Data from hundreds of thousands of U.S. adults suggests that each zip code increase of 10 µm/m3 in PM2.5 levels is associated with a doubling in eczema rates among residents
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People living in areas with higher levels of air pollution are more likely to have eczema, according to a new study published November 13, 2024 in the open-access journal PLOS ONEby Dr Jeffrey Cohen of Yale School of Medicine, USA.
The prevalence of eczema has increased globally with industrialisation, suggesting a possible contribution from environmental factors. In the new study, researchers used data from the U.S. National Institutes of Health All of Us Research Program, covering hundreds of thousands of U.S. adults. The current study included 286 862 people for whom there was available demographic, zip code and electronic health record data.
Overall, 12 695 participants (4.4%) were diagnosed with eczema. After controlling for demographics and smoking status, people with eczema were more likely to live in zip codes with high levels of fine particulate matter, or PM2.5, in the air. For every increase of 10 µm/m3 in average PM2.5 air pollution in their zip code, people were more than twice as likely to have eczema.
The authors conclude that increased air pollution, as measured by PM2.5, may influence the risk of developing eczema, likely through its effects on the immune system.
The authors add: “Showing that individuals in the United States who are exposed to particulate matter are more likely to have eczema deepens our understanding of the important health implications of ambient air pollution.”
A study in more than 3000 US counties, with 315 million residents, has suggested that air pollution is linked with stress and depression, putting under-65-year-olds at increased risk of dying from cardiovascular disease. The research was presented at ESC Preventive Cardiology 2024, a scientific congress of the European Society of Cardiology (ESC).1
“Our study indicates that the air we breathe affects our mental well-being, which in turn impacts heart health,” said study lead author Dr Shady Abohashemof Harvard Medical School, Boston, US.
According to the World Health Organization, air pollution is estimated to have caused 4.2 million premature deaths worldwide in 2019.2 Mental illness has also been linked with premature death.3 This study examined whether air pollution and poor mental health are interrelated and have a joint impact on death from cardiovascular disease.
The study focused on particles less than 2.5 micrometres in diameter, also referred to as fine particles or PM2.5. They come from vehicle exhaust fumes, power plant combustion, and burning wood, and present the highest health risk. To conduct the study, county-level data on annual PM2.5 levels were obtained from the Centers for Disease Control and Prevention (CDC).4 PM2.5 exposure was categorised as high or low according to World Health Organization (WHO) standards. The researchers gathered data on the average number of days (age-standardised) that county residents experienced mental health issues – including stress, depression, and emotional problems – from the CDC.5 Each county was then categorised into three groups based on these numbers. Counties in the top third reported the most days of poor mental health (PMH).4 Age-adjusted premature cardiovascular mortality rates (under 65 years of age) per county, were obtained from the CDC.6 County characteristics were sourced from the County Health Rankings project.
The study included 3047 US counties, representing 315 720 938 residents (with over 207 million aged 20 to 64 years and 50% females) in 2013. Between 2013 and 2019, some 1 079 656 (0.34%) participants died from cardiovascular disease before the age of 65 years. The researchers analysed the associations between pollution, mental health, and premature cardiovascular mortality after adjusting for factors that could influence the relationships.7
Counties with dirty air (high PM2.5 concentrations) were 10% more likely to report high levels of PMH days compared to counties with clean air (low PM2.5 concentrations). That risk was markedly greater in counties with a high prevalence of minority groups or poverty. The link between PMH and premature cardiovascular mortality was strongest in counties with higher levels (above WHO recommended levels: ≥10 µm2) of air pollution. In these counties, higher levels of PMH were associated with a three-fold increase in premature cardiovascular mortality compared to lower PMH levels. Further, one-third of the pollution-related risk of premature cardiovascular deaths was explained by increased burden of PMH.
Dr Abohashem said: “Our results reveal a dual threat from air pollution: it not only worsens mental health but also significantly amplifies the risk of heart-related deaths associated with poor mental health. Public health strategies are urgently needed to address both air quality and mental wellbeing in order to preserve cardiovascular health.”
1The abstract ‘Air pollution associates with poor mental health and amplifies the premature cardiovascular death in the United States: longitudinal nationwide analysis’ will be presented during the session ‘Young Investigators Award – Population Science and Public Health’ which takes place on 26 April 2024.
2World Health Organization: Ambient (outdoor) air pollution.
3Byrne P. Meeting the challenges of rising premature mortality in people with severe mental illness. Future Healthc J. 2023;10(2):98-102.
4CDC PLACES databases.
5CDC Behavioral Risk Factor Surveillance System.
6CDC WONDER databases.
7The analyses were adjusted for calendar year and county characteristics such as demographics, median household income, unemployment rates, violent crime rates, education level, food environment index, rates of health insurance, level of mental health provision, level of primary care provision.
A new study from Aarhus University has shown that young people with mild asthma can experience inflammation and irritation from candles as well as cooking fumes. The results, published in Particle and Fibre Toxicology, suggest that asthma sufferers should try and reduce exposure, for example by opening kitchen windows while cooking.
For this randomised controlled double-blind exposure study, exposed 36 young asthmatics to three different exposures in the climate chambers at Aarhus University. They were exposed to emissions from cooking, emissions from burning candles and finally clean air. Each time, the participants were exposed for five hours under highly controlled conditions. Particles and gases were measured during exposures, and participants reported symptoms related to irritation and general well-being. Biomarkers in relation to airway and systemic inflammatory changes were assessed before exposure, immediately after exposure and again the next morning.
Karin Rosenkilde Laursen, a postdoc at the university’s Department of Public Health and co-author of the study, says:
“Our study shows that indoor air pollution caused by fumes from cooking and burning candles can lead to adverse health effects such as irritation and inflammation in young individuals with mild asthma. Among other things, we’ve found indications of DNA damage and signs of inflammation in the blood.”
When ovens are turned, pans put on the hob, or candles are lit, particulate matter and gases are produced, which can be inhaled. Previous studies have shown that these particles and gases can be detrimental to health. What sets this study apart is that the researchers have focused on the effects on young individuals with mild asthma, aged between 18 and 25, says Karin Rosenkilde Laursen:
“In the study, we observed that even very young individuals with mild asthma can experience discomfort and adverse effects if the room is not adequately ventilated during cooking or when burning candles. Young people are generally fitter and more resilient than older and middle-aged individuals. Therefore, it is concerning that we observed a significant impact from the particles on this particularly young age group.”
But not only people diagnosed with asthma need to keep an eye on the indoor climate, she says.
“Even though the study focused on young asthmatics, its findings are interesting and relevant for all of us. Winter is approaching, a time when we tend to light many candles and perhaps are less likely to open doors and windows while cooking. By prioritising a healthier indoor climate, even when we’re cosying up indoors, we may be able to help reduce the incidence of serious lung and cardiovascular diseases, as well as cancer.”
Karin Rosenkilde Laursen plans to follow up this study with another examining how emissions from cooking and candles affect healthy adults.
A new study published in The Lancet Global Health, highlights the impact indoor air pollution can have on the development of child pneumonia, showing that increases in airborne particulate matter results in greater carriage of Streptococcus pneumoniae.
Streptococcus pneumoniae is a major human pathogen causing more than two million deaths per year; more than HIV/AIDS, measles and malaria combined, but it is also part of the normal microbial community of the nasopharynx. It is the leading cause of death due to infectious disease in children under five years of age; in sub-Saharan Africa, the burden of pneumococcal carriage and pneumonia is especially high.
Household air pollution from solid fuels increases the risk of childhood pneumonia. Nasopharyngeal carriage of S. pneumoniae is a necessary step in the development of pneumococcal pneumonia. More than 2.6 billion people are exposed to household air pollution worldwide. Inefficient indoor biomass burning is estimated to cause 3.8 million premature deaths annually and approximately 45% of all pneumonia deaths in children aged younger than five years. However, a causal pathway between household air pollution and pneumonia had not yet been identified.
In order to understand the connection between exposure to household air pollution and the risk of childhood pneumonia researchers from the UK, Malawi and the United States conducted the MSCAPE (Malawi Streptococcus pneumoniae Carriage and Air Pollution Exposure) study embedded in the ongoing CAPS (Child And Pneumonia Study) trial. The MSCAPE study assessed the impact of PM2.5, the single most important health-damaging pollutant in household air pollution, on the prevalence of pneumococcal carriage in a large sample of 485 Malawian children.
Through exposure-response analysis, a statistically significant 10% increase in risk of S. pneumoniae carriage in children was observed for a unit increase (deciles) of exposure to PM2.5 (ranging from 3.9 μg/m³ to 617.0 μg/m³).
Dr. Mukesh Dherani, the study principal investigator, indicated: “This study provides us with greater insight into the impact household air pollution can have on the development of child pneumonia. These findings provide important new evidence of intermediary steps in the causal pathway of household air pollution exposure to pneumonia and provide a platform for future mechanistic studies.”
Study author Professor Dan Pope said: “Moving forward further studies, particularly new randomized controlled trials comparing clean fuels (e.g. liquefied petroleum gas) with biomass fuels, with detailed measurements of PM2.5 exposure, and studies of mechanisms underlying increased pneumococcal carriage, are required to strengthen causal evidence for this component of the pathway from household air pollution exposure to ALRI in children.”
Professor Nigel Bruce, co-principal investigator, stated: “This study provides further important evidence that emphasises the need to accelerate to cleaner fuels, such as LPG, which are now being promoted by many governments across the continent in order to meet SDG7 by 2030.”
New WHO Global Air Quality Guidelines (AQGs) have lowered the acceptable limits of air pollution, providing evidence that even lower concentrations than previously understood have a negative health impact.
Increasing evidence showing how air pollution affects different aspects of health, WHO has adjusted almost all the AQGs levels downwards, warning that exceeding the new air quality guideline levels is associated with significant risks to health.
Air pollution is estimated to cause 7 million premature deaths and the loss of millions more healthy years of life. In children, this could include reduced lung growth and function, respiratory infections and aggravated asthma. In adults, deaths from ischaemic heart disease and stroke are the most common, as well as emerging evidence of diabetes and neurodegenerative conditions. This makes the disease burden from air pollution on par with others such as unhealthy diet and tobacco smoking.
Besides climate change, air pollution is one of the biggest environmental threats to human health. Improving air quality will also help mitigate climate change, thereby reducing the negative health impacts of both. WHO’s new guidelines recommend air quality levels for 6 pollutants, where evidence has advanced the most on health effects from exposure. When action is taken on these so-called classical pollutants – particulate matter (PM), ozone (O₃), nitrogen dioxide (NO₂) sulfur dioxide (SO₂) and carbon monoxide (CO), it also has an impact on other damaging pollutants.
Particulate matterequal or smaller than 10 and 2.5 microns (µm) in diameter (PM₁₀ and PM₂.₅, respectively) is a particular health concern. Both PM₂.₅ and PM₁₀ can penetrate deep into the lungs but PM₂.₅ can even enter the bloodstream, primarily resulting in cardiovascular and respiratory impacts, and also affecting other organs, and were classified as carcinogenic in 2013.
“Air pollution is a threat to health in all countries, but it hits people in low- and middle-income countries the hardest,” said WHO Director-General, Dr Tedros Adhanom Ghebreyesus. “WHO’s new Air Quality Guidelines are an evidence-based and practical tool for improving the quality of the air on which all life depends. I urge all countries and all those fighting to protect our environment to put them to use to reduce suffering and save lives.”
In 2019, over 90% of the world’s population lived in areas where concentrations exceeded the 2005 WHO air quality guideline for long term exposure to PM₂.₅.
Almost 80% of PM₂.₅-related deaths could be avoided if current air pollution levels were reduced to those proposed in the updated guideline. At the same time, reaching interim targets would reduce the burden of disease, of which the greatest benefit would be observed in countries with high concentrations of fine particulates (PM₂.₅) and large populations.
