In an about face, the government Tuesday disavowed a 12-year-old federal report that found little or no cancer risk for adults who lived on a Marine base where drinking water was contaminated for three decades.

Up to 1 million people could have been exposed to toxins that seeped from a neighboring dry cleaner and industrial activity at Camp Lejeune, North Carolina, federal officials say. Now, a report that minimized the cancer threat for adults has been discredited.

"We can no longer stand behind the accuracy of the information in that document," William Cibulas, director of health assessment for the Agency for Toxic Substances and Disease Registry, said at a meeting in Atlanta. "We know too much now."

Sick veterans, who became known as "poisoned patriots," and their advocates never believed the report's conclusions. Their families have filed claims for $33.8 billion in damages. A study continues on whether fetuses might have been harmed.

The agency, charged with protecting public health around toxic sites, said it was rescinding the 1997 assessment on health effects of water that residents of the base drank and bathed in, because of omissions and scientific inaccuracy. That study found the water contamination began in the 1950s and continued until wells were shut down in 1987.

Jerry Ensminger, a retired Marine who has spent years digging through military and health documents at Camp Lejeune and believes his daughter Janey's leukemia death at age 9 was due to the water, welcomed the government's reversal on the report.

"We are in Day 99 of change, and by God we're starting to see it," he said, meaning the change promised by President Barack Obama. The report in question dates to Bill Clinton's administration.

The flawed document is being pulled from the Internet while the agency incorporates new science to rewrite what Cibulas called "troublesome" sections.

Among its problems, the document omitted mention of the cancer-causing chemical benzene, which military sampling found in a base well in 1984. Researchers should have mentioned its high levels and tried to verify whether it reached the drinking water, said Cibulas. He said Ensminger recently brought the omission of benzene to his attention.

Additionally, the contaminating solvents that officials focused on have been characterized by new science as even more likely to cause cancer, he noted.

Cibulas also cited findings, reported in a 2007 Associated Press investigation of the water contamination, that the study underestimated the extent of the contamination on the base due to inadequate information from the Marines.

His unusual announcement came at a meeting of the health agency, part of the Health and Human Services Department, and its community advisory panel that works on follow-up to Camp Lejeune's past water problems.

Members of the panel have long criticized the health document's failings. Lawmakers who heard the Marines' stories last year dubbed them "poisoned patriots."

A table in the document stated unequivocally that adults faced no increased cancer risk from the water. Elsewhere, the report said cancer was not likely but more study was needed.

The agency estimated as many as 1 million people at the East Coast base could have been exposed to the toxins; the Marines have estimated 500,000.

According to the Navy's legal office, which handles claims, 1,500 people have filed claims for $33.8 billion in damages. The military is waiting for conclusions from the current study of fetal effects before deciding the claims.