Section V: Microplastics and POPs
Persistent Organic Pollutants (POPs)
: Persistent Organic Pollutants (POPs): A Real Threat to the Environment
M. Humam Zaim Faruqi and Faisal Zia Siddiqui
- 9.1 Introduction 151
- 9.2 Sources and Persistence of POPs 152
- 9.3 Current Scenario of POPs 153
- 9.3.1 Polychlorinated Biphenyls (PCBs) 153
- 9.3.2 Bisphenol A (BPA) 153
- 9.3.3 Polycyclic Aromatic Hydrocarbons (PAHs) 154
- 9.4 Health and Environmental Effects of POPs 154
- 9.5 Future Prospects 154
The contamination of world’s aquatic environment is an area of growing concern and research. Contaminants of emerging concern in the global environment comprise more than 40,000 different chemicals, which is increasing by six additional chemicals on a daily basis [1,2]. Moreover, plastic materials are estimated to release about 35-917 tonnes of chemical additives into the global marine environment each year .
Degradation of plastic products into smaller fragments such as microplastics or nanoplastics and their subsequent passage into the marine ecosystems result in their transport even to remote locations on Earth’s surface. Plastics are known to concentrate and transport toxic chemicals that are either added during their production as additives or are sorbed into the plastic matrix while microplastic fragments come in contact with polluted water.
Certain chemicals in Earth’s ecosystem are resistant to environmental degradation in terms of chemical, biological and photolytic reactions . Such chemicals in our environment that exist for a longer time duration are called persistent organic pollutants (POPs). POPs are persistent in the environment, having long half-lives in soils, sediments or the atmosphere. There is no universal consensus on how long the half-life in a given medium should be for the term “persistent” to be used. However, a POP could have a half-life of years or even decades in soil or sediment and several days in the atmosphere .
POPs are priority pollutants consisting of pesticides (dichlorodiphenvltrichloroethane [DDT] and its metabolites, toxaphene, chlordane), industrial chemicals (polychlorinated biphenyls [PCBs], polybrominated diphenyl ethers [PBDEs]), byproducts of industrial processes (dioxins and furans) and precursors to important plastics (bisphenol A) .
POPs are typically hydrophobic and lipophilic in nature. Plastic debris acts as a vector for organic contaminants owing to their hydrophobic nature. POPs partition strongly to solids in aquatic systems and soils, avoiding the aqueous phase. In organisms, these partition into lipids rather than entering the aqueous medium of cells and become stored in fatty tissue. POPs may also volatilize from soils, vegetation and water bodies into the atmosphere and travel long distances before being deposited because of their resistance to breakdown reactions in air. POPs can partition between particles and aerosol depending upon ambient temperature and physicochemical properties of the chemical. The unique combination of resistance to metabolism and lipophilicity leads to the accumulation of POPs in food chains .