Persistent organic pollutants (POPs), known also as “forever chemicals”, is a general term for carbon-containing compounds that share similar properties including resistance to photolytic, biological and chemical degradation leading to persistence in the environment, a semi volatile chemical composition responsible for their transportation to kilometers, as well as a lipophilic tendency responsible for accumulation in the fat of living organisms, bio-accumulation in the food chain in ecosystems, and biomagnification. Many international conventions manipulate exposure to these toxicants. However, exposure is still increased and related to reproductive, developmental, endocrine, immunologic and carcinogenic effects. Polycyclic aromatic hydrocarbons (PAHs), Polybrominated diphenyl ethers (PBDEs), Polychlorinated biphenyl compounds (PCBs), Polybrominated diphenyl ethers (PBDEs), Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are described. Indoor and outdoor pollution mainly by particulate matter becomes a problem in crowded cities.