Abattoirs: The Hidden Sources of Plants’ Heavy Metals and Other Pollutants in Lagos, Nigeria

Abstract

Abattoirs are places where animals are slaughtered and processed for human consumption leading to the production of huge wastes. Abattoir wastes contain several pollutants, most of which have growth limiting effects on soil microbes, plants, animals, and the entire ecosystem. A larger fraction of these wastes contains heavy metals. Heavy metals present in abattoir wastes are often acquired by plants through bioaccumulation, biomagnification and bioconcentration and remain persistent via food chain in the ecosystem. Most abattoirs in the developing nations such as Nigeria (Lagos) lack good personnel, equipment, and healthy practices. These ineffective management practices often provide bedrock for the occurrence of several negative effects evident in disease, disruption of wellness and so on. To prevent this effects, good abattoir waste management such as burying, composting, rendering, anaerobic digestion, blood processing, incineration with proper policies, laws and regulations must be put in place and enforced by necessary government agencies especially in Lagos State, Nigeria to minimize the pollutants released into the ecosystem. .

1. Introduction

Lagos State is one of the thirty-six (36) states in Nigeria with population estimated at over 200 million people. It is one the major industrial and business hubs of Nigeria. It has twenty (20) Local Government areas which are subdivided into five main divisions—Ikeja, Badagry, Ikorodu, Lagos and Epe divisions [1]. However, being the cash-driven center of the nation, it is without its own peculiar challenges. One of the prevailing challenges of Lagos, without exceptions from other parts of the country and the world is pollution.

Pollution involves the introduction of any material (solid, liquid or gas) or types of energy (heat, sound, or radiation) that is hazardous to the ecosystem-plants, animals, and human health [2]. Also, it could further be seen as any reaction, by individuals or bodies, which changes the biochemistry, metabolically and/or environment of other living things in a wider or localized area, where the causal link is clearly established [3, 4]. Pollution may be natural like flood, drought, cyclones, and many others and artificially (human activities) mediated and could be grouped into air pollution (affecting the health of the atmosphere), soil pollution (reducing the biodiversity of the soil and its health status) and water pollution (affects the overall quality and safety of water bodies). Several substances have been attributed to the rise in pollution levels in the state and these substances are generally referred to as pollutant [5].

Pollutants are materials that when released into these ecosystems (air, soil, and water) makes them intolerable to the inhabitants. Examples of some pollutants include heavy metals—lead, methane, carbon monoxide, particulate matter, bad smell, plastic, volatile organic compound, and many others have been attributed to pollutions [6]. The majority of man-made fine particles come from domestic sources, specifically biomass-based cooking, and the use of fossil fuels to power homes and vehicles. Some areas near deserts in Africa and West Asia are also important contributors due to windblown dust [6].

However, several sources have been documented which could either be point sources like industries, refineries, mining and many others or non-point sources like car, busses, trains and many more. But abattoirs in Lagos State of Nigeria have also been documented to house several heavy metals and other pollutants [7]. One of these contaminants that is frequently present in trace amounts is heavy metals. Many of these metals, even when present in trace amounts, are harmful to the environment and can accumulate in the bodies of living things through a process called bioaccumulation or bio-concentration [8, 9]. Abattoirs produce a significant quantity of secondary waste materials in the form of massive animal feces [10]. The inappropriate disposal of animal parts, such as flesh, blood, and innards, has been linked to an increase in soil acidity [11, 12]. Soil microorganisms, not just plants, are negatively affected by heavy metals present due to improper treatment of abattoir wastes. When soil is highly concentrated in metals, it can bring heavy metals into the food chain, which can be problematic because of the toxicity of these elements to humans, especially when they bioaccumulate in the body through the ingestion of plants.

2. Abattoir as sources of environmental pollutants

The impacts of pollution on ecosystems are much more pronounced today than they were in the past. Many people assert this, citing various factors such as a decline in soil fertility, a weakening of water quality, several health issues (including those that can lead to metabolic disorder), an ecological impact, and so on [13, 14, 15]. A major contributor to these pollutions is the careless disposal of trash in these ecosystems, which disrupts the balance of nature. Since there are no well-established management rules on waste disposal, this is a typical practice in Nigeria. However, the sudden increase in the amount of communicable, non-communicable and zoonotic diseases, for example, cancer and tuberculosis in our localities today makes abattoir waste a disease surveillance focus [16]. Abattoir operations result in the release of various wastes and pathogenic organisms that pollutes the environment and pose serious threat to human health and quality of life [17]. Tragically enough, most abattoirs in Lagos, Nigeria are known for poor and obsolete structural design which is accompanied with deteriorating environment.

An abattoir is a facility specifically designed to carry out the inspection of animals, the sanitary slaughtering, processing, and proper preservation, and storage of meat products for human consumption and is registered and certified by the regulatory body. A meat processing plant is a specialized building authorized to receive animals for slaughter, hold them, and conduct quality control inspections on meat products prior to their release for sale. Abattoirs aim to improve the efficiency with which consumable parts of the meat processing cycle are recovered for human consumption [10]. However, substantial quantities of secondary waste, such as organic and inorganic substances that aren’t fit for further exploitation, are produced anyway [18]. Land degradation, air pollution, water scarcity and contamination, loss of biodiversity (particularly plant life), and climate change are all blamed on animal production and the work of veterinary establishments like slaughterhouses [19, 20]. Abattoir waste is an emerging solid waste whose rate of generation is becoming alarming [21].

The soil and natural water bodies are often seriously threatened by the pollution caused by abattoir activities, which not only generate a large quantity of waste but are also a source of heavy metals, bacteria, and others that threaten plant health and human quality of life [17].

2.1 Types of abattoirs

2.1.1 Modern abattoir

They are the pinnacle of conventional abattoir design, equipment, and services, and are typically constructed and managed by centralized governments with the aid of foreign technical experts. These abattoirs are managed on factory lines and offer a variety of services, including cold storage, processing, by-product usage, and waste recycling. Being commercial or profit-driven establishments, most contemporary abattoirs have little interest in providing low-revenue services, such as direct slaughter for public consumption.

2.1.2 Slaughterhouses

Most public slaughters are performed in these establishments. These establishments essentially provide a place to slaughter animals in accordance with public health, inspection, and marketing regulations for a fee, and are used by licensed butchers and dealers. Typically, only operating in densely populated areas and larger cities, these businesses provide essential services under the watchful eye of state and regional authorities. Two types of slaughterhouses exist, they are:

2.1.3 Old slaughterhouses

These establishments just provide the necessary infrastructure for licensed butchers and traders to slaughter cattle in line with public health, inspection, and marketing standards, for the predetermined costs. They are service businesses supervised by city or state governments, typically catering to residents in densely populated urban regions. Most public slaughters are conducted by them.

2.1.4 Makeshift slaughterhouses

They are more often found in more rural or suburban settings (Figure 1). They could happen at the outskirts of major cities, though. In the second case, it is not recommended that they exist or continue to operate since their disregard for evident requirements in slaughterhouse architecture, equipment care, and hygiene is occasionally linked to illegal livestock dealing and the slaughter of sick and diseased animals. Animals and their products should only be permitted to leave these facilities if they are being inspected [22].

Figure 1.

A makeshift slaughterhouse.

2.2 Processing of animal products

Animal slaughter involves many stages, and there are several procedures and legislative requirements involved however, several methods are used in processing animal products in abattoirs [23]. The type of method used is dependent on the desired products. The following methods of animal products processing is common in Lagos state, Nigeria.

Boiling: Animal skin (known as ponmo in the Nigeria) is dipped into hot water to soften it so the hair can be more easily removed. To further soften the cow skin, it is steeped in water for several hours after being shaved, which induces a brief period of fermentation. The result of this procedure is ponmo of the white variety.

Burning: This is one of the most prevalently used methods for cow skin. In this technique, the animal skin is first softened by being put into a fire, at which point the hair is singed off and the softening process may begin. Used tires are used to create the flame, and other petrochemical agents (such kerosene, diesel, or gasoline) are often added to increase the intensity of the fire (Figure 2). This procedure yields the brownish ponmo [24].

Figure 2.

Processing of Ponmo.

2.2.1 Evisceration

Evisceration involves the removal of the viscera. This includes the heart, lungs and kidneys from both cattle, sheep, and cow. If not properly inspected by the meat inspector, this method is mostly prone to conditions such as tapeworm (e.g. Taenia saginata), liver flukes, abscesses, cysts and tumors [23].

2.2.2 Deboning

Deboning of meat is one of the several methods in the processing of animal meat, during which muscle, connective and or adipose tissue (meat), is removed from the bone content. This process is often done manually or using advance equipment.

2.3 Abattoir waste and its contamination potentials

Wastewater and solid waste from slaughterhouses can also be considered abattoir waste since they contain potentially harmful substances such feces, blood, fat, trimmings, paunch content, and urine [25]. Inadequate management or control of abattoir wastes can have negative consequences for human health, the environment, animal welfare, and the national economy. Solid, liquid, and gaseous waste categories exist for this category. Manure, feces, hair, horn, hoof, gallbladder, trimmings, internal organs, bones, condemned corpses or body parts, paper, carton, and plastics all fall under the category of solid wastes. Slaughterhouse liquid waste comprises of feces, blood, and wastewater. Slaughterhouse gaseous waste consists mostly of odors and emissions [26]. The contamination could be in.

2.3.1 Contamination of surface waters

There are oxygen-demanding substances in slaughterhouse scraps. Therefore, the quality of surrounding waterways can be impacted by runoff from abattoir waste piles. Fish mortality could arise from a lack of dissolved oxygen and the toxicity of ammonia in these streams. In addition, the nutrients (nitrogen and phosphorus) in abattoir effluent can promote eutrophication (excessive vegetative growth) in stream channels, which might diminish the size of receiving stream channels and lead to over-flooding and its concomitant damages. Abattoir effluent is known to degrade the physical and chemical quality of streams and may even provide a health risk to people who engage in water sports and other similar activities [27].

2.3.2 Contamination of underground water

Pollutants from abattoir wastes make their way into the earth and can degrade water quality [27]. Organic ground water pollutants manifest themselves through altered flavor, odor, foaming, or damage to irrigated crops. In their investigation, Elemile et al. [28] found that the quality of groundwater increased as distance from the slaughterhouse was decreased. Agbara abattoir in Lagos State was the subject of a separate study by Jimoh et al. [29], which examined the environmental effects of the wastes produced there. They found a high coliform level of 82.50 cfu/ml, and they also found residues of chromium.

2.3.3 Contamination of the abattoir environment

Abattoir wastes typically give off pungent odors that could be a source of localized air pollution and a nuisance to nearby residents. Certain odorous substances, such as sulphides, mercaptans, amines, organic acids, etc., are notoriously difficult to get rid of. They can adhere to fabric, last for extended periods of time, and be carried large distances [30].

2.3.4 Contamination of plants

Most abattoir waste runoff is a possible source of plant pollutants, especially heavy metals, because of rainfall. To make matters worse, the effluent flows and spreads to the surrounding habitats from most abattoirs in Lagos, Nigeria, which contain solid wastes, feces, corpse, horns, bits of tissue, etc. [5]. Animal wastes are known to include pathogenic organisms, producing salmonellosis, leptospirosis, tularemia, foot and mouth disease, hog cholera, etc. [31], and if abattoir effluent-polluted waterways are used to cultivate fruits and vegetables, transmission of illnesses is possible. This could cause heavy metals to build up in the food web.

3. Heavy metal contaminated abattoir wastes: mechanism of transfer in ecosystem

Abattoirs have repercussions for the environment because of the way they operate and dispose of their trash. Bleeding, treating wounds, removing the hide, eviscerating the animal (removing its internal organs), preparing the carcass (by cutting and boning it), and so on are all steps in the surgical. In many circumstances, disagreeable odors are produced alongside the massive amounts of solid waste and wastewaters with biochemical oxygen demands (BOD) that might be generated by any of these procedures. The effluents that are relevant and specific to abattoirs in Lagos include blood, excrement, hair, bones, and undigested stomach contents [32].

The processes involved in getting end-products in most abattoirs in Lagos State of Nigeria are unhealthy considering the type of abattoirs found, the personnel and the skills used in the processes [7]. However, these processes used in abattoirs in Lagos, often lead to the introduction, accumulation, and transfer of contaminants like heavy metals such as lead, cadmium, zinc etc. within the ecosystem [33].

Abattoir wastes such as organic and inorganic substances, as well as salts and chemicals added during processing, affects air, water, soil, plants, animals, and humans [33] (Figure 3). Heavy metals and other contaminants from the abattoirs firstly caused air pollution to the inhabitants and surrounding commuters very close to the abattoirs, leading to the inhalation of some virulent microorganisms which can cause air borne diseases [34] and irritation to the eyes and nose because of smokes and dust from animal skin (Ponmo) processing often done with burning of vehicular tyres.

Figure 3.

Heavy metals’ mechanism of transfer within the ecosystem from abattoir wastes.

Secondly, heavy metals in soil ecosystem (Figure 3), through discharge of abattoir effluents on soils thereby increasing heavy metal contaminants and other pollutants [12]. This effluent could kill the soil microbiota or increase the presence of virulent microbes which often causes diseases to plants, animals, and humans. The soil is the complex ecosystem of many plants. Thus, accumulation of metals has been reported in the soil and plants close to the abattoirs [7].

Thirdly, metals in surface and underground waters (Figure 3), this occurs through erosion and leaching of heavy metals in abattoir effluents. Improper discharge of effluents could lead to transfer of metals by rainwaters to nearby water bodies and increase the concentrations of metals in the aquatic bodies (Figure 3). This often discomfort the aquatic fauna and flora and increase the BOD of the water [28]. Also, leaching of this effluent containing heavy metals such as Pb and other contaminants could predispose the consumers of this water to toxins [35].

Finally, the mobilization of the metals into the air, soil, and water due to poor abattoir wastes management and personnel skills could not free plants, animals, and humans from the heavy metals’ poisons [36, 37]. Plants that are contaminated with heavy metals because of bad abattoir practices accumulate these metals in their tissues, herbivores and humans consume these plants, and continuous consumptions of these herbivores and plants by humans leads to bioaccumulations of these metals in tissues and remain in food chain, thereby causing lots of health problems (Figure 4).

Figure 4.

Trend of pollutants’ transfer within the food chain from abattoir wastes.

However, the continuous discharge of abattoir wastes and its poor management overtime, because of bioaccumulation, biomagnification and bioconcentration of heavy metals and other contaminants in the ecosystem in Lagos State, especially as it’s involved the heavy metal transfer would pose great threat to air, water, soil, plants, animals and human if not properly addressed (Figure 4). This in turn, may have negative effects on the economy of the country.

4. Effects of heavy metals on ecosystem

Most often found in greater concentrations in abattoir waste, heavy metals are hazardous to soils, plants, aquatic life, and human health. To exert their toxicity towards soil biota, heavy metals interfere with vital microbial processes, leading to a decrease in both the diversity and activity of soil microorganisms. The uptake of heavy metals by plants can be inhibited at low quantities, which can lead to their accumulation along the food chain and a possible threat to the health of animals and humans. However, at the level of aquatic systems, contaminants such as heavy metals encourage the creation of reactive oxygen species (ROS), which may harm fishes and other aquatic creatures.

4.1 Effects on soil

In industrialized countries, the issue of heavy metals such as copper, nickel, cadmium, zinc, lead, and thallium (etc.) in the soil is of critical relevance [38]. Soil microbial functions, such as respiration rate and enzyme activity, are important markers of soil contamination, and are typically impacted by an increase in metal concentration. Heavy metals have been shown to negatively impact soil’s biological, physicochemical, and biochemical properties [39, 40, 41]. Heavy metal contamination can affect the size, composition, and activity of the microbial population, which can then have knock-on impacts on a variety of plant quality and yield indices [42]. Because of this, heavy metals are thought to be a significant contributor to soil pollution.

Toxic effects of heavy metals on soil biota include interference with vital microbial functions and a subsequent decrease in the diversity and abundance of soil microbes. As stated by Shun-Hong et al. [43], heavy metals can alter the composition of soil microbes, which in turn affects soil enzyme activity. But prolonged exposure to heavy metals can boost bacterial tolerance, which is useful for cleaning up polluted environments [44]. Heavy metals led to a decline in the bacterial population. The abundance and variety of bacteria living in polluted soils may have suffered because of this shift. The chemical affinities of enzymes in the soil system for various metals have been shown to have an impact on their respective activity, as described by Karaca et al. [45]. For instance, cadmium’s (Cd) rapid mobility and low affinity for soil colloids makes it more hazardous to enzymes than lead (Pb). Lead (Pb) greatly reduces the activities of urease, catalase, invertase, and acid phosphatase; copper (Cu) lowers-glucosidase activity more than cellulose activity. Protease, urease, alkaline phosphatase, and arylsulfatase activities are negatively impacted by cadmium contamination, whereas invertase is unaffected [44]. As with enzymes, the sensitivity of different soil organisms to different metals varies.

4.2 Effects on plants

Some heavy metals, including arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), or selenium (Se), are not necessary for plant growth because they do not perform any recognized physiological function in plants, although others, like iron (Fe), copper (Cu), cobalt (Co), and zinc (Zn), are [46]. Chlorosis, stunted development, and decreased production are just some of the detrimental consequences that heavy metals can have on plants. Heavy metals can inhibit nitrogen fixation in plants, alter plant metabolism, and impair nutrient uptake. Temperature, pH, organic matter, moisture, and nutrient availability are just few of the variables that affect the uptake and accumulation of heavy metals in plant tissue. Root absorption is a significant pathway for heavy metals to enter the food chain and potentially affect animals and humans [46, 47]. Plant species and the efficiency of plant uptake of metals determine the accumulation of heavy metals in plants [48]. Lead (Pb) in soils can have a negative effect on plant productivity, and even trace amounts of lead can impede photosynthesis, cell division, and water uptake. Dark green leaves, elder leaves wilting, reduced growth, and brown, short roots are all possible manifestations of toxic effects [49].

4.3 Effects on aquatic environment

Extreme oxidative stress could be caused by even trace levels of heavy metals in aquatic species. Consequently, these contaminants are crucial to study in the field of ecotoxicology. Moreover, metals are frequently not degraded by microbes and hence persist in the marine environment indefinitely [50]. However, heavy metal contamination of a river could have catastrophic consequences for the aquatic ecosystem, reducing diversity of aquatic creatures and upsetting the delicate balance of the aquatic environment [51].

Particulate matter emitted into aquatic systems typically contains heavy metals, which settle and become a part of sediments. When it comes to metals and other pollutants in water, surface sediment is the most significant reservoir or sink. Aquatic macrophytes and other species with deep root systems can absorb sediment-bound contaminants [52]. Heavy metals could enter the food chain when an aquatic organism accumulates them. Many of the heavy metals used by carnivores like humans are found in marine life. The presence of fish makes this much more significant, as it could cause biomagnifications [51]. Increased formation of reactive oxygen species (ROS) due to the presence of heavy metals in aquatic systems is harmful to fish and other aquatic creatures [50]. Heavy metals are just one example of the environmental pollutants that could poison fish. Consequences for public health from these contaminants could be devastating. It is vital to be mindful of the sorts of fish you eat because of the potential health risks associated with heavy metal intake [53]. Mercury (Hg) is a significant contaminant due to the damage it could do to marine life and the health problems it can create for humans. Bacteria in watery sediments methylate organic mercury, forming a highly poisonous chemical compound known as methylmercury. Methylmercury makes up almost all the mercury found in fish muscles [53].

4.4 Effects on human health

Heavy metals in soil could be taken up by plants, and then by animals farther down the food chain, which could have serious consequences for human health. Growing plants in soil contaminated with heavy metals, such as that found near slaughterhouses, poses a threat since plant tissues can acquire these toxins [46]. When heavy metals are not broken down in the body, they accumulate in fat and muscle and become poisonous [54]. Negative impacts on human health are seen over long periods of time due to this buildup [48].

Toxic cadmium (Cd) has a specific gravity 8.65 times that of water, making it a heavy metal. Liver, placenta, kidneys, lungs, brain, and bones are particularly vulnerable to Cd poisoning [54]. It has been challenging to link morbidity and mortality to Cd′s environmental exposures, even though exposure to Cd has been linked to a wide range of clinical conditions, including anosmia, cardiac failure cancers, cerebrovascular infarction, emphysema, osteoporosis, proteinuria, and cataract formation in the eyes [55].

When administered orally, zinc (Zn) is quite secure. Overexposure to Zn could cause systemic dysfunctions that limit growth and reproduction. Zinc poisoning has been associated with gastrointestinal symptoms, hemorrhagic cystitis, icterus (yellow mucus membrane), hepatic failure, renal failure, and anemia [56].

Copper (Cu) is a component of metalloenzymes where it could donate or take electrons, making it a critical element for mammalian nutrition. Diet and drinking water are the two most common routes of Cu exposure for people. Ingestion by mistake is the most common cause of acute Cu poisoning, while certain persons may be more vulnerable due to genetics or illness [57]. Mucosal irritation and corrosion, extensive capillary damage, hepatic and renal damage, central nervous system irritation, and depression may result from excessive Cu intake in humans. Necrotic abnormalities in the liver and kidney are also possible, in addition to severe gastrointestinal discomfort. When exposed to Ni, people could experience a wide range of symptoms, from skin irritation to problems with their lungs, nervous system, and mucous membranes [58].

Humans are extremely vulnerable to lead’s (Pb) harmful effects on their physiology and nervous systems. Kidney, reproductive system, liver, and brain malfunction are possible outcomes of acute lead poisoning [59]. Even in trace amounts, Pb is the most dangerous element [60]. The synthesis of hemoglobin is inhibited by lead poisoning, and the cardiovascular system and the central nervous system (CNS) and the peripheral nervous system (PNS) are both damaged acutely and chronically (PNS). Anemia, exhaustion, gastrointestinal issues, and a lack of oxygen are some more long-term consequences. Low birth weights, hypertension, and muscle and joint pain are just some of the problems that lead exposure can bring [56, 59].

A strong oxidizing agent, caustic, soluble in alkaline and mildly acidic water, poisonous, and a possible carcinogen, chromium-Cr (VI) is harmful to plant and animal life [43, 61, 62]. Cr (VI) toxicity results from the fact that it can oxidize biological molecules despite being able to diffuse across cell membranes [61].

Mercury is poisonous and has no recognized biological or physiological function in humans. Inorganic mercury is linked to spontaneous abortion, congenital deformity, and gastrointestinal diseases (such as corrosive esophagitis and hematochezia) [56].

5. Management of abattoir wastes

Abattoir waste, like any other sort of waste, could be dangerous to humans and ecosystems if proper measures are not taken. Some slaughterhouse byproducts and wastes need to be repurposed as agricultural and industrial byproducts, but this requires recycling. Proper waste management techniques are necessary since this constitutes a significant threat to public health and is an annoyance in most slaughterhouses located in various market areas. This is because it pollutes the air, land, plant, and water and causes an infestation of flies and other disease vectors.

The risk of introducing enteric infections and extra nutrients into surface water is greatly exacerbated when slaughterhouse waste is disposed of unchecked into waterways. Furthermore, the extensive wastes produced by abattoir operations have been related to lower environmental air quality, potential patterns of transferable antibiotic resistance, plants contamination and various pathogenic pathogens with the potential to infect humans. But the following techniques are recommended for efficient abattoir waste management.

1. Burying: Most abattoirs use this approach, and it’s the best option available. Landfills used for the disposal of abattoir waste must be covered soon after they are used, have a system in place to prevent wildlife from gaining access, and retain records of the locations and volumes of waste disposed of there.

2. Composting: In this, abattoir waste or carcasses are layered between absorbent carbon sources like wood chips, shavings, bark, barn animal bedding, hay, straw, etc. in a compost pile. Composting works best when the right amount of carbon and nitrogen sources are used. If the compost pile were built correctly, proper composting may be achieved without the need for manual turning or mechanical aeration.

3. Rendering: This involves extensive treatment of animal wastes into a more usable form.

4. Incineration: This process involves the combustion of substances present in the waste material. This method has the advantage of reduced waste per volume, lowered cost of waste management and in some cases a way to generate energy.

5. Anaerobic digestion: This is a series of event that occurred mostly in a bioreactor in which microorganisms utilize the materials present in the abattoir waste in the absence of oxygen leading to the formation of biogas. The abattoir waste is a protein-rich substrate and may result in sulphide formation during anaerobic digestion. The increased concentration of sulphides in the bioreactor can lead to higher concentrations of hydrogen sulphide in the biogas produced which may inhibit methanogens.

6. Blood processing: In this process, blood is removed from the body and sent to a treatment facility. Businesses use blood to create a range of goods that contain or could include beneficial nutrients.

Finally, proper policies, laws and regulations must be put in place and enforced by necessary government agencies especially in Lagos State, Nigeria to minimize the pollutants released into the ecosystem.

6. Conclusion

From the foregoing discourse, it safe to say that most abattoirs especially those in Lagos generate wastes that are loaded with heavy metals and other pollutants. However, these heavy metals are known to affect the ecosystem vis-à-vis disruption of soil health, excessive accumulation in plants and animals, depletion of water quality and reduction in atmospheric quality. These often have a great impact on the earth biota; thus, efforts should be made on mitigating the effects caused by heavy metal contaminated abattoir wastes through judicious abattoir waste management practices and regulations. Thus, abattoirs in Lagos are hidden sources of heavy metals in plants and other pollutants within the ecosystem.

Conflict of interest

The authors declare no conflict of interest.