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US Environmental Protection Agency (EPA) has found that living next to a coal ash disposal site can increase ones risk of cancer and other diseases, especially if one lives near an un-lined wet ash pond that contains coal ash mingled with other coal wastes (USEPA, 2010).

According to the US environmental protection agency‟s peer-reviewed human and ecological risk assessment for coal combustion wastes,” people in those circumstances

Ghosh et al, 2015 in their review of the impact of coal ash from thermal power plant (TPP) on physicochemical properties of soil reported that coal ash contains significant amounts of fine powdered ferro-alumino-silicate material with Al, Ca, Mg, Fe, Na and Si as the predominant elements and toxic metals such as As, Ba, Hg, Cr, Ni, V, Pb, Zn and Se (Mishra et al, 2013; Ghosh et al., 2015; USEPA, 1999).

These toxic metals can cause several types of cancer, heart damage, lung disease, respiratory distress, kidney disease, reproductive problems, gastrointestinal illness, birth defect,impaired bone growth in children, nervous system impacts, cognitive deficiency, developmental delays and behavioral problems.

Studies have shown that the environmental and health problems associated with coal ash are numerous and worrisome (Ghosh et al , 2015; Carlson and Adriano, 1993; ). But to the best of our knowledge there is little or no published work focusing on the coal ash dump problems in Nigeria and Oji in particular. Also, little or nothing was known about neither the heavy metal concentration nor their chemical forms in the area of our study.

These ranges of toxicants in coal ash under study can leach, leak or spill out of coal ash disposal sites and adversely affect human and environmental health (USEPA, 2007):

2.9.1 Arsenic

Arsenic produces a variety of adverse health effects.Ingesting very high levels can result in death. Chronic exposure to arsenic in drinking water can cause several types of cancer, including skin cancer. Recent studies have linked arsenic ingestion to cardiovascular disease and diabetis mellitus (ATSDR, 2014).

Exposure to lower levels can cause nausea and vomiting, decreased production of red and white blood cells, and cardiovascular effects including abnormal heart rhythm, damage to blood vessels, and damage to the peripheral nervous system. Inhaling arsenic from coal ash fugitive dust can likewise pose a danger to human health (ATSDR, 2014).

2.9.2 Cadmium

Oral ingestion of cadmium results in low level s of absorption. The lungs however, readily absorb cadmium, so inhalation exposure results in much higher levels of absorption. This makes cadmium a potential hazard from coal ash, which may be released into the envionment when dry coal ash is stored , loaded, transported or kept in uncovered land fills.Chronic exposure can result in kidney disease and obstructive lung disease such as enphysema. Cadmium may also be related to increased blood pressure (hypertension) and is a possible lung carcinogen. Cadmium affects calcium metabolism and can result in bone mineral loss and associated bone pain, osteoporosis and bone fractures (ATSDR, 2012a).

2.9.3 Manganese

The most common health problems in workers exposed to high levels of manganese involve the nervous system. These health effects include behavioral changes and other nervous system effects, which include movements that may become slow and clumsy.

This combination of symptoms when sufficiently severe is referred to as "manganism."

Other less severe nervous system effects such as slowed hand movements have been observed in some workers exposed to lower concentrations in the work place.The inhalation of a large quantity of dust or fumes containing manganese may cause irritation of the lungs which could lead to pneumonia. Loss of sex drive and sperm damage has also been observed in men exposed to high levels of manganese in workplace air.The manganese concentrations that cause effects such as slowed hand movements in some workers are approximately twenty thousand times higher than the concentrations normally found in the environment. Manganism has been found in some workers exposed to manganese concentrations about a million times higher than normal air concentrations of manganese (ATSDR, 2012b).

2.9.4 Chromium

Chromium appear in two common oxidation states, chromium (III), and chromium (VI).

While chromium (III) is an essential nutrient in the body at trace amount, chromium (VI) is highly toxic and is frequently found in coal ash.When ingested via contaminated water, chromium (VI) can cause stomach and small intestine ulcers. Frequent ingestion can cause anemia and stomach cancer. Contact with the skin by some compound of chromium (VI) can result in skin ulcers. When inhaled in large amounts, chromium (VI) can cause lung cancer, breathing problems such as asthma and wheezing, and nose ulcers (ATSDR, 2011).

2.9.5 Lead

Lead is a very potent neurotoxicant that is highly damaging to the nervous system. Its dangers have been acknowledged for many years.Health effects associated with exposure to lead include, but not limited to neurotoxicity, developmental delays, hypertension, impaired hearing acuity, impaired haemoglobin synthesis, and male reproductive impairment (USEPA, 1992).

It is now well accepted that there is no safe level of lead exposure, particularly for children. Harmful levels of lead exposure can result from drinking water contaminated by coal ash and from exposure to coal ash contaminated soil (Gilbert and Weiss, 2006).

2.9.6 Mercury

Mercury is another well-known neurotoxicant. It has the dangerous capacity to bioaccumulate,or build up in animal tissue. Mecury is particularly toxic to the developing nervous system. Exposure during gestation, infancy, or childhood can cause developmental delays and abnormalities, reduced IQ and mental retardation and behavioural problems (Gilbert, 2008).

2.9.7 Molybdenum

Exposure to molybdenum can occur in mining, inhalation of dust or ingestion. Animal studies have shown that chronic ingestion of more than 10mg/day of molybdenum can cause diarrhea, slowed growth, low birth weight and infertility and can affect the lungs, kiddney and liver (CDC, 2012).

2.9.8 Nickel

Human exposure to highly nickel-polluted environments causes a variety of pathologic effects. The toxic effects of nickel on the lung were recognized first by Agricola in the 16th century (Aleksandra and Urszula, 2008). Some fatal cases were noted following exposure to nickel carbonyl, and by the early 1930s, nickel was a recognized cause of contact dermatitis. Elevated incidences of lung and nasal cancer in workers exposed to nickel were also observed (Aleksandra and Urszula, 2008).

2.9.9 Copper

Copper is essential for good health. However, exposure to higher doses can be harmful.

Long-term exposure to copper dust can irritate the nose, mouth, and eyes, and cause head aches, dizziness, nausea, and diarrhea. If you drink water that contains higher than normal levels of copper, you may experience nausea, vomiting, stomach cramps, or diarrhea. High intakes of copper can cause liver and kidney damage and even death. It is not known if copper can cause cancer in humans. EPA does not classify copper as a human carcinogen because there are no adequate human or animal cancer studies (ATSDR, 2004).

2.9.10 Selenium

Exposure to high level of selenium may lead to a condition known as “the blind staggers.” Symptoms include depressed appetite, impaired vision and staggering in

Extremely high levels of selenium have been found to accumulate in fish and amphibians living in coal ash contaminated waters and wetlands, if they survive exposure to the toxin. Selenium is bioaccumulative, meaning, it is passed up the food chain in increasing concentration (Lemly, 1997).

2.9.11 Zinc

There are three major routes of entry for zinc into the human body; by inhalation, through the skin, or by ingestion. Each exposure type affects specific parts of the body and allows the uptake of different amounts of zinc. Compared to several other metal ions with similar chemical properties, zinc is relatively harmless. Only exposure to high doses has toxic effects, making acute zinc intoxication a rare event. In addition to acute intoxication, long-term, high-dose zinc supplementation interferes with the uptake of copper. Hence, many of its toxic effects are in fact due to copper deficiency. While systemic homeostasis and efficient regulatory mechanisms on the cellular level generally prevent the uptake of cytotoxic doses of exogenous zinc, endogenous zinc plays a significant role in cytotoxic events in single cells. (Laura et al., 2010).

2.9.12 Cobalt

Cobalt is beneficial for humans because it is a part of vitamin B₁₂, which is essential for human health. However, too high concentrations of cobalt may damage human health.

When we breathe in too high concentrations of cobalt through air we experience lung effects, such as asthma and pneumonia. This mainly occurs with people that work with cobalt. When plants grow on contaminated soils they will accumulate very small particles of cobalt, especially in the parts of the plant we eat, such as fruits and seeds. Soils near mining and melting facilities may contain very high amounts of cobalt, so that the uptake by humans through eating plants can cause health effects.

Health effects that are a result of the uptake of high concentrations of cobalt are:

vomiting and nausea, vision problems, heart problems and thyroid damage (ATSDR, 2004).