In 2013, former NASA physicist Bonny Schumaker noted a "dearth of marine life" in a radius around the well, after flying over the area numerous times since May 2010. In 2013, researchers found that oil on the bottom of the seafloor did not seem to be degrading, and observed a phenomenon called a "dirty blizzard": oil in the water column began clumping around suspended sediments, and falling to the ocean floor in an "underwater rain of oily particles." The result could have long-term effects because oil could remain in the food chain for generations. A 2014 bluefin tuna study in "Science" found that oil already broken down by wave action and chemical dispersants was more toxic than fresh oil. A 2015 study of the relative toxicity of oil and dispersants to coral also found that the dispersants were more toxic than the oil. A 2015 study by the National Oceanic and Atmospheric Administration, published in "PLOS ONE," links the sharp increase in dolphin deaths to the "Deepwater Horizon" oil spill. On 12 April 2016, a research team reported that 88 percent of about 360 baby or stillborn dolphins within the spill area "had abnormal or under-developed lungs", compared to 15 percent in other areas. The study was published in the April 2016 " Diseases of Aquatic Organisms". By June 2010, 143 spill-exposure cases had been reported to the Louisiana Department of Health and Hospitals; 108 of those involved workers in the clean-up efforts, while 35 were reported by residents. Chemicals from the oil and dispersant are believed to be the cause; it is believed that the addition of dispersants made the oil more toxic. The United States Department of Health and Human Services set up the GuLF Study in June 2010 in response to these reports. The study is run by the National Institute of Environmental Health Sciences, and will last at least five years. Mike Robicheux, a Louisiana physician, described the situation as "the biggest public health crisis from a chemical poisoning in the history of this country." In July, after testing the blood of BP cleanup workers and residents in Louisiana, Mississippi, Alabama, and Florida for volatile organic compounds, environmental scientist Wilma Subra said she was "finding amounts 5 to 10 times in excess of the 95th percentile"; she said that "the presence of these chemicals in the blood indicates exposure." Riki Ott, a marine toxicologist with experience of the Exxon Valdez oil spill, advised families to evacuate the Gulf. She said that workers from the Valdez spill had suffered long-term health consequences.