Should the hundreds of thousands of New Orleans residents still displaced by Hurricane Katrina listen to the “all-clear” messages and return home? In a special March/April 2006 post-hurricane package, E – The Environmental Magazine reports on independent testing, which reveals that significant, toxic threats to human health still remain.

The report also shows that the Bush administration — recently revealed to have seriously delayed its initial response to the crisis despite knowing that levees had broken and the city was flooding — is now drastically underfunding the environmental cleanup, with the media spotlight having long ago moved on.

Last December, an Environmental Protection Agency (EPA) advisory assured residents that most samples taken in the previous two months showed chemical concentrations “below acceptable levels.” The EPA doesn’t say whether it’s safe for residents to move back to New Orleans.

So how worried should people be, as they contemplate moving back to the Big Easy? Environmental consultant and chemist Wilma Subra says they should be very worried indeed. The big problem, she said, is sediment that had been sitting at the bottom of rivers and other water bodies collecting industrial chemical contamination and agricultural runoff from nearby industry. The sediment was relatively harmless sitting undisturbed, but it did not stay put and was deposited all over New Orleans by Katrina.

Subra’s own tests, conducted at 33 locations in Louisiana, Mississippi and Alabama for the Sierra Club and the Natural Resources Defense Council, showed especially elevated levels of arsenic, but also high amounts of lead, dioxin, chromium and other hazardous substances well above safe standards. The EPA’s results were radically different, she says, because they’re based on the extremely relaxed state standards.

The EPA warns New Orleans residents to avoid contact with the sediment, but Subra says that it has now become airborne and would be very difficult to avoid even if residents had access to the protective clothing, respirators and gloves the environmental agency recommends (but doesn’t provide). The worst danger from the sediment is in New Orleans’ poorest neighborhoods. According to the Brookings Institution, 38 of the city’s 49 poorest districts were flooded. And 80 percent of the neighborhoods under water had non-white majorities.

Southeast Louisiana was an environmental nightmare before Katrina. “Cancer Alley,” as the stretch of the Mississippi between New Orleans and Baton Rouge is called, has more than 100 polluting chemical plants, oil refineries and other industries routinely sending their waste discharge downwind or downstream, mostly into neighborhoods that are both black and poor.

“We’re seeing what’s called the ‘Katrina cough,’ ” says Mary Lee Orr, executive director of the Louisiana Environmental Action Network. “There are a lot of respiratory illnesses. And especially among people who have been in the flood waters, we’re seeing skin infections that don’t respond to normal antibiotic treatment.”

Dita McCarthy, whose 15-year-old daughter is temporarily attending classes at DeLisle Elementary School in Harrison County, Miss., (where unsafe arsenic levels were found in Subra’s tests), says she’s seen “clouds of dust” that the kids walk through on their way to classes. “We thought it looked like the Dust Bowl, and we thought it was funny,” she says. “But then we heard about the arsenic and it wasn’t so amusing. There really needs to be more testing.”