**5. Pentachlorophenol**

Pentachlorophenol (PCP) is one of the World's worst chemical ever produced [61]. PCP was developed in the 1930s as one of the first synthetic organic wood preservatives [62]. PCP (C6Cl5OH) is well known as a highly chlorinated organic pollutant with stable aromatic ring structure and as highly persistent in the soil system [63]. The U.S. Environmental Protection Agency [64] regulates PCP as one of the priority pollutants. PCP pollutants has been released in large quantities into the environment as a wood preservative, pesticides, insecticides, fungicides and solvents [65]. PCP is also formed as a by-product during disinfection of water by chlorinated oxidants [66]. It is a synthetic organochlorine pesticide, a conjugate acid of pentachlorophenolate and a member of pentachlorobenzenes, which comprises aromatic fungicides and a chlorophenol (CPs) [67]. PCP is also a metabolite of lindane and other polychlorinated phenolic compounds [68]. Due to its stable aromatic ring structure and high chlorine content, PCP is chemically stable and not prone to degradation [69]. It is a significant environmental contaminant due to its widespread

**Figure 4.** *Pentachlorophenol application and impact description.*

use and chemical stability, persistency, and high toxicity. Human exposure to PCP occurs through inhalation, absorption through the skin, and consumption of contaminated water and food (**Figure 4**) [70]. It, therefore, has a very long half-life in the environment. PCP accumulates in the environment due to its lipophilicity and contaminates water and soil [71]. PCP used as a fungicide, insecticide, herbicide, and bactericide [72, 73]. that is widely employed as a wood preservative, especially for logs and wooden utility poles. There are many reports on the toxicity of PCP, including cases with fatal outcomes [70, 74]. The liver, thyroid, immune system, and reproductive system are the primary targets of PCP toxicity [70]. PCP inhibits spermatogenesis and has adverse effects on reproductive and inter-renal system at environmentally relevant concentrations [75].

In addition, PCP exposure is associated with renal, neurological, and carcinogenic effects. Several epidemiological studies suggest that PCP exposure is linked to human cancer [76]. PCP accelerates the incidence of hematopoietic cancer, multiple myeloma, lymphoma, soft tissue sarcoma, leukemia, and aplastic anemia [77]. This results in bioaccumulation of PCP in human testes, kidney, prostate gland, liver, and adipose tissue [78]. PCP is classified as possible human carcinogen (class 2B) by the International Agency for Research on Cancer [79]. PCP concentration at contaminated sites has been reported between 100 and 500 mg kg−1 in soil and 10–1000 mg L−1 in groundwater [80].
