'Biodiversity time machine' provides insights into a century of loss

Scientists have run the first proof of concept of their DNA 'time machine' to shed light on a century of environmental change in a freshwater lake -- including warming temperatures and pollution, leading to the potentially irreversible loss of biodiversity.

Their approach, which uses AI applied to DNA-based biodiversity, climate variables and pollution, could help regulators to protect the planet's existing biodiversity levels, or even improve them.

Researchers from the University of Birmingham, in collaboration with Goethe University in Frankfurt, used sediment from the bottom of a lake in Denmark to reconstruct a 100-year-old library of biodiversity, chemical pollution, and climate change levels. This lake has a history of well-documented shifts in water quality, making it a perfect natural experiment for testing the biodiversity time machine.

Publishing their findings today (7 Nov) in eLife, the experts reveal that the sediment holds a continuous record of biological and environmental signals that have changed over time -- from (semi)pristine environments at the start of the industrial revolution to the present.

The team used environmental DNA -- genetic material left behind by plants, animals, and bacteria -- to build a picture of the entire freshwater community. Assisted by AI, they analysed the information, in conjunction with climate and pollution data, to identify what could explain the historic loss of species that lived in the lake.

Principal investigator Luisa Orsini, Professor of Evolutionary Systems Biology and Environmental Omics at the University of Birmingham and Fellow of the Alan Turing Institute, explained: "We took a sediment core from the bottom of the lake and used biological data within that sediment like a time machine -- looking back in time to build a detailed picture of biodiversity over the last century at yearly resolution. By analysing biological data with climate change data and pollution levels we can identify the factors having the biggest impact on biodiversity.

"Protecting every species without impacting human production is unrealistic, but using AI we can prioritise the conservation of species that deliver ecosystem services. At the same time, we can identify the top pollutants, guiding regulation of chemical compounds with the most adverse effect. These actions can help us not only to preserve the biodiversity we have today, but potentially to improve biodiversity recovery. Biodiversity sustains many ecosystem services that we all benefit from. Protecting biodiversity mean protecting these services."

The researchers found that pollutants such as insecticides and fungicides, alongside increases in minimum temperature (a 1.2-1.5-degree increase) caused the most damage to biodiversity levels.

However, the DNA present in the sediment also showed that over the last 20 years the lake had begun to recover. Water quality improved as agricultural land use declined in the area surrounding the lake. Yet, whereas the overall biodiversity increased, the communities were not the same as in the (semi)pristine phase. This is concerning as different species can deliver different ecosystem services, and therefore their inability to return to a particular site can prevent the reinstatement of specific services.

Niamh Eastwood, lead author and PhD student at the University of Birmingham said: "The biodiversity loss caused by this pollution and the warming water temperature is potentially irreversible. The species found in the lake 100 years ago that have been lost will not all be able to return. It is not possible to restore the lake to its original pristine state, even though the lake is recovering. This research shows that if we fail to protect biodiversity, much of it could be lost forever."

Dr Jiarui Zhou, co-lead author and Assistant Professor in Environmental Bioinformatics at the University of Birmingham, said: "Learning from the past, our holistic models can help us to predict the likely loss of biodiversity under a 'business as usual' and other pollution scenarios. We have demonstrated the value of AI-based approaches for understanding historic drivers of biodiversity loss. As new data becomes available, more sophisticated AI models can be used to further improve our predictions of the causes of biodiversity loss."

Read more at Science Daily

Bit by bit, microplastics from tires are polluting our waterways

Urban stormwater particles from tyre wear were the most prevalent microplastic a new Griffith-led study has found.

Published in Environmental Science & Technology, the study showed that in stormwater runoff during rain approximately 19 out of every 20 microplastics collected were tyre wear particles with anywhere from 2 to 59 particles per litre of water.

"Pollution of our waterways by microplastics is an emerging environmental concern due to their persistence and accumulation in aquatic organisms and ecosystems," said lead author Dr Shima Ziajahromi, a research fellow at the Australian Rivers Institute.

"Stormwater runoff which contains a mixture of sediment, chemical, organic and physical pollutants, is a critical pathway for microplastics to washed off from urban environments during rain and into local aquatic habitats.

"But to date, our knowledge of the amount of microplastics in urban stormwater, particularly tyre wear particles, is limited, as is the potential strategies we can use to minimise this source."

Tyre rubber contains up to 2500 chemicals with the contaminants that leach from tyres considered more toxic to bacteria and microalgae than other plastic polymers.

"Due to the analytical challenges in measuring this source of microplastics in stormwater, research to date often lacks information about the actual number of tyre wear particles water samples," said Dr Ziajahromi.

Quantitative information of this type is crucial to improve our understanding of the amount of tyre wear particles in stormwater, assess the risk to the environment, and to develop management strategies.

"Our study quantified and characterize microplastics and tyre wear particles in both stormwater runoff and sediment of stormwater drainage systems in Queensland," said co-author Professor Fred Leusch, who leads the Australian Rivers Institute's Toxicology Research Program.

"We also assessed the effectiveness of a stormwater treatment device to capture and remove these contaminants from stormwater and evaluated the role of a constructed stormwater wetland for capturing microplastics in the sediment, removing it from stormwater runoff.

"The device is a bag made of 0.2 millimetre mesh which can be retrofitted to stormwater drains. Although originally designed to capture gross pollutants, sediment, litter and oil and grease, it significantly reduced microplastics from raw runoff, with up to 88% less microplastics in treated water which had passed through the device."

Sediment samples collected from the inlet and outlet of a constructed stormwater wetland contained between 1450 to 4740 particles in every kilogram of sediment, with more microplastics in the sediment at the inlet than the outlet, indicating the wetland's ability to remove them from stormwater.

"Microplastics that enter constructed wetlands for stormwater drainage systems settle in the sediment and form a biofilm, leading to their accumulation over time, removing them from stormwater runoff," said Dr Ziajahromi.

"Urban stormwater runoff typically requires treatment for the removal of suspended solids and nutrients such as nitrogen and phosphorus in many jurisdictions in Australia, with some also requiring the removal of gross pollutants. However, regulations are lagging behind when it comes to microplastics and tyre wear particles."

Read more at Science Daily

Microplastic pollution: Plants could be the answer

Could plants be the answer to the looming threat of microplastic pollution? Scientists at UBC's BioProducts Institute found that if you add tannins -- natural plant compounds that make your mouth pucker if you bite into an unripe fruit -- to a layer of wood dust, you can create a filter that traps virtually all microplastic particles present in water.

While the experiment remains a lab set-up at this stage, the team is convinced that the solution can be scaled up easily and inexpensively once they find the right industry partner.

Microplastics are tiny pieces of plastic debris resulting from the breakdown of consumer products and industrial waste. Keeping them out of water supplies is a huge challenge, says Dr. Orlando Rojas, the institute's scientific director and the Canada Excellence Research Chair in Forest Bioproducts.

He noted one study which found that virtually all tap water is contaminated by microplastics, and other research which states that more than 10 billion tons of mismanaged plastic waste will be dispersed in the environment by 2025.

"Most solutions proposed so far are costly or difficult to scale up. We're proposing a solution that could potentially be scaled down for home use or scaled up for municipal treatment systems. Our filter, unlike plastic filters, does not contribute to further pollution as it uses renewable and biodegradable materials: tannic acids from plants, bark, wood and leaves, and wood sawdust -- a forestry byproduct that is both widely available and renewable."

Captures a wide variety of plastics

For their study, the team analyzed microparticles released from popular tea bags made of polypropylene. They found that their method (they're calling it "bioCap") trapped from 95.2 per cent to as much as 99.9 per cent of plastic particles in a column of water, depending on plastic type. When tested in mouse models, the process was proved to prevent the accumulation of microplastics in the organs.

Dr. Rojas, a professor in the departments of wood science, chemical and biological engineering, and chemistry at UBC, adds that it's difficult to capture all the different kinds of microplastics in a solution, as they come in different sizes, shapes and electrical charges.

"There are microfibres from clothing, microbeads from cleansers and soaps, and foams and pellets from utensils, containers and packaging. By taking advantage of the different molecular interactions around tannic acids, our bioCap solution was able to remove virtually all of these different microplastic types."

Collaborating on sustainable solutions

The UBC method was developed in collaboration with Dr. Junling Guo, a professor at the Center of Biomass Materials and Nanointerfaces at Sichuan University in China. Marina Mehling (she/her), a PhD student at UBC's department of chemical and biological engineering, and Dr. Tianyu Guo (she/her), a postdoctoral researcher at the BioProducts Institute, also contributed to the work.

Read more at Science Daily

Drought, heat waves worsen West Coast air pollution inequality

A new study led by North Carolina State University researchers found drought and heat waves could make air pollution worse for communities that already have a high pollution burden in California, and deepen pollution inequalities along racial and ethnic lines.

Published in Nature Communications, the study also found financial penalties for power plants can significantly reduce people's pollution exposure, except during severe heat waves.

"We have known that air pollution disproportionally impacts communities of color, the poor and communities that are already more likely to be impacted by other sources of environmental pollution," said the study's lead author Jordan Kern, assistant professor of forestry and environmental resources at NC State. "What we know now is that drought and heat waves makes things worse."

For the study, researchers estimated emissions of sulfur dioxide, nitrogen oxides and fine particulate matter from power plants in California across 500 different scenarios for what the weather could look like in future years, which they called "synthetic weather years." These years simulated conditions that could occur based on historical wind, air, temperature and solar radiation values on the West Coast between 1953 and 2008. Then by using information about the location of power plants in California and how much electricity they would be generating under different weather conditions, they estimated air pollution within individual counties.

They saw the worst air pollution in the hottest, driest years, which Kern said is due to the demand for more air conditioning during hot years. In addition, drought can impact the availability of hydropower. The excess electricity has to come from somewhere else, which is where fossil fuel plants come in.

"One of the things we were interested in was teasing apart the relative roles of drought, which can be chronic, lasting for months or years, versus heat waves, which can happen like a flash in a pan," Kern said. "We found drought is a driver of chronic pollution exposure, but heat waves are responsible for these incredible spikes in emissions in a short period of time."

They also saw that counties with a higher existing pollution burden were disproportionately impacted by pollution during drought and heat waves. Counties that were more diverse by race and ethnicity were also far more likely to be impacted by increased emissions from power plants during droughts and heat waves.

"The more diverse your county is by race and ethnicity, the more likely you are to be impacted by air pollution on an annual basis," Kern said. "During a drought, the relationship is more pronounced."

When they simulated the impact of three different policies that taxed power generators for emitting air pollution locally, overall, or both, they found that penalties helped reduce pollution health damages in more than 99% of days. However, during extreme heat waves, penalties failed to reduce emissions.

"Penalties make the more damaging power plants more expensive to operate, while it makes clean power plants comparatively less expensive," Kern said. "It incentivizes the system to switch to rely on more clean power plants, but that stops happening during really massive heat waves. The power operators have no choice but to turn on every power plant. They can't switch from the dirty power plants to the clean ones."

Read more at Science Daily

Study links adoption of electric vehicles with less air pollution and improved health

Electric vehicles are widely hailed as a key way to mitigate climate change through reduced emissions, but research on the dual benefits of reduced air pollution and improved health has been largely hypothetical.

A team of researchers from the Keck School of Medicine of USC have now begun to document the actual impact of electric vehicle adoption in the first study to use real-world data to link electric cars, air pollution and health. Leveraging publicly available datasets, the researchers analyzed a "natural experiment" occurring in California as residents in the state rapidly transitioned to electric cars, or light-duty zero emissions vehicles (ZEVs). The results were just published in the journal Science of the Total Environment.

The team compared data on total ZEV registration, air pollution levels and asthma-related emergency room visits across the state between 2013 to 2019. As ZEV adoption increased within a given zip code, local air pollution levels and emergency room visits dropped.

"When we think about the actions related to climate change, often it's on a global level," said Erika Garcia, PhD, MPH, an assistant professor of population and public health sciences at the Keck School of Medicine and the study's lead author. "But the idea that changes being made at the local level can improve the health of your own community could be a powerful message to the public and to policy makers."

The researchers also found that while total ZEVs increased over time, adoption was considerably slower in low-resource zip codes -- what the researchers refer to as the "adoption gap." That disparity points to an opportunity to restore environmental justice in communities that are disproportionately affected by pollution and related health problems.

"The impacts of climate change on health can be challenging to talk about because they can feel very scary," said Sandrah Eckel, PhD, an associate professor of population and public health sciences at the Keck School of Medicine and the study's senior author. "We're excited about shifting the conversation towards climate change mitigation and adaptation, and these results suggest that transitioning to ZEVs is a key piece of that."

Benefits for health and the climate

To study the effects of electric vehicle adoption, the research team analyzed and compared four different datasets. First, they obtained data on ZEVs (which includes battery electric, plug-in hybrid, and hydrogen fuel cell cars) from the California Department of Motor Vehicles and tabulated the total number registered in each zip code for every year between 2013 and 2019.

They also obtained data from U.S. Environmental Protection Agency air monitoring sites on levels of nitrogen dioxide (NO2), an air pollutant related to traffic, and zip code level asthma-related visits to the emergency room. Asthma is one of the health concerns long linked with air pollutants such as NO2, which can also cause and exacerbate other respiratory diseases, as well as problems with the heart, brain and other organ systems.

Finally, the researchers calculated the percentage of adults in each zip code who held bachelor's degrees. Educational attainment levels are frequently used as an indicator of a neighborhood's socioeconomic status.

At the zip code level, for every additional 20 ZEVs per 1,000 people, there was a 3.2% drop in the rate of asthma-related emergency visits and a small suggestive reduction in NO2 levels. On average across zip codes in the state, ZEVs increased from 1.4 to 14.6 per 1,000 people between 2013 and 2019. ZEV adoption was significantly lower in zip codes with lower levels of educational attainment. For example, a zip code with 17% of the population having a bachelor's degree had, on average, an annual increase of 0.70 ZEVs per 1,000 people compared to an annual increase of 3.6 ZEVs per 1,000 people for a zip code with 47% of the population having a bachelor's degree.

Past research has shown that underserved communities, such as lower-income neighborhoods, tend to face worse pollution and associated respiratory problems than more affluent areas. If ZEVs replace gas-powered cars in those neighborhoods, they could stand to benefit substantially.

"Should continuing research support our findings, we want to make sure that those communities that are overburdened with the traffic-related air pollution are truly benefiting from this climate mitigation effort," Garcia said.

More to learn

While climate change is a massive health threat, mitigating it offers a massive public health opportunity, Eckel said. As one of the first studies to quantify the real-world environmental and health benefits of ZEVs, the research can help demonstrate the power of this mitigation measure, including possibly reduced health care utilization and expenditures.

The findings are promising, Garcia said, but many questions remain. Future studies should consider additional impacts of ZEVs, including emissions related to brake and tire wear, mining of materials for their manufacture, and disposal of old cars. The researchers also hope to study additional types of pollutants and other classes of vehicles, in addition to conducting a follow-up study of the effects of the ever-growing share of ZEVs in the state.

Moving forward, transitioning to ZEVs is just one part of the solution, Eckel said. Shifting to public transport and active transport, including walking and biking, are other key ways to boost environmental and public health.

Read more at Science Daily

Evolution of tree roots may have driven mass extinctions

The evolution of tree roots may have triggered a series of mass extinctions that rocked the Earth's oceans during the Devonian Period over 300 million years ago, according to a study led by scientists at IUPUI, along with colleagues in the United Kingdom.

Evidence for this new view of a remarkably volatile period in Earth's pre-history is reported in the Geological Society of America Bulletin. The study was led by Gabriel Filippelli, Chancellor's Professor of Earth Sciences in the School of Science at IUPUI, and Matthew Smart, a Ph.D. student in his lab at the time of the study.

"Our analysis shows that the evolution of tree roots likely flooded past oceans with excess nutrients, causing massive algae growth," Filippelli said. "These rapid and destructive algae blooms would have depleted most of the oceans' oxygen, triggering catastrophic mass extinction events."

The Devonian Period, which occurred 419 million to 358 million years ago, prior to the evolution of life on land, is known for mass extinction events, during which it's estimated nearly 70 percent of all life on Earth perished.

The process outlined in the study -- known scientifically as eutrophication -- is remarkably similar to modern, albeit smaller-scale, phenomenon currently fueling broad "dead zones" in the Great Lakes and the Gulf of Mexico, as excess nutrients from fertilizers and other agricultural runoff trigger massive algae blooms that consume all of the water's oxygen.

The difference is that these past events were likely fueled by tree roots, which pulled nutrients from the land during times of growth, then abruptly dumped them into the Earth's water during times of decay.

The theory is based upon a combination of new and existing evidence, Filippelli said.

Based upon a chemical analysis of stone deposits from ancient lake beds -- whose remnants persist across the globe, including the samples used in the study from sites in Greenland and off the northeast coast of Scotland -- the researchers were able to confirm previously identified cycles of higher and lower levels of phosphorus, a chemical element found in all life on Earth.

They were also able to identify wet and dry cycles based upon signs of "weathering" -- or soil formation -- caused by root growth, with greater weathering indicating wet cycles with more roots and less weathering indicating dry cycles with fewer roots.

Most significantly, the team found the dry cycles coincided with higher levels of phosphorus, suggesting dying roots released their nutrients into the planet's water during these times.

"It's not easy to peer over 370 million years into the past," said Smart. "But rocks have long memories, and there are still places on Earth where you can use chemistry as a microscope to unlock the mysteries of the ancient world."

In light of the phosphorus cycles occurring at the same time as the evolution of the first tree roots -- a feature of Archaeopteris, also the first plant to grow leaves and reach heights of 30 feet -- the researchers were able to pinpoint the decay of tree roots as the prime suspect behind the Devonian Periods extinction events.

Fortunately, Filippelli said, modern trees don't wreak similar destruction since nature has since evolved systems to balance out the impact of rotting wood. The depth of modern soil also retains more nutrients compared to the thin layer of dirt that covered the ancient Earth.

But the dynamics revealed in the study shed light on other newer threats to life in Earth's oceans. The study's authors note that others have made the argument that pollution from fertilizers, manure and other organic wastes, such as sewage, have placed the Earth's oceans on the "edge of anoxia," or a complete lack of oxygen.

"These new insights into the catastrophic results of natural events in the ancient world may serve as a warning about the consequences of similar conditions arising from human activity today," Fillipelli said.

Read more at Science Daily

Air pollution, including during wildfires, shows ill effects in children

New research linking air pollution data from federal monitors in the Sacramento area of California, including during significant fires, is showing ill effects of pollution exposure among children, a new University of California, Davis, study suggests.

Blood samples show that children have elevated markers of inflammation, such as interleukin 6, if they were exposed to higher air pollution. Further, higher air pollution was linked to lower cardiac autonomic regulation in children, which impacts how fast the heart beats and how hard it pumps, according to the study.

In the study, published Aug. 3 date in the journal New Directions for Child and Adolescent Research, researchers looked at blood samples from more than 100 healthy children ages 9-11 in the Sacramento area where pollutants near their homes were recorded by the Environmental Protection Agency. The study was authored by Anna M. Parenteau, a doctoral student, and Camelia E. Hostinar, associate professor, both from the UC Davis Department of Psychology. The work took place at UC Davis.

These findings are important because exposure to pollutants released during wildfires has been related to numerous negative health outcomes in children, who have smaller bodies and organ systems than adults, including asthma and decreased lung function, as well as neurodevelopmental outcomes like attention deficit hyperactivity disorder, autism, and deficits in school performance and memory, researchers said.

Looked at particulates

Researchers looked at fine particulate matter data from the EPA (PM2.5) -- or the fine particles that can penetrate lungs and pass into the bloodstream -- finding the children's blood contained markers of systemic inflammation. Additionally, PM2.5, which refers to particulate matter measuring 2.5 micrometers or smaller by the EPA, was linked to lower cardiac autonomic regulation assessed using an electrocardiogram. Specifically, researchers used data files maintained by the EPA, which have daily air quality summary information from each outdoor monitor in the country.

In total, 27 of the children studied had inflammation markers in their blood recorded during significant fires when their neighborhoods recorded significant levels of PM2.5 in the air. These times when fires were burning included during the Mendocino Complex Fire in 2018, which was active about 100 miles from the lab where blood was drawn. The findings were similar to those found in an earlier study, in which the blood of young primates was collected by UC Davis researchers after significant wildfires.

"By examining daily and monthly levels of particulate matter in relation to children's inflammation and autonomic physiology, this study further demonstrates the immediate consequences of exposure to air pollution, which may increase risk of future disease," Parenteau said. Furthermore, Parenteau added: "As climate change continues to impact children and families, it is paramount to understand the impact of environmental contaminants such as air pollution on children's physiology."

Previous studies with children have shown significant associations between ambient air pollution and allergic sensitization, respiratory symptoms, and ultra-structural and cellular changes to their lungs and airways, researchers said.

Researchers have found children may be especially susceptible to the effects of air pollution, given that, compared to adults, they have a higher intake of contaminants and greater lung surface area relative to their body weight.

Continued developmental research on environmental contaminants can sound the alarm about the effects of air pollution and inform policy changes that could promote long-term population health, researchers concluded.

Read more at Science Daily

Agriculture emissions pose risks to health and climate

Agricultural pollution comes from the prairie, but its economic impact on humans is a problem for cities.

A study led by environmental scientists at Rice University's George R. Brown School of Engineering puts numbers to the toll of reactive nitrogen species produced in America's croplands.

The study led by Daniel Cohan, an associate professor of civil and environmental engineering, and graduate student Lina Luo quantifies emissions of nitrogen oxides, ammonia and nitrous oxide from fertilized soils over three years (2011, 2012 and 2017) and compares their impacts by region on air quality, health and climate.

While seasonal and regional impacts differ across types of emission, the study found total annual damages from ammonia were much larger overall -- at $72 billion -- than those from nitrogen oxides ($12 billion) and nitrous oxide ($13 billion).

Air pollution damages are measured by increased mortality and morbidity and the value of statistical life, while monetized damages from climate change include the threats to crops, property, ecosystem services and human health.

On that basis, the researchers found the health impact of air pollution from ammonia and nitrogen oxides, which react to form particulate matter and ozone, substantially outweighed climate impact from nitrous oxide in all regions and years.

The highest social costs arose from agriculture-heavy regions of California, Florida and the Midwest, where ammonia and nitrogen oxides form air pollution upwind of population centers. For both pollutants, emissions peak in the spring after fertilizers are applied.

The study in the American Chemical Society journal Environmental Science & Technology concludes air pollution, health and climate should all be considered in future assessments of how farming practices affect reactive nitrogen emissions.

"We always talk about how carbon dioxide and methane contribute to greenhouse gases, but nitrous oxide is about 300 times more potent than carbon dioxide for its global warming potential," Luo said.

She noted farming strategies that reduce greenhouse gases can increase air pollutants and vice versa. "We need to see if they can reduce all three nitrogen species -- or make some tradeoffs -- and still not decrease crop yield," Luo said.

Nitrogen is essential for crop growth, Cohan added, but the study shows the importance of controlling agricultural emissions has been largely neglected by air quality management and climate policy, even as the Environmental Protection Agency considers tightening air quality standards and the Biden administration seeks to slash greenhouse gas emissions.

He said federal agencies have focused on controlling transportation and industrial emissions, leaving agriculture as the largest source of damaging nitrogen pollutants in the United States, a problem exacerbated by climate change and increased crop production.

"Our group had been studying nitrogen oxide emissions for a number of years and began to realize that we can't just focus on that," Cohan said. "We needed to consider the range of emissions that come from soils, and we became curious about the relative impacts of different air pollutants and greenhouse gases the emanate from agricultural soils.

"A big part of our motivation was realizing that choices in farming practices might cause some emissions to go up and other emissions to go down," he said. For instance, switching from surface broadcast to deep injection of fertilizers would lower ammonia but raise nitrogen oxide emissions. That would benefit nearby cities sensitive to particulate matter levels, but harm regions where ozone is of more concern.

Cohan said when all the emissions are quantified on a monetary basis, ammonia and nitrogen oxides that form air-polluting particulate matter and ozone and contribute to global warming have the greatest impact.

"Those of us who study these pollutants for a living know how potent ammonia is, but the message hasn't gotten through to most regulators and policymakers," Cohan said. "In fact, ammonia is one of the most potent sources of particulate matter because of how it binds with other pollutants to have a multiplying effect.

"That's an important message: We need to take more steps to control ammonia," he said.

If there's a silver lining, Cohan said, it's that pollution from other sources has dropped enough to make agriculture's impact prevalent.

"What's crucial is to take steps that have more of the nitrogen go to the crops, and less of it be released to the air and water," he said. That could involve adding biochar or other amendments to soil, a topic of ongoing study at Rice.

"Before we can do that, we needed to establish a baseline of emissions coming from the soil," Cohan said. "This paper lays that out."

Read more at Science Daily

Pollution from cooking emissions hangs in the air

Organic aerosols -- such as those released in cooking -- may stay in the atmosphere for several days, because of nanostructures formed by fatty acids as they are released into the air.

By identifying the processes which control how these aerosols are transformed in the atmosphere, scientists will be able to better understand and predict their impact on the environment and the climate.

Experts at the Universities of Birmingham and Bath have used instruments at the Diamond Light Source and the Central Laser Facility, both based at the Harwell Campus in Oxford, to probe the behaviour of thin films of oleic acid -- an unsaturated fatty acid commonly released when cooking.

In the study, published in Atmospheric Chemistry and Physics, they were able to analyse the particular molecular properties that control how rapidly aerosol emissions can be broken down in the atmosphere.

Then, using a theoretical model combined with experimental data the team was able to predict the amount of time aerosols generated from cooking may hang around in the environment.

These types of aerosols have long been associated with poor air quality in urban areas, but their impact on human-made climate change is hard to gauge. That's because of the diverse range of molecules found within aerosols, and their varying interactions with the environment.

By identifying the nanostructure of molecules emitted during cooking that slows down the break-up of organic aerosols, it becomes possible to model how they are transported and dispersed into the atmosphere.

Lead author Dr Christian Pfrang, of the University of Birmingham's School of Geography, Earth and Environmental Sciences, said: "Cooking aerosols account for up to 10 per cent of particulate matter (PM) emissions in the UK. Finding accurate ways to predict their behaviour will give us much more precise ways to also assess their contribution to climate change."

Co-author Dr Adam Squires, of the University of Bath, said: "We're increasingly finding out how molecules like these fatty acids from cooking can organise themselves into bilayers and other regular shapes and stacks within aerosol droplets that float in the air, and how this completely changes how fast they degrade, how long they persist in the atmosphere, and how they affect pollution and weather."

Read more at Science Daily

Pollution from freight traffic disproportionately impacts communities of color across 52 US cities

In urban areas across the U.S., low-income neighborhoods and communities of color experience an average of 28% more nitrogen dioxide (NO2) pollution than higher-income and majority-white neighborhoods. The disparity is driven primarily by proximity to trucking routes on major roadways, where diesel trucks are emitters of NO2 and other air pollutants.

Nitrogen dioxide is a common air pollutant that can cause a range of health problems, such as chronic respiratory illness and asthma. But it can be difficult to trace.

A new study used high-resolution air pollution data measured with satellites to track NO2 for nearly two years in major cities across the U.S. The researchers then paired the pollution data with both demographic data and metrics that analyze the degree of racial segregation in a community.

Cities with bigger populations tended to have larger disparities in NO2 pollution between low-income neighborhoods of color and high-income white neighborhoods, according to the study. Phoenix, Los Angeles and Newark, N.J., have the highest NO2 inequalities, all with a discrepancy in NO2 exposure of over 40%.

Both commuter traffic and heavy-duty trucks contribute NO2 and other pollutants, but diesel trucks are the dominant source, contributing on average up to half of a city's NO2 despite being at most 5% of traffic. Because diesel trucks also emit other harmful gases and particulates, changes in NO2 are also thought to reflect exposure to other pollutants as well.

The findings are detailed in the AGU journal Geophysical Research Letters, which publishes high-impact, short-format reports with immediate implications spanning all Earth and space sciences.

"One of the novel things we looked at was the integration of segregation metrics and air quality. Previously, we had been limited in our ability to address air pollution inequality, but with improvements in satellite resolution we are now able to get spatially and temporally continuous data at finer resolutions within cities," said Angelique Demetillo, an atmospheric chemist at the University of Virginia and lead author of the study.

Measuring pollutants like NO2 is difficult to do at a scale that's useful to local policymakers. While previous studies have shown disparities in air quality, the new findings offer near-daily pollution data at small scales, providing important quantitative information policymakers can use to guide zoning and public health and that can reflect the lived experience of community members.

The new study found a 60% drop in heavy trucking on weekends results in a 40% decrease in air pollution inequality. That can point policymakers to a clear emissions-reducing target.

"In terms of environmental justice, one of the things we have lacked is these observations across an entire city that also have temporal variability that we can use to understand the sources [of pollution]," said Sally Pusede, an atmospheric chemist at the University of Virginia who co-authored the study.

"We have these new data and methodologies that continue to show us what we already know through experience, but in the U.S., it's [quantitative] data that informs policy," said Regan Patterson, a transportation and public health expert at the Congressional Black Caucus Foundation.

Bigger city, bigger disparity

Transitioning to electric heavy-duty trucks could be one way of reducing pollution exposure in neighborhoods close to highways. California already has a mandate of doing this by 2045. But, Pusede pointed out, while emissions from diesel trucks are the biggest driver of exposure inequality, other pollution sources contribute to the problem. "Even if we eliminated emissions from trucking, we would still see inequalities present because there are other sources of inequality."

Discrepancies in exposure to pollution between communities of color and white communities are well-documented. They often stem from zoning practices that result in communities of color forming in less desirable areas or infrastructure like highways being built in close proximity to -- or through -- a neighborhood.

Patterson said over the long term, transformative changes are needed to truly begin to remove NO2 pollution disparity. "How do you rectify the inequities that have literally been built into the environment, where certain groups are more likely to be adjacent to major roadways?" she asked.

Both Patterson and Pusede referenced a bill in the new infrastructure package aimed at physically reconnecting communities by removing freeways as a necessary step toward equalizing air quality. More immediately, Demetillo hoped her study and studies like it will help put air-quality information into the hands of community members.

Read more at Science Daily

Reliably measuring oxygen deficiency in rivers or lakes

 When wastewater from villages and cities flows into rivers and lakes, large quantities of fats, proteins, sugars and other carbon-containing, organic substances wind up in nature together with the fecal matter. These organic substances are broken down by bacteria that consume oxygen. The larger the volume of wastewater, the better the bacteria thrive. This, however, means the oxygen content of the water continues to decrease until finally the fish, muscles or worms literally run out of air. This has created low-oxygen death zones in many rivers and lakes around the world.

No gold standard for measurements until now

In order to measure how heavily the waters are polluted with organic matter from feces, government bodies and environmental researchers regularly take water samples. One widely used measurement method uses a chemical reaction to determine the content of organic substances. As an international team of scientists now shows, this established method provides values from which the actual degree of the water pollution can hardly be derived. Prof. Helmuth Thomas, Director of Hereon's Institute of Carbon Cycles is also a contributor to the study, which has now been published in the scientific journal Science Advances. "In the paper, we are therefore also introducing a new method for making the measurements much more reliable in the future," he says.

Using the conventional measurement method, water samples are mixed with the chemicals permanganate or dichromate. These are especially reactive and break down all organic substances in a short time. The quantity of consumed permanganates or dichromates can then be used to determine how much organic substance was contained in the water sample. Experts refer to this measurement as "chemical oxygen demand," COD. The problem with the COD measurements is that they do not differentiate between the organic substances that wind up in the water with the sewage, and those that arise naturally -- such as lignin and humic acids -- which are released when wood decays. This means that the water pollution can hardly be distinguished from the natural content of organic substances. "For the Han River in South Korea, for example, we have shown that the pollution with organic substances from wastewater in the past twenty-five years has decreased. The COD measurements, however, still show high values as they were before," says Helmuth Thomas, "because here the natural substances make up a large portion of the organic matter in the water."

Complicated biological analysis

But how can the actual pollution be measured more reliably? A biological measurement method has been established here for decades, but it is much more complex than the COD method and is therefore used more seldomly by government bodies and research institutions. In this case, a water sample is taken from the river or lake and the oxygen content of the water is measured as an initial value. Another "parallel sample" is immediately sealed airtight. Then this water sample rests for five days. During this time, the bacteria break down the organic substance, whereby they gradually consume the oxygen in the water. After five days, the container is opened and the oxygen is measured. If the water contains a great deal of organic matter, then the bacteria were particularly active. The oxygen consumption was then correspondingly high. Experts refer to the "biological oxygen demand" (BOD) in this measurement. "The BOD measurement is far more precise than the COD because the bacteria preferentially break down the small organic molecules from the wastewater but leave the natural ones, such as lignin, untouched," says Thomas. Nevertheless, the BOD measurement has its disadvantages, too. On the one hand, the BOD measurement takes five days, while the COD value is available after a few minutes. On the other, while filling, storing and measuring the water samples, meticulous care must be taken to ensure that no oxygen from the ambient air winds up in the sample and falsifies the measurement value. "Only a few people with a great deal of laboratory experience have mastered how to entirely handle the BOD measurement," says Thomas. "Therefore, government bodies and researchers even today still prefer the COD despite its greater uncertainties."

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Coastal cities leave up to 75% of seafloor exposed to harmful light pollution

The global expansion of coastal cities could leave more than three quarters of their neighbouring seafloor exposed to potentially harmful levels of light pollution.

A study led by the University of Plymouth (UK) showed that under both cloudy and clear skies, quantities of light used in everyday street lighting permeated all areas of the water column.

This could pose a significant threat to coastal species, with recent research showing the presence of artificial skyglow can disrupt the lunar compass species use when covering long distances.

However, the current study found that the colour of the wavelengths shone at the surface had a marked difference on how much biologically important light pollution reached the seafloor.

Many of the white LEDs now being used to illuminate the world's towns and cities use a mixture of green, blue and red wavelengths to generate their brightness.

Green and blue wavelengths left up to 76% and 70% of the three-dimensional seafloor area exposed to light pollution respectively, while the presence of red light was less than 1%.

The research -- which also involved Bangor University, the University of Strathclyde and Plymouth Marine Laboratory -- is published in Scientific Reports, an online journal from the publishers of Nature.

It is the first study in the world to quantify the extent to which biologically important artificial light is prevalent on the seafloor and could, in turn, be having a detrimental effect on marine species.

Dr Thomas Davies, Lecturer in Marine Conservation at the University of Plymouth and the paper's lead author, said: "The areas exposed here are not trivial. Our results focused on a busy marine area and demonstrate the light from coastal urban centres is widespread across the sea surface, sub surface and seafloor of adjacent marine habitats. But Plymouth is still just one coastal city with a population of 240,000 people.

"Seventy-five per cent of the world's megacities are now located in coastal regions and coastal populations are projected to more than double by 2060. So unless we take action now it is clear that biologically important light pollution on the seafloor is likely to be globally widespread, increasing in intensity and extent, and putting marine habitats at risk."

The study focussed on Plymouth Sound and the Tamar Estuary which together form a busy waterway and are home to the largest naval port in Western Europe.

It was conducted over four nights in 2018, when there was little or no moonlight, and blue, green, and red artificial light was shone at the sea surface during both clear and cloudy conditions, and at low and high tide.

A combination of mapping and radiative transfer modelling tools were then used to measure exposure at the surface, beneath the surface, and at the seafloor.

The researchers are now calling for a more comprehensive review of the full impacts of coastal light pollution, to try and mitigate against the most harmful effects as coastal cities grow globally.

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Air pollution can worsen bone health

Some of the effects of air pollution on health are well documented -lung cancer, stroke, respiratory diseases, and a long etcetera- but for others there is less scientific evidence. Such is the case of bone health: there are only a few studies and results are inconclusive. Now, a study in India led by the Barcelona Institute for Global Health (ISGlobal), an institution supported by "la Caixa," has found an association between exposure to air pollution and poor bone health.

Osteoporosis is a disease in which the density and quality of the bone is reduced. Globally, it is responsible for a substantial burden of disease and its prevalence is expected to increase due to aging of the population.

The new study performed by the CHAI Project, led by ISGlobal and published in Jama Network Open, analysed the association between air pollution and bone health in over 3,700 people from 28 villages outside the city of Hyberabad, in southern India.

The authors used a locally-developed model to estimate outdoor exposure at residence to air pollution by fine particulate matter (suspended particles with a diameter of 2.5 ?m or less) and black carbon. The participants also filled a questionnaire on the type of fuel used for cooking. The authors linked this information with bone health assessed using a special type of radiography that measures bone density, called dual-energy x-ray absorptiometry, and measured bone mass at the lumbar spine and the left hip.

The results showed that exposure to ambient air pollution, particularly to fine particles, was associated with lower levels of bone mass. No correlation was found with use of biomass fuel for cooking.

"This study contributes to the limited and inconclusive literature on air pollution and bone health," explains Otavio T. Ranzani, ISGlobal researcher and first author of the study. Regarding the possible mechanisms underlying this association, he says "inhalation of polluting particles could lead to bone mass loss through the oxidative stress and inflammation caused by air pollution."

Annual average exposure to ambient PM2.5 was 32.8 ?g/m3, far above the maximum levels recommended by the World Health Organisation (10 ?g/m3). 58% of participants used biomass fuel for cooking.

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Environmental toxins impair immune system over multiple generations

Industrial pollution concept illustration.

New research shows that maternal exposure to a common and ubiquitous form of industrial pollution can harm the immune system of offspring and that this injury is passed along to subsequent generations, weakening the body's defenses against infections such as the influenza virus.

The study was led by Paige Lawrence, Ph.D., with the University of Rochester Medical Center's (URMC) Department of Environmental Medicine and appears in the Cell Press journal iScience. The research was conducted in mice, whose immune system function is similar to humans.

"The old adage 'you are what you eat' is a touchstone for many aspects of human health," said Lawrence. "But in terms of the body's ability to fights off infections, this study suggests that, to a certain extent, you may also be what your great-grandmother ate."

While other studies have shown that environmental exposure to pollutants can have effects on the reproductive, respiratory, and nervous system function across multiple generations, the new research shows for the first time that the immune system is impacted as well.

This multigenerational weakening of the immune system could help explain variations that are observed during seasonal and pandemic flu episodes. Annual flu vaccines provide some people more protection than others, and during pandemic flu outbreaks some people get severely ill, while others are able to fight off the infection. While age, virus mutations, and other factors can explain some of this variation, they do not fully account for the diversity of responses to flu infection found in the general population.

"When you are infected or receive a flu vaccine, the immune system ramps up production of specific kinds of white blood cells in response," said Lawrence. "The larger the response, the larger the army of white blood cells, enhancing the ability of the body to successfully fight off an infection. Having a smaller size army -- which we see across multiple generations of mice in this study -- means that you're at risk for not fighting the infection as effectively."

In the study, researchers exposed pregnant mice to environmentally relevant levels of a chemical called dioxin, which, like polychlorinated biphenyls (PCBs), is a common by-product of industrial production and waste incineration, and is also found in some consumer products. These chemicals find their way into the food system where they are eventually consumed by humans. Dioxins and PCBs bio-accumulate as they move up the food chain and are found in greater concentrations in animal-based food products.

The scientists observed the production and function of cytotoxic T cells -- white blood cells that defend the body against foreign pathogens, such as viruses and bacteria, and seek out and destroy cells with mutations that could lead to cancer -- was impaired when the mice were infected with influenza A virus. This weakened immune response was observed not only in the offspring of the mice whose mothers where exposed to dioxin, but in the subsequent generations, including as far out as the rodent equivalent of great-grandchildren. The researchers also found that this effect was more pronounced in female mice.

The study authors' hypothesis that the exposure to dioxin -- which binds a protein in cells called AHR -- in some fashion alters the transcription of genetic instructions. The exposure itself does not trigger a genetic mutation, rather the cellular machinery by which genes are expressed is altered and this phenomenon is passed onto subsequent generations.

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Carbon emissions soar as tourism reaches new heights

A researcher at The University of Texas at San Antonio (UTSA) is examining how the flight routes people take to get to tourist destinations impact the amount of pollution in the air in a newly published study he coauthored in the Annals of Tourism Research.

"This paper provides one of the first efforts to quantify the carbon emissions associated with tourist air travel in the continental United States," explained Neil Debbage, assistant professor of geography and environmental sustainability in UTSA's Department of Political Science and Geography.

The researchers wanted to know whether nonstop routes to tourist destinations can mitigate air travel carbon emissions compared to connecting routes through big airline hubs.

Using International Civil Aviation Organization data, USTA researchers analyzed carbon emissions for direct and connecting routes between the 10 most-populated metropolitan areas in the northeastern United States (New York, Philadelphia, Boston, etc.) and 13 different tourist destinations located in the Sunbelt and Western regions of the United States (Bexar County, Texas; Los Angeles County, California; Miami-Dade County, Florida; etc.).

Some of the key findings:

• Nearly half of the routes analyzed exceeded an individual's annual mobility carbon budget for all forms of transportation.
• Direct routes tended to outperform connecting routes regarding carbon emissions.
• On average the difference between direct and connecting routes was equivalent to operating a refrigerator for an entire year (or roughly 100 carbon dioxide kg/person).
• The majority of direct routes in the database generated carbon emissions below the 575 carbon dioxide kg/person annual mobility cap.

"One potential tactic to mitigate the carbon footprint associated with tourist air travel is to select nonstop routes whenever possible," replied Debbage, who worked on the paper with Keith G. Debbage, professor of geography at the University of North Carolina at Greensboro.

The researchers said they hope this paper will help policymakers consider making new initiatives that accelerate technological innovations regarding aircraft fuel usage, jet engines and jet fuel. Additionally, they also emphasized the importance of broader structural shifts such as implementing realistic carbon pricing for air travel.

Neil Debbage's research focuses on climate change, natural hazards and resiliency. He utilizes geographic information systems, statistical modeling and numerical weather modeling to better understand the changing climate at various scales.

From Science Daily

Air pollution found to affect marker of female fertility in real-life study

Ovarian reserve, a term widely adopted to reflect the number of resting follicles in the ovary and thus a marker of potential female fertility, has been found in a large-scale study to be adversely affected by high levels of air pollution.

Results from the Ovarian Reserve and Exposure to Environmental Pollutants (ORExPo study), a 'real-world data' study using hormone measurements taken from more than 1300 Italian women, are presented today at the Annual Meeting of ESHRE by first investigator Professor Antonio La Marca from the University of Modena and Reggio Emilia, Italy.

Behind the study lay emerging evidence that many environmental chemicals, as well as natural and artificial components of everyday diet, have the potential to disturb the physiological role of hormones, interfering with their biosynthesis, signaling or metabolism. The hormone in this case, anti- Müllerian hormone or AMH, is secreted by cells in the ovary and is now widely recognised as a reliable circulating marker of ovarian reserve.(1)

'The influence of age and smoking on AMH serum levels is now largely accepted,' explains Professor La Marca, 'but a clear effect of environmental factors has not been demonstrated so far.'

The ORExPo study was in effect an analysis of all AMH measurements taken from women living in the Modena area between 2007 and 2017 and assembled in a large database. These measurements were extended to a computing data warehouse in which AMH levels were linked to patients' age and residential address. The analysis was completed with environmental data and a 'geo-localisation' estimate based on each patient's residence. The assessment of environmental exposure considered daily particulate matter (PM) and values of nitrogen dioxide (NO2), a polluting gas which gets into the air from burning fuel.

Results from the 1463 AMH measurements collected from 1318 women firstly showed -- as expected -- that serum AMH levels after the age of 25 were inversely and significantly related to the women's age. However, it was also found that AMH levels were inversely and significantly related to environmental pollutants defined as PM10, PM2.5 and NO2. This association was age-independent.

These results were determined by dividing the full dataset into quartiles reflecting PM10, PM2.5 and NO2 concentrations. The analysis found significantly lower levels of AMH in the fourth quartile than in the lowest quartiles, which, said Professor La Marca, 'again confirms that independently of age the higher the level of particulate matter and NO2, the lower the serum concentration of AMH'. The lowest concentration of AMH -- reflecting 'severe ovarian reserve reduction' -- was measured in subjects who were exposed to levels of PM10, PM2.5 and NO2 above 29.5, 22 and 26 mcg/m3 respectively. Nevertheless, these were values well below the upper limits recommended by the EU and local authorities (ie, 40, 25 and 40 mcg /m3 respectively).

Severe ovarian reserve reduction, as reflected in a serum AMH concentration below 1 ng/ml, was significantly more frequent in the fourth quartile than in the first three quartiles for PM10 (62% vs 38%), for PM2.5, and for NO2. 'This means by our calculations,' said Professor La Marca, 'exposure to high levels of PM10, PM2.5 and NO2 increases the risk of having a severely reduced ovarian reserve by a factor between 2 and 3.'

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Researchers tap rare pristine air to reveal pollution's impact

Data was collected by a research aircraft zigzagging between pristine air over the Amazon rainforest and polluted air nearby.

Five years ago, researchers spent three hours packed aboard a steamy Gulfstream-1 research aircraft as it zig-zagged between pristine air over the Amazon rainforest and polluted air nearby. It was like a trip back (and forth) through time, as scientists weaved between the two vastly different settings, snagging air samples characteristic of today's industrial environment as well as samples of unpolluted air, like that before the industrial age.

An international team of scientists led by Manish Shrivastava of the U.S. Department of Energy's Pacific Northwest National Laboratory has analyzed some of the data and found that human-caused pollution spurs the production of climate-changing particles known as secondary organic aerosols much more than previously thought. The team published its results in Nature Communications.

The findings illustrate how pollution from cars, power plants and other sources combines with natural emissions from trees in the Amazon to spur a marked increase in tiny particles that can reflect or absorb sunlight, help create clouds, change rainfall patterns, and determine how carbon flows between the land and atmosphere -- all with dramatic effects on our planet.

The result comes from a research campaign, known as GOAmazon, led by the Atmospheric Radiation Measurement Research Facility, a Department of Energy Office of Science user facility. The campaign focused on the region near and around Manaus, a Brazilian city of more than 2 million people that is surrounded by tropical forests for hundreds of miles. Scientists refer to the vast forest canopy around Manaus as a "Green Ocean," giving the campaign's name its first letters.

The region offers a research environment hard to find anywhere else on earth. On one side of an undefined boundary is a straight-up tropical rainforest with crystal-clear air and levels of 300 aerosol particles per cubic centimeter; on the other side is the air over Manaus, with particle concentrations 100 times higher due to human activity.

"To really understand how pollution has influenced the atmosphere, we need to compare today's atmosphere with times before the industrial age," said Shrivastava. "This is challenging; of course, we cannot go back in time. But the Amazon is one of the few places on earth where we can study atmospheric chemistry both past and present simultaneously."

On that sunny day five years ago, the ARM aircraft ambled from one side of the boundary to the other, flying about the length of a football field every second, taking air samples from the pristine and then the polluted.

"The region provides a wonderful natural laboratory to understand how anthropogenic emissions have an impact on atmospheric chemistry and climate," said Shrivastava.

While only a tiny sliver of our planet provides the unique opportunity for this study, the findings apply to atmospheric chemistry that takes place everywhere on earth every moment.

This chemistry is behind the refreshing scents of a forest meadow or fresh flowers. When those scents hit our olfactory nerve, we're actually sensing an array of gases, such as carbon-containing isoprene and terpenes, which are given off naturally by trees and other vegetation. The gases contribute to ozone and other forms of haze that affect the amount of sunlight reaching the earth.

When these natural carbon emissions interact in sunlight with nitrogen oxide -- naturally emitted from soils but also a common product largely emitted by human activity -- one result is the formation of tiny particles known as secondary organic aerosols. Though aerosols are tiny, much smaller than the width of a human hair, they are no bit players when it comes to earth's climate. They're an important component in the planet's energy and carbon cycles, determining in part the fate of the planet's vast reservoir of carbon and how it flows between the land and the atmosphere.

Shrivastava and colleagues sought to learn how anthropogenic emissions increase the production of these naturally occurring carbon particles -- just how extensive the effects of human activity are in spurring the transformation of gases ejected from vegetation to these powerful climate-changing particles.

The team integrated this data with other laboratory measurements to develop an advanced computer model to simulate chemical reactions that form particles in the atmosphere. The model does double duty, reproducing both pre-industrial and present-day chemistry. Most models have largely been created based on present-day conditions; the Amazon measurements provide information about pre-industrial chemistry conditions that improved the model's predictive abilities.

The team found that nitrogen oxide emitted from human activities like traffic and oil refineries promotes the creation of these particles from natural forest carbon much more than previously thought, causing an average increase of anywhere from 60 to 200 percent and even up to 400 percent in some cases. That's compared to the 20 percent previously estimated by scientists based on data in more polluted continental locations.

The team also showed that most of these secondary carbon-containing particles were formed by this phenomenon.

"The impact of pollution in creating secondary organic aerosols has been very difficult to tease out," says Shrivastava. "Our findings indicate the earth's atmosphere in many continental locations has already been substantially altered by human activities, and there's a much larger and widespread impact than has been appreciated."

In their paper, Shrivastava and the other authors conclude: "Our results provide a clear picture of how anthropogenic emissions are likely to have greatly modified biogenic SOA [secondary organic aerosol] formation since preindustrial times over the Earth, and imply that rapid urbanization in future years might substantially enhance biogenic SOA formation in the pristine forested regions of the Amazon."

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A warming world increases air pollution

Climate change is warming the ocean, but it's warming land faster and that's really bad news for air quality all over the world, says a new University of California, Riverside study.

The study, published February 4 in Nature Climate Change, shows that the contrast in warming between the continents and sea, called the land-sea warming contrast, drives an increased concentration of aerosols in the atmosphere that cause air pollution.

Aerosols are tiny solid particles or liquid droplets suspended in the atmosphere. They can come from natural sources, like dust or wildfires, or human-made sources such as vehicle and industrial emissions. Aerosols affect the climate system, including disturbances to the water cycle, as well as human health. They also cause smog and other kinds of air pollution that can lead to health problems for people, animals, and plants.

"A robust response to an increase in greenhouse gases is that the land is going to warm faster than the ocean. This enhanced land warming is also associated with increased continental aridity," explained first author Robert Allen, an associate professor of earth sciences at UC Riverside.

The increase in aridity leads to decreased low cloud cover and less rain, which is the main way that aerosols are removed from the atmosphere.

To determine this, the researchers ran simulations of climate change under two scenarios. The first assumed a business-as-usual warming model, in which warming proceeds at a constant, upward rate. The second model probed a scenario in which the land warmed less than expected.

In the business-as-usual scenario, enhanced land warming increased continental aridity and, subsequently, the concentration of aerosols that leads to more air pollution. However, the second model -- which is identical to the business-as-usual model except the land warming is weakened -- leads to a muted increase in continental aridity and air pollution. Thus, the increase in air pollution is a direct consequence of enhanced land warming and continental drying.

The results show that the hotter Earth gets, the harder it's going to be to keep air pollution down to a certain level without strict control over the sources of aerosols.

Because the researchers wanted to understand how greenhouse gas warming affects air pollution, they assumed no change to human-made, or anthropogenic, aerosol emissions.

"That's probably not going to be true because there's a strong desire to reduce air pollution, which involves reducing anthropogenic aerosol emissions," cautioned Allen. "So this result represents an upper bound."

But it also suggests that if the planet keeps warming, larger reductions in anthropogenic aerosol emissions will be required to improve air quality.

"The question is what level of air quality are we going to accept," said Allen. "Even though California has some of the strictest environmental laws in the country we still have relatively poor air quality, and it's much worse in many countries."

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A mountain of evidence on air pollution's harms to children

A new study led by researchers at the Columbia Center for Children's Environmental Health (CCCEH) organizes the available scientific evidence on the effects of air pollution on children's health. The paper in the journal Environmental Research is the first comprehensive review of the associations between various fossil fuel combustion pollutants and multiple health effects in children in the context of assessing the benefits of air pollution and climate change policies.

The researchers say their goal is to expand the kinds of health outcomes used in calculations of the health and economic benefits of implementing clean air and climate change policies which are largely limited to the effects of air pollution on premature deaths and other outcomes in adults. The new paper aggregates research on outcomes, including adverse birth outcomes, cognitive and behavioral problems, and asthma incidence.

"Policies to reduce fossil fuel emissions serve a dual purpose, both reducing air pollution and mitigating climate change, with sizable combined health and economic benefits," says first author Frederica Perera, PhD, director of CCCEH and professor of Environmental Health Sciences. "However, because only a few adverse outcomes in children have been considered, policymakers and the public have not yet seen the extent of the potential benefits of clean air and climate change policies, particularly for children."

The researchers reviewed 205 peer-reviewed studies published between January 1, 2000 and April 30, 2018 which provided information on the relationship between the concentration of exposures to air pollutants and health outcomes. The studies relate to fuel combustion by-products, including toxic air pollutants such as particulate matter (PM2.5), polycyclic aromatic hydrocarbons (PAH), and nitrogen dioxide (NO2). A table provides information on the risk of health outcomes for exposure by study, encompassing research on six continents.

"There is extensive evidence on the many harms of air pollution on children's health," says Perera. "Our paper presents these findings in a convenient fashion to support clean air and climate change policies that protect children's health."

The World Health Organization (WHO) has estimated that more than 40 percent of the burden of environmentally related disease and about 90 percent of the burden of climate change is borne by children under five, although that age group constitutes only 10 percent of the global population. The direct health impacts in children of air pollution from fossil fuel combustion include adverse birth outcomes, impairment of cognitive and behavioral development, respiratory illness, and potentially childhood cancer. As a major driver of climate change, combustion of fossil fuel is also directly and indirectly contributing to illness, injury, death, and impaired mental health in children through more frequent and severe heat events, coastal and inland flooding, drought, forest fires, intense storms, the spread of infectious disease vectors, increased food insecurity, and greater social and political instability. These impacts are expected to worsen in the future.

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Many Arctic pollutants decrease after market removal and regulation

Polar bears

Levels of some persistent organic pollutants (POPs) regulated by the Stockholm Convention are decreasing in the Arctic, according to an international team of researchers who have been actively monitoring the northern regions of the globe.

POPs are a diverse group of long-lived chemicals that can travel long distances from their source of manufacture or use. Many POPs were used extensively in industry, consumer products or as pesticides in agriculture. Well-known POPs include chemicals such as DDT and PCBs (polychlorinated biphenyls), and some of the products they were used in included flame retardants and fabric coatings.

Because POPs were found to cause health problems for people and wildlife, they were largely banned or phased out of production in many countries. Many have been linked to reproductive, developmental, neurological and immunological problems in mammals. The accumulation of DDT, a well-known and heavily used POP, was also linked to eggshell-thinning in fish-eating birds, such as eagles and pelicans, in the late 20th century, and caused catastrophic population declines for those animals.

In 2001, 152 countries signed a United Nations treaty in Stockholm, Sweden intended to eliminate, restrict or minimize unintentional production of 12 of the most widely used POPs. Later amendments added more chemicals to the initial list. Today, more than 33 POP chemicals or groups are covered by what is commonly called the "Stockholm Convention," which has been recognized by182 countries.

"This paper shows that following the treaty and earlier phase-outs have largely resulted in a decline of these contaminants in the Arctic," says John Kucklick, a biologist from the National Institute of Standards and Technology (NIST) and the senior U.S. author on the paper, published August 23 in Science of the Total Environment. "When POP use was curtailed, the change was reflected by declining concentrations in the environment."

"In general, the contaminants that are being regulated are decreasing," says Frank Rigét from the Department of Bioscience, Aarhus University, Denmark, and lead author.

POPs are particularly problematic in the Arctic because the ecosystem there is especially fragile, and pollution can come from both local sources and from thousands of miles away due to air and water currents. POPs also bioaccumulate. This means that they build up faster in animals and humans than they can be excreted, and that exposure can increase up the food chain. Plankton exposed to POPs in water are eaten by schools of fish, which are in turn eaten by seals or whales, and with each jump up the food chain the amount of POPs increases. The same is true for terrestrial animals. A large mammal's exposure, therefore, can be large and long-lasting.

Indigenous people living in northern coastal areas such as Alaska often consume more fish and other animals that come from higher on the food chain than the average American. Such communities, therefore, are potentially exposed to larger amounts of these pollutants.

For almost two decades beginning in 2000, Kucklick and Rigét worked in conjunction with scientists from Denmark, Sweden, Canada, Iceland and Norway to track POPs in the fat of several marine mammals and in the tissue of shellfish and seabirds. They also monitored air in the Arctic circle for pollution.

To gain a fuller picture of how the deposition of POPs might have changed over time, the study included specimens archived since the 1980s and '90s in special storage facilities around the globe. The U.S. specimens were provided by the NIST Biorepository, located in Charleston, South Carolina. Samples archived in that facility are part of the Alaska Marine Mammal Tissue Archival Project (AMMTAP) or the Seabird Tissue Archival and Monitoring Project (STAMP). Both collections are conducted in collaboration with other federal agencies.

The study pooled more than 1,000 samples taken over the course of several decades from many different locations throughout the Arctic Circle. In general, the so-called legacy POPs -- those that have been eliminated or restricted from production -- were shown to be decreasing over the past two to three decades, although some had decreased more than others.

The biggest decreases were in a byproduct of the pesticide lindane, a-HCH, with a mean annual decline of 9 percent in Arctic wildlife.

The research team found PCBs had decreased as well. Most industrial countries banned PCBs in the 1970s and '80s, and their production was reduced under the Stockholm Convention in 2004. Previously, the compounds had been widely used in electrical systems. In this study, it was found that their presence had decreased by almost 4 percent per year across the Arctic region since being pulled from the market.

Two of the legacy POPs listed under Stockholm, β-HCH and HCB, showed only small declines of less than 3 percent per year. β-HCH was part of a heavily-used pesticide mixture with the active ingredient lindane and HCB was used both in agriculture and industry.

A small number of the legacy POPs had increased in a few locations, although some of those were at sites suspected to be influenced by strong, still-existing local pollution sources.

Notably, the flame retardant hexabromocyclododecane (HBCDD) showed an annual increase of 7.6 percent. HBCDD was one of 16 additional POPs added to the Stockholm Convention as of 2017 and is recommended for elimination from use, with certain exemptions.

Most of the research conducted for this paper was a direct result of the 2001 treaty stipulations, which included a requirement that sponsors participate in ongoing, long-term biological monitoring. Although the U.S. participated in the research, it has not ratified the treaty. It is expected that work on the treaty will continue as new POPs are identified.

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