Hundreds of barrels of all types and all colors - filled with everything from discarded lithium batteries and oil filters to powerful chemicals such as hydrochloric acid - are stacked in a dusty compound on a U.S. base at Tikrit, north of Baghdad.

This and a sister facility on another base have so far processed 32 million pounds of "regulated" waste - more than half of it soil contaminated with petroleum products. The material has been decontaminated, crushed or shredded, and then sold as scrap in Iraq, or recycled and shipped abroad.

"We don't use the word 'hazardous', because in Arabic that translates into chemical, biological, and nuclear waste," U.S. military spokesman Maj. Gen. Stephen Lanza said during a tour of the site.

"Everything we do here, as we process these materials, is so there is no adverse effect on Iraqis. No materials are left behind," said Lanza. "This highlights how we are not only good stewards here, but our relations with the Iraqi people."

The official tour, which included Iraqi government officials, was part of an effort to dispel perceptions among Iraqis that the seven-years occupation by American troops, who once numbered more than 170,000, has left behind tons of waste at hundreds of bases that are now being handed over to the Iraqis. U.S. troop strength is to drop to 50,000 by Sept. 1.

The U.S. military has been stung by recent news reports that portrayed a profligate dumping of hazardous materials, in violation of Pentagon rules. The Times (of London) reported that "open acid canisters sit within easy reach of children, and discarded batteries lie close to irrigated farmland."

The Times did not give details of those two cases. But it did quote a Fallujah scrap dealer with blistered skin on his legs and hands, saying: "I got this when I worked on what was supposed to be American scrap metal." The dealer said a doctor told him "these are the effects of dangerous chemicals."

U.S. officials say they've sought to locate such sites, but also insist that the military has been largely effective in collecting most of the hazardous material created or found since 2003 at 14 sites around the country. The waste was further consolidated in mid-2009, after the completion of the two facilities at Tikrit's Camp Speicher, 95 miles north of Baghdad, and at Al Asad Airbase, 100 miles to the west of the capital.

"Everything is done here to U.S. standards," said Bradley Banker, the manager for both sites for the past year whose employer, URS Corporation of San Francisco, handles engineering jobs as diverse as U.S. government hydroelectric and nuclear power plants to managing infrastructure of NASA's Kennedy Space Center. Banker himself was a school teacher in Bangkok for nearly a year before assuming his current job. Before that, he worked on oil pipeline and platforms in Nigeria.

"Everything we do here could be moved to America, and we would be up to standard in America," Banker said.

Some barrels are packed with used batteries, others are labeled with triangular "Hazardous Waste" warning stickers, with words scrawled across them like "Paint Related Waste," "Resin - Flammable," and "Used Oil Filters."

Two drums have Cyrillic lettering on them, left over from Iraq's close relationship with the Soviets in the 1970s. Also collected and disposed of was a 1950s-era gallon jug of a toxic cyanide-based pesticide - with dangerous instructions, said Banker, to sprinkle by hand and then simply wash hands afterwards.

"Anything we found in Iraq was brought here for treatment," said Banker.

Iraqi officials with their first access to such a treatment site took photographs of the barrels and their labels, the wooden rinsing rack, the evaporation ponds where acids are neutralized and turned into salt, and the nearby $15 million incinerator for burning everything from grease to solvents.

In open spaces nearby, sprinklers sprayed water to keep alive microbes that were slowly - in a three- to six-month cycle - eating petroleum products in contaminated soil that had been spread out in the sun.

"You cannot feel safe through one visit to one site. This site ... is reassuring, but what about the rest of the sites?" asked Hikmat Gabriel Gorgees, an engineer in charge of planning with Iraq's environment ministry. Two Iraqi committees have been set up to investigate the scale of the problem and the U.S. handling of hazardous wastes.

The ministry had read the news reports about U.S. dumping. "We have heard about them but never seen them by our own eyes," said Gorgees. "This is the first site being visited by environment ministry teams, we have not seen the rest, but the Americans have opened all doors for us, plus we did ask them to allow us to take samples, soil samples, underground water samples."

An Iraqi Ministry of Defense spokesman, Mohammed al Askari, stood before television cameras at the site and sought to reassure Iraqis. "Understand that these are war leftovers, and we are making efforts to keep them away from people," he said.

Reports of "regulated waste being left all over the countryside" also prompted the U.S. military to investigate - and then to counter the claims, said Army Brig. Gen. Kendall Cox, the U.S. commander in charge of engineering in  Iraq.

"The intent was to insure, through the media ... there's a clear understanding that we are taking every measure possible ... to protect the environment and treat all regulated waste and materials appropriately," he said.

"We have a very systematic process in place to receive materials, treat them and dispose of them properly," he added. "We haven't identified any problems with our processes. What we did identify is potentially there are contractors who aren't dealing with their regulated waste properly."