What's Bubbling Up From Newtown Creek? Reached aboard a boat in Newtown Creek the other day, John Lipscomb of the advocacy group Riverkeeper described the water by phone. "It's this green-blue chalky color," he said. You're floating around and there are dead rats, condoms, and there's this stench of sewage - this sulphuric smell. Which goes a long way toward explaining why the city's Department of Environmental Protection has been pumping air into the four-mile-long waterway between Brooklyn and Queens for years in an effort to oxygenate its fetid waters. Oxygen levels are a crucial component of a water body's health. Yet the value of the aeration process has been called into question by a new study suggesting that stirring up polluted waters this way adds higher levels of harmful bacteria to the air. The researchers warn that this airborne bacterial plume could be damaging to the environment and to human health. Aeration increases circulation and improve the water's health. Along the creek's bottom, close to the Metropolitan Avenue Bridge, the Department of Environmental Protection has installed pipes that push columns of compressed air into the water for this purpose, said M. Elias Dueker, a postdoctoral researcher at the Lamont-Doherty Earth Observatory at Columbia University and the lead author on the study, for which Riverkeeper is a collaborator. "They're bubbling the creek from the bottom -- the technique is borrowed directly from waste treatment plants," he said. It's just one more element in the city's multibillion-dollar investment in infrastructure intended to reduce the impact of combined sewer overflows, according to the Department of Environmental Protection. (The aeration is unrelated to the 2010 decision by the Environmental Protection Agency to designate Newtown Creek as a toxic Superfund site that will undergo an arduous cleanup. Preparatory field sampling for the cleanup began last year.) The researchers set out to compare the relative levels of invisible fallout - the settling of matter that circulates in the air -- by taking air samples when the creek's aerators were on and when they were off, The team placed petri dishes on a patrol boat in the creek so they could capture the matter driven upward by bubbles that burst at the water's surface. They found that while the amount of general fallout was the same whether the aerators were on or off, the content was different when they were on. Not only were there were much higher levels of particulate matter, but higher levels of bacteria associated with the sewage and oil in the water, they said. "When the bubbles are released and travel to the surface, they are actually gathering bacteria as they go," Dr. Dueker said. And when they burst at the surface, they eject the material that was around the bubble into the air. While the finding, published in the journal Environmental Science and Technology, is not altogether surprising, the researchers are urging the city's environmental regulators to consider the possibility that the air pollution is a tangible threat to public health. Gregory O'Mullan, an assistant professor and microbiologist at Queens College who is one of the report's authors, said that if the bacteria existed in high concentrations in the air, it could potentially cause respiratory or gastrointestinal illness. "This raises the potential that water quality may not just be something that people who swim or wade or fish should be concerned about," Dr. O'Mullan said. It may be something that people who live along water bodies should be concerned about, too. The Department of Environmental Protection said this week that studies by the federal Occupational Health and Safety Administration indicate that there are no adverse health risks for workers at wastewater treatment plants, where sewage levels are far higher than in Newtown Creek. "We're always welcoming new scientific evidence, and we'll review this study and determine if any further steps are warranted," a spokesman said.