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Daily Archives: August 21, 2022

Charts: U.S. Rent Is Moving Higher at the Highest Pace in Three Decades

Source : CoreLogic and RealPage

Humour: News in Cartoons

Chart: The State of Unemployment in Europe

Source : Statista

Breakthrough Might Break Down PFAS ‘Forever Chemicals’

Dennis Thompson wrote . . . . . . . . .

PFAS compounds are known as “forever chemicals” because they degrade slowly in the environment and accumulate in the body, potentially harming human and animal health.

Bacteria can’t eat them. Fire can’t incinerate them. Water can’t dilute them.

Instead, these per- and polyfluoroalkyl substances break down on their own schedule, posing a potential health hazard for generations to come.

Until now.

A team of researchers say they’ve figured out a cheap, easy and effective way to break down two of the major classes of PFAS compounds, leaving behind harmless end products.

The new process uses two readily available chemicals — lye and dimethyl sulfoxide — to break down PFAS compounds that are capped with carbon dioxide, according to the scientists.

The process also works at a temperature much lower than previous efforts to break down PFAS compounds.

The breakdown occurs at 248 degrees Fahrenheit, just above the boiling point of water; earlier methods have required temperatures as high as 752 degrees Fahrenheit, the researchers said.

“We were pleased to find a relatively low temperature, low energy input method where one specific portion of these molecules falls off and sets off a cascade of reactions that ultimately breaks these compounds down to relatively benign products,” said senior researcher William Dichtel, a professor of chemistry at Northwestern University in Illinois.

The resulting products of PFAS disintegration “are in many cases found in nature already and do not pose serious health concerns,” Dichtel said.

PFAS are everywhere

PFAS chemicals have been in use for 70 years, researchers said in background notes. They’re commonly found in nonstick cookware, waterproof cosmetics, firefighting foams, water-repellent fabrics, and products that resist grease and oil.

But because they don’t easily break down, PFAS have made their way out of consumer goods and into the environment. PFAS chemicals can be found in the blood of 97% of Americans, researchers have found.

“These pollutants are pervasive throughout the world. They contaminate drinking water at low levels throughout the U.S. and in several places to relatively high levels, and this is true throughout the world,” Dichtel said.

“Chronic low-level exposure to these compounds is associated with a number of health effects, including low birth weight, reduced immune response, liver damage, high cholesterol and many cancers,” Dichtel continued. “And more of these health effects are emerging as the effects of this very large class of pollutants are continuing to be understood.”

Looking at ways to break down PFAS chemicals, Dichtel and his team looked closely at a class of them called “carboxylic” because they are capped with carbon dioxide at one end of the chemical chain.

Soaking carboxylic PFAS in dimethyl sulfoxide and then adding lye, water and heat causes “the carboxylic acid group that is found across this entire class of compounds to fall off,” Dichtel said.

Once the carbon dioxide cap pops off the chemical chain, “the entire molecule starts to fall apart in a cascade of complex reactions,” Dichtel said.

Initial attempts to use this method worked too well, producing corrosive glass-eating fluoride acids, said lead researcher Brittany Trang, at the time a graduate research fellow at Northwestern University.

“In the course of my screening there was one reaction that did indeed etch the glass tube that I was working the reaction in, which was great because it showed that the reaction was working,” Trang explained.

To nail down the most effective process, Dichtel and Trang turned to UCLA’s Ken Houk, a pioneer in the use of computers to better understand chemical reactions.

Fine-tuning the breakdown process

“Experimentally, you can take A and end up with B, but how does that happen? Is it one step? Is it two steps? Or as we found, is it like 50 steps?” said Houk, a distinguished research professor at the University of California, Los Angeles.

“Computations nowadays provide the most efficient way to study [chemical] mechanisms,” Houk said. “I say nowadays because even 10 years ago, when computers were 100 times slower and 100 times more expensive, we really could not take on anything this complicated.”

In this case, what seems like a simple process involving a couple of chemicals is actually “amazingly complex,” Houk said. “If you’ve looked at the paper, you’ll see the many reactions that are occurring” as the process breaks down PFAS.

The researchers settled on one process and then used it to successfully degrade 10 different perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl ether carboxylic acids (PFECAs).

These include two of the most prominent PFAS compounds, perfluorooctanoic acid (PFOA) and one of its common replacements, known as GenX.

The research team believes this process could be used to break down PFAS chemicals found in drinking water, once those chemicals have been removed from the water supply and stored in a concentrated form.

“It’s very inefficient to treat every gallon of water that we have that has this trace level of contamination with any method, including our own,” Dichtel said, noting that this process is “not something that you would just down the drain or dump into waterways.”

The next step for the researchers will be to find ways to make the process even more efficient, possibly with different chemicals that would work at even lower temperatures.

In addition, this process doesn’t help break down PFAS chemicals containing sulfonates, which are the other major class of PFAS. Those will be the next target, the study authors said.

“The biggest gap in what we have today versus what is needed is that we really would like to degrade sulfonates as well as carboxolates, as well as the other sort of PFAS that have more exotic head groups,” Dichtel said.

“I really think that the fundamental knowledge of how these materials degrade is probably the single most important thing coming out of this study. There is certainly the possibility of activating sulfonates in similar ways that we’ve done carboxylates, but all that has to happen in the future,” Dichtel concluded.

The findings were published online in the journal Science.

Source: HealthDay

Infographic: The Most and Least Livable Cities in 2022

See large image . . . . . .

Source : Visual Capitalist

Real-world Study Details Average Duration of Infectiousness for COVID-19

Emily Head, Ryan O’Hare wrote . . . . . . . . .

A new study of 57 people with mild COVID-19 estimates how long people are infectious for and when they can safely leave isolation.

The research, which is led by Imperial College London and published in The Lancet Respiratory Medicine journal, is the first to unveil how long infectiousness lasts for after natural COVID-19 infection in the community. The study team conducted detailed daily tests from when people were exposed to SARS-CoV-2 to look at how much infectious virus they were shedding throughout their infection.

The findings suggest that in people who develop symptoms, the majority are not infectious before symptoms develop, but two-thirds of cases are still infectious five days after their symptoms begin.

They also suggest that while lateral flow tests do not detect the start of infectiousness well, they more accurately identify when someone is no longer infectious and can safely leave isolation.

Study author, Professor Ajit Lalvani, Director of the NIHR Respiratory Infections Health Protection Research Unit at Imperial, said: “We closely monitored people in their homes from when they were first exposed to the virus, capturing the moment when they developed infection through until they ceased being infectious. Before this study we were missing half of the picture about infectiousness, because it’s hard to know when people are first exposed to SARS-CoV-2 and when they first become infectious. By using special daily tests to measure infectious virus (not just PCR) and daily symptom records we were able to define the window in which people are infectious. This is fundamental to controlling any pandemic and has not been previously defined for any respiratory infection in the community.”

He added: “Combining our results with what we know about the dynamics of Omicron infections, we believe that the duration of infectiousness we’ve observed is broadly generalisable to current SARS-CoV-2 variants, though their infectious window may be a bit shorter. Our evidence can be used to inform infection control policies and self-isolation guidance to help reduce the transmission of SARS-CoV-2.”

Co-author, Dr Seran Hakki, also from Imperial’s National Heart and Lung Institute, said: “There is no longer a legal requirement to self-isolate if you test positive for COVID-19, but most people still want to isolate until they are not infectious. Despite this, there is lack of clarity around how to come out of self-isolation safely. Our study is the first to assess how long infectiousness lasts for, using real life evidence from naturally acquired infection. Our findings can thus inform guidance as to how to safely end self-isolation.”

She added: “If you test positive for COVID-19 or have symptoms after being in contact with someone with confirmed COVID-19, you should try to stay at home and minimise contact with other people.”

Most complete picture of the course of infectiousness to date

Previous studies estimating how long someone is infectious for have been a laboratory-based human challenge study or have used mathematical modelling.

The new study followed people who were exposed to someone with PCR-confirmed COVID-19 in their home between September 2020 and March 2021 (pre-Alpha SARS-CoV-2 virus and Alpha variant waves) and May-October 2021 (Delta variant wave), including some who were vaccinated and others who were not.

Participants completed daily questionnaires about their symptoms and did daily nasal and throat swabs that were sent to a laboratory for PCR-testing. PCR-positive samples were then tested to determine if they contained infectious virus and how infectious the virus was. The researchers also completed 652 lateral flow tests on the samples to determine how accurate lateral flow tests were at identifying actual infectiousness as opposed to PCR-positivity.

Samples from a total of 57 people were used, but not all were included in some analyses because of some participants not sharing information about their symptoms, some people not shedding culturable virus, and some people shedding infectious virus before or beyond the sampling period. As a result, the duration of infectiousness was measured in 42 people. There were 38 people with a confirmed date of when their symptoms started and three were asymptomatic.

Real-world timeline of infectiousness

The study found that the overall median amount of time that people were infectious was five days.

Though 24 out of 38 people tested positive on a PCR test before they developed symptoms of COVID-19 this does not indicate infectiousness and most people only became infectious after they developed symptoms. Only one in five participants were infectious before symptom onset (7 out of 35 cases).

Although levels of infectiousness reduced during the course of infection, 22 of 34 cases continued to shed infectious virus five days after symptoms began, and eight of these people continued to shed infectious virus at seven days.

Current NHS guidance suggests that people should try to stay at home and avoid contact with others for just five days.

Safely self-isolating

To help understand when people may be able to safely leave isolation, the researchers compared levels of infectiousness with lateral flow test results.

They found that the sensitivity of these tests in identifying when someone was infectious was poor at the start of infection, but high after peak levels of infectiousness (sensitivity of 67% vs 92%, respectively). This suggests lateral flow tests are good at spotting when someone is no longer infectious and testing to release people from isolation may work, but they are not reliable for early diagnosis unless used daily.

Based on their findings, the researchers recommend that people with COVID-19 isolate for five days after symptoms begin, then complete lateral flow tests from the sixth day. If these tests are negative two days in a row, it is safe to leave isolation. If a person continues to test positive or does not have access to lateral flow devices, they should remain in isolation and, in order to minimise transmission to others, only leave on the 10th day after their symptoms began.

Professor Lalvani said: “Self-isolation is not necessary by law, but people who want to isolate need clear guidance on what to do. The NHS currently advises that if you test positive for COVID-19 you should try to stay at home and avoid contact with other people for five days, but our data suggest that under a crude five-day self-isolation period two-thirds of cases released into the community would still be infectious – though their level of infectiousness would have substantially reduced compared to earlier in the course of their infection.”

He added: “NHS guidance for those with symptoms but who test negative is less clear about how long people should isolate for. Our study finds that infectiousness usually begins soon after you develop COVID-19 symptoms. We recommend that anyone who has been exposed to the virus and has symptoms isolates for five days, then uses daily lateral flow tests to safely leave isolation when two consecutive daily tests are negative.”

The study did not assess the Omicron variants currently circulating. There is some evidence that Omicron variants have a lower viral load and shed for less time than other variants, and the researchers note that their recommendations may be cautious, but still applicable, if this is true.

Most participants in the study were white, middle-aged, had a healthy BMI, and had no medical conditions. In other age groups and in those with medical conditions, these results may vary as they may be slower at clearing the virus.

A person’s infectiousness is one factor involved in transmission, alongside behavioural and environmental factors, such as where people are mixing, and if they are in close proximity to one another.

Source: Imperial College London