Research Paper on Heavy Metals: Causes of Global Environmental Pollution

Introduction

Environmental pollutants have gained global concern due to their widespread pollution to the environment. In the environment, pollutants exists in different types namely biological, organic and inorganic. Metals are inorganic environmental pollutants and exist in trace elements in natural waters. The trace amounts are highly dangerous because they can bio-accumulate in the food chain. Major heavy metals include chromium, selenium, cadmium, arsenic, lead, mercury, cobalt, nickel and zinc. Heavy metals are major environmental pollutants introduced to the environment through the anthropogenic activities. Heavy metals are non-biodegradable and as such tend to bio accumulate in the food chain where they become metabolized by the body and then accumulate in the soft tissues. Although many of the metals are essential nutrients in the human body and the ecosystem, heavy metals are major chemical pollutants and highly toxic hence a major threat to human, plant and animal life.

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Background

A periodic table has various elements of differing atomic numbers and mass number. The elements occurring naturally and with high atomic weight and density are known as heavy metals. According to Dinis, Fiuza (2011) heavy metals are metallic elements whose densities are above 5 g/cm3. These heavy metals are known to be heavy environmental pollutants. Heavy metals are considered to be some of the most fatal pollutants in the environment. Although heavy metals like zinc and copper are toxic in high concentrations, others such as chromium, cadmium, and lead are toxic even at very low concentrations. Even at low concentrations, heavy metals can bioaccumulate in human beings. Hence, when human beings become exposed to the heavy metals which consequently accumulate in their body tissues, severe health impacts are experienced (Simeonov, Kochubovski & Simeonova, 2011). Heavy metals are known to cause fatal health impacts such as mental impairment, causes cancer among others. Compared to lead, chromium and cadmium, zinc is relatively less toxic and harmless. According to Plum, Rink, & Haase (2010) zinc intoxication is a rare occurrence albeit, high concentration levels show toxic effects. When at high concentration, zinc hinders uptake of copper causing copper deficiency in the body. The health effects of high zinc concentrations in the body is causing cell death in the brain. Igic, Lee, Harper & Roach (2002) and Plum, Rink, & Haase (2010) identified five health effects of high concentration of zinc and these include lethargy and focal neuronal deficits, respiratory tract disorder, elevated risk of prostate cancer, altered functioning of lymphocyte function and disorder in gastrointestinal tract.

NIOSH set the permissible exposure limit to lead as 0.005 mg/m3 over a duration of 8 hours. Any exposure surpassing the permissible exposure limit, cause a continuum of health effects such as decreased kidney function, damage to the brain, miscarriage, nervous and cardiovascular effects and anemia (Nazri, 2015). Children are the most affected by lead exposure from paints compared to adults. As established by UNEP (2013), low levels exposure of lead interferes with the growth and development of a child's brain resulting in damage to the brain. The child experiences mental retardation while the genes become reprogramed leading to reduced intelligence. Kessler (2014) further posit that exposure to lead compounds can cause cardiovascular and Alzheimer's diseases. Unlike zinc, cadmium is highly toxic even at low environmental exposure. Bernard (2008) and Trzcinka-Ochocka, Jakubowski, Szymczak, Janasik & Brodzka (2010) found that low concentrations of cadmium in the human body, is linked to bone disorder and kidney dysfunction. Acute exposure to Cadmium damages the lung, bones and kidney and can cause cancer. Hexavalent chromium is carcinogenic. Nazri (2015) posits that exposure to chromium leads to the development of lung cancer. However, the development of lung cancer is dependent on the use of PPE, duration exposed to chromium and its amount. Exposure to chromium is also linked to respiratory effects such as distress and asthma. According to OSHA (2012i), chromium damages both kidney and liver and causes skin irritation, perforated eardrums, pulmonary congestion and edema (Yu, 2013).

Historical Context

According to Nriagu (1996), the pollution arising from heavy metals originates from the fire domestication. When the firewood burned, trace amounts of metals were deposited hence altering the level of metals in the cave environments. Imperatively, the link between the metal pollutants, metals, and the human history can be attributed to the discovery of the various mining techniques used in the ancient times that formed part of the human history. In the ancient times, mining was widely practiced and involved extraction of metals from underneath the earth's surface. The economy depended on the earnings from the minerals while people used them to sustain their living. Various metals that were mined include zinc, lead, mercury, tin and copper among others (Nriagu, 1996). The mining was done in small scale and hence, there was no regulation or control of smelting process even when dealing with large quantities of ores. Basically mining involved excavation of the top soil to reach the underground minerals, hence, people had to clear the bush and penetrate underneath using open fires. Such fires substantially released some small quantities of metals which polluted the environment. Later on in 11th century AD, smelters started using large furnaces hence slowly introduced industrial expansions and installations (Nriagu, 1996). The age of industrial revolution begun and this led to increased demand for the metal use and emissions of toxic metal compounds. Minerals were mined commercially and this increased the rate of release of toxic metal pollutants such as zinc, cadmium, zinc, nickel and lead among others. The rate of release of heavy metals has since then been on the rise and it is expected to continue rising unless stern measures are adopted to avert the situation (Nriagu, 1996). Currently, the carbon dating techniques reveal that the heavy metals trace their root from the ancient times with various sediments such as ones found in the South Bay confirming the association.

Ecological Context

Metal pollution is a major threat to the ecological system that comprises of animals, plants, landscape, and weather among others. Basically, ecosystem refers to both the biotic and abiotic parts of the environment. Heavy metals alter the stability of the ecosystem because they contaminate only water, and animals. It affects every living and non-living creatures. Soil is highly affected by heavy metal wastes since it is the precursor that holds metals before becoming absorbed by the plants and animals through the food chain. According Kolawole, Olatunji, Jimoh, and Fajemila (2018), to the topsoil and stream sediments within the industrial environs are highly contaminated with heavy metals which pose great health hazards to the children and general human life. Also, weathering rock release the trace elements and due to alterations in chemical and morphologies, geogenic soil become contaminated. When industrial wastes get released into the environment in form of particulate matter, they settle on the topsoil (Kolawole, Olatunji, Jimoh, & Fajemila, 2018). Soil tries to incorporate the absorbed metals through dissemination to soil organisms such as crustaceans, earthworms and snails which feed on the organic matter found on soil.

These heavy metal among others, get into the food chain, air and water through pollution emanating from the surface and underground water sources, mining, and industrial wastes. Surface and underground sources of water are polluted through the flow of wastes from the dump sites containing toxic elements and other wastes. Besides, mining wastes are dumped in how hence when it rains, the rain water sweeps most of the metals into the water systems while others infiltrate. Such pollutants not only pollutes water but also soil along which it passes. This discharge of heavy metals into the water systems is referred to as chemical pollution. Polluted water is drunk by people, animals and even taken up by plants. Also, the plants absorb the metals from the soil hence becoming contaminated. Animals that drink water from polluted sources take up the metals into their body (Ayangbenro, & Babalola, 2017). In this regard, heavy metals have serious environmental and health effects and need to be eliminated or minimized to prevent the serious implications.

Legal Context

In small scale mining, there are no guidelines, rules and standards guiding the smelters on how to mine the minerals. This is a great problem that contribute to the release of heavy metals into the environment. Various bodies have raised concern over the manufacture of products and on the release of heavy metals into the environment. For instance, European Union has developed guidelines that stipulates the maximum admissible levels of heavy metals in the environment and fishery products. Through such regulations, it is able to regulate the use of heavy metals and their release into the environment. Anybody found violating the regulation faces the consequences of justice. In other areas OSHA has been instrumental in instituting regulations that helps in the amount of heavy metals that can be found in products, drinking water and other regions.

Positions of Stakeholders in the Problem

The various stakeholders consider metal pollution to be a serious problem due to its underlying problems that affect the human health. Different metals pollute the basic human necessities such as water and food making its effects some of the most lethal impacts on human beings. When metal pollutant enter the water systems they cause chemical pollution and the human beings consume it when it is contaminated. Moreover, deposited metals on the soil are absorbed by the plants and enter the food chain. Human beings become poisoned when they take the food products that have content of meal pollutants. As a result of these and other far reaching effects, the stakeholders who advocate for low levels of metal pollutants such as OSHA have come up with standards to regulate the availability of heavy metals. For instance, NIOSH has set the permissible allowable limits for lead to be 0.005 mg/m3 over a duration of 8 hours. These regulatory standards carry out tests to ascertain the guidelines are followed. Moreover, governments of various countries ensures that companies within the area of jurisdiction also regulates the amount of metal wastes that is released by the industries and factories in their effluents. Also, the companies that manufacture products whose heavy metals are components, such as paints, are monitored to ensure that they manufacture products that are within the set standards and regulations. Failure to follows the guidelines and standards are liable to serious legal implications and they risk having their certificates of operation withdrawn. Other stakeholders such as region organizations also advocate for low or no use of heavy metals in various products. In this regard, the stakeholders advocate for the elimination of metal pollution in the wastes and a variety of products.

Conclusion

In conclusion, metal pollutants pose great danger to the environment and the health of human beings and as a result, it has become a threat to the ecosystem. Heavy metals are the major pollutants since they are highly toxic and hence a threat to the various life forms in the environment. The historical origin of heavy metals can be traced from the ancient times when the smelters mined and s...