Thousands of hurricane survivors who spent hours trapped in or wading through floodwaters likely exposed themselves to a wide range of bacteria and other contaminants.
Microbiologist Paul Pearce found total sewage bacteria in a water sample from in New Orleans' Ninth Ward to be 45,000 times what would be considered safe for swimming in a pond or a lake. The Ninth Ward was one of the city's hardest-hit neighborhoods.
"In terms of total microorganisms in floodwater, this is about as bad as it can get," Pearce told ABC News. Pearce also found 2.2 million parts per unit of human waste bacteria in the floodwater, which is off the charts.
On "Good Morning America," Pearce demonstrated at Nova Biologicals lab in Conroe, Texas, how polluted water glows under a black light. He first sampled normal pond water -- the light barely glowing, indicating slight contamination. He then examined the floodwater, which fully lit up, a clear sign that the water was loaded with bacteria, according to Pearce.
The precise extent of the contamination is not yet known. Louisiana's chief environmental officer today said there is no evidence yet that the New Orleans waterways are a toxic wasteland. He acknowledged the presence of fecal matter, fuel, oil and other contaminants, but said testing had not detected traces of truly toxic substances like pesticides and metals. A full analysis is expected in two days.
Nonetheless, officials are advising people in the region to avoid all contact with the trash-laden, brown water flowing through the city.
"The health problems associated with sewage contamination and specifically with these types of organisms can be gastrointestinal problems, dysentery, diarrhea," Pearce said. He also found low levels of what appears to be the bacteria associated with cholera and salmonella.
Pearce stressed that simply coming into contact with the floodwater could be enough to make a person sick. Drinking the water should be out of the question.
However, some said they had little choice but to be exposed to the fetid waters. One woman, who was walking through the water, said anything was better than her time spent living in the Superdome, which had by the end of last week turned into a chaotic location strewn with garbage and human waste that evacuees were desperate to leave.
"If I had a choice to be in the water or in the dome it would be the water," said Connie Craig.
And although food, fresh water and support have started trickling in New Orleans, Pearce fears that the huge amount of sewage contamination may cause problems long after the floodwaters recede.
"Just because the water's gone does not mean the contaminating bacteria are gone," Pearce said.
Dr. Nancy Snyderman contributed this report for Good Morning America.