*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].

**Figure 1.** *A makeshift slaughterhouse.*

*Abattoirs: The Hidden Sources of Plants' Heavy Metals and Other Pollutants in Lagos, Nigeria DOI: http://dx.doi.org/10.5772/intechopen.110339*

**Figure 2.** *Processing of Ponmo.*

### *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.
