Carbon Chemist

Tag: Air Pollution

  • Study reveals risk factors for faster aging in the brain

    Study reveals risk factors for faster aging in the brain

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    The researchers had previously identified a ‘weak spot’ in the brain, which is a specific network of higher-order regions that not only develop later during adolescence, but also show earlier degeneration in old age. They showed that this brain network is also particularly vulnerable to schizophrenia and Alzheimer’s disease.

    In this new study, published in Nature Communications, they investigated the genetic and modifiable influences on these fragile brain regions by looking at the brain scans of 40,000 UK Biobank participants aged over 45.

    The researchers examined 161 risk factors for dementia, and ranked their impact on this vulnerable brain network, over and above the natural effects of age. They classified these so-called ‘modifiable’ risk factors – as they can potentially be changed throughout life to reduce the risk of dementia – into 15 broad categories: blood pressure, cholesterol, diabetes, weight, alcohol consumption, smoking, depressive mood, inflammation, pollution, hearing, sleep, socialization, diet, physical activity, and education.

    Prof. Gwenaëlle Douaud, who led this study, said: ‘We know that a constellation of brain regions degenerates earlier in aging, and in this new study we have shown that these specific parts of the brain are most vulnerable to diabetes, traffic-related air pollution – increasingly a major player in dementia – and alcohol, of all the common risk factors for dementia.’

    ‘We have found that several variations in the genome influence this brain network, and they are implicated in cardiovascular deaths, schizophrenia, Alzheimer’s and Parkinson’s diseases, as well as with the two antigens of a little-known blood group, the elusive XG antigen system, which was an entirely new and unexpected finding.’

    In fact, two of our seven genetic findings are located in this particular region containing the genes of the XG blood group, and that region is highly atypical because it is shared by both X and Y sex chromosomes. This is really quite intriguing as we do not know much about these parts of the genome; our work shows there is benefit in exploring further this genetic terra incognita.”


    Prof. Lloyd Elliott, co-author from Simon Fraser University in Canada

    Importantly, as Prof. Anderson Winkler, a co-author from the National Institutes of Health and The University of Texas Rio Grande Valley in the US, points out: ‘What makes this study special is that we examined the unique contribution of each modifiable risk factor by looking at all of them together to assess the resulting degeneration of this particular brain ‘weak spot’. It is with this kind of comprehensive, holistic approach – and once we had taken into account the effects of age and sex – that three emerged as the most harmful: diabetes, air pollution, and alcohol.’

    This research sheds light on some of the most critical risk factors for dementia, and provides novel information that can contribute to prevention and future strategies for targeted intervention.

    Source:

    Journal reference:

    Manuello, J., et al. (2024). The effects of genetic and modifiable risk factors on brain regions vulnerable to ageing and disease. Nature Communications. doi.org/10.1038/s41467-024-46344-2.

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  • Wildfire smoke may be deadliest effect of climate change in US

    Wildfire smoke may be deadliest effect of climate change in US

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    Increased exposure to wildfire smoke is one of the most damaging effects of climate change

    Nasa's Earth Observatory

    Exposure to rising levels of wildfire smoke could lead to more than 10,000 additional deaths each year in the US by 2050. This could make deaths due to wildfire smoke the costliest consequence of climate change for the country, accounting for nearly as much economic damage as all other climate-related impacts combined.

    “It completely reshapes how we think about the climate impact in the US,” says Minghao Qiu at Stanford University in California. Exposure…

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  • Dust clouds from the Sahara are reaching Europe more frequently

    Dust clouds from the Sahara are reaching Europe more frequently

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    Dust being carried by the wind from the Saharan desert over the Canary Islands and Cabo Verde in January 2024

    European Union, Copernicus Sentinel-3 imagery

    Dust blown from the arid expanses of the Sahara desert is regularly carried into the sky above parts of Europe, with harmful impacts on air quality. But recently there has been an eightfold increase in these dust intrusions – even during colder months when they are unusual – and the spike in frequency and intensity has researchers concerned they are becoming more common.

    “In 2024, we are having these extreme events again,” says …

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  • What coping strategies are most effective?

    What coping strategies are most effective?

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    In a recent review article published in the Journal of Clinical Medicine, researchers summarized the results of a systematic review that explored the impact of different coping strategies for people living with inflammatory bowel disease (IBD).

    Study: Coping Strategies and Inflammatory Bowel Disease: A Narrative Review. Image Credit: PeopleImages.com - Yuri A/Shutterstock.comStudy: Coping Strategies and Inflammatory Bowel Disease: A Narrative Review. Image Credit: PeopleImages.com – Yuri A/Shutterstock.com

    Background

    Through keyword searches, they identified 57 articles published in English in medical databases such as the Cochrane Library, PubMed, EBSCOhost, and EMBASE, concluding that personalized interventions can help diverse populations with IBD rehabilitation and management.

    Challenges treating IBD

    The two forms of IBD, namely ulcerative colitis (UC) and Crohn’s disease (CD), are thought to occur as a result of mucosal barrier dysfunctions, gastrointestinal microbiome disturbances, immune response dysregulation, genetic background, and environmental risk factors including smoking, air pollution, diet, and stress.

    As many as four in 10 IBD patients show no response to biological therapy, though patient education regarding risk factors can improve the management of the disease.

    Since IBD can be chronic, it has significant psychosocial effects and can affect work and quality of life.

    Patients may cope with these stresses through adaptive strategies that could mitigate their psychological burden, while maladaptive strategies like denial or avoidance could lead to worsening symptoms.

    Effects of coping mechanisms

    Researchers identified active coping strategies in which individuals act directly to solve problems and address stressors, known as problem-focused coping.

    This could include actively monitoring the disease and its symptoms to identify triggers, changes, and patterns. However, becoming overly focused on monitoring can increase stress.

    Another form of emotion-focused coping involves reframing thoughts, regulating emotions, and seeking support systems. While these strategies can improve mental well-being, they can also reduce adherence to treatment and lead to individuals delaying seeking medical care.

    Disease severity, complications, and activity influence the health-related quality of life (HRQoL) of people living with IBD. However, effectively managing stress, seeking support, being physically active, and adhering to medicine can improve their symptomology and overall well-being.

    Adaptive coping mechanisms can lead to perceiving the illness more positively and reduce distress. People with IBD often show resilience by adapting to the side effects of treatments, psychosocial stressors, and symptom flares with problem-solving skills and psychological flexibility.

    Individuals may experience reduced psychological resilience after being diagnosed with IBD, but mindfulness can be an effective form of therapy.

    Maladaptive coping strategies that are negatively associated with HRQoL include negative religious coping, acceptance-resignation, catastrophizing, low acceptance, passive coping, decreased cognitive flexibility, emotion-focused coping, and perceived control.

    Some strategies are also correlated with higher levels of anxiety and depression and lower work productivity.

    Researchers have found differences in coping strategies between people with UC and CD. People with CD may experience higher levels of psychological distress and neuroticism while being more likely to adopt maladaptive coping strategies.

    In another study, people with UC were more likely to cope by modifying meal content, sleeping more, and seeking medical care.

    People with CD, however, adopted strategies like skipping meals or switching to elemental diets as they perceived these as more useful.

    Interventions for IBD patients

    Educational programs can reduce disease-related anxiety and depression while improving knowledge and the use of adaptive coping strategies. Notably, these improvements have been observed despite disease activity remaining similar.

    This suggests that uncertainty around IBD can lead to worse outcomes and that individuals who know more about their condition benefit from this understanding.

    Cognitive behavioral therapy (CBT) has also been shown to improve symptoms of depression and anxiety, while interventions focusing on mind-body relaxation additionally improved symptoms and reduced expression of genes directly linked to inflammatory processes.

    Another study found that transcranial direct current stimulation reduced pain in the short term, but the effects faded after one week.

    People with inactive IBD show a higher inclination to participate in treatment; they also experience lower depression and a higher quality of life.

    Some patients with IBD may also experience joint and back pain; they show greater adaptability and flexibility but are less likely to perceive medical interventions as effective.

    Conclusions

    Individuals living with IBD experience severe challenges to their health and quality of life. As the prevalence of this condition increases, effective coping strategies must be identified to improve the treatment and management of this disease.

    The review indicates that patients adopt a multitude of coping mechanisms, some adaptive and some maladaptive.

    Their experience of the disease in terms of duration and severity modifies their coping strategies, and these strategies may also affect their condition.

    Understanding these complex interplays can help health professionals tailor interventions to groups of people who have specific needs, providing the necessary level of social support and promoting resilience and treatment adherence.

    Journal reference:

    • Popa, S.L., Stanculete, M.F., Grad, S., Brata, V.D., Duse, T., Badulescu, A., Dragan, R., Bottalico, P., Pop, C., Ismaiel, A., Turtoi, D., Dumitrascu, D.I., Pojoga, C., Gherman, C., David, L. (2024) Coping strategies and inflammatory bowel disease: a narrative review. Journal of Clinical Medicine. doi: https://doi.org/10.3390/jcm13061630. https://www.mdpi.com/2077-0383/13/6/1630

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  • How residential green spaces impact bone health and osteoporosis risk

    How residential green spaces impact bone health and osteoporosis risk

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    In a recent study published in the Annals of the Rheumatic Diseases, scientists investigate whether green spaces in residential areas were associated with a lower risk of incident osteoporosis and changes in bone mineral density.

    Study: Associations of residential greenness with bone mineral density and osteoporosis: the modifying effect of genetic susceptibility. Image Credit: Roschetzky Photography / Shutterstock.com

    The prevalence and health effects of osteoporosis

    Osteoporosis is a highly prevalent metabolic disorder in which the bone microarchitecture deteriorates and bone density decreases. Since the incidence of osteoporosis is often higher with progressing age, it is rapidly becoming a global problem due to rising life expectancy rates throughout the world. Changes in lifestyles due to modernization and the spread of urban spaces also contribute to the increasing risk of osteoporosis.

    Health problems associated with reduced bone density include chronic pain, increased probability of fractures, decreased mobility, and an overall reduction in quality of life, which impose significant economic and social burdens on patients and their families. Previous studies have found that environmental factors can play an important role in the development of osteoporosis, with high air pollution levels strongly associated with a higher risk of developing osteoporosis.

    Green spaces in urban landscapes have been shown to reduce the risk of serious health concerns such as cardiovascular disease and improve mental health by lowering air pollution levels, providing open spaces for exercise, and reducing psychological stress.

    About the study

    The present study analyzed whether long-term exposure to green spaces was associated with a reduced risk of osteoporosis and improved bone mineral density. The scientists also examined whether genetic susceptibility and exposure to green spaces affected the risk of incident osteoporosis.

    A prospective study using data from the United Kingdom Biobank was conducted, which included information on physical examination findings, demographic characteristics, lifestyle factors, and socioeconomic status of the participants. Green spaces in residential areas were characterized using the normalized difference vegetation index, which is based on the spectral reflectance difference between visible and near-infrared reads in a specified region.

    An ultrasound device was used to estimate the mineral density of the bone. Additionally, T-scores were calculated based on the body mass index (BMI) of the participant and BMI of a healthy adult of matching age and gender. A T-score value of less than -2.5 was set as the cut-off to define prevalent osteoporosis.

    Follow-up information such as medical records, registry data for primary care or death, and self-reports were used to confirm incident osteoporosis. Polygenic risk scores for osteoporosis from the U.K. Biobank, which were calculated using data from genome-wide association studies that were conducted to examine genetic predisposition to osteoporosis, were also included in the analysis.

    The postal codes of the participants’ areas of residence were used to determine whether they resided in rural or urban areas. Other covariates such as sex, age, education levels, annual income, ethnicity, and lifestyle factors such as smoking behavior, consumption of alcohol, and intake of healthy foods were also included as potential confounding factors in the analysis.

    Study findings

    Exposure to green spaces in residential areas was independently associated with a lower risk of developing osteoporosis and higher mineral density in the bones. The incidence of osteoporosis was also consistently lower in areas with a higher percentage of green spaces, natural environments, and domestic gardens.

    Air pollution, specifically involving nitrogen dioxide (NO2) and particulate matter smaller than 2.5 microns (PM2.5), had a significant role in mediating the association between exposure to green spaces and the risk of osteoporosis. Psychological stress and physical activity levels also influenced the impact of green spaces on osteoporosis risk.

    Genetic susceptibility and exposure to green residential spaces together exhibited a dose-response association with the risk of osteoporosis. Exposure to green residential spaces had a stronger impact in reducing the risk of osteoporosis among individuals with low genetic susceptibility as compared to those who were genetically more susceptible to the disease.

    Conclusions

    The study findings reinforce the positive impact of urban green spaces on human health and elucidate possible mechanisms through which air pollution and exercise impact the risk of osteoporosis.

    More green spaces in urban residential areas were found to lower the risk of osteoporosis by decreasing air pollution, providing residents with green, open spaces to exercise, and lowering psychological stress. The impact of green spaces on osteoporosis risk was also associated with genetic susceptibility to the disease, with individuals who were genetically less susceptible and had more exposure to green spaces having the lowest risk of osteoporosis.

    Journal reference:

    • Tan, T., Tang, L., Guo, X., et al. (2024). Associations of residential greenness with bone mineral density and osteoporosis: the modifying effect of genetic susceptibility. Annals of the Rheumatic Diseases. doi:10.1136/ard-2023-224941

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  • Sinusitis tied to elevated rheumatic disease risk

    Sinusitis tied to elevated rheumatic disease risk

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    The common inflammatory condition sinusitis is linked to a 40% heightened risk of a subsequent diagnosis of rheumatic disease, particularly in the 5 to 10 years preceding the start of symptoms, finds research published in the open access journal RMD Open.

    The risks seem to be greatest for a blood clotting disorder (antiphospholipid syndrome) and a condition that affects the body’s production of fluids, such as spit and tears, known as Sjögren’s syndrome, the findings indicate.

    Sinusitis refers to inflammation of the lining of the sinuses, the small, air-filled cavities behind the cheekbones and forehead. And previously published research points to a link between various types of lung irritants, including air pollution and respiratory infections, and the development of rheumatoid arthritis, for example.

    But it’s not clear if sinusitis might also be a potential predisposing factor for other types of rheumatic disease. In a bid to plug this knowledge gap, the researchers carried out a case-control study.

    They used data from the Rochester Epidemiology Project (REP), a medical records-linkage system of over 500,000 people resident in Olmsted County, Minnesota at some point between 1966 and 2014.

    The study sample included 1729 adults, newly diagnosed with a systemic autoimmune rheumatic disease, such as rheumatoid arthritis, antiphospholipid syndrome, and Sjögren’s syndrome; or vasculitis (blood vessel inflammation), such as giant cell arteritis (temporal artery inflammation) and polymyalgia rheumatica (muscle pain and stiffness).

    Each of these patients (average age 63; two thirds women) was matched with 3 people (5187 in total) with no rheumatic disease, based on age at diagnosis and sex.

    Cases of sinusitis before the diagnosis of rheumatic disease were divided into time segments of 1 to 5 years; 5 to 10 years; and 10 or more years.

    Potentially influential factors were accounted for: age, weight (BMI), and smoking status at rheumatic disease diagnosis, sex, race and ethnicity.

    The average time that elapsed between an episode of sinusitis and diagnosis of rheumatic disease was just over 7.5 years, with the most common diagnosis, rheumatoid arthritis (688) and polymyalgia rheumatica (610).

    A history of sinusitis was associated with a 40% heightened risk of any new diagnosis of rheumatic disease, with the association strongest for systemic autoimmune rheumatic diseases, such as antiphospholipid syndrome–7-fold increased risk-;and Sjögren’s syndrome-;more than double the risk.

    Acute sinusitis was associated with an 18% heightened risk of seronegative rheumatoid arthritis (symptoms but no detectable antibodies).

    The association between sinusitis and newly diagnosed rheumatic disease was strongest in the 5–10 years preceding symptom start, where the risk was 70% higher, overall, but 3-fold higher for Sjögren’s syndrome and twice as high for polymyalgia rheumatica.

    And the more frequent the episodes of sinusitis, the greater were the chances of a new rheumatic disease diagnosis. For example, those experiencing 7 or more were nearly 5 times as likely to be diagnosed with systemic autoimmune disease, nearly 9 times as likely to be diagnosed with Sjögren’s syndrome, and twice as likely to be diagnosed with vasculitis.

    Serial episodes of sinusitis without a previous history also showed a significant dose-response association with seronegative rheumatoid arthritis, rising to a quadrupling in risk for 5 or more episodes.

    And overall, the association between sinusitis and rheumatic disease was strongest in people who had never smoked.

    This is an observational study, and therefore no definitive conclusions can be drawn about causal factors. The researchers also acknowledge several limitations to their findings, including a predominantly White study population and few cases of certain types of rheumatic disease.

    And reverse causation, whereby the rheumatic diseases themselves increase the risk of sinusitis, can’t be ruled out, they add.

    But bacterial pathogens, such as those involved in sinusitis, might have a role in rheumatic disease, added to which sinusitis is associated with speeding up artery hardening, lending extra weight to its potential inflammatory effects, explain the researchers.

    And they conclude: “Overall, these findings point towards a role for sinus inflammation in the presentation, and possibly pathogenesis, of rheumatic disease.“

    Source:

    Journal reference:

    Kronzer, V. L., et al. (2024) Association between sinusitis and incident rheumatic diseases: a population-based study. RMD Open. doi.org/10.1136/rmdopen-2023-003622.

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  • Major study of 59 million Americans finds fine particulate matter from air pollution increases heart disease risks

    Major study of 59 million Americans finds fine particulate matter from air pollution increases heart disease risks

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    In a recent study published in BMJ, researchers assessed exposure-response relationships between chronic fine-size particulate matter (PM2.5) exposure and the probability of first-time hospitalization for cardiovascular disease (CVD) subgroups.

    Study: Exposure-response associations between chronic exposure to fine particulate matter and risks of hospital admission for major cardiovascular diseases: population based cohort study. Image Credit: Kzenon/Shutterstock.comStudy: Exposure-response associations between chronic exposure to fine particulate matter and risks of hospital admission for major cardiovascular diseases: population based cohort study. Image Credit: Kzenon/Shutterstock.com

    Background

    PM2.5, a minor component of air pollution, contributes considerably to CVD by inducing inflammation, vasoconstriction, cardiac electrical abnormalities, and blood clot formation.

    Chronic exposure raises the risk of CVD-related hospitalization and death. Studies frequently focus on one or two CVD subtypes, neglecting to detect susceptible ones.

    Comparing effect sizes across subtypes might help us understand processes and advise targeted strategies to lessen the impact of PM2.5.

    About the study

    In the present population-based cohort study, researchers evaluated exposure-response correlations between chronic PM2.5 exposure and the probability of initial hospitalization for seven main CVD subtypes and their composite.

    The study covered Medicare beneficiaries aged 65 years and above in the continental United States (US) from 2000 to 2016. The team linked calibrated fine particulate matter estimations to each participant’s residence postal code as a proxy for exposure assessment.

    The primary outcome measures were the initial hospitalization risks for cerebrovascular diseases, ischemic heart diseases, cardiomyopathy, heart failure, valvular heart diseases, abdominal and thoracic aortic aneurysms, arrhythmia, or a combination of these cardiovascular disease subtypes.

    The researchers created a causal-type framework resistant to confounding effects and bias caused by inaccuracies in exposure-response estimations.
    The study included Medicare beneficiaries aged 65 years and above residing in the United States (US) and registered with the fee-for-service program from 2000 to 2016.

    The researchers created a distinct cohort for each CVD subtype by tracking each beneficiary annually till the initial hospitalization for that CVD subtype, death, or study termination, whichever came first.

    They created another study cohort by monitoring each beneficiary year till the initial hospitalization for the examined CVDs, mortality, or study termination, whichever occurred first, to investigate the risk of the initial hospitalization for the composite CVD outcome.

    The researchers utilized spatially weighted logistic regressions to estimate ambient PM2.5 values daily at 1.0 km2 grids across the United States from 2000 to 2016.

    They blended predictions from machine-learning-based algorithms and incorporated information sources such as weather, satellite imagery, land use factors, monitoring information, and chemical model simulations.

    They used regression calibrations to improve grid-level particulate matter estimations and eliminate biases in health-effect estimations caused by exposure errors.

    Results

    The research included 59,761,494 individuals with 476,953,892 follow-up years; the majority were white (84%), with a higher number of female beneficiaries (55%). Most participants (75%) were between the ages of 65 and 74 when they began the research.

    During the trial, 18% of participants registered with Medicaid. 22% required hospitalization due to a combination of cardiovascular diseases. The most frequent CVD subtype was ischemic heart illness, which affected 8.8% of recipients.

    Other common illnesses were cerebrovascular disease (7.7%), heart failure (6.6%), and arrhythmia (6.5%). Three-year mean exposure to PM2.5 was related to an increase in the relative risk of initial hospitalization for cerebrovascular illnesses, ischemic heart diseases, cardiomyopathy, heart failure, abdominal and thoracic aortic aneurysms, and arrhythmia.

    Exposure-response curves for composite cardiovascular disease showed a monotonically elevated risk related to fine particulate matter exposure.  

    Compared to exposures ≤5.0 µg m-3 [air quality standard issued by the World Health Organization], the relative risks at exposures ranging from 9.0 to 10 µg m-3, encompassing the United States mean of 9.70 µg m-3 during the analysis, was 1.3.

    Composite CVD-related hospitalization risk rose from 2.6% with exposures of less than or equal to 5.0 µg m-3 to 3.4% with exposures ranging from 9.0 to 10 µg m-3.

    The effects lasted for ≥3.0 years following PM2.5 exposure. Education, age, healthcare access, and neighborhood socioeconomic deprivation influenced PM2.5 sensitivity.

    The highest risk for composite cardiovascular disease and the most common cardiovascular disease CVD subtypes (cerebrovascular disease, ischemic heart disease, and cardiac failure) was related to immediate PM2.5 exposure at lag 0, and a significantly reduced impact at lag 1.0 followed by a decrease at lag 2.0.

    Female beneficiaries were more likely to develop composite cardiovascular disease, heart failure, and ischemic heart disease, although cardiomyopathy risk was lower.

    Younger beneficiaries and individuals aged between 65 and 74 years are more likely to be admitted to the hospital for CVD and subtypes. Those living in areas with lower high school graduation rates, higher deprivation levels, or longer hospital distances likely experienced the most outcomes.

    Conclusion

    The study findings showed that chronic exposure to fine-sized particulate matter increases the risk of cerebrovascular illnesses, ischemic heart diseases, cardiomyopathy, heart failure, arrhythmia, and abdominal and thoracic aortic aneurysms.

    Exposure-response curves for several CVD subtypes shifted, indicating a lack of a safe threshold for cardiovascular health.

    Adhering to the WHO’s air quality standards of ≤5 µg/m3 can provide considerable advantages. Susceptibility varied by participant age, healthcare access, educational achievement, and neighborhood deprivation.

    Cardiac arrhythmia and heart failure are among the most vulnerable CVD subtypes in patients exposed to PM2.5.

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  • Fine particulate matter exposure linked to increased hospital admissions for major diseases

    Fine particulate matter exposure linked to increased hospital admissions for major diseases

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    Short and long term exposure to fine particulate matter (PM2.5) air pollution is linked to an increased risk of hospital admission for major heart and lung diseases, find two large US studies, published by The BMJ today.

    Together, the results suggest that no safe threshold exists for heart and lung health.

    According to the Global Burden of Disease study, exposure to PM2.5 accounts for an estimated 7.6% of total global mortality and 4.2% of global disability adjusted life years (a measure of years lived in good health).

    In light of this extensive evidence, the World Health Organization (WHO) updated the air quality guidelines in 2021, recommending that an annual average PM2.5 levels should not exceed 5 μg/m3 and 24 hour average PM2.5 levels should not exceed 15 μg/m3 on more than 3-4 days each year.

    In the first study, researchers linked average daily PM2.5 levels to residential zip codes for nearly 60 million US adults (84% white, 55% women) aged 65 and over from 2000 to 2016. They then used Medicare insurance data to track hospital admissions over an average of eight years.

    After accounting for a range of economic, health and social factors, average PM2.5 exposure over three years was associated with increased risks of first hospital admissions for seven major types of cardiovascular disease – ischemic heart disease, cerebrovascular disease, heart failure, cardiomyopathy, arrhythmia, valvular heart disease, and thoracic and abdominal aortic aneurysms.

    Compared with exposures of 5 μg/m3 or less (the WHO air quality guideline for annual PM2.5), exposures between 9 and 10 μg/m3, which encompassed the US national average of 9.7 μg/m3 during the study period, were associated with a 29% increased risk of hospital admission for cardiovascular disease.

    On an absolute scale, the risk of hospital admission for cardiovascular disease increased from 2.59% with exposures of 5 μg/m3 or less to 3.35% at exposures between 9 and 10 μg/m3. “This means that if we were able to manage to reduce annual PM2.5 below 5 µg/m3, we could avoid 23% in hospital admissions for cardiovascular disease,” say the researchers.

    These cardiovascular effects persisted for at least three years after exposure to PM2.5, and susceptibility varied by age, education, access to healthcare services, and area deprivation level.

    The researchers say their findings suggest that no safe threshold exists for the chronic effect of PM2.5 on overall cardiovascular health, and that substantial benefits could be attained through adherence to the WHO air quality guideline.

    “On February 7, 2024, the US Environmental Protection Agency (EPA) updated the national air quality standard for annual PM2.5 level, setting a stricter limit at no more than 9 µg/m3. This is the first update since 2012. However, it is still considerably higher than the 5 µg/m3 set by WHO. Obviously, the newly published national standard was not sufficient for the protection of public health,” they add.*

    In the second study, researchers used county-level daily PM2.5 concentrations and medical claims data to track hospital admissions and emergency department visits for natural causes, cardiovascular disease, and respiratory disease for 50 million US adults aged 18 and over from 2010 to 2016.

    During the study period, more than 10 million hospital admissions and 24 million emergency department visits were recorded.

    They found that short term exposure to PM2.5, even at concentrations below the new WHO air quality guideline limit, was statistically significantly associated with higher rates of hospital admissions for natural causes, cardiovascular disease and respiratory disease, as well as emergency department visits for respiratory disease.

    For example, on days when daily PM2.5 levels were below the new WHO air quality guideline limit of 15 μg/m3, an increase of 10 μg/m3 in PM2.5 was associated with 1.87 extra hospital admissions per million adults aged 18 and over per day.

    The researchers say their findings constitute an important contribution to the debate about the revision of air quality limits, guidelines, and standards.

    Both research teams acknowledge several limitations such as possible misclassification of exposure and point out that other unmeasured factors may have affected their results. What’s more, the findings may not apply to individuals without medical insurance, children and adolescents, and those living outside the US.

    However, taken together, these new results provide valuable reference for future national air pollution standards.

    Source:

    Journal reference:

    Wei, Y., et al. (2024) Exposure-response associations between chronic exposure to fine particulate matter and risks of hospital admission for major cardiovascular diseases: population based cohort study. BMJ. doi.org/10.1136/bmj-2023-076939.

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  • Are urban green spaces beneficial to air quality?

    Are urban green spaces beneficial to air quality?

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    A study published in the journal PNAS claims that urban green space has only a moderate effect on air pollution control and that street-level vegetation can actually increase air pollution by restricting ventilation.

    Study: Reassessing the role of urban green space in air pollution control. Image Credit: taka1022 / ShutterstockStudy: Reassessing the role of urban green space in air pollution control. Image Credit: taka1022 / Shutterstock

    Background

    Air pollution is a leading cause of respiratory diseases and premature death globally. Among various air pollutants, small-diameter (2.5 µm) particulate matter (PM) is estimated to cause approximately ten million excess deaths worldwide. The World Health Organization (WHO) considers air pollution as the most significant environmental threat to human health.

    About 70% of all health complications arising from air pollution can be attributed to greenhouse gases emitted by human activities (anthropogenic emissions). Major strategies that have been taken into consideration for reducing anthropogenic emissions include cleaner energy production, efficient discharging of industrial smoke, reduced dependency on fossil fuel vehicles, and sustainable agriculture practices.

    The literature has given immense attention to the utilization of vegetation as a passive abatement method for outdoor air pollution and the installation of physical-chemical filters as an active abatement method for indoor air pollution.

    In this study, scientists have investigated the effect of urban green space on ambient air pollution.

    Study design

    The scientists utilized 2,615 air quality monitoring stations over Europe and the United States to derive annual concentrations of major air pollutants (NO2, PM10, PM2.5, and O3) between 2010 and 2019. They determined the changes in urban green space around each air quality station using moderate-resolution satellite data and very high-resolution aerial imagery.

    They conducted a series of appropriate statistical analyses to determine the association between urban green space and air quality after adjusting for changes in anthropogenic emissions and climate.

    Important observations

    Air quality station-derived data showed a decline in NO2 (nitrogen dioxide), PM10, and PM2.5 between 2010 and 2019, which was relatively consistent across the United States and Europe. In contrast, an induction in O3 concentration in the ambient air was observed during the same period. Overall, these observations indicate that recent strategies to reduce anthropogenic emissions might be useful in controlling air pollution.

    Distribution of the air quality–monitoring stations across biomes in Europe (n = 2,127) and the United States (n = 488) (A). Inset histograms show the proximity of stations to roads and the building footprint within 30 m. Air pollutant time series along with linear trends are shown in (B).Distribution of the air quality–monitoring stations across biomes in Europe (n = 2,127) and the United States (n = 488) (A). Inset histograms show the proximity of stations to roads and the building footprint within 30 m. Air pollutant time series along with linear trends are shown in (B).

    Considering biome-specific vegetation types, the study found that stations situated within the forest biome exhibit the highest decline in air pollutants, especially PM, compared to those situated in the Mediterranean shrubland and savanna/grassland biomes. This might be due to higher pollutant deposition and dispersion capacity of forest vegetation than Mediterranean shrubland. Another possibility could be that dry environments in Mediterranean shrublands may facilitate long-range aerosol transport of dust and smoke.

    The study further analyzed how changes in total urban green space and tree cover can impact air quality at the street, borough, and city levels. The analysis revealed a weak and highly variable effect of green space changes on air pollution, particularly at the street level. This could be because of the fact that planting vegetation, especially tall vegetation, near emission sources, such as across streets, can reduce microscale ventilation and subsequently increase the concentrations of pollutants in the air.   

    Considering the changes in tree cover, the analysis revealed a negative association with air pollution at both the borough level and city level. This association was particularly evident for O3 and PM. Overall, the study found that an induction in tree cover has a significantly higher effect in reducing air pollution than total green space augmentation.

    Furthermore, the study found that the effect of urban green space on air quality was negligible in magnitude than climatic drivers, including wind speed, precipitation, and humidity. These climatic drivers showed a negative association with all types of air pollutants except for O3. 

    Example of an extreme increase (A−C) and decrease (D−F) in green space within a 60-m buffer (street-level) of two air quality–monitoring stations. Aerial photographs from Google Earth Pro shown for reference.Example of an extreme increase (A−C) and decrease (D−F) in green space within a 60-m buffer (street-level) of two air quality–monitoring stations. Aerial photographs from Google Earth Pro shown for reference.

    Study significance

    The study finds that urban green space is not always a good strategy to improve air quality and reduce air pollution. According to the findings, the effect of green space on air quality can widely vary depending on the type of green space (total green space vs. tree cover), spatial scale (street-level versus borough-level versus city-level), and biome (forest versus Mediterranean shrubland).

    One interesting finding of the study is that increased vegetation along roadsides can actually increase air pollution by restricting the ventilation of vehicle-emitted pollutants. The aerodynamic effects of green space can be effective in channeling pollutants away from pedestrians. However, in areas with unfavorable aerodynamic conditions, the pollutant dispersion effect of green space can overshadow its pollutant deposition effect.

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