Before 2019, an estimated 500 million plastic straws (吸管) were used in the U.S. alone every single day, according to the National Geographic. Since then, they have been banned in numerous states, encouraging many businesses to offer paper alternatives in an attempt to cut plastic waste.

But, according to a new study, published in the journal Food Additives and Contaminants, these straws come with their own problems.

“Straws made from plant-based materials, such as paper and bamboo, are often advertised as being more sustainable and eco-friendly than those made from plastic,” Thimo Groffen, an environmental scientist at the University of Antwerp in Belgium who is involved in the study, said in a statement. “However, the presence of PFAS (全氟和多氟烷基物质) in these straws means that’s not necessarily true.” After analyzing 39 different brands, Groffen and his team found that paper straws were more likely to contain toxic-forever chemicals than those using other materials.

These forever chemicals, known as PFAS, can be found in a range of everyday products. And they can lead to increased blood cholesterol and blood pressure, reduced immunity and an increased risk of certain cancers. Not only are these chemicals dangerous to human health, but they can build up in the environment too.

Of the brands tested, 90 percent of paper straws contained these chemicals, compared to 75 percent made of plastic and 40 percent of glass. They were not detected in any of the steel straws investigated.

The study did not test whether the PFAS could leach out into (浸入) the surrounding liquid so further tests are needed to determine the full impact of these products. While more work is needed, the study has highlighted that paper and bamboo straws are perhaps not as “clean” as they claim to be.

As warming continues, scientists warn the oxygen content of oceans across the planet could be more and more reduced, with serious consequences for the future of fish and other sea life.

【小题1】. One is the simple fact that as water gets warmer, it can hold less dissolved(溶解的)oxygen. The other reason is less obvious.【小题2】—either from the atmosphere, or from photosynthesizing algae floating at the top of the sea. The oxygen then spreads to the deep ocean as the surface water slowly sinks.

Global warming is expected to reduce the mixing of the ocean by making surface seawater lighter. That's because in a warmer world we can expect more rainfall and more melting of glaciers, icebergs, and ice sheets.【小题3】.The extra heat from the warming atmosphere will also make surface water expand and thus make it lighter still.【小题4】. Instead, more of the oxygen will remain near the surface, where it will be used up by oxygen-breathing organisms.

A low-oxygen ocean may become an inescapable feature of our planet. A team of Danish researchers wondered how long oxygen levels would drop if we could somehow reduce our carbon dioxide emissions to zero by 2100. They determined that over the next few thousand years oxygen levels would continue to fall, until they declined by 30 percent. The oxygen would slowly return to the oceans, but even 100,000 years from now they will not have fully recovered.【小题5】

What would you think is the most plentiful man-made material on earth? Steel, plastic, glass? The answer is concrete.

And while it’s an incredibly useful material existing everywhere, the energy intensive process of making concrete releases massive amounts of CO₂ into the atmosphere, and its main component, which is a mixture of rocks, sand, water and most importantly, cement (水泥) to glue it altogether, is responsible for 7 percent of global CO₂ emissions, leaving a huge carbon footprint. But without cement, concrete doesn’t hold up skyscrapers.

What if there was a way that instead of releasing carbon dioxide, concrete could trap it forever? Carbon Cure is kind of the brains of the technology. This innovation puts carbon dioxide into the concrete as it’s being mixed. When the concrete hardens, those otherwise harmful emissions are trapped forever, before they even reach our atmosphere. Christie Gamble, part of the team behind Carbon Cure’s technology, explained ,“ We actually transform the CO₂ into a mineral, and the real selling point is that the mineral itself improves the compressive (压缩的) strength for the concrete, which means producers like Thomas Concrete can use less cement in their mixtures and still achieve the same strength with fewer emissions.

Compression tests prove that the concrete made with Carbon Cure is just as hardy as the traditional stuff. If we can reduce 5 percent of the carbon footprint of the concrete industry, that’s a significant change from where we’re right now. Ultimately, if this technology was employed across the globe, we could reduce about 700 megatons of CO₂ every year, which is the same as taking 150 million cars off the road every year.

It’s going to change the way the concrete industry does things. Though companies pay to use Carbon Cure and buy CO₂ from a factory, they save money by using less of their most expensive cement.