2. Chemical Composition
Name: Polychlorinated Biphenyls (PCB)
General formula: C12H10-xClx, where x is an integer
from 1 to 9
3. Chemical Reactivity
Degraded by
Hydroxyl radicals
Photolysis
Bacteria and Eukaryotes
Reductive dechlorination – releases chloride ions
Oxidized by dioxygenase
4. Physical Characteristics
Odorless, tasteless, clear to pale-yellow viscous
liquid
Low water solubilities
0.0027-0.42 ng/L
High solubility in organic solvents (oils, fats)
5. Movement through
Environment
Accumulates in the hydrosphere, the organic
fraction of soil, and in organisms
Oceans dissolve a significant quantity of PCBs
Detected in atmosphere of urbanized areas
Found in regions north of Arctic Circle
Atmosphere is the primary route of global transport
6. Movement into Cells
Binds to aryl hydrocarbon receptor (AhR)
Alters the transcription of genes
Commercial PCB formed triacylglycerol-like
droplets that accumulate in hepatocytes
Mode of uptake is through hydrophobic domains of
lipids for the transport of PCBs by plasma fractions
Accumulates in adipose tissue
7. Major Sources
Landfills containing transformers, capacitors, and other PCB
waste
Incineration of municipal waste
Evaporation from contaminated water bodies
Wastewater effluent
Scrap metal recycling (heat transfer and hydraulic equipment)
Used oil (<50 ppm)
Asphalt roofing materials
Auto salvage yards (hydraulic fluid, ignition coils)
8. Toxicity
Maximum containment levels in drinking water
mandated by the EPA is 0.5 ppb
2,3,7,8-tetrachlorodibenzo[p]dioxin is assigned a
toxic equivalency factor of 1
9. Environmental Damage
Classified as a persistent organic pollutant
Bioaccumulation
Does not decompose readily
Long half life of 8 to 10 years
Generates toxic dibenzodioxins and dibenzofurans
Damages animal life
Liver damage
Hepatocarcinoma
Impaired reproduction
10. Health Effects
Endocrine disruption
Neurotoxin
Skin conditions, such as chloracne or rashes
Fatigue, headaches, coughs, unusual skin sores
Ocular lesions, irregular menstrual cycles, lowered
immune response
11. Link to Cancer
Imitates estrogen compound and can feed breast
cancer cells
Linked to cancer of the liver and biliary tract
Department of Health and Human Services
conclude PCBs are anticipated to be carcinogens