**5. Biomonitoring using birds through the invasive method**

### **5.1 Bones**

Animals are exposed to accumulative sources of metals through food consumption, which elevates over time with rising metal concentrations. Fish that are exposed to trace concentrations of heavy metals over an extended period experience damage to their skeletal, renal, and respiratory systems [25]. According to clinical investigations Engström et al. and Rodríguez and Mandalunis [26, 27], Cadmium exposure increases the risk of bone deterioration, osteoporosis, and kidney impairment. Brzóska and Moniuszko-Jakoniuk [28] also noted that exposure to Cd causes a decrease in mineralisation, affecting the biomechanical characteristics and making the bones more prone to deformation and fracture. Long-term exposure to cadmium reduces bone volume, according to Chen et al. [4], however, Rodríguez and Mandalunis [27] found that it increases the number of tartrate-resistant acid phosphatase (TRAP) positive cells in tibial bone. According to Papa et al. [29], cadmium causes osteoblast apoptosis, which causes the cytoskeleton to rupture, as well as DNA fragmentation, a rise in the frequency of micronuclei, and reactive oxygen species [27, 30].

According to Morais et al. [31], a high Ni concentration inhibits alkaline phosphatase activity, which has an impact on bone mineralisation [32]. However, it was concluded by Rodríguez and Mandalunis [27] that there is no literature on the effects of Nickel poisoning on human skeletal tissue or in vivo experimental models. Studies on Goldfish indicate that methylmercury directly affects and lowers the metabolism of scale bone cells, increases the production of metallothionein, and decreases the expression of calcaemic and oestrogen receptors [33]. According to

*Birds as Intrinsic Bio-Indicators for Probing Heavy Metal Contamination Signatures in Polluted… DOI: http://dx.doi.org/10.5772/intechopen.110449*

Yachiguchi et al. [34], there is a decrease in TRAP and alkaline phosphatase (ALP) expression along with an increase in the production of metallothioneins. Mercury would thus inhibit both osteoclast and osteoblast function. According to Abd El-Aziz [35], experimental models with methylmercury injection into laboratory animals slowed ossification and had detrimental effects on foetus development. According to Rodríguez and Mandalunis [27], there is a dearth of information on the impact of mercury on mammal skeletal tissue, with only a few studies having been conducted.

According to Bier et al. and Ma et al. [36, 37], lead (Pb) blocks the signalling pathway, which in turn limits osteoblastic activity. The findings of Lv et al. [38] mentions that Pb's autophagy can protect osteoblast apoptosis and it induces osteoblasts to apoptosis. Exposure to aluminium (Al) causes osteomalacia, osteoporosis, and renal osteodystrophy. Chappard et al. [39] found that in the hydroxyapatite crystals of exostotic patients, Ca2+ was replaced by Al3+ and Fe3+.

### **5.2 Tissues**

Due to industrial, agricultural, and urbanisation-related activities that injure organisms, the environment is polluted with both essential and non-essential metals including Zn, Cu, Cd, Cr, and Pb. The food chain helps to mitigate the impacts on the raptors, even when they are not deadly. Studying the risk effects on the species and the degrees of contamination in their habitat is aided by the degree and extent of metal concentration in tissues [40]. Because of their biological behaviour, several species are exposed to the contamination that can be found if abiogenic sampling is not done. According to Jagar et al. [41], data on the degree of contamination and the movement of contaminants through the food chain could be obtained from raptors during large-scale sampling. When compared to other species of a similar kind, some aerial species are more exposed to pollution [42]. Information on temporary and geographical exposure to pollutants was proposed by Burger et al. and Pérez-López et al. [43, 44]. According to Rothschild and Duffy [45], the habitat, distribution, feeding habits, and life span of wild birds can all be used as indicators of environmental contamination. Only a few wild bird species, according to Movalli [42], can serve as bioindicators on a larger scale and be used to predict future environmental changes [46]. Burger et al. [43] claimed that because birds are such sensitive species to specific pollutants, they can provide information regarding spatial and temporal exposure to certain pollutants. According to Kler et al. [47] soft tissues of birds, such as their muscle, kidney, spleen, liver, heart, lungs, blood, and brain, can be widely employed as bioindicators to identify metal contamination in studies. Since different organs contain different amounts of metal, it is required to estimate different tissues for evaluation at the population level.

According to Jin et al. [48], metals that are not needed by the living organism do not dissolve and occasionally accumulate in the body, causing negative effects. Additionally, the ionisation of these ions causes them to react with biological components like protein or nucleic acid, which has an impact on how enzymes are activated and how three-dimensional protein structures are formed. Additionally, sometimes essential metals that are centrally situated in metalloenzymes are replaced by heavy metals. Furness and Greenwood [49] concluded that birds can be utilised as biological indicator species for determining the degree of heavy metal contamination and its negative effects.

According to Fisher et al. [50], the main sources of lead discharge into the environment are mining, industries, and hunting activities. According to Snoeijs et al. [51], persistent exposure to high concentrations had an impact on the wild birds' reproductive rates, immunity, and physiological systems. Cadmium was listed as one of the harmful trace elements by Battaglia et al. [52] due to its toxicity and persistence in both food and the environment. According to references [53, 54], cadmium accumulation in birds' bodies caused harm to their renal tubular cells and a decline in their physical conditions. It was concluded by Carpenter et al. [55] that copper (Cu) and manganese (Mn) have positive effects on biological processes as well as negative effects at greater concentrations on the kidneys, reproductive health, and the potential to cause mortality. According to Kim and Oh [56], determining the extent of accumulation worldwide as well as excretion patterns allowed for the conclusion of contamination levels and unfavourable reactions to certain species.
