POPs and their toxic effects in nature is the matter of environmental concern. Biodegradation is only the ecofriendly option to cleanup the sites polluted with POPs. Therefore, it require to study the key properties of these POPs.
POPs are “chemical substances that persist in the environment for long, bio-accumulate in the fatty tissues of the living organisms through the food chain and are toxic to humans and wildlife“, therefore, poses risk through causing adverse effects to human health and the environment. POPs circulate globally and can cause damage wherever they travel.
The Stockholm Convention on POPs aims to protect human health and the environment by banning the production and use of some of the most toxic chemicals known to human kind. This list includes 12 organochlorine chemicals or 12 worst offenders (dirty dozens) that are listed as POPs under the convention
Dioxins for example have low solubility in water and high solubility in lipids as represented by its high log Kow values
Some organic pollutants as well as inorganic pollutants like some heavy metals are not biodegradable or self perishable. Organo-chlorinated/brominated compounds have long half life; so are dangerous from environment point of view. If proper microbes are discovered to degrade them/absorb them, then the same can be used for clean up purposes.
I'm happy to see such consciousness among the young researchers about the persistent environmental pollutants.Yes, many of them are biomagnified by entering in the food chain and land finally in human body to cause various health problems, sometimes without our knowledge. So be aware of them, limit their uses by all means and learn how to clean them up.
POPs are not exactly the same as PBTs (persistent, bio-accumulative and toxic substances). All POPs are organic compounds, while PBTs include all substances which meet the definition. For example, mercury is a PBT chemical but not POPs.
The Stockholm Convention is leading on global efforts on managing POPs (www.pops.int). For PBTs, see USEPA webpage http://www.epa.gov/pbt/. Each of the key properties - P, B, and T - can be estimated (very crudely, I think) using the "PBT Profiler" which can be accessed through this webpage.
Annex D of the Stockholm Convention identifies four key characteristics which define POPs with critical thresholds as to what is and what isn't suitable to meet the criteria for environmental persistence, potential for bioaccumulation, adverse health effects for humans and other species and the ability to travel long distance far from point of use.
Additionally UNECE has a protocol on POPs which again has qualifying criteria. The EU POPs regulation also provides critical thresholds for POPs contaminated wastes under Annex IV and V, this is important to help identify what is and isn't a POPs waste.
The Convention began with 12 substances (dirty dozen) largely dominated by agricultural chemicals many of which are now banned and present an issue as obsolete pesticides. Well worth checking out the IHPA website and work John Vijgen has done on that aspect: http://www.ihpa.info/
Since then the Convention has added further substances with increasing focus on industrial chemicals, particularly brominated flame retardants. These substances pose an interesting international problem with the management, use and recycling of plastics, particularly plastics in electrical goods that can move around on global markets and pose an analytic challenge to identify what does and doesn't contain a brominated POP.
Key Characteristics of Persistent Organic Pollutants:
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