Polychlorinated biphenyls (PCBs) are odorless, tasteless liquids that are degraded slowly and accumulate in the environment. They bind to the aryl hydrocarbon receptor in cells and can alter gene transcription. PCBs are classified as persistent organic pollutants due to their bioaccumulation and inability to decompose readily, with half-lives of 8 to 10 years. Long-term exposure to PCBs is linked to various health effects like endocrine disruption and cancer as well as environmental damage.

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