Persistent organic pollutants (POPs) encompass a group of chemical compounds defined by the Stockholm Convention in 2001, as characterized by four key attributes [1]. These substances exhibit persistence, meaning they resist degradation in the environment [2]. Additionally, they are bioaccumulative, meaning that they build up in living organisms over time. POPs are also known to possess toxicity and mobility. Primarily originating from human activities, these pollutants have been continuously emitted into the environment for several decades. Notably, they have been found to contain numerous carcinogens as well as compounds that disrupt the endocrine system [3].

The environment contains three distinct categories of POPs: (1) pesticides, specifically organochlorine pesticides (OCPs) such as dichlorodiphenyltrichloroethane (DDT) and its byproducts; (2) industrial and technical chemicals comprising polychlorinated biphenyls (PCBs), perfluorooctanesulfonate (PFOS) and polybrominated diphenyl ethers (PBDEs); (3) by-products resulting from industrial processes, such as polyaromatic hydrocarbons (PAHs), polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) [4]. Another study has classified the various types of POPs into four groups: those subjected to the elimination of production and usage, those with restricted production and usage, unintentionally produced substances, and chemicals currently under investigation. Chemically, POPs can be categorized as brominated, chlorinated, or fluorinated compounds [5].

POPs exhibit remarkable resilience to natural degradation within the environment, persisting in aquatic environments, soils, food chains, and ultimately, within the human body for prolonged periods, even after production has ceased. Possessing lipophilic characteristics, these pollutants can accumulate in various environmental elements and organisms’ tissues, and can also be transported through the atmosphere across substantial distances [6]. These attributes enable them to undergo biomagnification and bioaccumulation within animals, posing significant threats to both human health and the integrity of natural ecosystems [7].

These contaminants interrupt the food chain, thus threatening the survival of all humans and wildlife on Earth in the long term. Populations worldwide, including humans and animals, face potential prolonged exposure to POPs. These pollutants can accumulate within the fatty tissues of living organisms, leading to their increased concentration as they progress through the food chain [4]. Scientific evidence confirms the detrimental impact of POPs on human health. Exposure to these contaminants can give rise to a wide range of health issues, including endocrine disruption, cardiovascular diseases, cancer, diabetes, birth defects and impairments in immune and reproductive systems’ functionalities ^[4][7][8][9][4,7,8,9].

A recently published review on the distribution pattern of POPs in South Korea’s atmosphere reports a trend of increasing chemical concentrations such as POPs. They found the major pollutants to be PAHs, PCBs, brominated flame retardants (BFRs) and PBDEs, the combination of which had significantly polluted the atmosphere of South Korea. Based on their findings, South Korea is considered a hotspot for POP pollution, while the level of TBBPA is lower than expected [10]. BFRs, in the manner of other POPs, can accumulate in food chains and have even been found in human milk [11].

2. POPs in Food

Overall, the primary factor that determines the presence of environmental pollutants in food, irrespective of whether they are organically or conventionally produced, is the proximity of anthropogenic pollution sources [12]. Due to their lipophilic nature and ability to bioaccumulate within the food chain, POPs have the potential to accumulate in the adipose tissues of humans, thereby causing detrimental effects on human health [13]. Upon release into the atmosphere, POPs settle onto vegetation, soil and sediments. They subsequently bioaccumulate in aquatic fish and farm animals through the ingestion of contaminated feed, plants and sediment. As marine and freshwater organisms exhibit higher concentrations of POPs compared to their surrounding aquatic environment, they serve as valuable bioindicators. For the majority of individuals not occupationally exposed to POPs, the primary route of exposure (>90% of POP intake) stems from the consumption of animal products and seafood. Additionally, exposure can occur through the consumption of fruits and vegetables treated with pesticides, which serve as an additional source of exposure ^[4][14][4,14].

3. POPs in the Human Body

The protection of human health is the ultimate objective of the Stockholm Convention, with humans being the final link in the exposure chain [15]. To monitor the presence of POPs in humans, both invasive and non-invasive techniques are employed for biological monitoring. These techniques involve the analysis of breast milk, blood/serum, hair, saliva, semen, fingernails and urine. These biological samples provide insights into the accumulation of POPs in the body resulting from exposure and the potential transfer of POPs through the placenta and breast milk from mother to child, as well as the excretion of POPs and their metabolites through various bodily fluids. Research indicates that the primary route of exposure for the bioaccumulation of POPs in human fluids is through the intake of contaminated food. A secondary route of exposure includes inhalation of pollutants from e-waste sites and contaminated farms [14]. The high toxicity of POPs is attributed to their property of bioaccumulation. This ability to accumulate in living organisms for extended periods is facilitated by the high-fat solubility of hydrophobic POPs. This characteristic enables them to readily accumulate and persist in fatty tissues [7]. The primary routes through which POPs undergo bioaccumulation are outlined and presented in Table 1.

4. Health Effects of POPs

Despite the low level of POPs in humans, various health problems have been associated with this type of pollution. This is due to their metabolic and carcinogenic effects, which lead to human chronic diseases through the mechanism of DNA methylation deregulation [4]. In the current context of environmental pollution, virtually everyone carries traces of POPs in their bodies. Interestingly, even fetuses and embryos have been found to harbor POPs. These pollutants are detected in individuals across all age groups, with higher levels observed in older populations. Exposure to these contaminants poses significant health risks, including cardiovascular diseases, obesity, hormone disruption, reproductive and neurological disorders, cancer, endocrine disturbances, diabetes and learning disabilities [7]. Moreover, health problems such as dizziness, diarrhea, rashes, skin irritation and headaches can be the result of POP exposure. Thus, POPs have demonstrated the ability to induce a range of detrimental effects on human health, including compromising the immune system and rendering the body susceptible to microbial infections [3]. Upon entering the human body, POPs persist throughout an individual’s lifetime. Even small quantities of these substances can contribute to the development of diseases. For instance, certain chlorinated hydrocarbon pesticides such as aldrin and dieldrin have been associated with numerous cases of severe acute poisonings. They can result in gastrointestinal disorders and kidney and nervous system damage, and have the potential to impact immune response systems. Additionally, the combination of aldrin and dieldrin may elevate the risks of liver and biliary cancer [6]. Therefore, if these chemicals surpass their acceptable thresholds, POPs can have harmful effects on the human body. Some of the possible diseases caused by POPs in the human body are presented in Table 2.