Polychlorinated biphenyl

Polychlorinated biphenyls ( PCBs) (polychlorinated biphenyls, Chlordiphenyl, Eng. Chlorinated diphenyl ) are toxic and carcinogenic organic chlorine compounds, which until the 1980s, mainly in transformers, electric capacitors, in hydraulic systems as hydraulic fluid, as well as plasticizers in paints, sealants insulating means and plastics were used. PCBs are now one of the twelve 'dirty dozen ' persistent organic pollutants, which were banned under the Stockholm Convention of 22 May 2001 worldwide. PCBs have spread everywhere on earth, they are ubiquitous detected in the atmosphere, the waters and in the soil.

Production

From 1929 industrial syntheses for the production of polychlorinated biphenyls have been developed. In this case, biphenyl is reacted with iron or iron (III ) chloride as a catalyst for the reaction with chlorine. Depending on the reaction conditions, different degrees form chlorinated biphenyls. The resulting in the substitution reaction of hydrogen chloride is neutralized with sodium hydroxide solution. The mixture of polychlorinated biphenyls is then purified by distillation or separated. Commercial products came as askarels example, under the name Aroclor (Monsanto ) are used. The chlorine content here was between 21% ( Aroclor 1221 ) and 68 % ( Aroclor 1268 ).

Properties

PCB having a biphenyl backbone (two via a single bond linked benzene rings ) to which one or more hydrogen are replaced by chlorine atoms. The empirical formula is therefore C12H10 - xClx.

PCBs are yellowish in pure form, almost odorless liquids. Polychlorinated biphenyls are thermally and chemically stable, flame retardant, electrically non-conductive and superhydrophobic. They have a relatively high density from 1.4 g / ml. The biodegradation occurs with highly chlorinated PCBs under anaerobic conditions by the chlorine atoms can be used as electron, a so-called chlorine breathing. Low- chlorinated PCBs can be degraded aerobically or anaerobically. Since PCB -degrading organisms lack of nitrogen can not live alone of PCBs and in most cases, important nutrients also can be found elsewhere, PCBs are scarcely degraded biologically. Their degradation takes no advantage to the bacteria, and there are few strains having the genes for the appropriate enzymes.

After a mass poisoning with PCB - contaminated food in 1968 in Japan ( Yusho disease) production and use of PCBs were banned in 1978 generally first in open systems and 1989. Since the end of the transitional period 1999 PCB - contaminated sites must be reported and disposed of as hazardous waste. In Germany this takes place, for example in the underground storage Herfa - neurodegeneration. Can be loaded PCB old capacitors, inter alia, in fluorescent lights, washing machines, spin dryers and other older devices with capacitor motor and industrial systems for reactive power compensation.

In the Assembly PCB capacitors and PCB-containing insulating oils ( Chlordiphenyl, askarels ) were employed earlier. The capacitors can leak and contaminate the environment with mechanical destruction and decomposition processes. Chlordiphenyl smells over other insulating oils intensely fruity even in very small quantities and can be absorbed by the body already in contact with skin. Chlordiphenyl -containing capacitors were in the GDR after a certain point marked as such ( overprint " Chlordiphenyl ").

Congeners of PCBs

Polychlorinated biphenyls ( PCBs) are a group of 209 different congeners of chlorinated substances, which differ in their number and position of chlorine atoms on the biphenyl:

Health effects

The acute toxicity of PCBs is low, whereas chronic toxicity is yet to determine small quantities.

Typical effects of this poison are chloracne, alopecia, hyperpigmentation, liver damage, teratogenicity and damage to the immune system ( immunotoxicity ). PCBs bioaccumulate in the food chain and are suspected to be carcinogenic. In addition, the physical and mental development are delayed by PCB. They are suspected to be endocrine disruptors, which have hormonal activity and may be responsible for male infertility and male animals, undescended testicles, and for other hormone-related diseases. An EU study has found that phthalates, parabens, and PCBs among other hormone levels of male fetuses and children disturb, and so lead to feminization.

The chronic toxicity makes PCB as household poison, for example, of old, mechanically damaged capacitors, especially dangerous, because usually (children, sick and old people so ) indoors is the length of stay of immune-compromised people already particularly high. Due to the accumulation in adipose tissue smallest continuously recorded amounts are even harmful. The poison accumulates in organisms at the top of the food chain. Against this background, the ratings -off contamination are seen (eg the feed or pork - contamination case in early December 2008 in Ireland): a one-time intake of foods with a hundred times higher content of PCBs than the limit allows, is indeed questionable, but does not lead to acute poisoning as the limit for a daily, life-long recording was made ​​taking into account the enrichment.

As a result of accidents and improper waste management of PCBs have distributed in the environment and accumulate at the bottom of the food chain and can now even be detected in fish in the Antarctic, in mother's milk and in human adipose tissue.

Due to their lipid solubility PCBs are absorbed by the body even with the naked skin contact. In PCB - contaminated buildings, there may be an increased indoor exposure to PCBs. For persons residing in these polluted areas, partly elevated PCB levels can be detected in blood.

Defective capacitors or contamination can be identified by the fruity smell - oils based on hydrocarbons, however, hardly any smell.

In 1984, the biggest environmental scandal in the former Yugoslavia was revealed: the Slovenian river Krupa and the local karst landscape, have been for decades contaminated by improperly stored waste from the company Iskra Kondenzatorji from Semič with PCBs. The contamination was discovered by accident by scientists at the Health Department in Maribor and later in Ljubljana, as they investigated the source of the Krupa to investigate this source of drinking water for the Bela Krajina (see also PCB contamination of the Krupa ). Particularly problematic is the fact that this is a karst landscape. Even today, the burden of PCBs is high and can be detected in soil samples, fish in water, pets, etc..

In August 2003, a settlement was reached to compensate residents of the city of Anniston, Alabama, which were exposed for years with Monsanto's knowledge the harmful by-products of PCB production. ( The production was indeed prohibited by law in 1976, but the process dragged on for decades. ) Monsanto paid 390 million U.S. dollars, 160 million insurance and Solutia 50 million. Other costs such as waste disposal are said to have amounted to 100 million, so that the total volume amounted to 700 million U.S. dollars.

In June 2011, the Dortmund prosecutor brought charges against management and operational control of the Envio Recycling GmbH & Co. KG. They are from May 2006 to May 2010 regulatory requirements have willfully violated and have thereby taken, inter alia, PCB contamination of their employees in purchasing. On the premises of Envio AG PCB contaminated transformers and capacitors were broken down improperly. The accusation was made in four cases, including personal injury.

PCB Directive

The PCB Directive has two limits for PCBs: the precautionary and limit (300 or 3000 ng / m³ air). There are also limits for the presence of PCBs in foodstuffs; they are listed in the so-called pollutant maximum quantity regulation.

• Rooms with over 3000 ng / m³ must be repaired immediately.
• In rooms with more than 300 ng / m³ is possible, eliminate the cause of the stress, the room should be well ventilated as possible to keep the concentration as low as possible.

Limits

54% chlorine (eg Clophen A50 ): 0.7 mg / m³ ( other details: 0.5 mg / m³) 42% chlorine (eg Clophen A30): 1.1 mg / m³ ( ​​other details: 1.0 mg / m³) " When dealing with skin-resorptive substances (such as PCBs), compliance with exposure limit values ​​for the protection of health is not sufficient. Organizational and occupational hygiene measures is to ensure that the skin contact with these substances does not occur. "

Analysis

Initially prepared for the analysis of PCBs in environmental samples difficulties, which also led to a late discovery of PCBs in the environment because chemically similar pesticides and insecticides such as DDT difficult to prove. For determining the first sample is extracted with an organic solvent (e.g. hexane) and then concentrated on the PCB by column chromatography procedures. The subsequent quantitative analysis of PCB is then made with the gas chromatographic method.