Water
BP Gulf of Mexico oil spill
Otherwise known as the Deepwater Horizon Spill and the Macondo Blowout, the ongoing British Petroleum oil spill in the Gulf of Mexico is thought to be the worst to date.
The spill began on April 20, when an oil well 1,500m below the surface blew out, causing a catastrophic explosion on BP's Deepwater Horizon offshore oil drilling platform about 64 km southeast off the coast of Louisiana.
Eleven workers died in the blast and another 17 were injured.
Internal BP documents suggested in the worst case scenario about 100,000 barrels per day of crude could be spilling into the Gulf - way higher than US official estimates of 35,000 to 60,000 bpd.
BP says it is containing about 25,000 barrels a day, and has called in more ships and equipment to boost the effort.
But a key US congressman, Ed Markey, tore into the firm after releasing the document.
"First they said it was only 1000 barrels, then they said it was 5000 barrels; now we're up to 100,000 barrels," Markey told NBC television.
Exxon Valdez
In terms of volume, the Exxon Valdez oil spill on March 24, 1989 was relatively small, but it is considered to be one of the most devastating human-caused environmental disasters ever.
Prince William Sound's remote location in Alaska made it near impossible for response efforts to reach it, and the pristine region was a habitat for diverse wildlife.
Thousands of animals died immediately; including up to 250,000 seabirds.
Almost two decades years after the spill, scientists say the effects are lasting far longer than expected.
Exxon Mobil denies the problem, citing the conclusions of 350 peer-reviewed studies who say it will not cause any long-term impacts.
Oil spills have become extremely common in the 20th and 21st centuries. Here is a list of the major ones.
Air
Chernobyl
Ukraine's Chernobyl disaster of April 26, 1986 is considered the world's worst nuclear power plant disaster.
A meltdown in a reactor killed 31 people instantly and sent a plume of radioactive fallout into the atmosphere, which drifted over large parts of the western Soviet Union and much of Europe.
Over 800,000 workers were sent to clean up the site in the following years, with many of these becoming ill. About 60% of the fallout landed in Belarus, and 336,000 people were resettled.
The number of individuals affected today by the disaster has been estimated at 11 times that of cancer deaths from the 1945 bombings of Hiroshima and Nagasaki.
The accident raised concerns about the safety of nuclear power in general, slowing its expansion for a number of years.
Over 4 million people in the Ukraine, Belarus and western Russia are thought to still live in contaminated areas.
Health effects and fear of radiation sickness have reportedly raised suicide rates by 1,000 per cent inthe region.
Bhopal
Shortly after midnight on December 3, 1984, a poisonous gas cloud escaped from the Union Carbide India Limited pesticide factory in Bhopal, India.
The cloud contained 15 metric tons of methyl isocyanate, and covered more than 60 square kilometres.
At least 4,000 people died instantly, and somewhere between 50,000 and 500,000 suffered continuing health problems like oedema.
Another 15,000 died of health complications in the years that followed, and approximately 100,000 still suffer from chronic disease.
BBC research in 2004 found that people still fall ill, and ten die every year as a result of the gas poisoning. Bhopal is known as the worst industrial environmental disaster ever to have occurred.
The Great Smog of London
For four days in December 1952, London suffered the worst case of air pollution in the history of the Untied Kingdom when an anti-cyclone trapped pollution at ground level across the city.
Initially considered to be nothing more than an extended 'pea souper', the poisonous black smog took up to 900 lives each day during its peak.
Recent research indicates that the enduring effects of the four days of smog killed up to 12,000 people prematurely and caused respiratory tract illnesses in up to 100,000.
The smog was caused by windless conditions and pollution from coal fires, and was laced with sulphur dioxide, nitrogen oxides and soot from surrounding coal mines.
The impact of the smog was the motivating factor for the UK's Clean Air Act of 1956.
Land
Minamata disease
Minamata disease is a neurological syndrome resulting from mercury poisoning, which can lead to insanity, paralysis, coma and death. The disease can also affect unborn babies.
Minamata disease was discovered in Japan's Kumamoto prefecture in 1956, where the Chisso Corporation had been releasing methyl mercury into Minamata bay for two decades.
The chemical accumulated in shellfish and fish, which were then eaten by locals. Humans, cats, dogs and pigs continued to die for more than 30 years, but neither the government nor the company took meaningful steps to stop the pollution.
In March 2001, 2,265 victims had been officially recognised, 1,784 of whom had died, and Chisso had paid financial compensation to more than 10,000 victims.
It was not until 2004 that Chisso was ordered to clean up the contamination. A settlement was reached in March, 2010.
