Heavy metals in vegetables sold in some cities in the Visayas, Philippines

Every time we buy vegetables in the market, we do not doubt the quality of these farm products. We think they are clean, safe, nutritious and good for our health.

But the worsening environmental pollution due to the overuse and misuse of agricultural chemicals such as pesticides, the improper waste disposal, the manufacturing industry, and the transportation system may be affecting the quality of the food crops we eat everyday. Specifically, heavy metals most of which are toxic to humans at elevated concentrations, are starting to contaminate the vegetables we love to eat.

The scientific principle is simple: a contaminated soil will generally produce contaminated crops.

An interesting and very relevant student research conducted a few years ago revealed such alarming reality. Conducted to determine and compare the Pb, Cu and Zn contents of Alugbati (Basella rubra), Ampalaya (Momordica charantia), Kalabasa (Cucurbita maxima), Kangkong (Ipomoea aquatica), Pechay (Brassica rapa), and Talong (Solanum melongena) sold in markets in the cities of Baybay, Ormoc, and Tacloban (Leyte, Philippines), the study revealed that Ampalaya from Tacloban and Baybay contained excessive levels of Cu and may pose health problems to consumers. 

Likewise, Pechay from Baybay, Ormoc and Tacloban exceeded the safe level for Zn. All vegetable samples collected from the three cities were not contaminated with Pb. Cu and Zn levels varied with crop (vegetable) species and origin (production area). 

The results are very relevant in that they support and confirm the fear among consumers that some food crops sold in the local markets are not safe and may be one of the reasons for the various health problems experienced by many people.

The study was conducted in 2012 by Anna Luisa Ventulan, Christine Gay Cala, and Johannes Reiner Asio, all senior students at VSU Laboratory High School. The research adviser was Luz Geneston Asio of the Central Analytical Services Laboratory, Visayas State University, Baybay City, Leyte.

Ulrich’s soil acidification hypothesis on forest decline

In 1979, Bernhard Ulrich was the first researcher to discover the connection between air pollution and the forest decline or dieback (Waldsterben) in Germany. He hypothesized that acid rain results in soil acidification which in turn causes the forest dieback phenomenon. According to his soil acidification hypothesis, as soil becomes more acidic there is a release of aluminum that damages the roots of the trees. This leads to the following effects: reduction in uptake and transport of some cations, reduction in root respiration, damage to fine feeder roots and root morphology, and reduction in elasticity of the cell walls. The discovery was first published by Ulrich and co-workers in "Deposition von Luftverunreinigungen und ihre Auswirkungen in Waldökosystemen im Solling." Schriften Forstl. Fak. Univ. Goettigen 58, Sauerländer Verlag, Frankfurt a.M., 291pp. 

Photo source: www.museumplatkow.de

In 1986, Ulrich put forward his 8 theses on soil acidification which appeared in the Journal of Plant Nutrition and Soil Science 149: 702-717 (1986) as follows:

1. Rocks contain only bases and no acid precursors. Therefore, with the exception of sulfide containing rocks, soils cannot acidify as a result of atmospheric rock weathering.

2. A consumption of protons in rocks and soils results in a decrease of their acid neutralizing capacity and can result in the buildup of a base neutralizing capacity.

3. Weak acids (carbonic acid) lead in geological times to the depletion of bases without a larger accumulation of labile cation acids. Strong acids (HNO3, organic acids, H2SO4) can lead within a few decades to soil acidification.

4. The acid input caused by the natural emission of SO2 and NOx can be buffered by silicate weathering even in soils low in silicates.

5. The cause of soil impoverishment and soil acidification is a decoupling of the ion cycle in the ecosystem.

6. Acid deposition in forest ecosystems which persists over decades leads to acidification.

7. Formation and deposition of strong acids with conservative anions (SO4, NO3) shifts soil chemistry into the Al or Al/Fe buffer range up to a great soil depth.

8. In the long run, soil acidification by acid deposition results in the retraction of the root system of acid tolerant tree species from the mineral soil, and in water acidification.

Bernhard Ulrich was professor of forest soil science and forest nutrition at the University of Goettingen, Germany, from 1965 until his retirement in 1991. He obtained his PhD in agricultural science from the University of Hohenheim, Stuttgart, in 1953 based on a dissertation on the rapid determination of soil cation sorption capacity. He was widely recognized as the leading expert of soil acidification and forest ecosystem research.

Environmental pollution: the case of Xenobiotics

Xenobiotics are chemical substances that are foreign to the biological system. They include naturally occurring compounds, drugs, and environmental agents (Mondofacto online medical dictionary at www.mondofacto.com). The classes of xenobiotics include pesticides, polyaromatic hydrocarbons (PAHs), polychlorinated aromatics, solvents, hydrocarbons, and others (surfactants, silicones, and plastics).

Xenobiotics levels in soils are generally low (less than 100 ppm) unless they are concentrated by application as in the case of pesticides, by spills or by waste disposal. They can occur in soils in solid, dissolved, and gaseous phases and all undergo microbial and abiotic (chemical) transformations (Logan, 2000).

Photo source: www.cleanwaterfund.com

Pesticides are the most important xenobiotic pollutants because of their widespread use in agriculture. In many developing countries, the unregulated use of pesticides by poor farmers contributes not only to environmental pollution but to health problems as well.

In the soil, pesticides can be temporarily fixed through adsorption by soil particles. The persistence or decomposition of pesticides in the soil is influenced by soil moisture, organic matter content, redox potential, soil acidity, soil temperature, texture, adsorption potential, and clay minerals (Schactschabel et al., 1998; Sonon and Schwab, 2004).

References

Logan, T.J. 2000. Soils and environmental quality. In: Handbook of Soil Science (M.E. Sumner, ed.). CRC Press, Boca Raton, pp: G155-G169.

Schactschabel P., H.P. Blume, G. Brümmer, K.H. Hartge and U. Schwertmann. 1998. Lehrbuch der Bodenkunde (14th ed.). Ferdinand Enke Verlag, Stuttgart.

Sonon, L.S. and P.A. Scwab. 2004. Transport and persistence of nitrate, atrazine, and alachlor in large intact soil columns under two levels of moisture contents. Soil Science 169: 541-553.

How does mining affect the environment?

The major impact of mining on the environment is mainly due to the physical damage of the landscape and the production of a large volume of harmful wastes. In general, only a small fraction of the ore is valuable, the remaining large part is waste (tailings). For example, in the Cu mining industry, only about a kilogram of the metal is extracted from one-half ton rock. (Ore is an economic term for a rock from which a mineral can be extracted profitably).

The figure above summarizes the environmental impact of mining and smelting. It shows that mining and smelting produce solid, liquid, and gaseous wastes/contaminants. These cause serious environmental damage once they are discharged to the land (terrestrial ecosystem) and bodies of water (aquatic ecosystems) or when they are emitted into the ambient air. In particular, they cause soil and water acidification, air, water, soil and plant contamination by trace elements, deterioration of soil biology and fertility, and soil erosion.

Studies have shown that trace metals remain in the soil for a long time ranging from hundreds to thousands of years. Cd, Ni, and Zn have a relatively shorter residence time in the soil than Pb and Cr which may remain for several thousand years. This simply means that it is not easy and cheap to rehabilitate an abandoned mining site. In fact, the physical destruction of the landscape can be irreparable. And more importantly, the health risk of the contaminants that have already entered the food chain can remain for a long time.

Photo: Manicani island, Eastern Samar. Source: www.nickelore.blogspot.com (Feb 2, 2012)

References

Skinner B.J., S.C. Porter, and J. Park. 2004. Dynamic Earth. An introduction to Physical Geology. John Wiley and Sons, NJ.

Dudka S. And D.C. Adriano. 1997. Environmental impacts of metal ore mining and processing: a review. Journal of Envi. Quality 26: 590-602.

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.

Global warming and our local environmental problems

Global warming is the increase in the average global temperature. It is a real problem now and we are starting to experience its bad effects like the more frequent occurrence of strong typhoons, the warming of seawater resulting in decreased fish catch by fishermen, and the increased amount of rainfall resulting in catastrophic floods and landslides. It is predicted that the tropics where the Philippines is located will be most affected by global warming.

But apart from this global environmental problem, there are also serious local environmental problems that need urgent action. These include deforestation, land degradation, and soil and water pollution. Except for deforestation, these local problems have seldom grabbed the headlines and the endorsement of politicians and popular personalities hence most people are not well aware of the severity of these problems. But they are already threatening our lives and studies have indicated that these environmental problems may have already contributed to the loss of lives or have caused health problems of people.

The fact that much of the original or primary forest in most Philippine islands is now gone clearly indicates that we failed in protecting this vital natural resource. No need to cry over spilled milk says the popular expression. What we need to do is to see to it that the forest that remains is protected and the degraded uplands, the product of deforestation and kaingin in previous decades, are rehabilitated especially in critical watersheds across the country. A degraded land has reduced capacity to absorb rain so that much of the water during rainy days flow on the land surface resulting in floods and lowering of the water table (meaning, drying up of wells!). Degraded lands are also infertile and unproductive and thus are a threat to food security. Many of the poorest farmers are also living and farming in these marginal lands.

Soil and water pollution is largely caused by improper disposal of municipal solid wastes, the unregulated use of pesticides and fertilizers by farmers, and mining. Most towns in the country do not have proper dumpsites. Very disturbing is the fact that many municipalities use their mangrove areas (a vital breeding place for marine organisms) as dumpsites for solid municipal wastes. The unregulated use of pesticides and fertilizers by farmers also leads to soil and water pollution. You can easily notice this from the unusual vigorous growth of algae and aquatic plants around rice fields, ponds, rivers, and bays suggesting excess amount of nutrients from fertilizers and other sources. Mining is also a major cause of soil and water pollution. It is very unfortunate that more and more areas are opened to mining. The negative environmental effects of the Bagacay Mine which operated from 1954 to 1992 are still there. Recent major efforts to rehabilitate the site have not been successful.

One last thing: when you drink a glass of water, how do you know that it is not yet contaminated with harmful chemicals?

Photo source:
The global warming figure above was taken from the Renewable Energy Blog
http://www.solarpowerwindenergy.org