NASA's retired Compton mission reveals superheavy neutron stars

Peer-Reviewed Publication

NASA/GODDARD SPACE FLIGHT CENTER

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IMAGE: ASTRONAUTS IMAGED THE COMPTON GAMMA RAY OBSERVATORY DURING ITS DEPLOYMENT FROM SPACE SHUTTLE ATLANTIS IN APRIL 1991. view more 

CREDIT: NASA/STS-37 CREW

Astronomers studying archival observations of powerful explosions called short gamma-ray bursts (GRBs) have detected light patterns indicating the brief existence of a superheavy neutron star shortly before it collapsed into a black hole. This fleeting, massive object likely formed from the collision of two neutron stars.

“We looked for these signals in 700 short GRBs detected with NASA’s Neil Gehrels Swift Observatory, Fermi Gamma-ray Space Telescope, and the Compton Gamma Ray Observatory,” explained Cecilia Chirenti, a researcher at the University of Maryland, College Park (UMCP) and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who presented the findings at the 241st meeting of the American Astronomical Society in Seattle. “We found these gamma-ray patterns in two bursts observed by Compton in the early 1990s.”

A paper describing the results, led by Chirenti, was published Monday, Jan. 9, in the scientific journal Nature.

A neutron star forms when the core of a massive star runs out of fuel and collapses. This produces a shock wave that blows away the rest of the star in a supernova explosion. Neutron stars typically pack more mass than our Sun into a ball about the size of a city, but above a certain mass, they must collapse into black holes.

Both the Compton data and computer simulations revealed mega neutron stars tipping the scales by 20% more than the most massive, precisely measured neutron star known – dubbed J0740+6620 – which weighs in at nearly 2.1 times the Sun’s mass. Superheavy neutron stars also have nearly twice the size of a typical neutron star, or about twice the length of Manhattan Island.

The mega neutron stars spin nearly 78,000 times a minute – almost twice the speed of J1748–2446ad, the fastest pulsar on record. This rapid rotation briefly supports the objects against further collapse, allowing them to exist for just a few tenths of a second, after which they proceed to form a black hole faster than the blink of an eye.

“We know that short GRBs form when orbiting neutron stars crash together, and we know they eventually collapse into a black hole, but the precise sequence of events is not well understood,” said Cole Miller, a professor of astronomy at UMCP and a co-author of the paper. “At some point, the nascent black hole erupts with a jet of fast-moving particles that emits an intense flash of gamma rays, the highest-energy form of light, and we want to learn more about how that develops.”

Short GRBs typically shine for less than two seconds yet unleash energy comparable to what’s released by all the stars in our galaxy over one year. They can be detected more than a billion light-years away. Merging neutron stars also produce gravitational waves, ripples in space-time that can be detected by a growing number of ground-based observatories.

Computer simulations of these mergers show that gravitational waves exhibit a sudden jump in frequency – exceeding 1,000 hertz – as the neutron stars coalesce. These signals are too fast and faint for existing gravitational wave observatories to detect. But Chirenti and her team reasoned that similar signals could appear in the gamma-ray emission from short GRBs.

Astronomers call these signals quasiperiodic oscillations, or QPOs for short. Unlike, say, the steady ringing of a tuning fork, QPOs can be composed of several close frequencies that vary or dissipate over time. Both the gamma-ray and gravitational wave QPOs originate in the maelstrom of swirling matter as the two neutron stars coalesce.

While no gamma-ray QPOs materialized in the Swift and Fermi bursts, two short GRBs recorded by Compton’s Burst And Transient Source Experiment (BATSE) on July 11, 1991, and Nov. 1, 1993, fit the bill.

The larger area of the BATSE instrument gave it the upper hand in finding these faint patterns – the tell-tale flickering that revealed the presence of mega neutron stars. The team rates the combined odds of these signals occurring by chance alone at less than 1 in 3 million.

“These results are very important as they set the stage for future measurements of hypermassive neutron stars by gravitational wave observatories,” said Chryssa Kouveliotou, chair of the physics department at George Washington University in Washington, who was not involved in the work.

By the 2030s, gravitational wave detectors will be sensitive to kilohertz frequencies, providing new insights into the short lives of supersized neutron stars. Until then, sensitive gamma-ray observations and computer simulations remain the only available tools for exploring them. 

Compton’s BATSE instrument was developed at NASA's Marshall Space Flight Center in Huntsville, Alabama, and provided the first compelling evidence that gamma-ray bursts occurred far beyond our galaxy. After operating for almost nine years, the Compton Gamma Ray Observatory was deorbited on June 4, 2000, and destroyed as it entered Earth’s atmosphere.

Goddard manages both the Swift and Fermi missions.

 Neutron star merger simulation [VIDEO] | EurekAlert! Science News Releases

 

JOURNAL

Nature

DOI

10.1038/s41586-022-05497-0 

ARTICLE TITLE

Kilohertz quasiperiodic oscillations in short gamma-ray bursts

ARTICLE PUBLICATION DATE

9-Jan-2023

Cat locomotion could unlock better human spinal cord injury treatment

Peer-Reviewed Publication

GEORGIA INSTITUTE OF TECHNOLOGY

 

IMAGE: MODEL view more 

CREDIT: GEORGIA TECH

Cats always land on their feet, but what makes them so agile? Their unique sense of balance has more in common with humans than it may appear. Researchers at the Georgia Institute of Technology are studying cat locomotion to better understand how the spinal cord works to help humans with partial spinal cord damage walk and maintain balance.

Using a mix of experimental studies and computational models, the researchers show that somatosensory feedback, or neural signals from specialized sensors throughout a cat’s body, help inform the spinal cord about the ongoing movement and coordinate the four limbs to keep cats from falling when they encounter obstacles. Research suggests that with those motion-related sensory signals the animal can walk even if the connection between the spinal cord and the brain is partially fractured.  

Understanding the mechanisms of this type of balance control is particularly relevant to older people who often have balance issues and can injure themselves in falls. Eventually, the researchers hope this could bring new understanding to somatosensory feedback’s role in balance control. It could also lead to progress in spinal cord injury treatment because the research suggests activation of somatosensory neurons can improve spinal neural networks’ function below the site of spinal cord damage.

“We have been interested in the mechanisms that make it possible to reactivate injured networks in the spinal cord,” said School of Biological Sciences Professor Boris Prilutsky. “We know from previous studies that somatosensory feedback from moving legs helps activate spinal networks that control locomotion, enabling stable movement.”

The researchers presented their findings in “Sensory Perturbations From Hindlimb Cutaneous Afferents Generate Coordinated Functional Responses in All Four Limbs During Locomotion in Intact Cats” in the journal eNeuro.

Coordinated Cats

Although genetically modified mouse models have recently become dominant in neural control of locomotion research, the cat model offers an important advantage. When they move, mice remain crouched, meaning they are less likely to have balance problems even if somatosensory feedback fails. Humans and cats, on the other hand, cannot maintain balance or even move if they lose sensory information about limb motion. This suggests that larger species, like cats and humans, might have a different organization of spinal neural network controlling locomotion compared to rodents.

Georgia Tech partnered with researchers at the University of Sherbrooke in Canada and Drexel University in Philadelphia to better understand how signals from sensory neurons coordinate movements of the four legs. The Sherbrooke lab trained cats to walk on a treadmill at a pace consistent with human gait and then used electrodes to stimulate their sensory nerve.

The researchers focused on the sensory nerve that transmits touch sensation from the top of the foot to the spinal cord. By electrically stimulating this nerve, researchers mimicked hitting an obstacle and saw how the cats stumbled and corrected their movement in response. Stimulations were applied in four periods of the walking cycle: mid-stance, stance-to-swing transition, mid-swing, and swing-to-stance transition. From this, they learned that mid-swing and the stance-to-swing transition were the most significant periods because the stimulation increased activity in muscles that flex the knee and hip joints, joint flexion and toe height, step length, and step duration of the stimulated limb.

“In order to maintain balance, the animal must coordinate movement of the other three limbs, otherwise it would fall,” Prilutsky said. “We found that stimulation of this nerve during the swing phase increases the duration of the stance phase of the other limbs and improves stability.”

In effect, when the cat stumbles during the swing phase, the sensation triggers spinal reflexes that ensure the three other limbs stay on the ground and keep the cat upright and balanced, while the swing limb steps over the obstacle.

Computational Cats

With these Canadian lab experiments, the researchers at Georgia Tech and Drexel University are using observations to develop a computational model of the cat’s musculoskeletal and spinal neural control systems. The data gathered are used to compute somatosensory signals related to length, velocity, and produced force of muscles, as well as pressure on the skin in all limbs. This information forms motion sensations in the animal’s spinal cord and contributes to interlimb coordination by the spinal neuronal networks.

“To help treat any disease, we need to understand how the intact system works,” Prilutsky said. “That was one reason why this study was performed, so we could understand how the spinal networks coordinate limb movements and develop a realistic computational model of spinal control of locomotion. This will help us know better how the spinal cord controls locomotion.”

CITATION: Merlet AN, Jéhannin P, Mari S, Lecomte CG, Audet J, Harnie J, Rybak IA, Prilutsky BI, Frigon A (2022) Sensory Perturbations from Hindlimb Cutaneous Afferents Generate Coordinated Functional Responses in All Four Limbs during Locomotion in Intact Cats. eNeuro 9: 0178-22.

 

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The Georgia Institute of Technology, or Georgia Tech, is one of the top public research universities in the U.S., developing leaders who advance technology and improve the human condition. The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its more than 46,000 students, representing 50 states and more than 150 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.

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JOURNAL

eNeuro

DOI

10.1523/ENEURO.0178-22.2022 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Sensory perturbations from hindlimb cutaneous afferents generate coordinated functional responses in all four limbs during locomotion in intact cats

Less than four in 100 men accepted to be sperm donors

Peer-Reviewed Publication

UNIVERSITY OF SHEFFIELD

Less than four in 100 men accepted to be sperm donors

• An international team of researchers mapped the outcome of over 11,700 men who applied to be sperm donors in Denmark and the US
• Less than four in 100 men end of the process and have samples frozen and released for treatments
• Over half of the men who applied to be donors withdrew from the programme before having samples released and nearly a fifth of applicants were rejected because of a health issue or because they were a carrier for a genetic disease
• Four in 10 donor candidates initially agreed to be identifiable, and it was more common for applicants in Denmark to agree to waive their anonymity than applicants in the US
• The UK relies heavily on imported sperm from donors in the US and Denmark

Less than four in 100 men who apply to be sperm donors reach the end of the process and have samples frozen and released for treatments, according to a new study.

A European team of researchers led by the University of Sheffield, worked with the world’s largest sperm banks, Cryos International, to map the outcome of over 11,700 men who applied to be sperm donors.

The findings, published in the journal Human Reproduction, show that over half of the men (54.91 per cent) who applied to be donors at Cryos in Denmark and the US withdrew from the programme before having samples released for use.

Nearly a fifth of applicants (17.41 per cent) were rejected because of a health issue or because they were a carrier for a genetic disease or had an infectious disease which could not be treated.

The data also showed just over one in 10 of the applicants (11.71 per cent) failed a screening questionnaire about their lifestyle and another one in 10 (11.20 per cent) were rejected because their sperm quality was not good enough.

Lead author of the study, Professor Allan Pacey, Professor of Andrology and Head of the Department of Oncology and Metabolism at the University of Sheffield, said: “To our knowledge this is the largest study of sperm donor applicants outside China and given that the UK relies so heavily on imported sperm from the USA and Denmark it is important for us to understand the recruitment processes there and reassure ourselves that they are safe as well as see if there is anything we can do to improve them.”

Recent figures from the Human Fertilisation and Embryology Authority have shown that more than half of the new sperm donors registered in the UK were from imported sperm, mostly from sperm banks like Cryos in the US and Denmark.

Since 2006 it has been illegal in the UK to use sperm from donors who are unwilling to be identified to any people born from their donations. Therefore, in the new study, Professor Pacey and the team looked at how many of the donors at Cryos agreed to be identifiable compared to those that did not.

They found that more than four in 10 donor candidates (41.27 per cent) initially agreed to be identifiable, and it was more common for applicants in Denmark to agree to waive their anonymity than applicants in the USA.

Interestingly, the team found that as the screening and donation process continued (men donate regularly for many months) more of the donors who initially wanted to be anonymous, agreed to become identifiable.

Professor Pacey added: “The study with Cryos highlights how hard it is to become a sperm donor. It’s not like blood donation where once it’s done you can have a cup of tea and go home. Sperm donation is a regular commitment with lots of screening and regular testing as well as life-long implications for the donor if any children are born from their sample.

“What’s particularly fascinating is that more donors, who initially wanted to remain anonymous, were willing to be identifiable as the screening and donation process continued. This is particularly good news for patients in the UK undergoing fertility treatment, as it is a legal requirement for sperm donors to be identifiable to any children born from their donations.”

Dr Anne-Bine Skytte, Medical Director at Cryos International said: “We are very grateful to Professor Pacey and the team for their in depth analysis of sperm donors which has already been very valuable in helping Cryos look at its recruitment process and try to make them more efficient.

“If we can recruit donors more easily then this will help keep costs down for patients in the UK and elsewhere who often buy donor sperm with their own money because it’s not funded by the NHS.”

To be accepted as a sperm donor in the UK, men must be aged between 18 and 45 years old and be fit and healthy with good sperm quality. Donors undergo a range of screening tests for genetic conditions and infectious diseases as well as an analysis of their family medical history.

UK guidelines for sperm donor recruitment are published by the British Fertility Society and the recruitment and use of sperm donors in infertility treatments regulated by the Human Fertilisation and Embryology Authority.

Any males in the UK interested to donate sperm should contact their local licenced clinic or sperm bank (further details can be found here)

View the full paper: An analysis of the outcome of 11,712 men applying to be sperm donors in Denmark and the USA by Pacey, AA et al. Human Reproduction Journal: doi:10.1093/humrep/deac264

 

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JOURNAL

Human Reproduction

DOI

10.1093/humrep/deac264 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

People

ARTICLE TITLE

An analysis of the outcome of 11 712 men applying to be sperm donors in Denmark and the USA

ARTICLE PUBLICATION DATE

9-Jan-2023

Plastic pollution in the oceans is an equity issue, says new UW-led report

Reports and Proceedings

UNIVERSITY OF WASHINGTON

 

IMAGE: THIS ILLUSTRATION, BY SEATTLE-BASED ARTIST MARI SHIBUYA, DEPICTS HOW PLASTIC WASTE OF DIFFERENT SIZES CAN TRAVEL THROUGH THE MARINE ENVIRONMENT TO END UP IN FISH, ON BEACHES, OR INSIDE PEOPLE’S BODIES. view more 

CREDIT: MARI SHIBUYA

Many people are aware of plastic pollution in the oceans. Photos of turtles or seabirds entangled in plastic garbage first went viral in the 1990s, and the Great Pacific Garbage Patch is now the focus of highly publicized cleanup efforts.

Less recognized is how marine plastic waste affects human populations, and the unequal burden on different communities. A report, “Towards an Equitable Approach to Marine Plastics Pollution,” outlines the current situation and attempts to address the problem.

“We all benefit from plastics, but some people are paying more of the external costs in terms of the environmental damage, well-being issues and just horrendous scenes that they must live with in places they call home,” said project leader Yoshitaka Ota, a University of Washington professor of practice in marine and environmental affairs and director of The Nippon Foundation Ocean Nexus Center.

Increasingly, the greenhouse gases causing climate change are seen as an issue in which some countries produce most of the pollution while other countries or groups are more at risk from the long-term consequences. Plastic pollution, this report argues, is a similar issue for coastal communities.

The report, published in late November, includes 31 authors from nine countries. It incorporates case studies and analyses from around the world as well as larger, overarching recommendations for change.

The authors conclude that coastal communities most affected by marine plastic pollution should be better represented in drafting potential solutions. A free, virtual event in March will bring together stakeholders from around the world to draw up a road map for an equity-focused path to address marine plastics.

The Ocean Nexus Center was founded in 2019 as a 10-year initiative based in UW EarthLab that includes more than 20 member universities and organizations around the world. Its mission is to bring together equity and justice in the oceans on a global scale.

The recently published report covers topics such as:

• A call to replace the term “plastic litter” with “plastic pollution.” The word “litter” frames the issue on a small scale that can be addressed with better waste collection, disposal or recycling, rather than broader industry-wide changes to production.
• A discussion of the rise in plastic waste during the COVID-19 pandemic, through masks, gloves, face shields and a resurgence of single-use and individually wrapped products.
• Chapters that provide place-based case studies, including interviews with local residents about their experiences with marine plastics. Locations include a fishing community in Ghana, coastal mangrove forests in Ecuador, and an island in southern Japan that includes both tourists and local residents.
• Two analyses of waste cleanup programs — Washington state’s Marine Debris Action Plan and the “Fishing for Litter” program in the Netherlands.
• A section with multiple authors focused on the island of Aotearoa, New Zealand. Maori perspectives have been disregarded in efforts to address marine plastic pollution, authors write, despite the greater impact and importance of marine environments for Maori people’s livelihood and culture.
• A review of international rules for plastic waste disposal — a patchwork of regulations including the Basel Convention, a nonbinding agreement that the U.S. has not signed.
• A critique of Coca-Cola Co.’s “World Without Waste” initiative as an example of industry-backed solutions to marine plastic pollution that focus on individual consumers, rather than bigger, more permanent solutions that could reduce plastic waste.

“Coca-Cola is the world’s biggest producer of plastic waste, and it serves as a case study of how multinational corporations engage in waste reduction and corporate social responsibility,” said lead author Jessica Vandenberg, a UW postdoctoral researcher in marine and environmental affairs who wrote the analysis of Coca-Cola’s initiative.

“As we highlight in the report, one of the key actions we see as imperative for addressing marine plastic pollution is refocusing the problem as one of plastics production, rather than as an issue of waste management,” Vandenberg said.

Mari Shibuya, a Seattle-based artist, created digital watercolor paintings that appear throughout the document. The report is funded by The Nippon Foundation and is intended to be an accessible, comprehensive summary of the issue that can be read by policymakers, educators and other audiences, Ota said.

The March event will bring together audiences to implement the report’s main recommendations. Visit The Nippon Foundation Ocean Nexus Center website to find forthcoming event details.

 

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For more information, contact Ocean Nexus marketing and communications lead Ariel Wang at arielyw@uw.edu, Ota at yota1@uw.edu or Vandenberg at jvandenb@uw.edu (note: Vandenberg is currently a visiting scholar at Wageningen University & Research in the Netherlands, on Central European Time).

Evidence about gun policies grows and supports laws to reduce violence

Reports and Proceedings

RAND CORPORATION

There is now supportive evidence that child-access-prevention laws reduce firearm homicides and self-injuries among youth, and that shall-issue concealed-carry laws and stand-your-ground laws increase levels of firearm violence, according to a new RAND Corporation report.

 

The findings are part of a new report updating RAND’s Science of Gun Policy research synthesis, which reviewed the existing scientific literature to assess the strength of available evidence about the effects of 18 commonly discussed gun policies on a range of outcomes, including injuries and deaths, mass shootings, defensive gun use, and participation in hunting and sport shooting.

 

Several other policies are now found by RAND to have moderate scientific evidence of effects, the second highest evidence rating used by the researchers. These include private-seller background-check requirements, which appear to decrease total homicides; laws setting the minimum age to purchase firearms at 21, which appear to decrease suicides among young people; and state laws prohibiting individuals subject to domestic-violence restraining orders from possessing firearms, which appear to decrease intimate-partner homicides.

 

The conclusions build on prior work by the RAND team that had already identified supportive evidence for two laws. Specifically, in the last update to this report in 2020, the team identified supportive evidence that child access prevention laws reduce intentional and unintentional firearm injuries and deaths among children, and that stand-your-ground laws increase firearm homicides. (Supportive is the project’s highest level of evidence for a policy.)

 

Overall, the updated report found that for eight gun policies, the new research results incorporated into the review were sufficient to upgrade previous conclusions to a higher level of evidence.

 

Three of those strengthened findings are for child-access prevention, concealed-carry and stand-your-ground laws. Other areas with upgraded evidence ratings compared to the prior RAND report include limited evidence that bans on high-capacity magazines may reduce mass shootings and mass shooting fatalities; that surrender laws, in combination with prohibitions related to violent offenses, may reduce firearm-related intimate-partner homicides; and that more restrictive background check laws may reduce firearm homicides.

 

“While the state of research about gun policies is less well developed than in many other areas of social science, there is a growing body of evidence that provides suggestive evidence about the effects of several frequently discussed policies,” said Rosanna Smart, lead author of the new analysis and an economist at RAND, a nonprofit, nonpartisan research organization.

 

“More than 45,000 Americans died by gun violence in 2020, and our hope is that by highlighting where scientific evidence is accumulating, we can help build consensus around a shared set of facts established through a transparent and impartial review process,” Smart said. “In so doing, we also mean to highlight areas where more and better information could make important contributions to establishing fair and effective gun policies.”

 

The updated version of the project identified 152 studies that investigated the causal effects of gun polices on any of the targeted outcomes, 29 more than the previous edition of the project released in 2020.

 

Across the 18 classes of policies studied, only child-access-prevention laws, shall-issue concealed carry laws and stand-your-ground laws had any evidence of effects that were classified as supportive for a particular conclusion.

 

These three policies aim to affect how legal gun owners can legally store, carry or use their firearms. They differ from many of the other policies considered by the project that primarily affect the acquisition of new firearms (such as background checks or waiting periods) or that are designed to affect a relatively small proportion of gun owners (such as prohibitions that target domestic violence offenders).

 

Based on the report’s findings, RAND researchers recommend that states without child-access prevention laws consider adopting them as a strategy to reduce total and firearm suicides, unintentional firearm injuries and deaths, and firearm homicides among youth. (In 2020, firearm-related injuries surpassed motor vehicle crashes as the leading cause of death among children and adolescents aged 1 to 19.)

 

RAND researchers say that while shall-issue concealed-carry laws and stand-your-ground laws were adopted on the belief that they would reduce violent victimization either by deterring violent crime or by reducing barriers to victims defending themselves, a growing body of scientific evidence suggests these laws have the opposite effect.

 

As such, the RAND report recommends that states with stand-your-ground laws consider repealing or amending them as a strategy for reducing firearm homicides. States with shall-issue or permitless-carry laws should consider whether other regulations, either through requirements implemented as part of the permitting process or as through other aspects of law (such as rules that may prevent firearm theft), might ensure the effects of concealed-carry laws are aligned with public safety.

 

In total, the report makes 19 recommendations about gun policies that policymakers might consider to reduce firearm violence, as well as ways to improve available evidence about the effects of such policies.

 

“Although the base of evidence has grown since our first edition of this report in 2018, there remain a surprisingly large number of firearm policy effects for which we have no studies, or available studies are inconclusive,” said Andrew Morral, co-author of the report and leader of  the RAND Gun Policy in America project. “This does not mean that these policies are ineffective; they might well be quite effective. Instead, this reflects shortcomings in the contributions that scientific study has been able to contribute to policy debates in these areas.”

 

The United States has a large stock of privately owned guns in circulation, estimated to be somewhere between 265 million and 393 million firearms.

 

More than 45,000 Americans die annually from deliberate and unintentional gun injuries, just over half of which are suicides. Another 50,000 to 150,000 Americans per year receive care in a hospital for a nonfatal gun injury.

 

Support for the RAND Gun Policy in America project was provided by Arnold Ventures. The report, “The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of Gun Policies in the United States [Third Edition],” is available at www.rand.org. Other authors of the project are Rajeev Ramchand, Amanda Charbonneau, Jhacova Williams, Sierra Smucker, Samantha Cherney and Lea Xenakis.

 

The RAND Social and Economic Well-Being division seeks to actively improve the health, and social and economic well-being of populations and communities throughout the world.

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METHOD OF RESEARCH

Literature review

SUBJECT OF RESEARCH

People

ARTICLE TITLE

The Science of Gun Policy: A Critical Synthesis of Research Evidence on the Effects of Gun Policies in the United States [Third Edition],”

ARTICLE PUBLICATION DATE

10-Jan-2023

Children near airports may be exposed to dangerous levels of lead

Peer-Reviewed Publication

OXFORD UNIVERSITY PRESS USA

A new paper in PNAS Nexus, published by Oxford University Press, finds that children living near one California airport have higher lead levels in their blood. Since leaded gasoline is still used by piston-engine aircraft all around the United States, it appears children are still being exposed to toxic lead levels. This is despite policymakers’ efforts to reduce lead exposure since the 1970s.

Over the last four decades, the blood lead levels of children in the United States declined significantly due to policies that removed lead from paint, plumbing, food cans, and automotive gasoline. Scientists generally agree that the phase-out of tetraethyl lead from automotive gasoline under provisions of the Clean Air Act of 1970 was the most effective of these policies.

But leaded gasoline hasn’t disappeared entirely. It remains a standard part of aviation gasoline and is used by an estimated 170,000 piston-engine aircraft nationwide. Today, the use of lead-formulated aviation gasoline accounts for as much as two-thirds of lead emissions in the United States.

The U.S. Environmental Protection Agency estimates that four million people reside within half a mile of an airport servicing piston-engine planes. About 600 elementary or secondary schools are located near such facilities.

Researchers analyzed the blood lead levels of children under six years of age over a 10-year period (from 2011 to 2020) who lived near one such airport–Reid-Hillview Airport in Santa Clara County, California. The researchers found the probability that a child living near Reid-Hillview Airport had a blood lead level that exceeded the California Department of Public Health-defined threshold of 4.5 micrograms per decilitre increased the closer the child lived to the airport. The researchers also note that the blood lead levels were much higher when children live East (downwind) of the airport and find that child blood levels increase with piston-engine aircraft traffic and quantities of leaded aviation gasoline sold at the airport.

For children living a mile or more away from the airport, the probability of a blood sample that exceeded the threshold is 21.4% lower than for children living within a half mile of the airport. With respect to geographic direction, children residing east of the airport were 2.18 times more likely to present a blood lead level above the threshold of concern.  Adding to the evidence that exposure to aviation gasoline is a health risk to children, the researchers find that the blood lead levels of children residing within a half mile of the airport are especially responsive to an increase in piston-engine aircraft traffic. 

“Across an ensemble of tests, we find consistent evidence that the blood lead levels of children residing near the airport are pushed upward by the deposition of leaded aviation gasoline,” said the paper’s lead author, Sammy Zahran. “This indicates we should support policy efforts to limit aviation lead emissions to safeguard the welfare of at-risk children.”       

The paper “Leaded Aviation Gasoline Exposure Risk and Child Blood Lead Levels” is available (at midnight on January 10th) at: https://academic.oup.com/pnasnexus/article-lookup/doi/10.1093/pnasnexus/pgac285.

Direct correspondence to: 
Sammy Zahran
Professor and Associate Chair of Economics
Colorado State University
Fort Collins, Colorado
Sammy.Zahran@colostate.edu

To request a copy of the study, please contact:
Daniel Luzer 
daniel.luzer@oup.com

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JOURNAL

PNAS Nexus

DOI

10.1093/pnasnexus/pgac285 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Leaded Aviation Gasoline Exposure Risk and Child Blood Lead Levels

ARTICLE PUBLICATION DATE

10-Jan-2023

What if sodium in packaged foods was reduced for an entire continent?

A new study in the journal Hypertension speculates on the health impact of less salt in Australia’s packaged foods

Peer-Reviewed Publication

AMERICAN HEART ASSOCIATION

Research Highlights:

• Reformulating packaged foods available in Australia to contain less sodium may save about 1,700 lives per year, according to a new study.
• Using the World Health Organization’s (WHO) recommendations for reducing the population’s sodium intake, the researchers estimate following the WHO sodium guidance may also prevent nearly 7,000 annual diagnoses of heart disease, kidney disease and stomach cancer in Australia.

Embargoed until 4 a.m. CT/5 a.m. ET Tuesday, January 10, 2023

DALLAS, January 10, 2023 — Reformulating packaged foods in Australia to contain less sodium might save about 1,700 lives per year and prevent nearly 7,000 annual diagnoses of heart disease, kidney disease and stomach cancer, according to new research published today in Hypertension, an American Heart Association journal.

High sodium intake increases blood pressure, risk of heart disease and stroke, chronic kidney disease and stomach cancer. To reduce the incidence of these conditions, the World Health Organization (WHO) recommends reducing the population-wide average sodium intake by 30% by 2025, which limits total daily sodium intake per person to about 2 grams (g), or 2,000 milligrams (mg), per day. The U.S. Department of Agriculture’s Dietary Guidelines for Americans recommends that healthy adults limit sodium to less than 2,300 mg per day. Current daily sodium intake in the U.S. is estimated at 3,400 mg/day per person.

Most sodium in people’s diets comes from processed and packaged foods. The American Heart Association estimates that 75% or more of daily sodium intake in the U.S. is from processed/packaged foods and restaurant foods. Reducing sodium in packaged foods through product reformulation programs is considered by WHO as a “best buy” to prevent diseases related to high sodium intake. In 2021, the WHO released guidance for sodium levels in food categories that are the biggest contributors to sodium intake such as processed meats, bread and sauces. For example, the WHO benchmark for lunch meat is 540 mg of sodium per 100 g of product, and bread is 330 mg of sodium per 100 g of product. Many countries have implemented reformulation programs for processed foods; however, they may be poorly monitored and include fewer food categories than recommended by the WHO.

The Australian government established a voluntary reformulation program for 27 packaged food categories. The WHO benchmarks, however, include 58 packaged food categories.

“We had previously modeled the potential impact of the Australian program,” said the study’s co-lead author Kathy Trieu, M.P.H., Ph.D., lead author of the study and senior research fellow in food policy at The George Institute for Global Health, and a senior lecturer at the University of New South Wales, both in Sydney, Australia. “In this study, we wanted to estimate the potential number of additional premature deaths, new cases of disease and years lived with disability that may be averted with the WHO sodium benchmarks, which are above and beyond the Australian government’s sodium reformulation targets.”

In their previous study, Trieu and colleagues found that Australia’s plan reduced average sodium intake by 107 mg per day per person and may avert about 500 deaths, 1,900 new cases of cardiovascular disease, chronic kidney disease and stomach cancer (combined), and 7,355 disability-adjusted life years (DALYs) in Australia each year. DALYs are a measure of years of healthy life lost due to illness or premature death.

They applied the same statistical model to estimate the potential impact of extending the Australian plan to include all 58 packaged food categories in the WHO benchmarks. The model used national data from 2011-2012 on sodium intake, food composition and sales for the targeted food categories. The researchers first estimated the reduction in sodium intake that may occur if the WHO targets were met. Then, using published statistics on the relationship between sodium intake and high blood pressure, they calculated the potential effect of sodium reduction on rates of cardiovascular disease and chronic kidney disease. High blood pressure is a major risk factor for both conditions.

The impact on stomach cancer was calculated using risk estimates derived from published studies of sodium and stomach cancer. The analysis determined the potential number of deaths, new cases of disease and DALYs that may be avoided by following the WHO guidance.

The analyses estimated that implementing the WHO sodium targets in Australia may result in:

• An average of 404 mg per day reduction in sodium for adults;
• Approximately 1,770 fewer deaths from cardiovascular disease, kidney disease and stomach cancer each year, with most of the impact on deaths due to avoiding deaths from cardiovascular disease (1,450 of the total).
• About 4,500 fewer new cases of cardiovascular disease, 2,050 fewer new cases of kidney disease and 350 fewer new cases of stomach cancer per year; and
• A total of 25,670 fewer DALYs from the three conditions.

“Our findings indicate that compliance with WHO benchmarks compared with Australia’s current sodium targets may result in substantial health gains and prevent more than three times as many deaths and new cases of disease each year,” said Trieu, adding that the greater impact of the WHO benchmarks may be explained by both including more packaged food products and stricter sodium targets.

Study limitations include the use of national nutrition survey data that was collected in 2011-12 and based on a single 24-hour diet recall to estimate food consumption, therefore, this data may not reflect current sodium intake. In addition, estimates of disease burden may be less accurate than estimates of more easily measured outcomes such as death. Also, there may be other ways in addition to blood pressure that sodium reduction affects cardiovascular and kidney disease.

Co-authors are Daisy Coyle, Ph.D.; Emalie Rosewarne, M. Nutrition & Diet; Maria Shahid, M.P.H.; Rain Yamamoto, Ph.D.; Chizuru Nishida, Ph.D.; Bruce Neal, Ph.D.; Feng He, Ph.D.; Matti Marklund, Ph.D.; and Jason Wu, Ph.D. Authors’ disclosures are listed in the manuscript.

The study was funded by an Australian National Health and Medical Research Council Partnership Project.

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Additional Resources:

• Available multimedia is on right column of release link https://newsroom.heart.org/news/what-if-sodium-in-packaged-foods-was-reduced-for-an-entire-continent?preview=8ab29e27df1f572d8c3e686fd44f4b44
• After Jan. 10, view the manuscript online.
• AHA health information:
  • 7 Salty Sodium Myths Busted Infographic
  • Tips for building healthy habits
• AHA advocacy resource: Reducing Sodium in the US Diet(April 2020)
• AHA news releases:
  • Diet change may make biggest impact on reducing heart risk in people with hypertension (Sept. 2022)
  • Heart-healthy, lower sodium version of traditional Chinese cuisine lowered blood pressure (July 2022)
• AHA Scientific Statement: 2021 Dietary Guidance to Improve Cardiovascular Health (Nov 2021)
• Follow AHA/ASA news on Twitter @HeartNews
• Follow news from the AHA’s Hypertension journal @HyperAHA

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JOURNAL

Hypertension

DOI

10.1161/HYPERTENSIONAHA.122.20105 

ARTICLE TITLE

Estimated dietary and health impact of the World Health Organization’s global sodium benchmarks on packaged foods in Australia: A modeling study

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