Polychlorinated biphenyls formulations

TechXtract is an extraction technology that has been used to remove a variety of contaminants from the surfaces of concrete, steel, brick, and other materials. Target contaminant types include organics, heavy metals, radionuclides, and polychlorinated biphenyls (PCBs). The technology uses proprietary chemical formulations in successive steps to remove these contaminants. The process employs as many as 25 different components in 3 separate chemical formulations that are applied to the contaminated surface and then removed in a multi-step, multicycle sequence. TechXtract is commercially available and has been used at multiple sites. 

However, the use of perchlorates in pyrotechnic formulations is discouraged due to the supposed toxicity of this chemical which has been linked to causing thyroid disorders. Furthermore, the combustion of polychlorinated organic materials such as poly(vinyl) chloride has been shown to produce polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). These polychlorinated chemicals are highly toxic and are potent carcinogens. Therefore, the removal of perchlorates and chlorinated organic materials in pyrotechnic formulations would eliminate the formation of these aforementioned pollutants. 

Polychlorinated diphenyl ethers (PCDE) are common impurities in chlorophenol formulations, which were earlier used as fungicides, slimicides, and as wood preservatives. PCDEs are structurally and by physical properties similar to polychlorinated biphenyls (PCB). They have low water solubility and are lipophilic. PCDEs are quite resistant to degradation and are persistent in the environment. In the aquatic environment, PCDEs bioaccumulate. These compounds are found in sediment, mussel, fish, bird, and seal. PCDEs show biomagnification potential, since levels of PCDEs increase in species at higher trophic levels. PCDEs are also detected in human tissue. Despite the persistence and bio accumulation, the significance of PCDEs as environmental contaminants is uncertain. The acute toxicity and Ah-receptor-me-diated (aryl hydrocarbon) activity of PCDEs is low compared to those of polychlorinated di-benzo-p-dioxins (PCDD) and dibenzofurans (PCDF). Due to structural similarity to thyroid hormone, PCDEs could bind to thyroid hormone receptor and alter thyroid function. Furthermore, PCDEs might be metabolized to toxic metabolites. In the environment, it is possible that photolysis converts PCDEs to toxic PCDDs and PCDFs. 

Chlorobiphenyls (CBs) are used widely by industry, including transformers and capacitors in the electrical industry and inks, paints and paper in the printing and allied industries. Unwanted polychlorinated biphenyls (PCB) formulations and waste materials containing PCBs are normally incinerated. However, PCBs and waste products containing these materials are inadvertently or illegally disposed of at dump sites and landfill sites. Unsealed PCB sources are leached into the terrestrial and aquatic environment and incomplete combustion vaporises these compounds into the atmosphere therefore, they enter the wider global cycle of trace organic compounds and ubiquitous environmental contaminants that occur in bovine milk, milk powders and products as a result of intake via animal feed. 

Unwanted polychlorinated biphenyl (PCB) formulations and waste materials containing PCBs are normally destroyed by high temperature incineration. However, this is a relatively costly method of waste disposal and alternative, but illegal, practices are known to occur, such as dissolving PCBs in waste mineral oil. Unless the oil is chemically analysed for the presence of the CBs it will pass as waste oil which can be... 

The chemical is banned. Prohibition for the importation, formulation, manufacturing and final disposal in the national territory of the substances polychlorinated biphenyls, pentachlorofenol, crocidolite, polybrominated biphenois, polychlorinated terphenyts and tris (2,3-dibromopropyl) phosphate on the basis that they cause environmental pollution and have toxic effects against human health. Ail uses of crocidolite are banned. 

A decreasing incidence of chloracne may be attributed to the advent of plastics, the gradual substitution of chlorinated hydrocarbons with synthetic resins and the restriction of the use of polychlorinated biphenyls to only closed-system formulations (Kokelj 1992). 

T. Takasuga, K. Senthilkumar, T. Matsumura, K. Shiozaki, and S. Sakai, Isotope dilution analysis of polychlorinated biphenyls (PCBs) in transformer oil and global commercial PCB formulations by high resolution gas chromatography-high-resolution mass spectrometry, Chemosphere 62 (2006) 469-484. 

Perchloroethylene is used as an insulating fluid in some electrical transformers as a substitute for polychlorinated biphenyls (PCBs). Relatively small quantities of perchloroethylene are used in printing inks, aerosol specialty products, adhesive formulations, paper coatings, and silicones. In addition, perchloroethylene is a component of chemical maskant formulations used to protect surfaces from chemical etchants used in the aerospace and other industries. 

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