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Japanese-style Fish Set Meal (魚定食) at ひらまつ食堂 in Awaji Island, Japan

Faster Air Exchange in Buildings Not Always Beneficial for Coronavirus Levels

Tom Rickey wrote . . . . . . . . .

Vigorous and rapid air exchanges might not always be a good thing when it comes to addressing levels of coronavirus particles in a multiroom building, according to a new modeling study.

The study suggests that, in a multiroom building, rapid air exchanges can spread the virus rapidly from the source room into other rooms at high concentrations. Particle levels spike in adjacent rooms within 30 minutes and can remain elevated for up to approximately 90 minutes.

The findings, published online in final form in the journal Building and Environment, come from a team of researchers at the U.S. Department of Energy’s Pacific Northwest National Laboratory. The team includes building and HVAC experts as well as experts in aerosol particles and viral materials.

“Most studies have looked at particle levels in just one room, and for a one-room building, increased ventilation is always useful to reducing their concentration,” said Leonard Pease, lead author of the study. “But for a building with more than one room, air exchanges can pose a risk in the adjacent rooms by elevating virus concentrations more quickly than would otherwise occur.

“To understand what’s happening, consider how secondhand smoke is distributed throughout a building. Near the source, air exchange reduces the smoke near the person but can distribute the smoke at lower levels into nearby rooms,” Pease added. “The risk is not zero, for any respiratory disease.”

The team modeled the spread of particles similar to SARS-CoV-2, the virus that causes COVID-19, via air-handling systems. Scientists modeled what happens after a person has a five-minute coughing bout in one room of a three-room small office building, running simulations with particles of five microns.

Researchers looked at the effects of three factors: different levels of filtration, different rates of outdoor air incorporation into the building air supply, and different rates of ventilation or air changes per hour. For downstream rooms, they found an expected clear benefit from increasing outdoor air and improving filtration, but the effect of increased ventilation rate was less obvious.

More clean outdoor air reduces transmission

Scientists studied the effects of adding varying amounts of outdoor air to the building air supply, from no outside air to 33 percent of the building’s air supply per hour. As expected, the incorporation of more clean outdoor air reduced transmission risk in the connected rooms. Replacement of one-third of a building’s air per hour with clean outdoor air reduced infection risk in downstream rooms by about 20 percent compared to the lower levels of outdoor air commonly included in buildings. The team noted that the model assumed that the outdoor air was clean and virus free.

“More outside air is clearly a good thing for transmission risk, as long as the air is free of virus,” said Pease.

Strong filtration reduces transmission

The second factor studied—strong filtration—also was very effective at reducing transmission of the coronavirus.

The team studied the effects of three levels of filtration: MERV-8, MERV-11, and MERV-13, where MERV stands for minimum efficiency reporting value, a common measure of filtration. A higher number translates to a stronger filter.

Filtration decreased the odds of infection in the connected rooms markedly. A MERV-8 filter decreased the peak level of viral particles in connected rooms to just 20 percent what it was without filtration. A MERV-13 filter knocked down the peak concentration of viral particles in a connected room by 93 percent, to less than one-tenth of what it was with a MERV-8 filter. The researchers note that the stronger filters have become more common since the pandemic began.

Increasing ventilation — a more complex picture

The most surprising finding of the study involved ventilation—the effect of what researchers call air changes per hour. What’s good for the source room—cutting transmission risk within the room by 75 percent—is not so good for connected rooms. The team found that a rapid rate of air exchange, 12 air changes per hour, can cause a spike in viral particle levels within minutes in connected rooms. This increases the risk of infection in those rooms for a few minutes to more than 10 times what it was at lower air-exchange rates. The higher transmission risk in connected rooms remains for about 20 minutes.

“For the source room, clearly more ventilation is a good thing. But that air goes somewhere,” said Pease. “Maybe more ventilation is not always the solution.”

Interpreting the data

“There are many factors to consider, and the risk calculation is different for each case,” said Pease. “How many people are in the building and where are they located? How large is the building? How many rooms? There is not a great deal of data at this point on how viral particles move about in multiroom buildings.

“These numbers are very specific to this model—this particular type of model, the amount of viral particles being shed by a person. Every building is different, and more research needs to be done,” Pease added.

Co-author Timothy Salsbury, a buildings control expert, notes that many of the trade-offs can be quantified and weighted depending on circumstances.

“Stronger filtration translates to higher energy costs, as does the introduction of more outside air than would usually be used in normal operations. Under many circumstances, the energy penalty for the increased fan power required for strong filtration is less than the energy penalty for heating or cooling additional outside air,” said Salsbury.

“There are many factors to balance—filtration level, outdoor air levels, air exchange—to minimize transmission risk. Building managers certainly have their work cut out for them,” he added.

Additional experimental studies underway

The team is already conducting a series of experimental studies along the same lines as the modeling study. Like the newly published study, the additional analyses look at the effects of filtration, outdoor air incorporation and air changes.

These ongoing studies involve real particles made of mucus (not incorporating the actual SARS-CoV-2 virus) and consider differences among particles expelled from various parts of the respiratory tract, such as the oral cavity, the larynx, and the lungs. Investigators deploy an aerosolizing machine that disperses the viral-like particles much as they’d be dispersed by a cough, as well as fluorescent tracking technology to monitor where they go. Other factors include varying particle sizes, how long viral particles are likely to be infectious, and what happens when they drop and decay.

Source: Pacific Northwest National Laboratory

In Pictures: Kazari Maki Sushi (飾り巻き寿司)

More Belly Weight Increases Danger of Heart Disease Even If BMI Does Not Indicate Obesity

People with abdominal obesity and excess fat around the body’s mid-section and organs have an increased risk of heart disease even if their body mass index (BMI) measurement is within a healthy weight range, according to a new Scientific Statement from the American Heart Association published today in the Association’s flagship journal, Circulation.

“This scientific statement provides the most recent research and information on the relationship between obesity and obesity treatment in coronary heart disease, heart failure and arrhythmias,” said Tiffany M. Powell-Wiley, M.D., M.P.H., FAHA, chair of the writing committee and a Stadtman Tenure-Track Investigator and chief of the Social Determinants of Obesity and Cardiovascular Risk Laboratory in the Division of Intramural Research at the National Heart, Lung, and Blood Institute at the National Institutes of Health in Bethesda, Maryland. “The timing of this information is important because the obesity epidemic contributes significantly to the global burden of cardiovascular disease and numerous chronic health conditions that also impact heart disease.”

A greater understanding of obesity and its impact on cardiovascular health highlights abdominal obesity, sometimes referred to as visceral adipose tissue, or VAT, as a cardiovascular disease risk marker. VAT is commonly determined by waist circumference, the ratio of waist circumference to height (taking body size into account) or waist-to-hip ratio, which has been shown to predict cardiovascular death independent of BMI.

Experts recommend both abdominal measurement and BMI be assessed during regular health care visits because a high waist circumference or low waist-to-hip ratio, even in healthy weight individuals, could mean an increased risk of heart disease. Abdominal obesity is also linked to fat accumulation around the liver that often leads to non-alcoholic fatty liver disease, which adds to cardiovascular disease risk.

“Studies that have examined the relationship between abdominal fat and cardiovascular outcomes confirm that visceral fat is a clear health hazard,” said Powell-Wiley.

The risk-inducing power of abdominal obesity is so strong that in people who are overweight or have obesity based on BMI, low levels of fat tissue around their midsection and organs could still indicate lower cardiovascular disease risks. This concept, referred to as “metabolically healthy obesity,” seems to differ depending on race/ethnicity and sex.

Worldwide, around 3 billion people are overweight (BMI = 25 to 29.9 kg/m2) or have obesity obese(BMI ≥30 kg/m2). Obesity is a complex disease related to many factors, including biologic, psychological, environmental and societal aspects, all of which may contribute to a person’s risk for obesity. Obesity is associated with greater risk of coronary artery disease and death due to cardiovascular disease and contributes to many cardiovascular risk factors and other health conditions, including dyslipidemia (high cholesterol), type 2 diabetes, high blood pressure and sleep disorders.

For this statement, experts evaluated research on managing and treating obesity, particularly abdominal obesity. The writing group reports that reducing calories can reduce abdominal fat, and the most beneficial physical activity to reduce abdominal obesity is aerobic exercise. Their analysis found that meeting the current recommendations of 150 min/week of physical activity may be sufficient to reduce abdominal fat, with no additional loss from longer activity times. Exercise or a combination of dietary change and physical activity has been shown in some instances to reduce abdominal obesity even without weight loss.

Lifestyle changes and subsequent weight loss improve blood sugar, blood pressure, triglyceride and cholesterol levels – a cluster of factors referred to as metabolic syndrome – and reduce inflammation, improve blood vessel function and treat non-alcoholic fatty liver disease. However, studies of lifestyle change programs have not shown a reduction in coronary artery disease events (such as heart attack or chest pain).

In contrast, bariatric surgery for weight loss treatment is associated with a reduction in coronary artery disease risk compared to non-surgical weight loss. This difference may be attributed to the larger amount of weight loss and the resultant changes in metabolism that are typical after bariatric surgery.

“Additional work is needed to identify effective interventions for patients with obesity that improve cardiovascular disease outcomes and reduce cardiovascular disease mortality, as is seen with bariatric surgery,” said Powell-Wiley.

The statement also addresses the “obesity paradox,” which is sometimes observed in research, particularly in populations that have overweight or have Class I obesity (BMI = 30 to 34.9 kg/m2). The paradox suggests that even though overweight and obesity are strong risk factors for the development of cardiovascular disease, they are not always a risk factor for negative cardiovascular outcomes. The writing group notes that people with overweight or obesity are often screened earlier for cardiovascular disease than people with healthy weight, thus resulting in earlier diagnoses and treatment.

“The underlying mechanisms for the obesity paradox remain unclear,” said Powell-Wiley. “Despite the existence of the paradox for short-term cardiovascular disease outcomes, the data show that patients with overweight or obesity suffer from cardiovascular disease events at an earlier age, live with cardiovascular disease for more of their lives and have a shorter average lifespan than patients with normal weight.”

In reviewing the effects of obesity on a common heart rhythm disorder, the writing group reports there is now “convincing data” that obesity may cause atrial fibrillation, a quivering or irregular heartbeat. Estimates suggest obesity may account for one-fifth of all atrial fibrillation cases and 60% of recently documented increases in people with atrial fibrillation. Research has demonstrated people with atrial fibrillation who had intense weight loss experienced a significant reduction in cumulative time spent in atrial fibrillation.

“The research provides strong evidence that weight management be included as an essential aspect of managing atrial fibrillation, in addition to the standard treatments to control heart rate, rhythm and clotting risk,” said Powell-Wiley.

The statement identifies areas of future research, including a call for further study of lifestyle interventions that may be most effective in decreasing visceral adiposity and improving cardiovascular outcomes. Powell-Wiley said, “It’s important to understand how nutrition can be personalized based on genetics or other markers for cardiovascular disease risk.

She added, “as overweight and obesity prevalence increases among adolescents worldwide, it is critical to address how best to develop upstream primary prevention interventions and better treatment strategies, particularly for young patients with severe obesity.”

Source: American Heart Association

Mediterranean Sea Bass with Brown Butter Caper Sauce

Ingredients

1/4 cup butter
1 tablespoon vegetable oil
4 fillets Mediterranean sea bass
1/4 cup water
1 tablespoon chopped capers
1 tablespoon grated lemon rind
2 tablespoons lemon juice
2 tablespoons chopped flat leaf parsley

Method

  1. Heat butter and vegetable oil over medium heat in a large skillet. When butter foams, add fillets and cook skin-side down until golden, about 3 minutes. Turn over and cook second side for 2 minutes.
  2. Place fillets, flesh-side up on plate.
  3. The remaining butter in the pan should be a nut brown colour and smell nutty. Lower the heat and whisk in water and mixture should emulsify.
  4. Whisk in capers, lemon rind, lemon juice and parsley. Pour over fish before serving.

Makes 4 servings.

Source: Lucy Waverman


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