Persistent Organic Pollutants (POPs): Historical Risks, Current Challenges and Emerging Solutions

In 1962, Rachel Carson’s observations revealed that birds consuming DDT and other pesticides produced thin-shelled eggs, leading to morbidity and mortality in embryos [1,2]. And in 1968, it was reported that over 1,850 people were poisoned by PCBs in Yusho, Japan, and more than 2,000 people were poisoned by PCDFs in Yucheng, Taiwan, in 1979 due to consuming contaminated food [3-5]. Additionally, in 1999, the use of chemically contaminated animal feed on farms in Belgium led to a major food safety crisis involving poultry and eggs, resulting in the disposal of thousands of chickens and hundreds of thousands of eggs in accordance with EU procedures [6]. These incidents have underscored the need for international measures to protect global public health and the environment. In response, the Stockholm Convention on POPs was adopted during a diplomatic conference held on May 22-23, 2001, in Sweden and entered into force on May 17, 2004. Initially, 12 chemicals known as the “dirty dozen” were classified as POPs, with their production and use restricted and/or banned [7]. Subsequently, the list has been updated several times to include additional chemicals, totaling 16 more.

These include α-HCH, β-HCH, chlordecone, decabromodiphenyl ether, hexabromobiphenyl, hexabromocyclododecane, hexabromodiphenyl ether and heptabromodiphenyl ether, hexachlorobutadiene, γ-HCH, pentachlorobenzene, pentachlorophenol and its salts and esters, PFOS and its salts, perfluorooctane sulfonyl fluoride, polychlorinated naphthalenes, short-chain chlorinated paraffins, technical endosulfan and its isomers and tetrabromodiphenyl ether and pentabromodiphenyl ether [8]. These chemicals are generally characterized by their toxicity, low solubility in water, and high solubility in lipids [9,10].

But, despite international restrictions and prohibitions, numerous stocks of POPs have emerged globally in recent years. Improper storage conditions and environmental contamination from historical use of these chemicals have led to continued hazardous exposures. Even at low doses, these chemicals can cause endocrine disruption, immune system disorders, reproductive diseases, and an increase in obesity rates [11,12]. Current disposal methods, primarily incineration, face limitations due to inefficiencies and the potential formation of new pollutants, such as dioxin-like substances [13]. While biotechnological solutions have been explored as alternatives, challenges remain due to ideal environmental conditions (pH, salinity, temperature, etc.) for microbial species, low solubility of POPs in water, and high toxic concentrations in stockpiles [14]. Therefore, there is a growing need for new technologies for managing POPs. MCD is emerging as a promising technology for the degradation of POPs into less harmful or inorganic materials. MCD occurs in the solid state, eliminating the need for solvent regeneration or disposal and offering a simpler and more efficient alternative to conventional processes [15,16]. However, comprehensive and systematic basic research and evaluations of this technology are also needed. Therefore, this paper focuses on these aspects to highlight the mechanochemical degradation ability to degrade POPs. Overall, this paper reviews important specific information about mechanochemical treatment technology.

Mechanochemical degradation

MCD was first employed in the environmental field by Rowlands in 1993 for the degradation of DDT, achieving notable results after a 12-hour reaction [17]. Subsequently, MCD has been applied to the degradation of various POPs, including PFOS, mirex, PCBs, and PCDD/F [18-21]. Additionally, Japan’s Ministry of Agriculture, Forestry and Fisheries was the first to recognize mechanochemical degradation as a non-incineration alternative technology (Nomura et al., 2011). Therefore, MCD offers a more economical and environmentally sustainable approach for managing POPs with a greener method. Schematic representation of mechanochemical degradation is given in Figure 1 [22].

Figure 1:Mechanochemical degradation of organic pollutants [22].

Moreover, the European Cooperation in Science and Technology (COST) has funded the COST Action CA18112-Mechanochemistry for Sustainable Industry (MechSusInd), which has been running since 2019. This initiative promotes research and collaboration aimed at advancing environmentally friendly industry practices. It emphasizes mechanochemical protocols that do not require solvents, offering a new perspective on sustainable industry practices [23].

The historical instances of environmental and health crises caused by POPs highlight the urgent need for effective and innovative management strategies. Despite the significant progress made through international regulations like the Stockholm Convention, ongoing issues with improper storage and environmental contamination from these chemicals persist, posing continued risks to public health and ecosystems. Current disposal methods, including incineration and biotechnological solutions, face notable challenges and limitations. As such, there is a critical need for advanced technologies to address the degradation of POPs. MCD has emerged as a promising alternative, offering a simpler and more environmentally sustainable method for breaking down POPs into less harmful or inorganic materials. However, to fully realize its potential, further comprehensive and systematic research and evaluation are necessary.

Conflict of interest

The authors declare no competing interests.

Ethics approval

This article does not contain any studies on animals performed by any of the authors.

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