Persistent Organic Pollutants (POPs)
Persistence is an important characteristic of the environmental pollutants in an environmental medium (air/ water/ soil) or in a living tissue, in which the pollutants remain active for a longer time in a toxic form through chemical, biological, and photolytic processes.
Persistent organic pollutants (POPs) are organic compounds that, to a varying degree, resist photolytic, biological and chemical degradation.
- Due to persistence, the pollutants are capable of long-range transport, bioaccumulation and biomagnification.
Most of the POPs include pesticides, Industrial solvents, polyvinyl chloride, and pharmaceuticals.
The Other words used are PBTs (Persistent, Bioaccumulative and Toxic) or TOMPs (Toxic Organic Micro Pollutants.)
In May 1995, the United Nations Environment Programme Governing Council (GC) started investigations on the POPs. The process began with 12 POPs which were most common at that time. They were called “Dirty Dozen”.
The Dirty Dozen are:
aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and toxaphene.
The list enlarged later with inclusion of some more chemicals.
Common Characters of the POPs
They are mostly having:
- Low Water solubility
- High lipid solubility: This property leads them to bioaccumulation in animal tissues.
- Semi volatile: The property of their physico-chemical characteristics that permit these compounds to occur either in the vapour phase or adsorbed on atmospheric particles, thereby facilitating their long range transport through the atmosphere
- The POPs with higher Molecular weights are more toxic and more persistent generally .
- Most of the POPs are halogenated and many have Chlorine as a component.