Persistence dirty dozen, persistent organic pollutants

Chlorinated micropoUutants are harmful for man and environment due to their toxicity, persistence, and bioaccumulation. Persistent compounds are very stable and difficult to get metabolized and mineralized by biological and chemical processes in the environment, and as a result, they have become ubiquitous in water, sediments, and the atmosphere bioaccumulation is the result of the lipophilicity of these compounds. Polychlorinated dibenzodioxins and -furans (PCDD/F) are not produced purposely like many of other chlorinated technical products, such as chlorinated biocides DDT, lindane, and toxaphene. The production and use of persistent organic pollutants (POPs), the dirty dozen has now been banned worldwide by the Stockholm protocol. It should be mentioned that about 3000 halogenated products have now been isolated as natural products in plants, microorganisms, and animals," but the total amount of these products is much smaller compared to xenobiotics. 

These two positions were in conflict in 2001 when representatives from 127 nations met in Stockholm to consider a universal ban on 12 TOCs, commonly known as the "dirty dozen." The dirty dozen includes aldrin, chlordane, dieldrin, DDT, endrin, heptachlor, hexachlorobenzene, and Mirex. After extended discussion and debate, representatives adopted a final document now known as the Stockholm Convention on Persistent Organic Pollutants. The document was signed on May 22, 2001, and entered into force on May 17, 2004, at which point the required minimum of 50 nations had ratified the treaty. 

PAHs are not included in the list of dirty dozens POPs of the Stockholm Convention. However, in addition to 12 existing POPs, UN/ECE (United Unions Economic Commission for Europe) considers PAHs, HCHs, chlorodecone, and hexabromobiphenyl as potential POPs to be restricted based on The New Protocol on Persistent Organic Pollutants to the Convention on Long-range Trans-boundary Air Pollution adopted in 1998. PAHs may be listed as POP in the future Stockholm Convention. 

Fig. 2.2 The dirty dozen of persistent organic pollutants (POPs) and effects of photo-initiated processes (and of AOPs/AOTs in general) generating a convenient sink.

In 1972, the U.S. Environmental Protection Agency announced that DDT could no longer be used in the United States because of the risk it posed for human health and the environment. A number of other developed nations soon followed the EPA s action. In 2001, a conference sponsored by the United Nations, called the Stockholm Convention on Persistent Organic Pollutants, adopted a statement calling for the eventual elimination of a dozen pesticides, known as the dirty dozen, including DDT. Because of its effectiveness against malaria and other infectious diseases, DDT was given a waiver for use by public health officials in nations where the compound had not been banned. 

The EPA provides a list of twelve particularly persistent organic pollutants to watch out for. The list includes aldrin, chlorodane, dichlorophenyl trichloroethane (DDT), dield-rin, endrin, heptachlor, hexachlorobenzene, mirex, toxaphene, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans. The EPA has colloquially named this group of compounds as the dirty dozen. ... 

In Chapter 13, we learned about the "dirty dozen"—12 chemical compounds that have been targeted by governments arotmd the world to be banned. These compounds are known as persistent organic pollutants (POPs) because once they enter the environment, they remain for long periods of time. Examine the structures of the compounds shown here. What functional groups can you identify within the compounds (They may have more than one.) What structural features do many of these compounds have in common ... 

---