Tuesday, February 04, 2025

Exposure to air pollution associated with more hospital admissions for lower respiratory infections

Men, people over 65 and those diagnosed with hypertension are the most vulnerable population groups

Barcelona Institute for Global Health (ISGlobal)

Air pollution is a well-known risk factor for respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD). However, its contribution to lower respiratory infections —those that affect the lower respiratory tract, including the lungs, bronchi and alveoli— is less well documented, especially in adults. To fill this gap in knowledge, a team from the Barcelona Institute for Global Health (ISGlobal), a centre supported by the ”la Caixa” Foundation, assessed the effect of air pollution on hospital admissions for lower respiratory infections in adults, and investigated the existence of subgroups that are particularly vulnerable to these infections. The results have been published in the journal Environment International.

The research shows that long-term exposure to PM2.5, PM10, NO2 and ozone (O3) air pollution is associated with more hospital admissions for lower respiratory tract infections in adults. The associations were stronger in men, people over 65 years of age and those diagnosed with hypertension.

The study involved 3,800,000 adults from the COVAIR-CAT cohort, a large cohort of 7.7 million people based on the health system of Catalonia. The research team used exposure models to estimate annual average concentrations of PM2.5, PM10, NO2 and ozone during the warm season (May-September) between 2018 and 2020 at the participants' residences. Information on hospital admissions, mortality and comorbidities was obtained from various administrative databases. The study included hospital admissions for all lower respiratory infections and, separately, the subgroup of hospital admissions for influenza and pneumonia. A statistical model was then used to assess the association between air pollution and hospital admissions.

“The association between air pollution and hospital admissions for lower respiratory tract infections was observed even at pollution levels below current EU air quality standards,” says Anna Alari, ISGlobal researcher and first author of the study. “It is crucial to adopt stricter air quality standards, as more ambitious measures to reduce air pollution would decrease hospital admissions and protect vulnerable populations,” she adds.

Stronger association in men and people over 65

The association between air pollution and hospitalisations for lower respiratory tract infections was more pronounced in people over 65 years of age or with comorbidities, compared with younger people or those without comorbidities. Specifically, elevated levels of air pollution were associated with approximately three times higher rates of hospital admissions for lower respiratory infections among people aged 65 years and older compared with younger people.

In addition, exposure to elevated levels of NO2, PM2.5 or PM10 (but not O3) was associated with about a 50% increase in hospital admissions in men, while the association was about 3% higher in women.

The team observed the same pattern for hospital admissions for influenza or pneumonia, but with smaller associations compared to lower respiratory infections. “This may be due to the influence of available vaccines against the pathogens responsible for influenza and most cases of pneumonia,” says Cathryn Tonne, senior author of the study.

Reference:

Anna Alari, A., Ranzani, O., Milà, C., Olmos, S., Basagaña, X., Dadvand, P., Duarte-Salles, T., Nieuwenhuijsen, M., Tonne, C. Long-term exposure to air pollution and lower respiratory infections in a large population-based adult cohort in Catalonia. Environment International, 2025. Doi: https://doi.org/10.1016/j.envint.2024.109230

Journal

Environment International

DOI

10.1016/j.envint.2024.109230

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

Long-term exposure to air pollution and lower respiratory infections in a large population-based adult cohort in Catalonia

COI Statement

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Cathryn Tonne reports financial support was provided by Health Effects Institute. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this pape

High PM2.5 levels in Delhi-NCR largely independent of Punjab-Haryana crop fires

An analysis of observations across a network of 30 sites

Peer-Reviewed Publication

Research Institute for Humanity and Nature

image:
Figure 1. Soon after the kharif/summer crops (mainly rice paddies) are harvested, large number of farm fires are detected from the satellites in late October to November over northwestern India (a:2022, b:2023; top row). A network of about 30 low-cost sensors has been deployed during the intense CRB period since 2022 (black circles in a, b). Our measurements show rural area air pollution in Punjab (c, d; middle row) and Haryana (e, f; bottom row) was significantly caused by paddy crop residue burning in the October-November months for both 2022 (left column) and 2023 (right column). The FDC maps, at 0.05×0.05 degrees grid resolution, are created from Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the SNPP and NOAA20 satellites hotspot detections. The background shows the visible image of earth’s surface.
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Credit: Aakash Project, RIHN

nternational collaborative research led by Aakash Project* researchers at the Research Institute for Humanity and Nature (RIHN) show an unequivocal contribution of crop residue burning (CRB) to air pollution in the rural/semi-urban regions of Punjab and Haryana, and a relatively lower contribution than previously thought to the Delhi national capital region (NCR). We have installed 30 units of compact and useful PM2.5** in situ instrument with gas sensors (CUPI-Gs) and have continuously recorded air pollutants in 2022 and 2023. New analytical methods have been developed to assess and predict the formation and transport of air pollutants due to emissions from CRB.

The adverse impacts of air pollution on human health, economic activities and lifestyle have been a major concern for decades as pollution at an alert level occurs each year during the October-November months in Delhi-NCR. One of the many hypotheses, to explain rapidly built-up and sustained high PM2.5 concentrations in Delhi-NCR, implicates large contributions from the paddy CRB in Punjab and Haryana states of northwest India (Fig. 1). Burning of rice stubbles in the region is a common practice for land clearing since mechanised paddy harvesting is adopted and is thought to protect fields from pests and preserve soil fertility. Although this formation mechanism of air pollution in Delhi-NCR is debated till date (e.g., in media reports and research publications), policymakers at state and central government levels have targeted eradication of CRB by changing behaviour of farmers in land clearing. The debate continues mainly because of the lack of systematic measurements from the regions of concern. In this study, the research team used a combination of (1) measurements from the Aakash Project’s low cost CUPI-G network, (2) analyses of air mass trajectories, fire counts and wind patterns, and (3) chemistry-transport simulations to assess the impact of CRB on PM2.5 in rural, sub-urban and megacity regions.

The research findings highlight that, despite a significant reduction in the satellite fire detection counts (FDCs) over Punjab and Haryana from 2015 to 2023, PM2.5 concentrations in Delhi have remained high. The PM2.5 concentrations showed large day-to-day fluctuation from site-to-site in both 2022 and 2023 (Fig. 1). Both years saw significant fire counts in southwest Punjab with daily-mean PM2.5 exceeding 300 μg m–3 in Delhi, but the meteorological conditions were markedly different for the peak CRB days of November 1st – 12th of 2022 and 2023. November 2022 witnessed a prevalence of northwesterly winds allowing the transport of airmass from Punjab and Haryana to Delhi-NCR on two occasions. However, in November 2023, a southwesterly low wind condition with speed <1 m s–1 limited air movement causing an accumulation of local pollutants in Delhi-NCR (Fig. 2). Our analyses showed that the buildup and sustenance of PM2.5 in the Delhi-NCR is primarily of local origin and can be inferred from the rise/drop in concert with implementation/revocation of Graded Response Action Plan (GRAP) stages as administered by the Commission of air quality management (CAQM) (Fig. 2).

“With the measurements at a network of about 30 sites covering Punjab, Haryana and Delhi NCR, we are able to separate the contributions of paddy straw burning to Delhi’s PM2.5 variations on the basis of characteristic PM2.5 events and at week-monthly averages,” says Prof. Prabir Patra, the leader of Aakash Project and principal scientist at Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Multiple years of data (2022-2023; now 2024) gathered by the project helps to confirm the findings and (in)validate the hypothesis (Fig. 3).

Based on several types of analysis as presented in Mangaraj et al. (2025), we have been successful in processing the observation data and model-based analysis in near real-time. These data and plots have been shared online daily via the Aakash-RIHN website since 2023 (e.g., https://aakash-rihn.org/en/campaign2023-week13/). We have concluded that CRB in Punjab and Haryana cannot be made responsible for determining the air quality in Delhi-NCR, even during the peak rice stubble burning period (Oct-Nov). Apart from the fact that the horizontal wind flow is blocked by the Himalayas to the north (ref. Fig. 1a, c), the freshly emitted and photo-chemically formed PM2.5 is randomly transported in the other 3 directions horizontally and is diluted vertically through the planetary boundary layer ventilation (Fig. 3). “Our study underscores the importance of continuous monitoring of air pollutions in both source (Punjab), receptor (Delhi-NCR) and intermediate (Haryana) regions for implementation of targeted mitigation strategies to combat persistency of harmful air pollution,” says Dr. Poonam Mangaraj, the lead author of the article.

This research is conducted as part of the Aakash Project * (Project No. 14200133) of RIHN, a constituent member of NIHU. The intensive field campaigns of 2022-23 was conducted with support from the Centers for International Projects Trust (CIPT), India.

The measurement data of PM2.5 are made available from the RIHN database with open data sharing policy (https://aakash-rihn.org/en/data-set/).

*The Aakash project is exploring ways to shift people's behaviour to sustainable agriculture in the Punjab region to reduce the health hazards caused by air pollution, by clarifying observation-based relationship between straw burning and local air pollution; raising awareness of the importance of maintaining clean air among residents; and proposing the effective and beneficial use of rice straw by farmers.

**PM2.5: particulate matter less than 2.5 µm in diameter (popularly known as PM2.5). These fine particles can be inhaled during human breathing. Depending on chemical composition, defined by oxidative potential (OP), they damage the pulmonary cells. The particulates from materials burning usually have greater OP than those from natural sources, e.g., mineral dusts or secondary organics.

Article information

Title： Weak coupling of observed surface PM2.5 in Delhi-NCR with rice crop residue burning in Punjab and Haryana

Journal：npj Climate and Atmospheric Science

Authors: Poonam Mangaraj, Yutaka Matsumi, Tomoki Nakayama, Akash Biswal, Kazuyo Yamaji, Hikaru Araki, Natsuko Yasutomi, Masayuki Takigawa, Prabir K. Patra, Sachiko Hayashida, Akanksha Sharma, A. P. Dimri, Surendra K. Dhaka, Manpreet S. Bhatti, Mizuo Kajino, Sahil Mor, Ravindra Khaiwal, Sanjeev Bhardwaj, Vimal J. Vazhathara, Ravi K. Kunchala, Tuhin K. Mandal, Prakhar Misra, Tanbir Singh, Kamal Vatta, and Suman Mor

Article Publication Date： January 15, 2025

URL： https://doi.org/10.1038/s41612-025-00901-8

Figure 2. The PM2.5 concentration in megacity Delhi and its neighbourhood are mainly dominated by local emissions and can be managed reasonably well through the GRAP implementation focusing on the NCR (top row). Strong meteorological influences at synoptic and interannual are also observed as summarised by the plots in bottom row, for mean PM2.5 (c), wind speed (d; WS), wind direction (e; WD) and atmospheric mixing by boundary layer height (f; BLH) during the October-November period at an interval of 15 days.

Figure 3. Diagrams showing that Aakash/CUPI-G ground-based observation network allows us to track the movement of plumes from Punjab to Delhi. Four days of high PM2.5 in Delhi-NCR are shown in 2022 (top row) and 2023 (bottom row). The CRB effect always elevates the daily mean PM2.5 concentration (red circles) in South Punjab, while the direct effect of CRB rarely reaches to Delhi-NCR. The CUPI-Gs recorded PM2.5 continuously, even under hazy and cloudy conditions when satellites cannot detect CRB or related information.

Credit

Aakash Project, RIHN

About RIHN

The Research Institute for Humanity and Nature (RIHN) is a national institute established in Kyoto in 2001. RIHN aims, through research that integrates the humanities and sciences, to address environmental issues concerning the relationship between "humanity" and "nature" in a broad sense as fundamental issues of human culture. We strive not only to engage the research community but also to collaborate with diverse stakeholders in society, including local residents, to find solutions to global environmental problems.

For more detail, visit https://www.chikyu.ac.jp/rihn_e/.