Con il termine generico PCB (policlorobifenile) si intende una famiglia di 209 composti chimici, chiamati congeneri ed aventi formula generica C12H10-nCln con n <= 10.
[D.M. 29 gennaio 2007 (So n. 133 alla Gazzetta Ufficiale del 7 giugno 2007 n. 130) della Rep. italiana]

PCB – policlorobifenile (altre definizioni)

PCB – policlorobifenile (dalla Direttiva Europea)
– polychlorinated biphenyls;
– polychlorinated terphenyls;
– monomethyl-tetrachlorodiphenyl methane, monomethyl-dichloro-diphenyl methane,
monomethyl-dibromo-diphenyl methane;
– any mixture containing any of the above mentioned substances in a total of more than 0,005 % by weight
[Council Directive 96/59/EC Art. 2, a]

PCB – policlorobifenile (dall’Electropedia IEC) polychlorinated biphenyls
insulating liquid consisting of a mixture of several isomeric and homologous compounds, obtained by replacement of at least two hydrogen atoms in the biphenyl molecule by chlorine atoms.
Note – Due to the chlorine content, chlorinated compounds are considered harmful to the environment, and their use is prohibited in many countries.
IEV ref. 212-17-10 [fonte]

PCB – policlorobifenile (dalla Convezione di Stoccolma)
Listed under Annex A with specific exemptions and under Annex C
These compounds are used in industry as heat exchange fluids, in electric transformers and capacitors, and as additives in paint, carbonless copy paper, and plastics. Of the 209 different types of PCBs, 13 exhibit a dioxin-like toxicity. Their persistence in the environment corresponds to the degree of chlorination, and half-lives can vary from 10 days to one-and-a-half years.
PCBs are toxic to fish, killing them at higher doses and causing spawning failures at lower doses. Research also links PCBs to reproductive failure and suppression of the immune system in various wild animals, such as seals and mink.
[…] PCBs also suppress the human immune system and are listed as probable human carcinogens. [fonte]

PCB – policlorobifenile (dal libro Analytical chemistry of PCBs)
One of 2019 individual compounds having the molecular formula C12HnCl10-n , where n=0 to 9. 4-Chlorobiphenyls and 3,4,3’,4’-tetrachlorobiphenyls are examples. This definition includes monochlorobiphenyls but notbiphenyl
Ref. Appendix H – “Analytical chemistry of PCBs” M.D. Erickson, 1997

Apparecchiatura con PCB (dalla Direttiva Europea)

“equipment containing PCBs” means any equipment containing PCBs or having contained PCBs (e.g. transformers, capacitors, receptacles containing residual stocks) which has not been decontaminated. Equipment of a type which may contain PCBs shall be treated as if it contains PCBs unless it is reasonable to assume the contrary
(Directive 96/59/EC Article 2, b).

Questo principio è allineato con la legge federale sui PCB in USA US EPA 40 CFR part /761 del 31/05/1979 entrata in vigore il 2/7/1979. I dati disponibili indicano che all’entrata in vigore della legge federale circa il 38% delle apparecchiature elettriche con liquidi isolanti sul territorio degli Stati Uniti d’America contenevano PCB in concentrazione compresa fra 50 e 500 mg/Kg.

POPs – persistent organic pollutants (dalla Convenzione di Stoccolma)

What are POPs?

Persistent Organic Pollutants (POPs) are organic chemical substances, that is, they are carbon-based. They possess a particular combination of physical and chemical properties such that, once released into the environment, they:
– remain intact for exceptionally lotng periods of time (many years);
– become widely distributed throughout the environment as a result of natural processes involving soil, water and, most notably, air;
– accumulate in the fatty tissue of living organisms including humans, and are found at higher concentrations at higher levels in the food chain; and
– are toxic to both humans and wildlife.

Askarel (dall'Electropedia IEC)

Askarel – synthetic, fire-resistant insulating liquid which, when decomposed by an electric arc, will evolve predominantly non-combustible gaseous mixtures
Note 1 – Askarels used earlier consist of polychlorinated biphenyls with or without the addition of polychlorinated benzenes.
Note 2 – Due to the chlorine content, askarels are considered harmful to the environment, and their use is prohibited in many countries.
IEV ref. 212-17-09 [fonte]

Congeneri, Co-Planare, Omologo, Isomero (dal libro Analytical chemistry of PCBs)

Congeners – one of 209 PCBs or other group of compounds, not necessarily the same homolog
Ref. Appendix H – “Analytical chemistry of PCBs” M.D. Erickson, 1997

Co-Planar – Those PCB congeners lacking or containing only one chlorine in the ortho positions. Chlorine substituents are larger than hydrogens and thus constrain rotation about the carbon-carbon bond bridging the two rings in the biphenyl. PCBs with zero or one ortho-chlorines can form a co-planar conformation more readily than those congeners with 2, 3 or 4 chlorines in the ortho position. The mono-ortho-chloro congeners may or may not be included in the term “co-planar,” depending on the authors of the study.
Ref. Appendix H – “Analytical chemistry of PCBs” M.D. Erickson, 1997

Homolog – One of the ten degrees of chlorination of PCBs (C12H9Cl through C12Cl10) or other group of compounds varying by systematic addition of a substituent.
Ref. Appendix H – “Analytical chemistry of PCBs” M.D. Erickson, 1997

Isomer – Any PCB or other compound which has the same molecular formula, but different positional substitutions. 2.2-Dichlorobiphenyls and 2,3-dichlorobiphenyl are isometric; 4-chlorobiphenyl and 2,3,4-trichlorobiphenyl are not.
Ref. Appendix H – “Analytical chemistry of PCBs” M.D. Erickson, 1997

PCDD – Diossine e PCDF - Furani (dalla Convenzione di Stoccolma)

Polychlorinated dibenzo-p-dioxins (PCDD)
Listed under Annex C
These chemicals are produced unintentionally due to incomplete combustion, as well during the manufacture of pesticides and other chlorinated substances. They are emitted mostly from the burning of hospital waste, municipal waste, and hazardous waste, and also from automobile emissions, peat, coal, and wood.  There are 75 different dioxins, of which seven are considered to be of concern. One type of dioxin was found to be present in the soil 10 – 12 years after the first exposure.
Dioxins have been associated with a number of adverse effects in humans, including immune and enzyme disorders and chloracne, and they are classified as possible human carcinogens. Laboratory animals given dioxins suffered a variety of effects, including an increase in birth defects and stillbirths. Fish exposed to these substances died shortly after the exposure ended. Food (particularly from animals) is the major source of exposure for humans.

Polychlorinated dibenzofurans (PCDF)
Listed under Annex C
These compounds are produced unintentionally from many of the same processes that produce dioxins, and also during the production of PCBs. They have been detected in emissions from waste incinerators and automobiles. Furans are structurally similar to dioxins and share many of their toxic effects. There are 135 different types, and their toxicity varies. Furans persist in the environment for long periods, and are classified as possible human carcinogens. Food, particularly animal products, is the major source of exposure for humans. Furans have also been detected in breast-fed infants.

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