Sunscreen has been on the shelves of drugstores since the mid-1940s. And while new kinds of sunscreens have come out, some of the active ingredients in them have yet to be determined as safe and effective. A recent study conducted by the FDA showed that the active ingredients of four commercially available sunscreens were absorbed into the bloodstream—even days after a person stops using it. Ira talks to professor of dermatology and editor in chief of the Journal of the American Medical Association Dermatology Kanade Shinkai about what the next steps are for sunscreen testing and what consumers should do in the meantime. Often called the planet’s lungs, the trees of the Amazon rainforest suck up a quarter of Earth’s carbon and produce a fifth of the world’s oxygen. The National Institute for Space Research in Brazil has been using satellite images of tree cover to monitor the Amazon’s deforestation since the 1970s—and new data shows a potentially dangerous spike in deforestation. In the first seven months of 2019, the rainforest lost 50% more trees than during the same period last year. That spike in tree loss has coincided with Brazil’s new president, Jair Bolsanaro, taking office in January and slashing environmental protections. Bolsanaro even called the new data a lie. But climate scientists warn deforestation is pushing the Amazon rainforest to a tipping point that would disrupt both its ecosystem and the global climate. Ira talks to Carlos Nobre, a climate scientist at the University of Sao Paulo’s Institute of Advanced Studies, about the new data and why deforestation in the Amazon is so risky for the planet. When you think of algae, one of the first images that might come to mind is the green, fluffy stuff that takes over your fish tank when it needs cleaning, or maybe the ropy seaweed that washes up on the beach. But the diversity of the group of photosynthetic organisms is vast—ranging from small cyanobacteria to lichens to multicellular mats of seaweed. Author Ruth Kassinger calls algae “the most powerful organisms on the planet.” She talks about how this ancient group of organisms produces at least 50% of the oxygen on Earth, and how people are trying to harness algae as a food source, alternative fuel, and even a way to make cows burp less methane. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

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