1. Polychlorinated
Biphenyls
Aditya G

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