Levels of Fluorinated Compounds
Levels of a widely used class of industrial chemicals linked with cancer and other health problems – polyfluoroalkyl and perfluoroalkyl substances (PFASs) – exceed federally recommended safety levels in public drinking water supplies for six million people in the U.S., according to a new study led by researchers from Harvard T.H. Chan School of Public Health and the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS).
The study will be published August 9, 2016 in Environmental Science & Technology Letters.
"For many years, chemicals with unknown toxicities, such as PFASs, were allowed to be used and released to the environment, and we now have to face the severe consequences," said lead author Xindi Hu, a doctoral student in the Department of Environmental Health at Harvard Chan School and Environmental Science and Engineering at SEAS. "In addition, the actual number of people exposed may be even higher than our study found, because government data for levels of these compounds in drinking water is lacking for almost a third of the U.S. population – about 100 million people."
PFASs have been used over the past 60 years in industrial and commercial products ranging from food wrappers to clothing to pots and pans. They have been linked with cancer, hormone disruption, high cholesterol, and obesity. Although several major manufacturers have discontinued the use of some PFASs, the chemicals continue to persist in people and wildlife. Drinking water is one of the main routes through which people can be expo.
Flooded Canyons on Saturn's Moon
NASA's Cassini spacecraft has found deep, steep-sided canyons on Saturn's moon Titan that are flooded with liquid hydrocarbons. The finding represents the first direct evidence of the presence of liquid-filled channels on Titan, as well as the first observation of canyons hundreds of meters deep.
A new paper in the journal Geophysical Research Letters describes how scientists analyzed Cassini data from a close pass the spacecraft made over Titan in May 2013. During the flyby, Cassini's radar instrument focused on channels that branch out from the large, northern sea Ligeia Mare.
The Cassini observations reveal that the channels – in particular, a network of them named Vid Flumina – are narrow canyons, generally less than half a mile (a bit less than a kilometer) wide, with slopes steeper than 40 degrees. The canyons also are quite deep – those measured are 790 to 1,870 feet (240 to 570 meters) from top to bottom.
The branching channels appear dark in radar images, much like Titan's methane-rich seas. This suggested to scientists that the channels might also be filled with liquid, but a direct detection had not been made until now. Previously it wasn't clear if the dark material was liquid or merely saturated sediment – which at Titan's frigid temperatures would be made of ice, not rock.
Cassini's radar is often used as an imager, providing a window to peer through the dense haze that surrounds Titan to reveal the surface below. But during this pass, the radar was used as an altimeter, sending pings of radio waves to the moon's surface to measure the height of features there. The researchers combined the altimetry data with previous radar images of the region to make their discovery.