**4.1 Determination of heavy metals in fish species of the Mediterranean Sea (Libyan coastline) using atomic absorption spectrometry**

The toxicity of heavy metals when their concentration exceeds the allowable limit has made their presence in our environment a major source of worry [105]. The World Health Organization (WHO) has established the approved values of the Co, Cd, Pb, Fe, and Cu concentrations in fish, which are shown in **Table 3**. The document presents the Co concentrations in various tissues. The concentration of this metal was found to range from 0.570 mg/kg to 44.693 mg/kg, meaning that the levels of Co in all tissues that were investigated were higher than those that had been previously reported.
