Polychlorinated Biphenyls, PCBs

Polychlorinated Biphenyls, PCBs

 

Polychlorinated biphenyls (PCBs) are aromatic compounds with 1 to 10 chlorine atoms attached to a biphenyl structure (two benzene rings connected, C6H5-C6H5). They have not been identified as naturally occurring and are produced synthetically, combining multiple homologues to create a mixture. Commercial production of PCBs began in the United States in the 1920s, with global production peaking in the 1960s and 1970s. Starting in the 1970s, the production and use of PCBs were banned in many countries due to their toxicity to humans.

• Polychlorinated biphenyls (PCBs) are composed of chemicals such as benzene and chlorine. There are 209 types of PCB homologues, of which about 100 are in active use.
• Among these, 12 homologues are identified for their dioxin-like toxicity, referred to as dioxin-like PCBs, while the remaining are known as non-dioxin-like PCBs.
• PCBs are classified as Persistent Organic Pollutants (POPs), characterized by their high toxicity, resistance to degradation, and potential for bioaccumulation.
• PCBs are classified as Group 1 carcinogens by the International Agency for Research on Cancer (IARC), meaning they are substances are carcinogenic to humans.
• Dioxin-like PCBs

명칭	IUPAC chemical nomenclature 1)	CAS number2)
PCB-77	2,3,3′,4,4′-PentaCB	32598-13-3
PCB-81	3,4,4′,5-TetraCB	70362-50-4
PCB-105	2,3,3′,4,4′-PentaCB	32598-14-4
PCB-114	2,3,4,4′,5-PentaCB	74472-37-0
PCB-118	2,3′,4,4′,5-PentaCB	31508-00-6
PCB-123	2,3′,4,4′,5-PentaCB	65510-44-3
PCB-126	3,3′,4,4′,5-PentaCB	57465-28-8
PCB-156	2,3,3′,4,4′,5-HexaCB	38380-08-4
PCB-157	2,3,3′,4,4′,5′-HexaCB	68782-90-7
PCB-167	2,3′,4,4′,5,5′-HexaCB	52663-72-6
PCB-169	3,3′,4,4′,5,5′-HexaCB	32774-16-6
PCB-189	3,3′,4,4′,5,5′-HeptaCB	39635-31-9

1)     IUPAC: International Union of Pure and Applied Chemistry

2)     CAS: Chemical Abstract Service Register Number

 

■  Yusho disease

In 1968, the Kanemi Yusho incident, an environmental pollution case, occurred primarily in Fukuoka and Nagasaki prefectures in Japan. This incident involved rice bran oil produced by Kanemi Warehouse Co., Ltd., which became contaminated with polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans, and dioxins during the oil's deodorization process. The contaminated oil was consumed over a long period, leading to about 1,800 people suffering from symptoms similar to those of acne, known as Yusho disease. Victims also experienced liver failure, excessive tear secretion, stunted growth, reduced libido, endocrine disorders, peripheral nerve disorders, and hair loss. In 1972, the blood PCB concentration levels in the affected individuals ranged from 0 to 35 ppb (parts per billion), and by 1984, this level had decreased to 5 ppb (1, 2).

<Kanemi Yusho incident: generated by AI>

 

■   Environmental exposure

Polychlorinated biphenyls (PCBs) are lipid-soluble compounds that exhibit poor solubility in water, leading to their accumulation in soil and sediment and consequent persistence in the environment. These compounds have the ability to traverse non-aquatic environments, such as seawater and groundwater, and subsequently infiltrate the food chain, predominantly contaminating aquatic and terrestrial food sources including fish, meat, eggs, milk, and dairy products. The estimated average daily intake of PCBs for adults through dietary sources ranges from 27 to 50 nanograms per kilogram of body weight. Furthermore, PCBs can become airborne, contributing to approximately 15% of the overall exposure risk, while direct contact with outdated electronic equipment and appliances, such as televisions, refrigerators, and fluorescent lighting, may also pose additional exposure threats due to the presence of PCBs.

 

■    Occupational exposure

Artificially produced polychlorinated biphenyls (PCBs) were mainly used in electrical insulation and in manufacturing various products like paint and adhesives. Workers manufacturing and handling these products were primarily exposed to PCBs through inhaling contaminated air or skin contact. Specifically, employees in capacitor manufacturing experienced PCB exposure levels that were significantly higher (10 to 1,000 times) than non-exposed individuals, measured at 80 to 275 μg/m3 in the air and 2 to 22 μg/cm2 through skin absorption (3, 4).

Since the ban on commercial production and use of PCBs in the 1970s, current occupational exposure primarily occurs during incineration, recycling of PCB materials, and fires. For instance, the blood of Korean waste incinerator workers showed PCB concentrations of 214.93 ng/g (lipid). Moreover, firefighters dealing with transformer fires exhibited higher PCB blood levels (1.9-11.0 ppb) compared to the general population (1.0-2.0 ppb) (5).

 

■     References

IOM; Institute of Medicine (2003). Dioxins and dioxin-like compounds in the food supply. Washington (DC): The National Academies Press.

ATSDR (2000). Toxicological Profile for Polychlorinated Biphenyls (Update). Atlanta (GA): US Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry.

EFSA (2012). Update of the monitoring of dioxins and PCBs levels in food and feed. The EFSA Journal, 10(7):2832.

Yushō disease: https://en.wikipedia.org/wiki/Yush%C5%8D_disease.

(1)   Iida T, Hirakawa H, Matsueda T, Takenaka S, Yu ML, Guo YL (1999). Recent trend of polychlorinated dibenzo-p-dioxins and their related compounds in the blood and sebum of Yusho and Yu Cheng patients. Chemosphere, 38(5):981–93.

(2)   Ikeda M, Yoshimura T (1996). Survival of patients. In: Kuratsune M, Yoshimura H, Hori Y, Okumura Yusho M editors. A Human Disaster Caused by PCBs and Related Compounds. Fukuoka, Kyushu: University Press; pp. 316–23.

(3)   Park H, Ikonomou MG, Kim H-S, Choi JW, Chang YS (2009). Dioxin and dioxin-like PCB profiles in the serum of industrial and municipal waste incinerator workers in Korea. Environment International, 35(3):580–7.

(4)   Kelly KJ, Connelly E, Reinhold GA, Byrne M, Prezant DJ (2002). Assessment of health effects in New York City firefighters after exposure to polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans (PCDFs): the Staten Island Transformer Fire Health Surveillance Project. Archives of Environmental & Occupational Health, 57(4):282– 93.