Air Pollution Linked to High Blood Pressure in Children; Other Studies Address Air Quality and the Heart

A meta-analysis of 14 air pollution studies from around the world found that exposure to high levels of air pollutants during childhood increases the likelihood of high blood pressure in children and adolescents, and their risk for high blood pressure as adults. The study is published in a special issue on air pollution in the Journal of the American Heart Association, an open access journal of the American Heart Association.

Other studies look at: the effects of diesel exhaust on the muscle sympathetic nerve; the impact of pollutants on high blood pressure; rates of hospital readmission for heart failure among those exposed to high levels of ambient air pollution; and risk of stroke and heart attack after long-term exposure to high levels of particulate matter. The studies include health outcomes of people who were exposed to pollutants in the United States, China and Europe.

High blood pressure during childhood and adolescence is a risk factor for hypertension and heart disease in adulthood. Studies on air pollution and blood pressure in adolescents and children, however, have produced inconsistent conclusions. This systematic review and meta-analysis pooled information from 14 studies focused on the association between air pollution and blood pressure in youth. The large analysis included data for more than 350,000 children and adolescents (mean ages 5.4 to 12.7 years of age).

“Our analysis is the first to closely examine previous research to assess both the quality and magnitude of the associations between air pollution and blood pressure values among children and adolescents,” said lead study author Yao Lu, M.D., Ph.D., professor of the Clinical Research Center at the Third Xiangya Hospital at Central South University in Changsha, China, and professor in the department of life science and medicine at King’s College London. “The findings provide evidence of a positive association between short- and long-term exposure to certain environmental air pollutants and blood pressure in children and adolescents.”

The analysis included 14 studies published through September 6, 2020, exploring the impact of long-term exposure (≥30 days) and/or short-term exposure (<30 days) of ambient air pollution on blood pressure levels of adolescents and/or children in China and/or countries in Europe.

The studies were divided into groups based upon length of exposure to air pollution and by composition of air pollutants, specifically nitrogen dioxide and particulate matter with diameter ≤10 μm or ≤2.5 μm. (The majority of research linking heart disease with particulate matter focuses on particle matter mass, which is categorized by aerodynamic diameter – μm or PM.) Fine particles are defined as PM2.5 and larger; coarse particles are defined at PM10; and the concentrations of particulate matter are typically measured in their mass per volume of air (μg/m3).

The meta-analysis concluded:

  • Short-term exposure to PM10 was significantly associated with elevated systolic blood pressure in youth (the top number on a blood pressure reading).
  • Periods of long-term exposure to PM2.5, PM10 and nitrogen dioxide were also associated with elevated systolic blood pressure levels.
  • Higher diastolic blood pressure levels (the bottom number on a blood pressure reading) were associated with long-term exposure to PM2.5 and PM10.

“To reduce the impact of environmental pollution on blood pressure in children and adolescents, efforts should be made to reduce their exposure to environmental pollutants,” said Lu. “Additionally, it is also very important to routinely measure blood pressure in children and adolescents, which can help us identify individuals with elevated blood pressure early.”

The results of the analysis are limited to the studies included, and they did not include data on possible interactions between different pollutants, therefore, the results are not generalizable to all populations. Additionally, the analysis included the most common and more widely studied pollutants vs. air pollutants confirmed to have heart health impact, of which there are fewer studies.

Source: American Heart Association

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

Chart of the Day: How Much of Global Greenhouse Gas Emissions Come from Food?

See large image . . . . .

Source: Our World in Data

Study: Green Communities Lower Stroke Risk

Michael Merschel wrote . . . . . . . . .

The greener the neighborhood, the lower the stroke risk, a new study suggests.

Researchers matched images gathered from space to health data from residents to come up with their findings. The work adds to evidence that shows where someone lives affects their health, said study co-author Dr. William Aitken. He is a cardiology fellow at the University of Miami and Jackson Memorial Hospital in Florida.

“There’s a lot of evidence that our natural environment does influence health, and we wanted to look at it particularly with stroke,” Aitken said.

The study used records from more than 249,000 Medicare beneficiaries ages 65 and older who lived in Miami-Dade County in 2010 and 2011. The records were matched against satellite measures of their neighborhood’s greenness – “whether that be trees or shrubs or grasses or whatnot,” Aitken said.

Researchers adjusted for factors such as gender, income and race and ethnicity. They also took into account whether residents had health factors – such as diabetes, high blood pressure or high cholesterol – that would affect their risk of having a stroke.

When compared to people residing in the least-green areas, those living in the most-green had a 20% overall lower risk of a stroke or transient ischemic attack, also known as a TIA or “mini-stroke.”

Specifically, the greenest neighborhoods correlated with 26% lower odds of TIA and 16% lower odds of ischemic stroke, the most common type of stroke. The odds of hemorrhagic stroke weren’t reduced by a statistically notable amount.

But overall, the apparent effect of greenery was noteworthy, Aitken said. He estimated the increased stroke risk of living in the least-green neighborhoods as compared with the most-green may be comparable to what someone would get from developing diabetes.

The study was presented Wednesday at the American Stroke Association’s virtual International Stroke Conference. It’s considered preliminary until published in a peer-reviewed journal.

Previous research using the same Medicare data linked green spaces to reduced risk for heart disease and heart attacks.

Aitken said he and his colleagues couldn’t account for how much time people spent outside or how they interacted with the environment. But he said there are several possibilities.

Dr. Elizabeth Jackson agreed.

“It makes sense to most people that if you’ve got walking paths and green spaces, people will tend to take advantage of them,” said Jackson, the Bourge Endowed Professor in Cardiovascular Disease at the University of Alabama at Birmingham. Jackson, who was not involved in the study, noted that in the urban park near her, “It’s not hard to see lots of different people walking and running,” or doing outside yoga or aerobics classes.

People who don’t have access to such spaces or who face safety or other barriers to getting outside would have fewer opportunities to be physically active, which she called “super important” to their health.

Jackson, who helped write an American Heart Association statement on housing and cardiovascular risk in 2020, said green spaces might also provide a buffer against problems such as stress and air pollution.

Aitken said the study could help leaders and policymakers think about the potential of fighting stroke in large swaths of people at once, instead of just individuals.

It can be tough to convince large numbers of people to get regular exercise, quit smoking and watch their blood sugar and cholesterol, he said. But nudging cities to incorporate more green spaces and providing encouragement for people to spend “a little more time in the environment, maybe that would affect everybody living in that area.”

Jackson praised the researchers for being part of a trend of not just looking at people in isolation but “thinking about the whole person – where they live, where they work, where they play.”

Source: American Heart Association

Beyond Genes and Environment, Random Variations Play Important Role in Longevity

A new model of aging takes into account not only genetics and environmental exposures but also the tiny changes that randomly arise at the cellular level.

University Professor Caleb Finch introduced the “Tripartite Phenotype of Aging” as a new conceptual model that addresses why lifespan varies so much, even among human identical twins who share the same genes. Only about 10 to 35 percent of longevity can be traced to genes inherited from our parents, Finch mentioned.

Finch authored the paper introducing the model with one of his former graduate students, Amin Haghani, who received his PhD in the Biology of Aging from the USC Leonard Davis School in 2020 and is now a postdoctoral researcher at UCLA. In the article, they propose that the limited heritability of aging patterns and longevity in humans is an outcome of gene-environment interactions, together with stochastic, or chance, variations in the body’s cells. These random changes can include cellular changes that happen during development, molecular damage that occurs later in life, and more.

“We wanted to introduce a conceptual map and some new terminology that will motivate a more comprehensive understanding of what the limitations of genetic determinants in aging are, how important it is to consider the genetic variance in relationship to the environment, and include this new domain of stochastic variations, which is very well recognized by different fields,” said Finch, who holds the ARCO/William F. Kieschnick Chair in the Neurobiology of Aging at the USC Leonard Davis School. “It hasn’t really been put in a formal context in which the complete package can be discussed, and that’s what I hope our article achieves.”

Expanding on the exposome

The new model is a natural extension of the idea of the exposome, which was first proposed by cancer epidemiologist Christopher Paul Wild in 2005 to draw attention to the need for more data on lifetime exposure to environmental carcinogens. The exposome concept illustrates how external factors, ranging from air pollution and socioeconomic status to individual diet and exercise patterns, interact with endogenous, or internal, factors such as the body’s microbiome and fat deposits.

The exposome is now a mainstream model, eclipsing previous characterizations of environmental factors as affecting risk “one by one.” Finch has previously expanded on the exposome concept with the introduction of the Alzheimer’s disease exposome. The gero-exposome now considers how genes and the environment interact over the lifespan to shape how we age.

The new model illustrates that cell-by-cell variations in gene expression, variations arising during development, random mutations, and epigenetic changes – turning genes “off” or “on” – should be explicitly considered apart from traditional genetic or environmental research regarding aging, Finch said. More detailed study into these chance processes has been enabled by cutting-edge research techniques, including the study of gene transcription within single cells as well as ChIP-sequencing, which can illustrate how individual proteins interact with DNA.

Effects of happenstance on health

In the paper, Finch and Haghani discussed several examples of how risks of age-related disease are poorly predicted by DNA alone but are heavily influenced by environmental exposures as well as the time and duration of the exposure, including during development or over the course of decades.

One well-known example of a gene that is associated with increased Alzheimer’s risk is ApoE-4; however, having the ApoE-4 gene doesn’t definitively mean someone will get Alzheimer’s. Studies in both mice and humans revealed that ApoE-4 and clusters of related genes interact with exposures such as air pollution or cigarette smoke to influence risk, and Alzheimer’s patients also show differences in their epigenetics as compared to individuals without the disease.

He added that the idea of environmental exposure can stretch farther than many people expect. Disease exposure earlier in life can affect health risks later in life – and across generations.

“The environment that we’re exposed to goes back to our grandmothers because the egg we came from was in our mother’s ovaries at the time of her birth,” he explained. “So that means, in my case, because my grandmother was born in 1878, I might very well carry some traces of the 19th century environment, which included much greater exposure to infectious disease because there were no antibiotics.”

Finch said that he hopes the more comprehensive model on how genes, environment, and random variations over time interact to influence aging prompt a new discussion of what the rapidly developing field of precision medicine needs to take into account to promote healthy aging.

“I think that there will be a much greater recognition in understanding individual patterns of aging,” he said. “We can only define it up to a certain point by knowing the genetic risks; we must have a more comprehensive understanding of the lifetime exposures, environments and lifestyles of an individual to have a better understanding of genetic risk for particular diseases.”

Source: EurekAlert!