Accidents happen, but when they destroy the delicate balance of nature or cause a large number of people to suffer, they become disasters. Here are some of the largest disasters that have been caused by human activity. Love Canal
1953, New York, U.S.
Love Canal, a small town in upstate New York near Niagara Falls, was destroyed by waste from chemical plants. Beginning in 1947, chemical companies could legally dump their waste products into the canal. In the 1950s, families began to settle in the area without being told about the waste and the health problems it might cause. The area developed a foul smell, trees lost their bark, and leaves fell throughout the year. In the 1970s, scientists found that the drinking water contained excessive levels of 82 industrial chemicals, 7 of which were thought to cause cancer. The people of Love Canal had an unusually high rate of cancer and birth defects. Eventually, many of the houses had to be abandoned. By the 1990s, the town had been cleaned up enough for families to begin moving back to the area. Three Mile Island
1979, Pennsylvania, U.S.
On March 28, 1979, the worst accident in U.S. nuclear-reactor history occurred at the Three Mile Island power station, near Harrisburg, Pennsylvania. No one was killed, and very little radioactivity was released into the air when coolant (the fluid that keeps a machine cool) escaped from the reactor core due to a combination of mechanical failure and human error. Bhopal chemical leak
December 1984, Bhopal, India
An explosion in the Union Carbide chemical plant in Bhopal, India, released a deadly gas called methyl isocyanate, which is used to make pesticides. The gas formed a cloud that killed 2,500 people; another 50,000-100,000 people became ill. Trees and plants in the area became yellow and brittle. The explosion was caused by a mechanical failure that was not noticed in time to stop it. Chernobyl
April 1986, Ukraine, former Soviet Union
At 1:23 A.M. on Saturday, April 26, 1986, the reactor blew at the nuclear power plant in Chernobyl, ripping open the core, blowing the roof off the building, starting more than 30 fires, and allowing radioactive material to leak into the air. Some 31 people were killed and nearly 300 people were treated for radiation poisoning. Glaring violations of safety rules were at the bottom of this tragic event. Exxon Valdez oil spill
March 1989, Alaska, U.S.
On March 24, 1989, 11.2 million gallons of crude oil spilled into Prince William Sound from the tanker Exxon Valdez when its hull hit a reef and tore open. The spill, which cost billions of dollars to clean up and killed millions of birds, fish, and other wildlife, was caused by human error and could have been avoided. Jilin Chemical Plant Explosion
November 2005, Jilin City, China
On November 13, 2005, a series of explosions in a petrochemical plant killed six people, injured at least 70, and forced over 10,000 residents to evacuate. The explosions reached at least 200 meters in diameter and caused 80 kilometers of severe pollution in the Songhua River. The major pollutants, benzene and nitrobenzene, which are linked to leukemia, were recorded at levels over 100 times national safety standards. Water supplies were shut off in affected areas making it necessary to bring water from other nearby sources. Gulf of Mexico Oil Spill
April 2010, Gulf of Mexico
The Deepwater Horizon, a semi-submersible drilling rig, sank on April 22, after an April 20th explosion on the vessel. Eleven people died in the blast. When the rig sank, the riser—the 5,000-foot-long pipe that connects the wellhead to the rig—became detached and began leaking oil. In addition, U.S. Coast Guard investigators discovered a leak in the wellhead itself. As much as 5,000 barrels (200,000 gallons) of oil per day were leaking into the water, threatening wildlife along the Louisiana Coast. Homeland Security Secretary Janet Napolitano declared it a "spill of...