Data collected by the U.S. Environmental Protection Agency (EPA) shows the federal agency is struggling to safeguard or assess the potential health hazards of some 20 percent of America's Superfund sites, the worst hazardous waste sites in the nation.
Seventy million people, including some 10 million children, live within four miles of the nation's more than 1,230 Superfund sites.
Children are most vulnerable to the dozens of toxic chemicals including arsenic, DDT, lead and mercury that are found in the water and soil at these locations.
EPA data shows human exposure to these health threatening chemicals is not under control at some 111 Superfund sites and migration of groundwater pollution is not under control at 251 sites.
At hundreds of other sites, the EPA lacks sufficient data to determine if human exposure and migration of groundwater pollution are under control.
A report released Tuesday by the Sierra Club, a vocal and persistent critic of the Bush administration, says the data shows the program is faltering for lack of funds and commitment from the White House.
"This report makes clear that Superfund sites are toxic threats to Americans' health and that the Bush administration is failing to address this problem," said the report's author Ed Hopkins, environmental quality program director with the Sierra Club.
The Sierra Club says almost all of these sites are funded in whole or part by the Superfund trust fund and it blames the Bush administration for allowing the financial burden of the Superfund program to shift from polluters to U.S. taxpayers.

Some 85 percent of all Superfund sites have contaminated groundwater. (Photo courtesy U.S. Army Corps of Engineers)
"Our complaint is with the Bush administration for failing to renew the polluter pays principle and to fund the program," Hopkins said. "Without an effective funding mechanism for Superfund cleanups, dangerous chemicals will continue to seep into our air, water, and soil."
Agency officials contend the environmental group's study is misleading.
EPA Press Secretary Cynthia Bergman said in a statement that the Sierra Club "has mischaracterized EPA data and repackaged it with discredited funding myths about the Superfund program resulting in a misleading picture of the Superfund program."
It is unfair to infer that sites listed in the EPA's environmental indicators database represent actual exposure to toxic waste, Bergman said, and the Sierra Club overstates the importance of the Superfund trust fund.
Funding has been a controversial issue for the Superfund program since its inception - and few would argue the problem is daunting.
Started in 1980 as a relatively short-term project to clean up abandoned hazardous waste sites, the program has expanded as tens of thousands of waste sites have been discovered.
Many of these sites are owned by the federal government, and cleaning them up has proved to be far more complicated and costly than anticipated.

Cleaning up Superfund sites is often a long and costly process. (Photo courtesy U.S. Army Corps of Engineers)
But the sites that are not owned by the federal government are to either be cleaned up by the private parties responsible for contamination or by the EPA, which is then tasked with seeking reimbursement from those responsible.
Congress created a trust fund to pay for cleanups of non-government sites and devised "polluter pays fees" to fund it.
These fees consisted of a corporate tax that applies to profits of large corporations in excess of $2 million, a fee on the purchase of harmful chemicals and a fee on the purchase of crude oil by refineries.
But the polluter pays provision expired in 1995 when it was at a historic high of some $3.6 billion. President Bill Clinton requested a renewal of the provision but was denied by Congress.
President George W. Bush is the first president not to request the continuation of the polluter pays provision. Administration officials say the fees should not be reinstated unless industry friendly reforms of cleanup standards and polluters' liabilities are enacted.
Democratic presidential nominee John Kerry has pledged his support for the reinstatement of the polluters pays tax, but Congress has rejected renewal of the tax several times in recent years.
The trust fund is now empty of fees paid in by polluters, forcing the government to pay entirely for future Superfund cleanup.
This has happened against a backdrop of tight and declining budgets for the program.
A report released in February by the U.S. Government Accountability Office (GAO) - the investigative arm of Congress formerly known as the General Accounting Office - found appropriations for the Superfund program, when adjusted for inflation, have fallen some 35 percent or $633 million since 1993.
According to the GAO, funding for clean up of Superfund sites has fallen from more than $1.9 billion in 1993 to some $1.2 billion in 2004 in inflation adjusted dollars.
"Underfunding cleanup of America's toxic waste sites is yet another example of corporations trumping public health and safety under the Bush Administration's watch," said Hopkins. "Americans are paying twice: once with their health and again with their taxes."

This McDonalds restaurant now stands on the former Luminous Processors Superfund site in Athens, Georgia where crews remediated radioactive contamination in 1982. (Photo courtesy EPA)
Critics say the drop in funding is having a direct impact on cleanup.
In the mid and late 1990s, Superfund cleaned up an average of 86 sites per year, but this number has since fallen by more than 50 percent in the last two years.
The EPA completed work at only 40 sites in fiscal year 2003, compared to the 87 achieved in the last year of the Clinton administration.
Administration officials say such comparisons are misleading because the agency is now focused on larger, more complex and costlier Superfund sites.
They contend the budget for the Superfund program goes to much more than just cleanup, including emergency removals, site assessment, site cleanup, enforcement, and administration.
A study by the nonprofit research group Resources for the Future (RFF) says the Superfund program needs annual funding of between $1.4 billion to $1.7 billion.
Using these figures, critics say the Bush administration has under funded the Superfund program by some $1.2 billion to $1.8 billion from 2001 through 2004.
Reinstating the Superfund polluter-pays taxes would generate more than $14 billion over the next 10 years, which meets the low estimate of cleanup costs for the next decade, according to RFF.
Critics ignore the fact that the Superfund program has to compete with other agency programs for congressional funding, Bergman says, and "simply reinstating lapsed Superfund taxes would not necessarily provide an increase in annual congressional Superfund appropriations."