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Persistent Organic Pollutants (POPs)

Persistent Organic Pollutants (POPs)

Persistent organic pollutants (POPs) are toxic chemicals that adversely affect human health and the environment around the world. Because they can be transported by wind and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released.

They persist for long periods of time in the environment and can accumulate and pass from one species to the next through the food chain. To address this global concern, the United States joined forces with 90 other countries and the European Community to sign a groundbreaking United Nations treaty EXIT in Stockholm, Sweden, in May 2001.

Under the treaty, known as the Stockholm Convention, countries agreed to reduce or eliminate the production, use, and/or release of 12 key POPs (see box), and specified under the Convention a scientific review process that has led to the addition of other POPs chemicals of global concern.

Bio-accumulation, Bio-concentration and Bio-magnification

Bioconcentration is the intake and retention of a substance in an organism entirely by respiration from water in aquatic ecosystems or from air in terrestrial ones. Bioaccumulation is the intake of a chemical and its concentration in the organism by all possible means, including contact, respiration and ingestion.

Biomagnification occurs when the chemical is passed up the food chain to higher trophic levels, such that in predators it exceeds the concentration to be expected where equilibrium prevails between an organism and its environment (Neely, 1980). Thus the fatty tissues of animals may accumulate residues of heavy metals or organic compounds. These are passed up the food chain (e.g., through fish, shellfish, or birds) and reach greater, possibly harmful, concentrations at high trophic levels among top predators such as eagles, polar bears, and, indeed, human beings.

Bioconcentration can also be defined as the process by which a chemicalconcentration in an aquatic organism exceeds that in water as a result of exposure to a waterborne chemical. There are several ways in which to measure and assess bioaccumulation and bioconcentration.


Biomagnification is a cumulative increase in the concentrations of a persistent substance (e.g. pesticides, metals, etc.) as it moves up the food chain. This occurs when agricultural, industrial, or human waste pours into the ocean directly or via rivers, sewage, etc. Some of the most dangerous of these toxins settle in the sediment of the sea floor and are consumed by bottom feeders. With each step up the food chain, there is an increase in the concentration of these chemicals. This affects humans because a large percentage of the fish we consume are higher on the food chain and therefore likely to carry a high concentration of potentially harmful chemicals.

Dirty Dozen

The dirty dozen and the clean 15 refer respectively to the fruits and vegetables that are the most and least contaminated by pesticide use, according to the Environmental Working Group.

Stockholm Convention on Persistent Organic Pollutants

Being aware that persistent organic pollutants (POPs) pose major and increasing threats to human health and the environment, in May 1995 the Governing Council of UNEP requested in its decision 18/32 that an international assessment process be undertaken of an initial list of 12 POPs and that the Intergovernmental Forum on Chemical Safety (IFCS) develop recommendations on international action for consideration by UNEP Governing Council and World Health Assembly no later than 1997.

The Stockholm Convention on Persistent Organic Pollutants is a global treaty to protect human health and the environment from chemicals that remain intact in the environment for long periods, become widely distributed geographically, accumulate in the fatty tissue of humans and wildlife, and have harmful impacts on human health or on the environment. Exposure to Persistent Organic Pollutants (POPs) can lead to serious health effects including certain cancers, birth defects, dysfunctional immune and reproductive systems, greater susceptibility to disease and damages to the central and peripheral nervous systems. Given their long range transport, no one government acting alone can protect its citizens or its environment from POPs.

In response to this global problem, the Stockholm Convention, which was adopted in 2001 and entered into force in 2004, requires its parties to take measures to eliminate or reduce the release of POPs into the environment.

India and Stockholm Convention

India is a party to the Stockholm convention since 2005.

Stockholm Convention and Endusulphan

The Conference of Parties to the Stockholm Convention in Geneva on Friday approved the recommendation for elimination of production and use of endosulfan and its isomers worldwide, subject to certain exemptions.

The decision will not be binding on India unless specifically ratified by the country. However, the Indian delegation to the Convention concurred with the decision after its concerns about exemptions and financial assistance were addressed, according to information reaching here. The Persistent Organic Pollutants Review Committee to the Convention, which recommended the ban last year, will work with parties and observers to come up with alternatives to endosulfan. The Convention will also approve financial assistance to developing countries for replacing endosulfan with alternatives.

The actual decision is to list technical endosulfan and related isomers to the Convention with specific exemptions for production as allowed in the Register of Specific Exemptions and/or use on crop-pest complexes as listed with the decision. This would require 173 countries, which are parties to the Convention, to take steps for a ban on production and use of endosulfan. However, exemptions will be available for five years, extendable for another five years. The listing takes one year to be effective.

Exemptions will be available for application of endosulfan against 44 pests in 22 crops — cotton, jute, coffee, tea, tobacco, cowpeas, beans, tomato, okra, eggplant, onion, potato, chillies, apple, mango, gram, arhar, maize, paddy/rice, wheat, groundnuts and mustard. The pests include aphids in most of the exempted crops, bollworms, jassids, whiteflies, thrips and leafroller in cotton, Bihar hairy caterpillar and yellow mites in jute and berry borer and stem borer in coffee.

For tea, application of endosulfan is allowed for a host of pests including caterpillars and tea mosquitoes. Endosulfan will be allowed to be used against hopper and fruit fillies in mango and several pests in tomato. In rice, use will be permitted against white jassids, stem borer, gall midge and rice hispa and in wheat against termites and pink borer, besides aphids. The conference took the decision after considering the risk profile and risk management evaluation for endosulfan done by the Review Committee and the exemptions decided upon by contact group on endosulfan and new persistent organic pollutants.

Hazardous substances

Substances hazardous to health are defined under COSHH as those that are: ‘Very Toxic, Toxic, Corrosive, Harmful or Irritant.’ They include all substances allocated a Workplace Exposure Limit (WEL) in EH40, substantial quantities of dust and certain biological agents connected with work

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