Greenpeace is holding more than 160 candlelight vigils across the United States today to show support for the people of Japan as they continue to deal with the impacts of the March 11 earthquake, tsunami and still-unfolding crisis at the Fukushima nuclear plant.

The actions come on the anniversary of the 1979 Three Mile Island nuclear accident in Pennsylvania, when a relatively minor problem in one of the plant's two reactors sparked a series of mishaps that led to the meltdown of almost half of the uranium fuel and uncontrolled releases of radiation into the air and surrounding Susquehanna River. Nuclear power experts say the disaster in Japan has long since passed the level of TMI, which research found led to increases in cancer in people living immediately downwind of the plant.

As Americans gather to hold candles and pray for the Japanese people, there will be an invisible presence at many of the vigils: the radioactive fallout from the crippled Fukushima plant, where radiation levels 100,000 times above normal have been reported.

Progress Energy has detected radioactive iodine believed to be from the Japanese disaster at its nuclear plants in North Carolina, South Carolina and Florida. In addition, the Environmental Protection Agency reports that radioactive iodine-131 has been found in rainwater in Pennsylvania and Massachusetts at levels exceeding the maximum limits permitted in drinking water. The agency also says it has received "verbal reports" of elevated radiation levels in rainwater samples from other states.

The EPA says the levels of radiation being detected are below levels of public-health concern. However, a 2005 report from the National Academy of Sciences found there is no safe dose of radiation, with any exposure producing a corresponding increase in cancer risk.

And radioactive iodine, which decays relatively quickly with a half-life of eight days, is not the only contaminant of concern from the Fukushima plant. Computer models by an Austrian meteorological institute show that emissions of radioactive cesium from the plant might already amount to 50 percent of what was released from the 1986 Chernobyl disaster in what is now Ukraine, the Los Angeles Times reported. Data modeling by Edwin Lyman, a physicist with the Union of Concerned Scientists, confirmed the Austrian analysis, according to the paper.

Cesium-137, which is water-soluble, has a half-life of 30 years. After entering the body through inhalation or ingestion, it's distributed throughout the soft tissues, especially muscle, exposing those tissues to radiation and increasing cancer risk.

Meanwhile, nuclear watchdogs in the U.S. are raising concerns about whether information on the Fukushima disaster is being withheld from the public. Last week Friends of the Earth, the Nuclear Information and Resource Service, and Physicians for Social Responsibility filed Freedom of Information Act requests with the Nuclear Regulatory Commission and Department of Energy for data that led to the NRC's March 16 call for a 50-mile evacuation radius for Americans near the Fukushima plant.

"The radiation monitoring information being collected by the U.S. government in Japan is of urgent interest to the public in the U.S. and internationally and we expect an expedited response to the FOIA request," says Tom Clements with Friends of Earth's South Carolina office. "If the full data set is not immediately released, the government can rightly be accused of attempting to cover up the radiation threat posed by the disaster."