Fixing planet plastic: How we’ll really solve our waste problem

plastic bags

Stephen Wilkes/Gallery Stock

BY NOW, it is just a question of which heart-rending image you choose. There is the hawksbill turtle struggling to free itself from a plastic bag. The sea of polystyrene trash floating over a Caribbean nature reserve. Or the sperm whale washed ashore in Spain, its stomach filled with plastic waste.

Since the introduction of mass-produced plastics in the early 20th century, humanity has produced an estimated 8300 million tonnes of the stuff. Around three-quarters has been thrown away, and 80 per cent of that has drifted into the environment or gone into landfill. Eight million tonnes a year end up in the ocean – 5 trillion pieces and counting.

It is an environmental catastrophe and a human one, too, as some people in parts of the developing world live ankle-deep in filthy, non-biodegrading plastic trash. The long-term health implications for all of us remain uncertain, as ingested plastic works its way up the food chain.

Everyone agrees something must be done. From banning plastic straws to rebooting recycling systems to harnessing plastic-munching bacteria, there is no shortage of touted solutions. It is less clear what would work best. But fixing the plastic waste crisis is going to take some seriously joined-up thinking. If we make the wrong decisions now, we risk making the problem worse.

If plastics didn’t exist, we would have to invent them. Generally made of oil-derived polymers, they can be hung with different chemical groups and spiced up with additives to give them wildly differing properties such as hardness, strength, density and heat-resistance. This makes them just the thing for everything from colourful, durable kids’ toys …

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How can India clean up when all of its waste has an afterlife?

waste pile

Families defend their inherited rights to jobs picking over rubbish

Reuters/Ahmad Masood

“WHY is India so filthy?” asks a new book called Waste of a Nation. It wasn’t always – in the old days of rural India, almost everything was biodegradable. Animals and the weather soon dealt with it. Now garbage is everywhere: in backyards, on street corners and piled up across wasteland.

waste

True, the country is crowded. India has almost as many people as China, living in a third of the area. “Never in history have so many people had so much to throw away, and …

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Precise carries waste quite a lot of their own strength or potentially a dilemma

A polar bear with a GPS-video collar

A polar bear with a GPS-video collar

Maria Spriggs, Busch Gardens

Being a polar bear is harder work than biologists thought. As the bears roam the Arctic sea ice hunting seals, they use more energy than expected. That has ominous implications for a future in which sea ice is ever scarcer.

Anthony Pagano of the US Geological Survey in Anchorage, Alaska, and his colleagues studied 9 adult female polar bears on the Beaufort Sea ice north of Alaska. They fitted the bears with collars carrying GPS trackers, accelerometers and video cameras. They also injected the bears with water labelled with stable isotopes of hydrogen and oxygen.

When the team recaptured the bears 8 to 11 days later, changes in the ratio of isotopes in their blood gave a measure of metabolic rate. The researchers could compare this with the bears’ activity and hunting success.

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Researchers already knew that polar bears are inefficient walkers, but many assumed that they also saved energy by sitting quietly waiting for seals, and by reducing their metabolic rate when fasting. However, it seems these savings are small at best. The bears’ average metabolic rate during the study period was 1.6 times more than most previous estimates.

Not so thrifty

This means the bears must kill and eat more seals over the course of a year, to pay for this higher metabolic rate.

But as climate change melts ever more sea ice, the bears are likely to have to walk farther to find prey. “That has a cost, and the animal has to find the energy to do that – or take it out of growth, reproduction, or survival,” says polar bear biologist Andrew Derocher at the University of Alberta in Edmonton, Canada.

Though Pagano’s study focuses on just one population of polar bears, many of the other populations around the Arctic likely face the same challenges, says Derocher.

Journal reference: Science, DOI: 10.1126/science.aan8677

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Tasty tomatoes could be sacrificed in drive to cut food waste

Solitary tomato in fridge

Out in the cold

age fotostock/Alamy

Tomayto, tomahto – we’ve long agreed to disagree on pronunciation, but the debate on where to store them is just heating up. Yesterday, new guidelines on food labelling aimed at reducing waste were published in the UK. The most eye-catching recommendation was that consumers should be advised to keep fruit and vegetables refrigerated below 5°C. Potatoes, onions, pineapples and bananas are exceptions to the rule – but not tomatoes.

Food writer Jay Rayner called the advice “bizarre” on Twitter. “Every minute a tomato spends in a fridge it dies a little,” one of his followers replied.

There is some truth in that. Last year, a study found that chilling reduces the activity of hundreds of tomato genes, some of which produce enzymes that contribute to flavour. These enzymes don’t recover when tomatoes return to room temperature, and taste tests found that people

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New Study Reveals Breast Cancer Cells Recycle Their Own Ammonia Waste as Fuel

Repressing ammonia metabolism stunts tumor growth in mice, findings may inform the design of new therapies

 Article ID: 683421 Released: 18-Oct-2017 5:00 PM EDT

Source Newsroom: Harvard Medical School

Newswise — Breast cancer cells recycle ammonia, a waste byproduct of cell metabolism, and use it as a source of nitrogen to fuel tumor growth, report scientists from Harvard Medical School in the journal Science.

The findings, published online ahead of print on Oct. 12, show that the presence of ammonia accelerates proliferation of cultured breast cancer cells, while suppressing ammonia metabolism can stunt tumor growth in mice.

The insights shed light on the biological role of ammonia in cancer and may inform the design of new therapeutic strategies to slow tumor growth, the researchers said.

“Classically, ammonia was thought to be metabolic waste that must be cleared due to its high toxicity,” said senior study author Marcia Haigis, associate professor of cell biology at HMS. “We found that not only was ammonia not toxic for breast cancer cells, it could be used to feed tumors by serving as a source for the building blocks that tumors need to grow.”

Rapidly growing cells, particularly cancer cells, consume nutrients voraciously and generate excess metabolic waste. One such byproduct, ammonia, is normally transported in blood vessels to the liver, where it is converted into less toxic substances and excreted from the body as urea. Tumors, however, have few blood vessels, and as a result, ammonia accumulates in the tumor’s local environment at concentrations that would be toxic for many cells.

Tracing Fate

To investigate how tumors cope with high levels of ammonia, Haigis and her colleagues used a technique to label the nitrogen on glutamine. When glutamine is broken down during cell metabolism, ammonia containing labeled nitrogen is released as a byproduct.

Tracing the fate of this marked ammonia, the researchers analyzed more than 200 different cellular metabolites in breast cancer cells and in human tumors transplanted into mice.

They found cancer cells recycled ammonia with high efficiency, incorporating it into numerous components—primarily the amino acid glutamate, a fundamental building block for proteins, as well as its derivatives. Around 20 percent of the cellular glutamate pool contained recycled nitrogen.

Higher concentrations of ammonia appeared to accelerate the growth of lab-grown breast cancer cells. Ammonia-exposed cells doubled up seven hours faster than cells grown without ammonia. In 3-D cultures—a technique that allows cells to divide in all directions as they do inside the body—ammonia exposure increased the number of cells and surface area of cell clusters by up to 50 percent compared with cells grown without ammonia.

Ammonia also accelerated tumor growth and proliferation in mice with transplanted human breast cancer. When the team blocked the activity of glutamate dehydrogenase (GDH)—an enzyme that specifically assimilates ammonia to carry out its function—tumor growth slowed significantly compared to tumors with intact GDH activity.

“We found that repressing ammonia metabolism stunts tumor growth in mice,” said Jessica Spinelli, a graduate student in the Haigis lab and first author on the study. “Therefore, inhibition of ammonia assimilation or ammonia production may be rational strategies for therapy design.”

The team’s findings indicate that the biological role of ammonia should be reevaluated, laying the foundation for the investigation of new approaches to block tumor growth by depriving tumors of essential nutrients. The researchers are now exploring the therapeutic implications of ammonia metabolism in cancer.

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Additional authors on the study include Haejin Yoon and Alison Ringel, who are both postdoctoral researchers in the Haigis lab, as well as Sarah Jeanfavre, research associate, and Clary Clish, director of the Metabolomics Platform, at the Broad Institute of MIT and Harvard.

The study was supported by the Ludwig Center at Harvard, Glenn Foundation for Medical Research, National Institutes of Health (R01CA213062) and National Science Foundation Graduate Research Fellowship Program.

Relevant disclosures: Haigis and Spinelli are inventors on patent application HMV- 27560 submitted by Harvard Medical School that covers ammonia utilization in cancer.

About Harvard Medical School

Harvard Medical School (http://hms.harvard.edu) has more than 11,000 faculty working in 10 academic departments located at the School’s Boston campus or in hospital-based clinical departments at 15 Harvard-affiliated teaching hospitals and research institutes: Beth Israel Deaconess Medical Center, Boston Children’s Hospital, Brigham and Women’s Hospital, Cambridge Health Alliance, Dana-Farber Cancer Institute, Harvard Pilgrim Health Care Institute, Hebrew SeniorLife, Joslin Diabetes Center, Judge Baker Children’s Center, Massachusetts Eye and Ear/Schepens Eye Research Institute, Massachusetts General Hospital, McLean Hospital, Mount Auburn Hospital, Spaulding Rehabilitation Network and VA Boston Healthcare System.

Newswise: SciNews