Wednesday, February 01, 2023

Kobe University and AGC successfully convert dry cleaning solvent into useful chemical compounds

Safe, simple and inexpensive: New organic synthesis method efficiently produces pharmaceutical intermediates and polyurethane from perchloroethylene

Peer-Reviewed Publication

KOBE UNIVERSITY

Figure 1. — IMAGE: PHOTO-ON-DEMAND ORGANIC SYNTHESIS WITH PERCHLOROETHYLENE. view more
CREDIT: AKIHIKO TSUDA

A collaboration between Associate Professor TSUDA Akihiko’s research group at Kobe University’s Graduate School of Science and AGC Incorporated has succeeded in synthesizing various useful compounds from perchloroethylene (also known as tetrachloroethylene), a solvent commonly used to dry clean clothes. The compounds they synthesized include pharmaceutical intermediates (trichloroacetamide, urea derivatives and urethane derivatives) as well as a novel polyurethane containing a fluoroalkyl group. These useful chemical compounds are vital building blocks for manufacturing medicines, plastics and other products.

Utilizing Kobe University’s previously invention: the ‘photo-on-demand’ organic synthesis method, the research collaboration developed a new photo-oxidation method (chemical reaction and process) for perchloroethylene. This simple, safe and low cost method places less burden on the environment and can efficiently synthesize the aforementioned useful compounds.

Perchloroethylene is already used in large quantities for dry cleaning and other applications. As the world moves towards carbon neutral efforts and sustainability, this research development has gained attention as a novel way of using perchloroethylene and as method for recycling chemicals.

Patents were filed in relation to these research findings in March 2019 (domestic) and March 2020 (international). The academic paper was published online in ACS Omega on January 4, 2023.

Main Points

Successful joint research collaboration combined the strengths of Kobe University, with its photo-on-demand synthesis method, and AGC Inc.’s experience as a producer of perchloroethylene.
They developed a new organic synthesis method using perchloroethylene as raw material for the synthesis of chemical products. Perchloroethylene is commonly used for dry cleaning clothes (In 2018, Japan exported 6300 tons and imported 20 tons. Source: The Chemical Daily Co., Ltd.).
The research group succeeded in synthesizing a ~97% yield of trichloroacetamide (a precursor for pharmaceuticals and polymers) by merely irradiating a mixture of perchloroethylene and a reactant (amine) with light. They managed to synthesize 21 chemicals on a scale of up to ten grams (and this can be scaled up).
Using the above product, they successfully synthesized 11 pharmaceutical urea derivatives, 8 urethane derivatives and 1 fluorinated polyurethane on a gram scale.
Expensive specialized apparatus and agents are not required. These useful chemical products can be synthesized in large quantities on demand using light in a safe, inexpensive and simple manner, which has a low impact on the environment.
This could be utilized as a new method of recycling perchloroethylene.
It is hoped that this new chemical synthesis method will greatly contribute towards efforts to become carbon neutral and realize sustainable societies.

Research Background
Perchloroethylene is mainly used as a dry cleaning solvent and metal degreaser. Even though perchloroethylene is inflammable and chemically highly stable, various substances are produced if it is photo-oxidized under ultraviolet light. These include trichloroacetyl chloride, phosgene, carbon monoxide and chlorine (Figure 2). These substances are highly damaging to the environment due to their extremely toxic or corrosive properties, however they are valuable raw materials for organic synthesis. In light of current environmental pollution issues, the development of a method to recycle perchloroethylene would be beneficial. Despite this, there are hardly any examples of using photo-oxidation products specifically from perchloroethylene for organic synthesis.

Associate Professor Tsuda et al.’s research group were global pioneers in this regard, successfully synthesizing numerous useful chemical compounds using perchloroethylene’s photo-oxidation products. In 2012, they applied for a patent (patent number 5900920) and published a paper (Organic Syntheses with Photochemically Generated Chemicals from Tetrachloroethylene) on this innovation. However, there were two remaining issues with this previous method, one scientific and one safety-related, respectively: 1. The reaction efficiency was low, and 2. It was necessary to temporarily take the toxic and corrosive photo-oxidation products out of the reaction chamber to use them to synthesize the target compound. To resolve these issues, this research group began working with AGC Inc. This research collaboration between industry and academia led to the joint development of an organic synthesis method that could safely, inexpensively and easily turn perchloroethylene into high yields of organic chemical compounds at low cost to the environment.

Research Methodology
The researchers hoped that it would be possible to develop a novel organic synthesis method that resolved the previously mentioned safety issues. This would involve using a mixture of perchloroethylene and an amine, and would require an instant reaction to occur in situ between the perchloroethylene’s photo-oxidation products and the amine upon direct irradiation with ultraviolet light. However, the researchers hypothesized that perchloroethylene photooxidation would not occur based on the common scientific knowledge that amines absorb ultraviolet light. Even if the photoxidation did take place, they predicted that the subsequent reaction would not progress as hoped. This is because the hydrochloric acid (HCl) produced in the reaction between the photooxidation products and the amine would turn the amine into hydrochloride salt. In experiments under normal reaction conditions (below room temperature), the researchers found that the photooxidation of perchloroethylene proceeded slowly and the amine formed into hydrochloride salt at the same time. A long period of exposure caused part of the amine to photodecompose, resulting in strong coloration. These experiments showed that perchloroethylene photooxidation results in a highly complex series of chemical reactions.

Therefore, the research group heated a mixed solution of perchloroethylene and amine to over 70°C in the hope that (1) the gas-phase reaction rate would be increased by partially vaporizing the perchloroethylene and (2) the reaction would proceed even if the amine formed into hydrochloride salt. The researchers found that the expected reaction proceeded in a short amount of time and a single product was obtained.

Based on this discovery, the researchers synthesized ~97% yields of various N-Substituted Trichloroacetamides (NTCAs, which chemically protect isocyanates that serve as urethane precursors) (Figure 3). Therefore, it is thought that the mechanism behind perchloroethylene’s photooxidation is not merely a photooxidation reaction. Instead, it likely occurs as the result of a radical chain reaction caused by the chlorine radicals that are generated when the light cleaves the C-Cl bonds. The produced trichloroacetyl chloride instantly reacts in situ with amine and amine chloride, and this reaction is thought to be what causes NTCA to form.

The research group succeeded in synthesizing up to 10 grams of a total of 21 compounds including fluorinated ones, therefore this novel organic synthesis method can be applied to the production of a wide range of useful chemical compounds. Furthermore, it is possible to scale up the method merely by using larger reaction chamber.

The obtained NTCAs can be converted into urea derivatives and urethane derivatives through base-catalyzed substitution reactions with amines or alcohols. These reactions also produce chloroform as a by-product (which could be used as a recycled solvent or as a chemical precursor). It is thought that NTCA decomposes into isocyanates and then the subsequent addition of amines or alcohols progresses the reaction. In one application of this chemical reaction, the researchers successfully synthesized a new fluoroalkyl polyurethane from an NTCA containing fluorine. Fluoroalkyl compounds tend to have water repellent, oil repellent, flame retardant and weather resistant properties.

Further Research
Using the photo-on-demand synthesis method, the research group were able to synthesize various organic chemical compounds (including urea derivatives, urethane derivatives and polyurethane) from a solution of perchloroethylene and amine in a safe, inexpensive and relatively environmentally friendly manner. To develop this photoreaction method even further, Professor Tsuda et al. are currently using a flow reaction system in their efforts to develop a continuous organic synthesis method. With its potential to contribute towards the realization of a sustainable society, this research accomplishment is expected to be utilized in the future as a novel way of using the abundant chemical perchloroethylene and as a method to recycle chemicals.

Photochemical oxidation of perchloroethylene.

CREDIT

Akihiko Tsuda

Synthetic scheme for valuable organic compounds with the photooxidation products of perchloroethylene. DBU: Organic strong base

CREDIT

Akamatsu T.; Shele M.; Matsune A.; Kashiki Y.; Liang F.; Okazoe T.; Tsuda A.; Photo-on-Demand In Situ Synthesis of N-Substituted Trichloroacetamides with Tetrachloroethylene and Their Conversions to Ureas, Carbamates, and Polyurethanes, ACS Omega 2023, 8, 2, 2669–268

Acknowledgements
This research was supported by the Adaptable and Seamless Technology Transfer Program through Target-driven R&D (A-STEP) (seeds development type/academia and industry collaboration phase) from the Japan Science and Technology Agency (JST): ‘Developing highly functional and high added value polyurethane-materials through safe production processes using fluoroalkyl carbonates as key intermediates’ (Principle Researcher: Akihiko Tsuda).

Patent Information
Presentation Title: Method for Producing N-Substituted Trichloroacetamides
Patent application no. : 2019-060647 (Date of application: March 27, 2019).
International patent application no.: PCT/JP2020/013124 (Date of application: March 24, 2020).
Patent publication no.: WO/2020/196553 A1 (Date of publication: October 1, 2020).
Presenters: Akihiko Tsuda, Takashi Okazoe, Hiroshi Wada, Yoshitaka Sunayama, and Toshifumi Kakiuchi
Applicants: Kobe University and AGC Inc.

Journal Information
Title:
Photo-on-Demand In Situ Synthesis of N-Substituted Trichloroacetamides with Tetrachloroethylene and Their Conversions to Ureas, Carbamates, and Polyurethanes
DOI: doi.org/10.1021/acsomega.2c07233
Authors:
Toshiki Akamatsu1,§, Muge Shele1,§, Ayako Matsune1, Yoshiyuki Kashiki1, Fengying Liang1, Takashi Okazoe2, Akihiko Tsuda*,1
*Corresponding author, §equal contribution
1. Graduate School of Science, Kobe University
2. AGC Inc.
Journal:
ACS Omega

JOURNAL

ACS Omega

DOI

10.1021/acsomega.2c07233

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Photo-on-Demand In Situ Synthesis of N-Substituted Trichloroacetamides with Tetrachloroethylene and Their Conversions to Ureas, Carbamates, and Polyurethanes

ARTICLE PUBLICATION DATE

4-Jan-2023

COI STATEMENT

The authors declare the following competing financial interest(s): This research was funded by AGC Inc.

Seawater split to produce green hydrogen

Peer-Reviewed Publication

UNIVERSITY OF ADELAIDE

Researchers have successfully split seawater without pre-treatment to produce green hydrogen.

The international team was led by the University of Adelaide’s Professor Shizhang Qiao and Associate Professor Yao Zheng from the School of Chemical Engineering.

“We have split natural seawater into oxygen and hydrogen with nearly 100 per cent efficiency, to produce green hydrogen by electrolysis, using a non-precious and cheap catalyst in a commercial electrolyser,” said Professor Qiao.

A typical non-precious catalyst is cobalt oxide with chromium oxide on its surface.

“We used seawater as a feedstock without the need for any pre-treatment processes like reverse osmosis desolation, purification, or alkalisation,” said Associate Professor Zheng.

“The performance of a commercial electrolyser with our catalysts running in seawater is close to the performance of platinum/iridium catalysts running in a feedstock of highly purified deionised water.

The team published their research in the journal Nature Energy.

“Current electrolysers are operated with highly purified water electrolyte. Increased demand for hydrogen to partially or totally replace energy generated by fossil fuels will significantly increase scarcity of increasingly limited freshwater resources,” said Associate Professor Zheng.

Seawater is an almost infinite resource and is considered a natural feedstock electrolyte. This is more practical for regions with long coastlines and abundant sunlight. However, it isn’t practical for regions where seawater is scarce.

Seawater electrolysis is still in early development compared with pure water electrolysis because of electrode side reactions, and corrosion arising from the complexities of using seawater.

“It is always necessary to treat impure water to a level of water purity for conventional electrolysers including desalination and deionisation, which increases the operation and maintenance cost of the processes,” said Associate Professor Zheng.

“Our work provides a solution to directly utilise seawater without pre-treatment systems and alkali addition, which shows similar performance as that of existing metal-based mature pure water electrolyser.”

The team will work on scaling up the system by using a larger electrolyser so that it can be used in commercial processes such as hydrogen generation for fuel cells and ammonia synthesis.

Researchers have successfully split seawater without pre-treatment to produce green hydrogen.

The international team was led by the University of Adelaide’s Professor Shizhang Qiao and Associate Professor Yao Zheng from the School of Chemical Engineering.

A typical non-precious catalyst is cobalt oxide with chromium oxide on its surface.

“We used seawater as a feedstock without the need for any pre-treatment processes like reverse osmosis desolation, purification, or alkalisation,” said Associate Professor Zheng.

The team published their research in the journal Nature Energy.

Seawater electrolysis is still in early development compared with pure water electrolysis because of electrode side reactions, and corrosion arising from the complexities of using seawater.

The team will work on scaling up the system by using a larger electrolyser so that it can be used in commercial processes such as hydrogen generation for fuel cells and ammonia synthesis.

JOURNAL

Nature Energy

DOI

10.1038/s41560-023-01195-x

ARTICLE TITLE

Direct seawater electrolysis by adjusting the local reaction environment of a catalyst

ARTICLE PUBLICATION DATE

30-Jan-2023

Ancient fossils shed new light on evolution of sea worm

Peer-Reviewed Publication

DURHAM UNIVERSITY

ZZF_Iotuba ELI-S_001-complete (1).jpg — IMAGE: COMPLETE SPECIMEN OF THE CAMBRIAN CAGE WORM IOTUBA FROM THE CHENGJIANG FOSSIL DEPOSIT. view more
CREDIT: CREDIT: ZHANG ZHIFEI

Ancient fossils shed new light on evolution of sea worm

-With pictures-

Ancient fossils have shed new light on a type of sea worm linking it to the time of an evolutionary explosion that gave rise to modern animal life.

Researchers at Durham University, UK, and Northwest University, Xi’an, China, examined 15 exceptionally preserved fossils of the annelid worm Iotuba chengjiangensis dating from the early Cambrian period 515 million years ago.

The fossilised remains included evidence of the worms’ guts and kidneys and revealed they had an unexpectedly complex structure similar to that of other annelid worms.

The researchers say this means that annelids – or segmented worms – diversified into different lineages some 200 million years earlier than previously thought and were part of the evolutionary leap known as the Cambrian explosion.

The Cambrian explosion saw a huge rise in organisms between 540 and 530 million years ago – as shown by fossil records – and saw the appearance of many of the major groups that make up animal life on Earth.

The findings are published in the journal Proceedings of the Royal Society B.

Study co-author Dr Martin R. Smith, in the Department of Earth Sciences, Durham University, said: “We know that the main animal lines we see today emerged during the Cambrian explosion, but we always thought annelid worms were late to the party, and their major subgroups didn’t begin to diversify until nearly 200 million years later.

“But the amazingly preserved fossils we have studied and the structure of these amazing little creatures challenge this picture, and show that annelid worms – including Iotuba chengjiangensis – seemed to follow the pattern of events initiated by the Cambrian explosion.

“Detailed fossils of this type of worm are extremely rare, so it was great to be able to study the fossilised record of this tiny animal in such detail.

“It turns out they weren’t late to the party at all, they were just hiding in a side room.”

The researchers say that Iotuba chengjiangensis was a cage worm able to move its head in and out of a cage made of bristly spines.

This makes the worm a close relative of families of annelid sea worms such as Flabelligeridae and Acrocirridae.

Dr Smith added: “These families are like the top rungs on an evolutionary ladder. For these groups to have appeared so early in the day, there must have been a dramatic unseen origin of modern annelid diversity in the heat of the Cambrian explosion.

“It turns out that many of the annelids we know and love today may have begun to evolve much sooner than we think.”

Research lead author Dr Zhifei Zhang, Northwest University, Xi'an, China said: “Annelids are one of the largest and most successful phyla of animals that are flourishing in both terrestrial and marine ecosystems with the most diversified living lineage, Polychaeta, living in the sea.

“The most well-known are, for example, earth worms, leeches and clam worms. There are also at least 20,000 species and 80 families of Polychaete in the modern sea.

“However, their earliest geological records of fossils in Cambrian deposits, even in the well-known Konservat-Lagerstätten are quite rare.

“Is this because the delicate worms didn’t exist, or simply didn’t preserve? Our research gives the first insightful answer: biodiversification of the segmented worms occurs much earlier than thought before.”

The research was funded by the National Natural Science Foundation of China and Changjiang Scholars Program of the Chinese Ministry of Education.

ENDS

Artist's reconstruction of Iotuba – complete organism.

Artist's reconstruction of Iotuba, showing front of body with everted head (with branchial filaments and mouth) surrounded by cage of spines (chaetae).

Head-on reconstruction of Iotuba, showing cage of spines (chaetae) surrounding everted head, with branchial filaments and mouth.

CREDIT

Credit: Zhang Zhifei

Specimen of the Cambrian cage worm Iotuba from the Chengjiang fossil deposit.

CREDIT

Credit: Martin R. Smith

JOURNAL

Proceedings of the Royal Society B Biological Sciences

DOI

10.1098/rspb.2022.2014

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

The Cambrian cirratuliform Iotuba denotes an early annelid radiation

ARTICLE PUBLICATION DATE

1-Feb-2023

THE LANCET: Planting more trees could decrease deaths from higher summer temperatures in cities by a third, modelling study suggests

Peer-Reviewed Publication

THE LANCET

Peer-reviewed / Simulation or modelling / People

Modelling of 93 European cities finds that increasing tree cover up to 30% can help lower the temperature of urban environments by an average of 0.4 degrees and prevent heat-related deaths. (Average city tree coverage in Europe is currently at 14.9%.)
Of the 6,700 premature deaths attributed to higher temperatures in cities during 2015, one third of these (2,644) could have been prevented by increasing urban tree cover up to 30%.
The authors note that these findings highlight the need for more sustainable and climate-resilient strategies to be integrated into local policy decisions to aid climate change adaptation and improve population health.

One third of premature deaths attributable to higher temperatures in European cities during summer 2015 could have been prevented by increasing urban tree cover to 30%, reveals a modelling study published in The Lancet. The study also found that tree cover reduced urban temperatures by an average of 0.4 degrees during the summer.

“We already know that high temperatures in urban environments are associated with negative health outcomes, such as cardiorespiratory failure, hospital admission, and premature death. This study is the largest of its kind, and the first to specifically look at premature mortality caused by higher temperatures in cities and the number of deaths that could be prevented by increasing tree cover,” says lead author, Tamar Iungman, Barcelona Institute for Global Health. [1]

“Our ultimate goal is to inform local policy and decision-makers about the benefits of strategically integrating green infrastructure into urban planning in order to promote more sustainable, resilient and healthy urban environments and contribute to climate change adaptation and mitigation. This is becoming increasingly urgent as Europe experiences more extreme temperature fluctuations caused by climate change; despite cold conditions currently causing more deaths in Europe, predictions based on current emissions reveal that heat-related illness and death will present a bigger burden to our health services over the next decade.”

Urban environments record higher temperatures than the surrounding countryside generally referred to as “urban heat islands”. This temperature difference is caused by human modification of landscapes, such as removal of vegetation, the presence of asphalt and use of building materials that absorb and trap heat. As emissions continue to exacerbate climate change and global heating, increased temperatures in cities are predicted to become more intense, resulting in an increasingly urgent need for cities to adapt to improve health outcomes.

The researchers estimated mortality rates of residents over 20 years old in 93 European cities (listed in appendix) between June and August 2015, accounting for 57 million inhabitants in total. Mortality data from this period was analysed with daily average city temperatures in two modelling scenarios: the first comparing the city temperature without urban heat islands to city temperature with urban heat islands, and the second simulating the temperature reduction as a consequence of increasing the tree cover to 30%. Exposure response functions were used to estimate the number of deaths attributable to urban heat as well as the number of deaths that could be prevented through increasing the tree cover.

The population-weighted city average daily temperature difference between cities and countryside from June - August 2015 was 1.5 degrees warmer than the surrounding countryside, with the maximum temperature difference measured at 4.1 degrees hotter in Cluj-Napoca, Romania. Across all cities, 75% of the total population lived in areas with an average summer city temperature difference greater than one degree, and 20% with an average summer temperature difference greater than two degrees, compared to the surrounding countryside.

In total, 6,700 premature deaths could be attributed to hotter urban temperatures during the summer months, accounting for 4.3% of summer mortality and 1.8% of year-round mortality. One in three of these deaths (2,644 total) could have been prevented by increasing tree cover up to 30%, and therefore reducing temperatures. This corresponds to 39.5% of all deaths attributable to hotter urban temperatures, 1.8% of all summer deaths, and 0.4% of year-round deaths.

There was a large variability in temperature-related mortality rates between cities, from no premature deaths attributable to hotter urban temperatures in Goteborg, Sweden, to 32 premature deaths per 100,000 people in Cluj-Napoca, Romania. Overall, cities with highest temperature mortality rates were in Southern and Eastern Europe where the highest temperatures were reached, with these cities benefitting the most from an increase in tree coverage.

The results of this study support the idea that urban trees provide substantial public health and environmental benefits, however the authors acknowledge that increasing tree coverage should be combined with other interventions to maximise urban temperature reduction (for example, changing ground surface materials to reduce night-time temperatures such as replacing asphalt with trees). Meeting the target of 30% tree coverage can be very challenging for some cities due to urban design, with city average tree cover in Europe currently at 14.9%.

“Our results suggest large impacts on mortality due to hotter temperatures in cities, and that these impacts could be partially reduced by increasing the tree coverage to help cool urban environments. We encourage city planners and decision-makers to incorporate the urban green infrastructure adapted to each local setting whilst combining with other interventions to maximise the health benefits while promoting more sustainable and resilient cities, especially as we already know that green spaces can have additional health benefits such as reducing cardiovascular disease, dementia and poor mental health, improving cognitive functioning of children and the elderly, and improving the health of babies,” says study co-author Mark Nieuwenhuijsen, Director of Urban Planning, Environment and Health at the Barcelona Institute for Global Health. [1]

The authors acknowledge some limitations with this study. The study could not be conducted for a more recent year than 2015, due to unavailability of population data. In addition, a US dataset was used for building the cooling model in the study as opposed to a European dataset. Finally, this study focused on the health impacts of high temperatures but did not look at cold temperature. Whilst cold temperatures currently have greater impacts on health in Europe, health impacts due to heat are projected to exceed those caused by cold under current emission scenarios, highlighting the importance of adapting our cities now.

Writing in a Linked Comment, Kristie Ebi, University of Washington, USA, who was not involved in the research, said: “Essentially all heatwave-related deaths are preventable; no one needs to die from the heat. With climate change projected to increase the frequency, intensity, and duration of extreme heat events, communities need to understand the most effective interventions, particularly developing and deploying heatwave early warning and response systems. Equally important are Heat Action Plans that explicitly incorporate the consequences of a changing climate into longer-term urban planning. Heat Action Plans detail how to modify urban form and infrastructure to increase the resilience and sustainability of our communities as we face an even warmer future… Encouraging and enabling decision-makers and local communities to develop and implement Heat Action Plan is an effective way to promote climate resilience as soaring temperatures continue to be felt globally. The tools and guidelines are available; the gaps are in human and financial resources for implementation. The time to start is now.”

NOTES TO EDITORS

This study was funded by GoGreenRoutes, Spanish Ministry of Science and Innovation, Internal ISGlobal fund Medical Research Council-UK, and European Union’s Horizon 2020 Project Exhaustion. A full list of researcher institutes can be found in the paper.

[1] Quote direct from author and cannot be found in the text of the Article.

The labels have been added to this press release as part of a project run by the Academy of Medical Sciences seeking to improve the communication of evidence. For more information, please see: http://www.sciencemediacentre.org/wp-content/uploads/2018/01/AMS-press-release-labelling-system-GUIDANCE.pdf if you have any questions or feedback, please contact The Lancet press office pressoffice@lancet.com

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JOURNAL

The Lancet

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Cooling cities through urban green infrastructure: a health impact assessment of European cities

ARTICLE PUBLICATION DATE

31-Jan-2023

Over 4% of summer mortality in European cities is attributable to urban heat islands

A new study conducted with data from 93 European cities estimates that one third of deaths attributable to heat islands could be avoided if trees covered 30% of urban space

Peer-Reviewed Publication

BARCELONA INSTITUTE FOR GLOBAL HEALTH (ISGLOBAL)

Infographic — IMAGE: KEY RESULTS view more
CREDIT: ISGLOBAL

Over four percent of deaths in cities during the summer months are due to urban heat islands, and one third of these deaths could be prevented by reaching a tree cover of 30%, according to a modelling study published in The Lancet and led by the Barcelona Institute for Global Health (ISGlobal), an institution supported by “la Caixa” Foundation. The study results, obtained with data from 93 European cities, highlight the substantial benefits of planting more trees in cities to attenuate the impact of climate change.

Exposure to heat has been associated with premature mortality, cardiorespiratory disease and hospital admissions. This is particularly true for heat waves, but also occurs with moderately high temperatures in summer. Cities are especially vulnerable to higher temperatures. Less vegetation, higher population density, and impermeable surfaces for buildings and roads, including asphalt, lead to a temperature difference between the city and surrounding areas – a phenomenon called urban heat island. Given the ongoing global warming and urban growth, this effect is expected to worsen over the next decades.

“Predictions based on current emissions reveal that heat-related illness and death will become a bigger burden to our health services over the next decades,” says ISGlobal researcher Tamara Iungman, first author of the study.

An international team led by Mark Nieuwenhuijsen, director of the Urban Planning, Environment and Health Initiative at ISGlobal, estimated mortality rates of residents aged over 20 in 93 European cities (a total of 57 million inhabitants), between June and August 2015, and collected data on daily rural and urban temperatures for each city. The analyses were performed at a high-resolution level (areas of 250m x 250m). First, they estimated the premature mortality by simulating a hypothetical scenario without urban heat island. Second, they estimated the temperature reduction that would be obtained by increasing tree cover to 30% and the associated mortality that could be avoided.

“Our goal is to inform local decision-makers about the benefits of integrating green areas into all neighborhoods in order to promote more sustainable, resilient and healthy urban environments,” explains Nieuwenhuijsen.

The protective effect of trees

The results show that, from June to August 2015, cities were on average 1.5oC warmer than the surrounding countryside. In total, 6,700 premature deaths could be attributed to hotter urban temperatures, which represents 4.3% of total mortality during the summer months and 1.8% of year-round mortality. One third of these deaths (2,644) could have been prevented by increasing tree cover up to 30%, thereby reducing temperatures. Overall, cities with the highest excess heat-mortality rates were in Southern and Eastern Europe, with these cities benefiting the most from an increase in tree cover.

The study highlights the substantial benefits of planting more trees in cities, although the authors acknowledge that this can be challenging in some cities due to their design, and that tree planting should be combined with other interventions such as green roofs or other temperature-reducing alternatives.

“Our results also show the need to preserve and maintain the trees that we already have because they are a valuable resource and it takes a long time to grow new trees. It is not only about increasing trees in the city, it is also about how they are distributed,” says Nieuwenhuijsen.

The analyses were done for 2015 because population data were not available for later years, but, as Iungman points out, the study provides valuable information for adapting our cities and making them more resilient to the health impact of climate change. “Here we only looked at the cooling effect of trees, but making cities greener has many other health benefits, including longer life expectancy, fewer mental health problems and better cognitive functioning”, she adds.

“Vulnerability to heat changes from city to city depending on several factors. Understanding the benefits of policies such as increasing tree cover can help inform action to reduce risks and prevent avoidable deaths, especially with climate change", says Antonio Gasparrini, Professor of Biostatistics and Epidemiology at the London School of Hygiene & Tropical Medicine (LSHTM) and one of the authors of the study.

Supplementary material

Dataset: Check the resulting data for the 93 European cities.

Videos: Quotes Mark Nieuwenhuijsen; Quotes Tamara Iungman

Reference

Iungman T, Cirach M, Marando F., Pereira-Barboza E., Khomenko S., Masselot P., Quijal-Zamorano M., Mueller N., Gasparrini A., Urquiza J., Heri M., Thondoo M., Nieuwenhuijsen M. Cooling cities for health through urban green infrastructure: a health impact assessment for European cities. The Lancet, 2023. https://doi.org/10.1016/S0140-6736(22)02585-5

JOURNAL

The Lancet

DOI

10.1016/S0140-6736(22)02585-5

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Cooling cities for health through urban green infrastructure: a health impact assessment for European cities

ARTICLE PUBLICATION DATE

31-Jan-2023

Deer carry SARS-CoV-2 variants that are extinct in humans

Peer-Reviewed Publication

CORNELL UNIVERSITY

ITHACA, N.Y. – Cornell University researchers have found white-tailed deer – the most abundant large mammal in North America – are harboring SARS-CoV-2 variants that were once widely circulated, but no longer found in humans.

Whether or not deer could act as long-term reservoirs for these obsolete variants is still unknown, as scientists continue to collect and analyze new data.

The study, published January 31 in the journal Proceedings of the National Academy of Sciences, represents one of the most comprehensive studies to date to assess the prevalence, genetic diversity and evolution of SARS-CoV-2 in white-tailed deer.

“One of the most striking findings of this study was the detection of co-circulation of three variants of concern – alpha, gamma and delta – in this wild animal population,” said Diego Diel, associate professor of population medicine and diagnostic sciences at Cornell.

Over the course of the pandemic, deer have become infected with SARS-CoV-2 through ongoing contact with humans, possibly from hunting, wildlife rehabilitations, feeding of wild animals or through wastewater or water sources.

“A virus that emerged in humans in Asia, most likely after a spillover event from an animal reservoir into humans, apparently, or potentially, has now found a new wildlife reservoir in North America,” Diel said.

The 5,700 samples used in the study were collected over two years in New York from 2020-22.

When the researchers compared the genomic sequences of the variants found in deer with sequences of the same variants taken from humans across New York, they found the viruses had mutated in the deer, suggesting the variants had likely been circulating in deer for many months. By the time alpha and gamma variants were detected in deer, for example, there was no evidence of these viral strains still circulating in humans. In fact, when they were found in deer, neither variant had been detected in humans in New York for four to six months.

“When we did sequence comparisons between those viruses recovered from white-tailed deer with the human sequences, we observed a significant number of mutations across the virus genome,” Diel said, adding that some of the viruses had up to 80 mutations compared with the human sequences, providing further evidence that the viruses had likely been circulating in the deer for some time. The mutations suggest the virus has adapted to deer, possibly making it more transmissible between them.

More study is needed to confirm whether these variants will disappear in deer over time or whether there is risk of SARS-CoV-2 spreading to other wildlife, including predators.

“Because of the evidence obtained in our study, it is very important to continue to monitor the virus in these animal populations to really understand and track changes that could lead or favor spill back into humans and other wildlife,” Diel said.

There are an estimated 30 million white-tailed deer in the United States. A 2022 study by Diel and others found that across five states surveyed in 2021, SARS-CoV-2 was found in up to 40% of white-tailed deer.

For additional information, see this Cornell Chronicle story.

Cornell University has dedicated television and audio studios available for media interviews.

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JOURNAL

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2215067120