from monsanto. wisconsin from 1954 until 1971, the fox river in appleton, wisconsin, had pcbs deposited into it from appleton paper/ncr, p.h. gladfelter, georgia-pacific and other notable local paper manufacturing facilities. the wisconsin dnr estimates that after wastewater treatment the pcb discharges to the fox river due to production losses ranged from 81,000 kg to 138,000 kg. (178,572 lbs. to 304,235 lbs). the production of carbon copy paper and its byproducts led to the discharge into the river. fox river clean up is ongoing. pacific ocean polychlorinated biphenyls have been discovered in organisms living in the mariana trench in the pacific ocean. levels were as high as 1,900 nanograms per gram of amphipod tissue in the organisms analyzed. regulation japan in 1972 the japanese government banned the production, use, and import of pcbs. sweden in 1973, the use of pcbs in "open" or "dissipative" sources (such as plasticisers in paints and cements, casting agents, fire retardant fabric treatments and heat stabilizing additives for pvc electrical insulation, adhesives, paints and waterproofing, railroad ties) was banned in sweden. united kingdom in 1981, the uk banned closed uses of pcbs in new equipment, and nearly all uk pcb synthesis ceased; closed uses in existing equipment containing in excess of 5 litres of pcbs were not stopped until december 2000. united states in 1976, concern over the toxicity and persistence (chemical stability) of pcbs in the environment led the united states congress to ban their domestic production, effective january 1, 1978, pursuant to the toxic substances control act. to implement the law, epa banned new manufacturing of pcbs, but issued regulations that allowed for their continued use in electrical equipment for economic reasons. epa began issuing regulations for pcb usage and disposal in 1979. the agency has issued guidance publications for safe removal and disposal of pcbs from existing equipment. epa defined the "maximum contaminant level goal" for public water systems as zero, but because of the limitations of water treatment technologies, a level of 0.5 parts per billion is the actual regulated level (maximum contaminant level). methods of destruction physical pcbs are technically attractive because of their inertness, which includes their resistance to combustion. nonetheless, they can be effectively destroyed by incineration at 1000 °c. when combusted at lower temperatures, they convert in part to more hazardous materials, including dibenzofurans and dibenzodioxins. when conducted properly, the combustion products are water, carbon dioxide, and hydrogen chloride. in some cases, the pcbs are combusted as a solution in kerosene. pcbs have also been destroyed by pyrolysis in the presence of alkali metal carbonates. thermal desorption is highly effective at removing pcbs from soil. chemical pcbs are fairly chemically unreactive, this property being attractive for its application as an inert material. they resist oxidation. many chemical compounds are available to destroy or reduce the pcbs. commonly, pcbs are degraded by basic mixtures of glycols, which displace some or all chloride. also effective are reductants such as sodium or sodium naphthalene. vitamin b12 has also shown promise. microbial the use of microorganisms to degrade pcbs from contaminated sites, relying on multiple microorganisms' co-metabolism, is known as bioremediation of polychlorinated biphenyl. some micro-organisms degrade pcbs by reducing the c-cl bonds. microbial dechlorination tends to be rather slow-acting in comparison to other methods. enzymes extracted from microbes can show pcb activity. in 2005, shewanella oneidensis biodegraded a high percentage of pcbs in soil samples. a low voltage current can stimulate the microbial degradation of pcbs. fungal there is research showing that some ligninolytic fungi can degrade pcbs. bioremediation the remediation, or removal, of pcbs from estuarian and coastal river sediments is quite difficult due to the overlying water column and the potential for resuspension of contaminants during the removal process. the most common method of pcb extraction from sediments is to dredge an area and dispose of the sediments in a landfill. this method is troubling for a number of reasons, namely that it has a risk of resuspension of the chemicals as the sediments are disturbed, and this method can be very damaging to ecosystems. a potential cost effective, low risk remediation technique is bioremediation. bioremediation involves the use of biota to remediate sediments. phytoremediation, the use of plants to remediate soils, has been found to be effective for a broad range of contaminants such as mercury pcb and pahs in terrestrial soils. a promising study conducted in new bedford harbor found that ulva rigida, a type of seaweed common throughout the world, is effective at removing pcb from sediments. during a typical bloom in new bedford harbor, u. rigida forms a thick mat that lies on top of and in contact with the sediment. this allows for u. rigida to uptake large amounts of pcb from the sediment with concentrations of pcb in u. rigida reaching 1580 μg kg−1 within 24 hours of the bloom. live tissue tended to take up higher concentrations of pcb than dead tissue, but this is not to say that dead tissue did not still take up large amounts of pcb as well. homologs for a complete list of the 209 pcb congeners, see pcb congener list. note that biphenyl, while not technically a pcb congener because of its lack of chlorine substituents, is still typically included in the literature. pcb homolog casrn clsubstituents number ofcongeners biphenyl (not a pcb) 92-52-4 0 1 monochlorobiphenyl 27323-18-8 1 3 dichlorobiphenyl 25512-42-9 2 12 trichlorobiphenyl 25323-68-6 3 24 tetrachlorobiphenyl 26914-33-0 4 42 pentachlorobiphenyl 25429-29-2 5 46 hexachlorobiphenyl 26601-64-9 6 42 heptachlorobiphenyl 28655-71-2 7 24 octachlorobiphenyl 55722-26-4 8 12 nonachlorobiphenyl 53742-07-7 9 3 decachlorobiphenyl 2051-24-3 10 1