metabolism and the utilization of amino acids. Its biological function is also closely associated with that of insulin and most Cr-stimulated reactions depend on insulin. However, excessive amounts can cause toxicity. Toxic levels are common in soils applied with sewage sludge.

Lead (Pb). This has been known to be toxic since the 2nd century BC in Greece. It is a widespread contaminant in soils. Lead poisoning is one of the most prevalent public health problems in many parts of the world. It was the first metal to be linked with failures in reproduction. It can cross the placenta easily. It also affects the brain, causing hyperactivity and deficiency in the fine motor functions, thus, it results in damage to the brain. The nervous systems of children are especially sensitive to Pb leading to retardation. It is also cardiotoxic and contributes to cardiomyopathy (disease of the heart muscle leading to the enlargement of the heart).

Mercury (Hg). This heavy metal is toxic even at low concentrations to a wide range of organisms including humans. The organic form of mercury can be particularly toxic, and the methyl-and ethyl-forms have been the cause of several major epidemics of poisoning in humans resulting from the ingestion of contaminated food, e.g. fish. Two major epidemics in Japan were caused by the release of methyl and other mercury compounds from an industrial site followed by the accumulation of the chemicals in edible fish. The poisoning became well-known as Minamata disease.

Nickel (Ni). Nickel occurs in the environment only at very low levels. Humans use nickel for many applications like the use of nickel as an ingredient of steel and other metal products. Foodstuffs have a low natural content of nickel but high amounts can occur in food crops grown in polluted soils. Humans may also be exposed to nickel by inhalation, drinking water, smoking, and eating contaminated food. Uptake of high quantities of nickel can cause cancer, respiratory failure, birth defects, allergies, and heart failure (www. Lenntech.com/periodic-chart-elements/Ni-en.htm)

References

Oliver, M.A. 1997. Soil and human health: a review. European Journal of Soil Science 48: 573-592.
Puschenreiter M., O Horak, W. Friesel, and W. Hartl. 2005. Low-cost agricultural measures to reduce heavy metal transfer into the food chain- a review. Plant Soil Environ 51: 1-11.
Susaya JP. 2007. MSc thesis. Institute of Tropical Ecology, Visayas State University, Baybay, Leyte, Philippines.

Environmental pollution and the safety of herbal and alternative medicinal products

There is scientific evidence that many over-the-counter health foods, neutraceuticals, and alternative medicinal products may not be safe. This was revealed in a paper written by Dr. K. Chan of Hongkong Baptist University and published in the international scientific journal Chemosphere.

The paper concluded that “the increase in popularity of such products has brought concerns and fears over the professionalism of practitioners and the quality, efficacy, and safety of their treatment methods and products from herbal and natural sources. These products maybe contaminated with excessive or banned pesticides, microbial contaminants, heavy metals, chemical toxins or adulterated with orthodox drugs."

"The excessive pesticides, microbial contaminants and heavy metals maybe related to the source of these herbal materials if they are grown under contaminated environment or during the collection of these plant materials. Chemical toxins may come from unfavorable or wrong storage conditions or chemical treatment due to storage. The presence of orthodox drugs maybe related to unprofessional practice of manufacturers."

Just a little explanation for the above. Plants growing in polluted soils may absorb the pollutants like heavy metals, pesticides and other harmful substances and store them in their tissues. Studies have shown (e.g. Susaya, 2007) that succulent plant species generally absorb high amounts of heavy metals from the soil. The pesticides may also come from excessive pesticide application to control pests during the production of the herbal plants.

The article is just a reminder to all of us. It may not be true to the products that you are now using. But it may turn out that the fresh herbal plants that we can get from our own backyard maybe safer than the beautifully packed but expensive ones produced somewhere else.

(Photo shows part of the medicinal plant garden of a 12th century castle along Rhein River in Germany.)

Reference

Chan K. 2003. Some aspects of toxic contaminants in herbal medicines. Chemosphere 52: 1361-1371

Selection of plants for phytoremediation of sites contaminated with several metals

Phytoremediation refers to the use of higher plants to rehabilitate contaminated sites without the need to excavate the contaminant material and dispose of it elsewhere. The use of plants capable of taking up high amounts of metals has been proven effective in the rehabilitation of metal-contaminated soils. Plants are grown for a certain period of time and are then harvested and subjected to composting, compaction, incineration, ashing, pyrolysis, direct disposal or liquid extraction. In principle, the best plants for the purpose are those that can tolerate the polluted soil condition, can absorb high amounts of the contaminants, and have economic value (e.g. flowering plants) so that they can also be a source of income. Thus, selection of the suitable plant species is crucial to the success of any phytoremediation program.

In a recent study by HY Lai of MingDao University and and ZS Chen of National Taiwan University published in the International Journal of Phytoremediation, 33 flowering plant species were tested on a 1.3-ha field in central Taiwan. The site is contaminated with multiple metals (As, Cr, Ni, Cu and Zn) due to the continuous irrigation of wastewater from surrounding chemical plants in the last decade. The study used three models for the selection of suitable species: 1) a relative percentage weighting of the growth condition and the metal accumulation capacity of 80% and 20%, respectively; 2) a relative percentage weighting of the growth condition and the metal accumulation capacity of 50% and 50%, respectively; and 3) a relative percentage weighting of the growth condition and the metal accumulation capacity of 0% and 100%, respectively.

The 33 plants included bougainvillea (Bougainvillea spp.), rainbow pink (Dianthus chinensis), serissa (Serissa japonica), French marigold (Tagetes patula), rose of Sharon (Hibiscus syriacus), water willow (Salix warburgu), Chinese ixora (Ixora chinensis), sunflower (Helianthus annuus), Chinese hibiscus (Hibiscus rosasinensis), gold dewdrop (Duranta repens), kalanchoe (Kalanchoe blossfeldiana), creeping trilobata (Wedelia trilobata), garden canna (Canna generalis), garden verbena (Verbena hybrida), Malabar chestnut (Pachira macrocarpa), purslane (Portulaca oloraua), common lantana (Lantana camara), fancy leaf caladium (Caladium xhortulanun), coleus (Coleus blumei), golden trumpet (Allamanda cathartica), common melastoma (Melastoma candidum), Carland flower (Hedychium coronarium), Manaca raintree (Brunfelsia uniflora), yellow cosmos (Cosmos sulphureus), silver apricot (Ginkgo biloba), temple tree (Plumeria acutifolia), orchid tree (Aglaia odorata), star cluster (Pentas lanceolata), blue daza (Evolvulus nuttallianus), cockscomb (Celosia cristata), scandent scheffera umbrella tree (Schefflera arboricola), Bojers spurge (Euphorbia splendens), and croton (Codialum variegatum).

Some of the highlights of the study: Twelve (12) plants out of the 33 tested were selected based on two key factors: 1) ability to tolerate the toxicity of metals (i.e. good growth of the plant) and 2) ability to accumulate high concentrations of metals in the shoot. Using equal weighting (meaning 50% to 50%) of good growth condition (factor No. 1) and of accumulated metal concentrations (factor No. 2), six (6) woody and six (6) herbaceous plant species showed the best potential for phytoremediation of the contaminated site and thus were selected for further testing. These included the following plant species: purslane, garden canna, Bojers spurge, Chinese ixora, croton, kalanchoe, serissa, garden verbena, rainbow pink, French marigold, scandent scheffera umbrella tree, Chinese hibiscus, and sunflower.

The study also revealed that the herbaceous species accumulated higher concentrations of metals and thus have higher “bioconcentration factor” (ratio of metal concentration in shoots to that of the soils) compared to the woody species. The increase of metal concentrations for the herbaceous species were 9.4-fold for Cu, 5.1-fold for Cr, and 8.9-fold for Zn while for the woody species they were 3.1-fold for Cu, 2.5-fold for Cr, and 4.3-fold for Zn.

Reference

Lai HY and ZS Chen. 2009. In-situ selection of suitable plants for the phytoremediation of multi-metals contaminated sites in central Taiwan. International Journal of Phytoremediation 11: 235-250.

Heavy metal pollution and nutrient deficiency problems in the abandoned Bagacay mine in Samar island

The National Policy Agenda on the Revitalization of Mining in the Philippines in 2004 gives top priority to the remediation and rehabilitation of abandoned mining sites all over the country. Consequently, the Department of Environment and Natural Resources (DENR) has identified remediation and rehabilitation of several abandoned mining sites as one of its top priorities (MGB-MESD 2006). Among all abandoned mining sites throughout the country needing urgent rehabilitation, the Bagacay Mine ranks first (MGB-MESD 2006).

Bagacay Mine, located at the border of a nature reserve in the western part of Samar Island, was formerly worked for the recovery of pyrite (FeS2) and copper (Cu) for nearly 50 years until its abandonment in 1992. It exhibits many environmental problems such as heavy metal pollution of soil and water and the formation of Acid Mine Drainage. Recent efforts to rehabilitate the area by re-vegetating it with introduced trees species such as mahogany (Swietenia macrophylla), mangium (Acacia mangium) and ipil-ipil (Leucaena leucocephala) as well as some grass species like tiger grass (Thysanolaena maxima) were a total failure.

An environmental assessment by the Mines and Geosciences Bureau (MGB-MESD, 2006) revealed very high levels of heavy metals in sediments (and soils) collected from various parts of the abandoned mining site. For the upstream sediments (soil and sediments deposited by various tributaries unaffected by mining activities), the levels of heavy metals (in mg/kg) were: Fe (5,900 to 96,000), Cu (9 to 2,216), Zn (<1 to 516) and Pb (22 to 694). The midstream materials which included rock and soil materials from the main pit and waste dumps, silt and sediments in the pit, and tailings from the tailing dams were more polluted and showed the following concentrations (mg/kg): Fe (36,400 to 487,500), Cu (220 to 50,100), Zn (100 to 187,700), Pb (8 to 2,341), As (6 to 5,969) and Hg (1 to 13). For the downstream sediments (from the Taft River), the heavy metals concentrations in mg/kg were: Fe (104,300 to 373,500), Cu (466 to 5,279), Zn (2,314 to 7,138), Pb (44 to 354), As (352 to 693) and Hg (2 to 5).

Some native plant species are starting to grow in clumps even in the most polluted portions of the abandoned site. Edralin (2008) collected soil samples around each clump of the native plants as well as plant tissues for chemical analysis. Findings revealed that the soil in the spots where the plants are starting to grow still have very low fertility status and are extremely acidic aside from containing excessive levels of the heavy metals. The study showed that the native plants that start to grow in the area have low nutrient (N and P) requirement and are able to tolerate the polluted condition either by not absorbing (avoiding) the heavy metals or by absorbing high levels of the metals (the study considered only Cu and Pb). The concentration of Cu in the plants such as Saccharum spontaneum L. and Neonauclea formicaria (Elm.) Merr. was positively correlated with the soil OM content. Two fern species Pityrogramma calomelanos (L.) Link and Lycopodium cernuum L. showed the highest concentrations of Cu in their tissues with values that fall within the toxic range for plants. Also, the highest concentration of Pb was shown by Lycopodium cernuun L. and Dicranopteris linearis (Burm.) Underw. with some of their Pb values also falling within the plant toxicity range.

References

Doyle C, Wicks C, Frank N 2007. Mining in the Philippines Concerns and Conflicts. Fact Finding Mission to the Philippines Report. Society of St. Columban, Widney Manor Rd., Knowle, Solihull B93 9AM, West Midlands, UK

Edralin Don Immanuel A. 2008. Copper, lead, nitrogen and phosphorus levels in soils and plants in the abandoned Bagacay mine in Western Samar. MSc thesis in tropical ecology, Visayas State University, Baybay, Leyte, Philippines.

Kabata-Pendias A 2004. Soil-plant transfers of trace element- an environmental issue.
Geoderma 122: 143-149

Mines and Geosciences Bureau - Mining Environment and Safety Division (MGB-MESD) 2006). Environmental Assessment of Abandoned Bagacay Mine Relative to the Proposed Interim Remediation Measures of the World Bank Supported Project. North Avenue, Diliman, Quezon City.