**3. Anthropogenic activities**

Anthropogenic activities offer a delicate balance between the needs of a community/government and the biodiversity spots and their contribution to nature [21]. The country's development process should be in tandem with the environmental concerns [20]. Therefore, activities like oil exploration in biodiversity spots should be allowed to execute with guiding regulations and policy. If the works go on unregulated, the destruction to the environment and the associated costs of restoration are quite prohibitive. The cost of an oil spill to wildlife range from losses due to acute toxicity of the aquatic and terrestrial species, the cost of rehabilitation of those that can be recovered, and the cost of clean up to and the length of 1300 km length of the oil pipe for crude oil. The work on oil spills is much needed in the Lake Albert Graben given the fact that 4 million gallons per day in the kingfisher project shall be produced come 2023. The Lake Albert Graben has over 7 blocks of which the kingfisher project lies in one of the blocks [2, 22]. The Lake Albert Graben is synonymous with the Niger delta in Nigeria. Oil-related studies in Nigeria exhibited a range of between 230 and 1200 spills per year in the Niger delta between 1981 and 2015 [3]. The amounts per oil spill in the oil mining areas and between the path of oil pipelines can only be estimated to be between 50,000 barrels and 300,000 barrels per year in the same study period in Niger delta [3]. Based on the oil spills, fish are contaminated with potentially toxic substances and this not only leads to health risks in high-level trophic fish but also has a negative effect on fish breeding in the water sources. Adding the restoration costs to the 3.5 billion US\$ initial cost of construction of the pipeline is a tall order [3].

### **3.1 Hazards**

Pollution attributed to quest for energy in Uganda and world over is related to cancers and other severe health burdens to animals and humans. Some of the detrimental hazards associated with oil spills are potentially toxic substances, especially mercury. Considering the Lake Albert Graben where oil wells are located both inland and in lake water, aquatic fish and captive animals will be exposed to levels of Mercury exceeding the maximum allowable limits of WHO and FAO. Exposure of animals and aquatic species to Mercury results in neurotoxicity, kidney damage, cancers, and teratogenicity [6, 10, 23]. One of the gaps identified in the study is the absence of an investigation into the establishment of potentially toxic substances levels in plants, wildlife, and aquatic species, establishment of the associated health risks, and lack of the PTEs distribution map for the MFCA.

The hazard identification study employs teams of epidemiologists, researchers, wildlife veterinarians, game park staff, statisticians, lab specialists, and policy analysts. The study approach utilizes quantitative approach of research involving semi-structured interviews, sample collection, lab investigation, data mining, and dissemination of findings/report/policy and these translate into risk assessments. The evidence generated is what is utilized to reduce oil pollution effects on wildlife and aquatic species in MFCA. Efforts like these steer the reduction of pollutants in areas where biodiversity is paramount and sustainable management of the ecosystem is warranted. Areas that have oil wells and parks in Uganda and other developing countries can utilize study findings to design appropriate interventions for reduction in the negative effects of oil spills in the MFCA. The resultant interventions will result in ecosystem recovery.

### **3.2 Current literature**

Pollution attributed to expedition for energy in Uganda and world over is closely linked to several health burdens to animals, humans, and environment [24]. This evidence can be much more pronounced in the potentially toxic substances, which have been documented to cause cancers in animals and human populations [19, 23, 25]. Furthermore, the plants have equally been shown to contain traces of potentially toxic elements in amounts beyond acceptable levels [23]. It is imperative to note that some of the detrimental hazards associated with extraction and refining of petroleum and associated products are the oil and potentially toxic elements spill-overs [3, 26]. Mercury and its compounds are one such PTEs that is linked to deleterious effects in the nervous system, kidneys, and liver and disturb immune response processes, causing tremors, impaired vision and hearing, paralysis, and emotional instability [27, 28]. Mercury is one of the most common contaminants associated with oil spills [29]. Methods of biological control where eco-friendly bacteria can be utilized to solve the issue of environmental degradation post an oil spill have been attempted [30].

## **3.3 Mercury entry into the ecosystem**

At the human-animal-environment interface, mercury can exist in three forms; elemental (or metallic) mercury, inorganic mercury compounds, and organic mercury compounds. At this point, mercury can be highly persistent, bioaccumulative, and toxic. Mercury occurs naturally in the environment, but it is generally safely contained in minerals and does not present any significant risk, except when anthropogenic activities precipitate its release in large amounts into the environment, consequently circulating freely for a long time [31]. An environment can grossly become polluted with mercury following oil and gas leaks, alkali and metal processing, coal incineration, gold and mercury mining, and from improper medical and other waste disposals. In the environment, microbial organisms can uptake the elemental form of mercury and this signals the transcription of the genes hgcA and hgcB are transcribed to synthesize the HgcA and HgcB proteins [32].

These proteins can then start the methylation reaction to form methylmercury. Mercury and methylmercury exposure to sunlight (specifically ultra-violet light) has an overall detoxifying effect. Sunlight can break down methylmercury to Hg(II) or Hg(0), which can leave the aquatic environment and reenter the atmosphere as a gas as shown in **Figure 4**.

In the food chain, each rung of the food chain consumes more mercury because animals acquire it faster than they expel it. Small ambient quantities of methylmercury can easily build in fish, fish-eating species, and people. Even at low atmospheric deposition rates in remote regions, mercury biomagnification can be harmful to aquatic food chain consumers.

Mercury-associated risks at the wildlife-domestic animal-environment interface.

mercury in water and sediments is the primary concern, as it is in a highly toxic form and can easily be taken up by animals, thus finding its way into the human food chain. Health concerns in Uganda center on human and animal consumption of fish and fish products contaminated with methylmercury. Particularly in humans, neurotoxicity is the most important concern associated with mercury exposure. When methylmercury reaches the bloodstream, it is distributed to all tissues and can cross the normally protective blood–brain barrier to the brain. Methylmercury can also readily move through the placenta to the developing fetus(es) and, therefore, of

*Mercury Contamination and Spill-Over at Human-Wildlife-Environment Interface DOI: http://dx.doi.org/10.5772/intechopen.109492*

#### **Figure 4.**

*Mercury's entry into the environment [33].*

more concern to pregnant women and women of childbearing age. Mercury exposure in humans (RfD between 1.0 and 3.0×10−4 mg/kg per day) can lead to a variety of negative health effects, including neurological, kidney, gastrointestinal, genetic, cardiovascular, and developmental disorders, and even death [32]. Wildlife and domestic animals that consume fish and fish products, depending on their feeding behavior, may ingest large amounts of methylmercury in their diet, often interfering with their reproductive potential. Raptorial bird species, otters, and others that commonly consume water-based foods are at the greater risk of mercury contamination. In birds, reproductive problems are the primary concern related to mercury poisoning. Other mercury effects in wildlife and other animals are liver damage, kidney damage, and neurobehavioral effects.
