( CNN ) -- A year ago , the worst environmental disaster in U.S. history began on April 20 -- which , ironically , also marked Earth Day . The catastrophe started with a massive explosion on an offshore oil drilling rig that killed 11 workers and sparked a huge fire that eventually sank the rig . More than 200 million gallons of crude oil gushed into the Gulf of Mexico over the next five months , killing thousands of marine animals and affecting thousands of people in the fishing industry -- already struggling in the economic downturn . CNN 's full coverage of the Gulf oil disaster . The exact toll on the Gulf 's ecosystem is still as murky as the ocean waters affected by the disaster . This year , as Earth Day approaches , tragedy and uncertainty may once again temper the mood of the annual event : Japan is still assessing what could be its worst environmental disaster -- the damage to its Fukushima Daiichi nuclear power plant by the March 11 earthquake and tsunami . The situation has forced other countries , including the United States , to take a closer look at the safety of nuclear power plants within their borders . The nuclear issue is still a fierce topic of debate , and environmental experts think it will be an important theme for this year 's Earth Day on April 22 . Recent polls suggest that Americans are divided over nuclear energy . More than half of the 1,012 respondents in a recent CNN poll said they opposed building more nuclear plants , while 46 % said they favored it . When asked by CNN if they are OK with nuclear energy as a source of electricity , 57 % of the respondents said they approved , while 42 % disapproved . Despite the crisis in Japan , nuclear energy is still a centerpiece of President Obama 's clean energy policy . His administration 's fiscal year 2012 budget request includes $ 36 billion in loan guarantee authority to help spur growth in the nuclear industry . Energy secretary defends U.S. nuclear industry . Nuclear energy produces practically no pollution , and it is more reliable than other clean alternative sources -- like wind and solar energy -- that depend on the weather , according to nuclear power advocate Burton Richter , a Nobel Prize-winning physicist . While nuclear is his favorite clean energy source , there are other ways to create electricity that Richter believes can help achieve a reduction in greenhouse gases . Two years ago , Richter and 34 other Nobel laureates wrote a letter to Obama to encourage him to put more money into alternative energy research , including nuclear , wind and solar energy and renewable fuels . Richter , who also teaches at Stanford University , says the American public needs to pay close attention to how Congress is handling environmental issues . He is worried that too many people in Washington are more concerned about politics than the environment . `` We 're not going to see a fee on carbon emissions , we 're not going to see cap and trade , we 're going to see a fight to see whether the EPA [ Environmental Protection Agency ] is going to be able to regulate anything , '' he predicted . `` It 's not going to be a pretty year . '' Richter encouraged everyone to use this year 's Earth Day to speak out about the environmental issues that they care about . `` They should be thinking about their grandchildren and the world that those children are going to get left with , '' he said . `` People need to let their government know , let their representatives know , that they are very concerned about this issue and they are going to hold their representatives accountable for their actions . '' Besides being a call to action , Earth Day also continues to be a good opportunity for public education , he said . On April 22 , Richter says he 'll probably be speaking on campus about nuclear power , because Stanford students are interested in what happened in Japan and want to be assured that nuclear power is safe . Michael Vandenbergh , director of the Climate Change Research Network , says he hopes nuclear concerns do n't overshadow other pressing environmental issues that Americans should remember as Earth Day approaches . `` We have to continue to discuss climate change , because if we get that problem wrong , many of the other things we talk about in the environmental area wo n't matter , '' said Vandenbergh , who also teaches at Vanderbilt University Law School . Both professors were encouraged to see that their students -- although probably not as politically outspoken as their counterparts when Earth Day began in 1970 -- are anxious to learn as much as they can about being environmentally friendly . Everyone should realize the importance of doing his or her part to help improve the environment for future generations , Vandenbergh said . `` Sometimes , people focus on the upfront cost rather than on the net benefit , '' Vandenbergh said , referring to the price of more efficient cars , home weatherization products or new heating and cooling units for our houses . `` Individuals have a much larger role than they realize in both contributing to environmental problems and to the solutions . ''
Earth Day will be held on April 22 . A year ago , the environmental community was concerned about the Gulf oil spill . The issue of nuclear power is top of mind this year after the crisis in Japan . Experts say individuals can effect change in themselves , government .