| Pollutant |
Source |
Entry pathway |
Biological effect |
Figures |
|
CFC’s (Chlorofluorcarbons)
 |
Coolants in fridges and propellants in aerosol cans. |
Slowly rise into the ozone layer in the stratosphere (15-35kms above the ground) |
Depletion of the ozone layer leading to more harmful ultraviolet (UV) radiation reaching the ground. Harmful to humans and damage to producers in food chains e.g. kills plankton |
CFC levels peaked in 1990. They have a long life in the atmosphere and recovery will only take place in the middle of the 21 st century. |
|
Sulphur dioxide
 |
Combustion of fuels containing sulphur. |
May remain in gaseous form or dissolve in rainwater to form sulphurous acids |
Effects on human health (asthmatics). Damage to plant growth as seen by destruction of some forests. |
70% of emissions come from coal-fired power stations. UK in 2002 produced 1002 thousand tonnes of Sulphur Dioxide. |
|
PCB’s (Polychlorinated biphenols)
 |
Found in protective sealants for wood and metal. Used as a coolant in electrical transformers. |
PCB’s are given off during incineration.
Layer on surface of water. |
Concentrate in marine mammal fat and oily fish. Can be toxic at the top of the food chain. |
PCB sales were virtually stopped in 1973. It is estimated that 31% of PCB’s ever produced are free in the environment – 1.2 million tonnes. |
|
Nitrates
 |
Nitrate fertilisers |
Leaching into waterways |
Eutrophication and human health hazard due to high nitrate levels in drinking water. |
31% of rivers in England have nitrate levels higher than 30mg nitrates/litre. Legal drinking level is 50mg nitrates/litre |
|
Pesticides
 |
Runoff from agricultural land, spraying. |
Spray drifting. Pesticides into waterways |
Bioaccumulation in food chains – toxic to the higher consumer levels. |
 UK persticide figures
|
|
Carbon Dioxide
 |
Released from the combustion of fossil fuels. |
Enters atmosphere. |
Increases the greenhouse effect leading to global warming and climate change |
In 2003, UK produced 550 million tonnes of Carbon Dioxide. |
|
Heavy metals (e.g. lead and mercury)
 |
Direct discharge of leakage.
Mining. |
Enter waterways and long-term contamination of soils. |
Directly toxic or accumulate in food chains. |
Mercury is used in gold extraction. Lakes near gold mines (Brazil, Indonesia) have fish within 200kms that have mercury levels which make them unfit to eat. |
|
Organic chemicals (oil)
 |
Discharge and leakage. |
Into waterways |
Directly toxic to some organisms. Kills fish and waterfowl. Disruption of food chains. |
Biggest oil spill in 25 years: |
|
Radioactivity
 |
Mining, nuclear power generation, weapons testing. |
Enters the atmosphere, contaminates soil. |
Causes cancer and genetic defects. |
In the UK, 85% of radiation comes from natural radiation sources. Of the 15% artificial radiation, most comes from medical sources. |
|
Organic waste
 |
Sewage, biodegradable industrial waste, agricultural waste (slurry). |
Released into waterways.
Discharge from sewage farms. |
Raw sewage is toxic to many organisms, pathogens affecting human health. Treated sewage (high in nitrates) may cause eutrophication. |
In England and Wales, discharge of effluent into rivers needs permission – there are over 100,000 consents in place. |
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Agricultural Pollution
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