Skip to main content
NCBI home page
BMC Public Health logoLink to BMC Public Health
. 2025 Jul 7;25:2398. doi: 10.1186/s12889-025-23445-1

Systematic review of the literature on indoor air quality in healthcare units and its effects on health

António Loureiro 1,2,✉, Ana Ferreira 1, Nelson Barros 2,3
PMCID: PMC12232835  PMID: 40624466

Abstract

Background

Indoor air quality in healthcare facilities such as hospitals and health centres is increasingly considered an important factor for the health and well-being of their occupants, namely workers and patients/users.

Methods

The principal objective of this study was to identify the recent research interests on the subject by carrying out a systematic literature review using the PRISMA methodology applied to systematic reviews and meta-analyses. Of the articles published between 1st January 2019 and 31st March 2024, 38 were selected and analysed.

Results

The results indicated that there has been considerable worldwide interest in the subject of Indoor Air Quality in healthcare units, particularly hospitals, and that it is spread across a wide variety of scientific journals. Hospitals were the healthcare unit with the greatest interest in the evaluated studies and the most studied locations were wards, intensive care units, operating theatres, and emergency rooms. A textometric analysis of the selected articles using IRaMuTeQ software identified five main topics studied: (i) physicochemical parameters; (ii) temperature and humidity assessment; (iii) measures to be adopted to improve the quality of environmental factors and symptoms and/or diseases associated with poor indoor air quality; (iv) infrastructure design and management; and (v) assessment of microbiological parameters. Most of the analysed articles reported data assessed by experimental methods, with the most frequently assessed parameters being carbon dioxide and particulate matter, temperature and relative humidity and chemical parameters (total volatile organic compounds, carbon monoxide, formaldehyde, and nitrogen dioxide).

Conclusions

The study provides an overview of recent literature on this subject, presenting guidelines for preserving and improving indoor air quality in healthcare units.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-025-23445-1.

Keywords: Indoor air quality, Hospitals, Healthcare units, Public health, Occupational health

Background

Atmospheric pollution has become a global problem, associated with a growing degradation of air quality, especially in developing countries, driven by a notable rise in atmospheric concentrations of harmful substances, largely originating from industrial, rural and urban activities [1, 2].

Indoor air pollution is regarded as one of the five most significant threats to public health, within buildings can be two to five times greater than outdoor levels, and in severe cases, may reach up to a hundred times higher [1, 3]. Currently, people spend most of their time indoors, around 80 to 90%, making these contamination levels extremely important, as they are more exposed to indoor air pollution than outdoor air pollution [1, 4–6].

Exposure to indoor pollution levels varies significantly and is the result of various factors, such as the type of pollutant source (such as building materials and finishes, furniture, cleaning products, and chemicals), the activities carried out inside, the reactivity of pollutants, the emission rate of single or multiple contaminants, proximity to a source, air mixing volume and heating, ventilation and air conditioning (HVAC) systems, and contributions from outside air [1, 3, 5, 7–12]. On the other hand, the health condition, vulnerability of each person (age, gender, weight) and susceptibility of the building’s users are other factors that must be considered regarding the variability of pollution levels that can exist in indoor air [1].

Indoor air quality (IAQ) can greatly affect human health, especially for children, the elderly, and individuals with comorbidities, and/or who suffer from respiratory and/or cardiovascular pathologies who are particularly at risk [13–15]. There has been an increasing concern recently regarding the negative health impacts of various chemicals emitted by building materials and household items used indoors [9, 13–15].

The health problems associated with poor air quality, often identified as Sick Building Syndrome, that can affect humans are similar to the symptoms of a cold or a flu: congestion, sinus problems, nausea, motion sickness, headaches, irritation of the nose, throat, and eyes, and fatigue [16–18]. The indoor environment is rarely considered to be the cause of the symptoms manifested by the occupants, except when these symptoms are common by several people, persistent or coincide with visibly abnormal and suspicious air quality [4, 5, 10].

In the past years, numerous studies have been developed with the objective of investigating the relation between poor IAQ and outdoor air quality, as well as its adverse effects, both in the short and long term, on human health. These effects can vary from respiratory symptomatology and sensory irritations to cardiovascular and respiratory diseases and are associated with air pollutants or the mixture of various contaminants, their toxicity and exposure time [8, 9].

Knowledge of IAQ in susceptible environments, such as healthcare institutions, is a fundamental question [12, 18]. As well as being affected by the outside environment, pollution inside hospital units can be related to specific substances released by different products used, such as disinfectants, sterilisers and cleaning, pharmaceutical and laboratory chemicals, healthcare activities, waste management and treatment, furniture and building materials, the occupants themselves and biological contaminants, among others [19–21]. In addition, factors related to HVAC systems, including cooling towers and humidifiers, can also contribute to indoor air pollution in hospital units [1, 22, 23]. On the other hand, these are generally buildings that are heavily used, with a high occupancy density, partly with vulnerable occupants and often operating 24 h a day, 365 days a year.

Considering the relevance of this research topic, the objectives of this review were to:

  • present a comprehensive review of the latest literature on indoor air quality in healthcare units, particularly in hospitals;

  • determine the main factors influencing indoor air quality within healthcare units;

  • determine the main effects of indoor air quality on the health of occupants;

  • identify future prospects for research on the subject.

Based on a systematic literature review centred on recent studies (between 1st January 2019 and 31st March 2024), the aim of this review was to answer the following research questions (RQ):

  • RQ1: How does each country collaborate in research on this topic?

  • RQ2: What kind of healthcare units are being studied?

  • RQ3: Which physicochemical parameters of Indoor Air Quality are being analysed?

  • RQ4: What is the research trend on Indoor Air Quality?

In terms of structure, this article is organized as follows: Sect. 1 offers a concise introduction, Sect. 2 describes and explains the research methodology used, Sect. 3 shows the results obtained and discusses them with a view to answering the investigation questions and Sect. 4 shows the main conclusions drawn from the review carried out and highlights the prospects for further studies.

Materials and methods

This systematic literature review was carried out with the aim of identifying, selecting, analysing and systematising information published in review articles or recent scientific studies, with a special focus on IAQ in healthcare units and its effects on the health of their occupants. It should be emphasised that the work tended to be carried out only on physicochemical contamination. All articles relating only to microbiological contamination were not considered. However, there were situations in which the articles included microbiological contamination as well as physicochemical contamination. In these specific cases, and in order not to lose the information relating to the physicochemical branch, which is the scope of this review, manuscripts that covered both the physicochemical and microbiological components were considered.

Systematic literature reviews are based on a scientific, transparent and replicable process that involves a succession of steps [24]: (1) organising the review process; (2) carrying out the review process; (3) reporting and disseminating the results. Through a systematic literature review it is possible to consolidate knowledge on a particular investigation topic, identifying the main trends, existing limitations and areas that need further research [25].

The first stage of the systematic literature review, the planned process of reviewing was carried out by choosing the search engines in databases of scientific publications to be used. Four search engines were utilized: Web of Science, Science Direct, Pubmed, and B-on. Considering the objective of this study, the following keywords were used: {‘indoor air quality’} combined with {‘health’ or ‘health effects’} and {‘hospital’ or ‘hospitals’ or ‘healthcare’ or ‘health care’ or ‘healthcare units’ or ‘clinic’ or ‘clinics’}. For the research, the following inclusion criteria were considered: peer-reviewed research articles, published between 1st January 2019 and 31st March 2024, written in English, and featuring a combination of the keywords selected in the abstract.

Even before applying the PRISMA method [25], a preliminary check was carried out and it was detected that some of the articles found were not supposed to be present in the search, namely duplicate articles within the search engines and publications that did not fulfil the selection criteria. As a result of this check, 767 articles were identified as eligible for application of the PRISMA methodology.

Figure 1 shows the PRISMA flow diagram [25] resulting from the systematic literature review carried out in this study. The search identified a total of 767 records were found among the four search engines consulted in the defined period (January 1, 2019 and March 31, 2024), which were reduced to 598 articles after the process of removing duplicate records.

Fig. 1.

Fig. 1

Open in a new tab

Flowchart of the systematic literature review

The first selection of articles was based on analysing the title, excluding all those that did not particularly address IAQ in healthcare units and health effects resulting from air quality.

This stage reduced the sample to 92 articles, which were then analysed by reading the abstracts. At this stage, 33 articles were excluded because they were outside the scope of this work and focused exclusively on the microbiological contamination of buildings. The complete reading of the remaining 59 articles led to the exclusion of 21 from the sample, seven because they were inaccessible and the others because for not meeting the previously outlined inclusion criteria.

As a result, the final sample consisted of 38 articles. The full list of references can be consulted in the Supplementary Materials.

The 38 articles identified were assessed in terms of their scientific quality, considering the position of the journal in which they were published in the Scimago Journal & Country Rank (SJR) [26], using two indicators: the H-index and the quartile. Journals that were not indexed in the SJR database or lacked a ranking, were duly noted.

The second stage of the systematic literature review involved analysing the content to produce a set of data that was recorded in a spreadsheet after being extracted from the four search engines consulted with the help of the Mendeley bibliographic reference management software, version 2.131.0 [27], which enabled the storage and organization of the articles sampled. Using this file, the following data was taken from each article sampled: title; year of publication; authors; journal/magazine; type of health establishment analysed; country and continent where the study was carried out; type of article; type of sensor used to measure the parameters assessed and data (point campaigns or fixed networks) and the physicochemical IAQ parameters evaluated.

IRaMuTeQ software was used to carry out the textual analysis of the keywords and abstracts of the articles analysed. Developed in 2009 by Pierre Ratinaud, IRaMuTeQ is based on the R software and uses the Python programming language [28].

The keywords from the analysed articles were standardised by using underlining to connect compound words, as well as harmonising acronyms and treating synonyms equivalently. A word cloud was created, this is a visual resource that shows the relative frequency of the most used keywords in the articles analyzed, applying the IRaMuTeQ program. The most recurrently applied keywords appeared more prominent (larger) than the rest, with the word size being proportional to how often they appeared. It should be noted that one of the 38 articles analysed had no keywords.

The textometric analysis was carried out on the abstracts of the 38 articles that were included in the review after the screening process. After the corpus had been created, the text was proofread to avoid any possible spelling mistakes. As in the previous analysis, abbreviations and symbols were consistently used, and underlining was applied to link compound words. A lemmatization process was applied which consisted of replacing each word (occurrence) with its root word or canonical form. It should also be noted that the textometric analysis only considered active forms, i.e. grammatical categories that play a fundamental role in the construction of meaning, which included: adjectives, adverbs, common nouns, verbs and unrecognized forms. Supplementary forms such as pronouns, conjunctions and prepositions were excluded from the analysis to avoid bias in the interpretation of the results.

To study the content of the abstracts of the articles sampled, Descending Hierarchical Classification (DHC) was used to identify thematic groupings in the textual corpus, based on the distribution of active forms and the analysis of the co-occurrence of terms [29]. This method is inspired by Reinert algorithm (1990) and allows the textual corpus to be divided into subsets of words that share similar contexts of use [30]. In this way, it is possible to recognize semantic and thematic groupings that emerge naturally from the text. Confirmatory Factor Analysis (CFA) was also used to verify the factor structure underlying the classes identified [29, 31]. CFA made it possible to assess the suitability of the groupings obtained, based on the chi-square correlation between the classes and the regularity of occurrence of the active forms [29, 31].

The textual corpus was separated into homogeneous divisions based on the chi-square correlation between the classes and the frequency of occurrence of the active forms. To assess the significance of the thematic clusters identified in the textometric analysis, we used the chi-squared test, which measures the association between the classes resulting from the DHC and the frequency of active lexical forms [29, 32]. The chi-squared value was calculated by comparing the observed and expected frequencies of the words within each cluster, using the test’s standard formula. The degree of freedom was determined by the number of clusters (4) less one (df = number of clusters formed − 1), giving a degree of freedom equal to 3. The significance threshold adopted was p < 0.05, corresponding to a critical value of 7.82, with chi-squared values greater than this indicating a statistically significant association between the word and the corresponding class, allowing the thematic clusters identified to be validated [32]. In cases where the value exceeded 11.35, the significance was considered more robust (p < 0.01), and above 16.27, the association between the cluster and the terms was highly significant (p < 0.001).

The combination of DHC and CFA, together with complementary techniques such as lemmatization and the elimination of supplementary forms, made it possible to carry out a robust and in-depth analysis of the textual structure of the abstracts of the scientific articles analyzed.

Results and discussion

Analysing of bibliographic results

According to the analysis of the tendency, between 1st January 2019 and 31st March 2024, there has been a clear upward in publications focusing on IAQ in healthcare units, demonstrating growing interest in this topic (Fig. 2).

Fig. 2.

Fig. 2

Open in a new tab

Number of selected articles distributed by years of study (2019–2024)

Analysing Fig. 2, there was a significant growth in the number of articles published between 2020 and 2023, growing from three articles in 2020 to 11 in 2023. It should be noted that only one article was published in 2024, but this year only includes the months of January, February and March. Analysing by month, the average number of articles published between 2019 and 2023 was 0.6. Although only three months were representative, there was a loss of production on this topic in the period analysed in 2024, as the average in this period was 0.33 articles per month. The low number of articles published in 2020 and 2021, compared to 2019, 2022 and 2023, can be explained by the global impact of the COVID-19 pandemic, which was declared by the World Health Organization on March 11, 2020. Social confinement and the challenges imposed by the pandemic have restricted access to healthcare units, making it difficult to carry out research studies, particularly in the scope of Indoor Air Quality. This scenario may have contributed to a reduction in scientific production on this topic, since institutions were primarily focused on combating the pandemic.

The 38 articles analysed in this study were distributed in 30 different journals, with the most represented covering 26.3% of the articles in the sample: Building and the Environment (five articles), Sustainability (two articles) and Toxics (two articles).

To assess the scientific quality of the sample articles in study, it was utilized the H-index and quartile indicators of the publications, obtained using the SJR database. It should be noted that 28 (representing 93.3%) of the 30 journals identified in this sample were classified in the SJR database.

Figure 3 shows the division of the articles included in the review by quartiles and revealed that the majority (71.1%) were published in Q1 and Q2 journals. However, two articles (5.3%) were published in periodicals that did not have an H-index listed in the SJR database.

Fig. 3.

Fig. 3

Open in a new tab

Distribution of the selected articles, by quartile, according to the period in which they were published

The remaining 36 articles, the H-index of the journals ranged from 11 to 353, with a median of 108.5. It should be noted that 47.4% of the sample (18 articles) were featured in periodicals whose H-index was over 100.

Figure 4 shows the tendency in the distribution of the percentage of papers analysed in the Q1 and Q2 quartiles between 2019 and 2024. The annual percentage of articles in the Q1 and Q2 quartiles rose from 57.1% in 2019 to 66.7% in 2020. It should be noted that in the years 2021 and 2024 all the articles analysed were in the first and second quartiles, which shows that there was an increase in the quality of research in these years compared to other years under study. It should be noted that in the years 2022 and 2023 the percentage of articles analysed in the Q1 and Q2 quartiles fell to 87.5% and 63.6%, respectively, when compared to the year 2021. This fall could be linked to the disruption caused by the COVID-19 pandemic, but the reason for this drop in the quality of production is unclear, particularly if we take into consideration that the production increased over the same period.

Fig. 4.

Fig. 4

Open in a new tab

Percentage distribution between 2019 and 2024 of the articles analysed in quartiles Q1 and Q2

Methodology for analysing articles

According to Fig. 5, of the 38 articles selected after the screening process and included in this systematic review, 28 articles presented research based on objective methods (quantitative, field measurements) and 10 articles presented objective and subjective methods (qualitative, questionnaires, observations).

Fig. 5.

Fig. 5

Open in a new tab

Number of articles selected by type of methodology used

Contributions per country and continent

The publication trend (Fig. 6) indicates that in the period under analysis (2019–2024), the articles sampled came from several geographical locations around the world.

Fig. 6.

Fig. 6

Open in a new tab

Number of articles selected by place of study (country)

There were 21 countries in the sample, spread across five continents. As for the distribution by continent, 73.7% of the studies were carried out in Asia, 18.4% (seven articles) in Europe, 5.2% (two articles) in America and one article in Africa. The current dynamics of the Asian continent in this area of research should be emphasised, since 28 of the 38 scientific articles that made up the sample of this study were developed on this continent. By country, China and Iran led the way, with 26.3% (10 articles) and 10.5% (four articles) of the 38 articles in the sample.

Healthcare units under study

In terms of the type of healthcare establishment, hospitals were the healthcare unit of greatest interest for IAQ studies, accounting for 76.7% of the study sample. Regarding other healthcare units, nine studies highlighted concerns about IAQ in elderly care centres, public health centres, specialised nursing centres, dental practices and other healthcare units. The most evaluated locations were wards, intensive care units, operating rooms, emergency rooms, consulting rooms and waiting rooms.

91.2% (35 articles) presented quantitative data resulting from one-off campaigns. Only three articles referred to data from fixed networks in the healthcare units evaluated [12, 33, 34].

Parameters under study

The experimental data published revealed that most articles focused on the analysis of four to six IAQ parameters (Fig. 7). However, the sample contained five articles presenting results from the analysis of seven to nine parameters [18, 33, 35–37]. On the other hand, 10.5% of the articles evaluated only two to three IAQ parameters [12, 38–40].

Fig. 7.

Fig. 7

Open in a new tab

Percentage of selected articles with experimental data according to the number of parameters analysed

Figure 8 shows the parameters that were evaluated in the selected articles. Considering the parameters that were most assessed, carbon dioxide (CO2) and particulate matter (PM) stood out in 55.3% of the articles evaluated. Regarding the other most regularly assessed chemical parameters, total volatile organic compounds (TVOC), carbon monoxide (CO), formaldehyde (CH2O) and nitrogen dioxide (NO2) were evaluated in 44.7%, 23.7%, 18.4% and 13.2% of the articles selected, respectively. Other pollutants that were monitored in at least one of the selected articles were ozone (O3) [33, 36, 37], sulphur dioxide (SO2) [36], radon [41], isoflurane [42], ultrafine particles [43], benzene [44] and nicotine [38]. Temperature and relative humidity, parameters related to thermal comfort and environmental quality, were assessed in 52.6% of the articles selected. Air velocity was another parameter that was assessed in three of the articles that made up the sample [18, 40, 45, 46].

Fig. 8.

Fig. 8

Open in a new tab

Parameters evaluated in the selected articles with experimental data

In the case of the articles that evaluated particulate matter (21 articles), 42.9% evaluated PM2.5 exclusively, 38.1% evaluated PM2.5 and PM10, 9.5% evaluated PM1.0, PM2.5 and PM10 and two articles evaluated PM10 exclusively [36] and total suspended particles [47] (Fig. 9).

Fig. 9.

Fig. 9

Open in a new tab

Distribution of particulate matter in the selected articles with experimental data

It should also be noted that some of the selected articles with experimental data evaluated other types of parameters, particularly physical ones, such as lighting and noise [16, 34, 48], and microbiological, such as fungi and bacteria [11, 23, 36, 47, 49, 50].

As for the type of sensor used to monitor the parameters evaluated, it was 71.1% used portable sensors, 26.3% used low-cost sensors and only one article used fixed reference sensors (Fig. 10).

Fig. 10.

Fig. 10

Open in a new tab

Distribution of the type of sensor used to evaluate the parameters studied in the selected articles with experimental data

Textometric analysis

The textometric analysis of the keywords in the articles analysed revealed that 15 keywords appeared at least three times. “Indoor Air Quality” was the most predominant keyword with 19 repetitions, followed by the words “hospital” with nine and “particulate matter” with seven (Fig. 11).

Fig. 11.

Fig. 11

Open in a new tab

Word cloud obtained from the keywords of the selected articles

A word cloud was also made by analysing the text of the abstracts of the 38 articles selected, showing which words appeared most frequently (Fig. 12). According to the frequency with which the words appeared in the abstracts, a total of 385 words were found, with a minimum of three repetitions. In this case, the most frequent word was “hospital” with 89 repetitions, followed by the words “indoor air quality”, “study” and “concentration” with 71, 70 and 62 repetitions, respectively. By analysing the words in the abstracts, we found a wide range of key concepts, some of which represented the keywords in the articles. However, it was also noted that some of the key concepts did not represent the keywords of the selected articles, which is why guidelines and criteria for the use of keywords should be adopted to improve and systematise research procedures.

Fig. 12.

Fig. 12

Open in a new tab

Word cloud of key concepts from the abstracts of selected articles

The lexicographic analysis of the abstracts text of the of the 38 articles selected produced 8.050 events, showing 1.438 active forms for a total of 1.721 words (lexical forms). Among the prevalent active forms have included “hospital” (89), “indoor air quality” (71), “study” (70), “concentration” (62), and “health” (43), and 385 of the active forms was presented an occurrence equal to or greater than three.

The cluster dendogram, obtained using the IRaMuTeQ software (Fig. 13), shows four clusters produced considering the branched divisions of the studies of the selected articles and considering only the active forms. One of the branches includes Clusters 1 and 2 and the other Clusters 3 and 4. The percentage identified in each of the boxes corresponds to the proportion of words in the summaries related to each cluster, the largest cluster being Cluster 3 with 37.6% of the 1438 active forms. The colour scheme presented is intended to simplify the observation of each of the clusters.

Fig. 13.

Fig. 13

Open in a new tab

Dendogram of the clusters obtained from the abstracts of the selected articles with the respective percentage

Figure 14 shows the factorial reproduction, which demonstrates the interconnection resulting from the four clusters constituted in the shape of a factor scheme. Clusters 1 and 2 are visibly linked and Clusters 3 and 4 stand out as the least connected to the other clusters, as illustrated in Figs. 13 and 14. In Fig. 14, the word sizes are proportional to their respective chi-squared values, indicating their impact on the formation of the clusters.

Fig. 14.

Fig. 14

Open in a new tab

Graphical reproduction of the factor representation carried out with the abstracts of the selected articles

Observing of the semantic fields of the clusters presented in Fig. 14 shows the following categorisation of the studies carried out in the articles selected under study:

  • Cluster 1– is associated to air quality research focussing on physicochemical parameters in healthcare units. The most impactful words (with the highest Chi-squared values) were: PM2.5 (Inline graphic59.1, p<0.0001), NO2 (Inline graphic47.9, p < 0.0001), PM10 (Inline graphic41.9, p < 0.0001), VOC (Inline graphic22.4, p < 0.0001) CO2 e (Inline graphic21.4, p<0.0001). The catalogued articles analysed in this cluster reveals the following questions: the importance of assessing IAQ in hospital units, particularly in wards [39, 40, 51–53], emergency rooms [33, 35, 51, 54], examination and consultation rooms [39, 54, 55], waiting room [52, 56] and intensive care unit [33] ensuring adequate air quality in these spaces and safeguarding the health of workers and users; human presence and activities contribute to increasing concentrations of CO2, PM2,5 and VOC in the indoor air of hospital spaces [21, 35, 37, 39, 52–57].

  • Cluster 2– is mainly related to the evaluation of temperature and relative humidity as indicators for assessing air quality and thermal comfort in indoor spaces. The most impactful words (with the highest Chi-squared values) were: ventilation (Inline graphic), indoor air (Inline graphic10.2, p<0.05) and temperature (Inline graphic7.47, p < 0.05). Evaluation of thermal comfort parameters, namely temperature and relative humidity [10, 23, 45, 58, 59] is well evidenced in the articles that are part of this cluster, and the possible influence of relative humidity levels in healthcare units on the growth and reproduction of microorganisms, particularly fungi, is also highlighted [23, 49, 59]. It is also important to monitor the occupancy levels of the various spaces in hospital units (wards, emergency services and waiting rooms) since an excess of occupants in a given space can negatively affect the IAQ in these spaces, namely with an increase in CO2 concentration [10, 60], and can increase the transmission of viruses (e.g. SARS-CoV-2, among others) between workers and patients [43, 60]. Finally, a highlight should be made to the evaluation of an isolated parameter, radon, in a hospital unit [41].

  • Cluster 3– identifies measures to be adopted in order to improve the quality of environmental factors in a hospital environment, as well as possible symptoms and/or illnesses associated with poor IAQ. The most impactful words (with the highest Chi-squared values) were: hospital (Inline graphic24.9, p<0.0001), health (Inline graphic14.7, p < 0.001), environmental (Inline graphic11.6, p < 0.001) and study (Inline graphic9.45, p < 0.05). Some studies in this cluster refer to various symptoms and/or illnesses associated with the Sick Building Syndrome that have been reported by healthcare workers and users and which are related to poor IAQ, such as dryness and irritation of the eyes and nose, dizziness, headaches, coughing, sneezing and runny nose, dryness of the throat and skin, difficulty concentrating, fatigue and breathing difficulties [16–18, 44]. There are many measures that can be taken to improve IAQ in hospital environments: proper selection of construction and renovation materials in the design of facilities [16], choice of chemical disinfection and cleaning products that release fewer atmospheric pollutants and therefore pose less risk to health [17, 44], the existence of an adequate ventilation system taking into account the activities that take place in the different spaces, proper maintenance of heating, ventilation and air conditioning systems [16, 18, 40] and the adoption, whenever possible, of natural ventilation [16–18], deployment of indoor air quality monitoring sensors and periodic measurements of the physicochemical parameters that affect indoor air quality [16], and a proper review of the various procedures carried out in hospital environments that can contribute to the release of atmospheric pollutants. This cluster also presents a study focused on the evaluation of isoflurane, an anaesthetic gas, in hospital operating theatres and its effects on the health of their occupants [42].

  • Cluster 4– is related to the design and management of infrastructure in terms of filtration and ventilation systems, the influence of outdoor pollutants and microbiological parameters on worsening IAQ. It also highlights occupational exposure to formaldehyde. The most impactful words (with the highest Chi-squared values) were: exposure (Inline graphic43.5, p<0.0001), risk (Inline graphic36.0, p < 0.0001), formaldehyde (Inline graphic33.5, p < 0.0001) and hazard (Inline graphic19.2, p < 0.0001). Special emphasis is also placed on the synergistic approach between indoor and outdoor pollutants and their potential effects on the health of patients and workers resulting from exposure to these risk factors, highlighting some climatic phenomena and/or anthropogenic actions, such as forest fires [46] which can worsen a hospital’s indoor air quality by infiltrating particulate matter and other pollutants from smoke present in outdoor air. This cluster also highlights the occupational exposure of health professionals, namely doctors, medical laboratory professionals and auxiliaries, to formaldehyde, which often comes from the medical procedures themselves and the use of chemical products used in these procedures and in cleaning and disinfecting facilities [59, 61]. In addition to evaluating some of the physicochemical parameters assessed in articles from other clusters, importance is given to evaluating microbiological parameters such as bacteria and fungi [11, 50]. The importance of having adequate high-efficiency particle filtration systems is also emphasised [3, 46] and heating, ventilation and air-conditioning systems, as well as their regular maintenance and cleaning [3, 11, 22, 46, 50] in order to guarantee a reduction in the exposure of hospital occupants to indoor air pollutants, significantly improving their health and quality of life.

During the preparation of this systematic review, some limitations were found, such as the low number of scientific articles selected in the years 2020 and 2021, when compared to the other years under analysis, which may be related to the COVID-19 pandemic that affected the whole world and made it difficult to carry out research studies in healthcare units, as well as the inclusion of studies only published in English, which may have excluded relevant research published in other languages, introducing a potential selection bias. On the other hand, although the authors believe they have included the main databases in this study, some may have been excluded, which could be considered a limitation of this work. In addition, the authors have no way of controlling this variable, which is clearly an unavoidable limitation of this study.

Conclusion

Analysing the 38 articles selected through a systematic literature review focusing on IAQ in healthcare facilities and its effects on health, particularly in hospitals, it was found that there has been significant worldwide interest in this subject, with publications in 21 different countries on four continents.

There are a variety of scientific journals publishing articles on the subject, and the scientific quality of the studies published and analysed has been increasing. This is particularly relevant given that 73.1% of the articles in the sample were published in first- and second-quartile journals (Q1 and Q2).

Regarding each country’s contribution to the topic under study (research question RQ1), it was noted that China and Iran led the way, with 26.3% and 10.5% of the 38 articles that made up the sample, respectively.

As for the type of healthcare establishment (research question RQ2), hospitals were the healthcare unit of greatest interest, representing 84.2% of the sample under study, with the most studied locations being wards, intensive care units, operating rooms and emergency rooms.

Most of the articles analysed (73,7%) presented studies carried out using objective methods, with the most frequently evaluated parameters (research question RQ3) being CO2 and particulate matter (52.6% of the articles assessed), thermal comfort and environment quality (relative humidity and temperature and were analysed in 55.9% of the articles selected) and chemical parameters (TVOC, CO, CH2O and NO2 were assessed in 44.7%, 23.7%, 18.4% and 13.2% of the articles assessed, respectively). It should also be noted that 71.1% of the articles that published quantitative results used portable sensors to monitor the parameters assessed, 26.3% used low-cost sensors and only one article used fixed reference sensors.

The textometric analysis of the abstracts showed that the articles in the sample focused mainly on four topics (research question RQ4): physicochemical parameters, temperature and humidity assessment, measures to be adopted to improve the quality of environmental factors and symptoms and/or diseases associated with poor indoor air quality, and infrastructure design and management regarding filtration and ventilation systems and assessment of microbiological parameters. Analysing the selected articles showed that the studies tended to be repetitive in terms of their objectives, the location of the healthcare units and the type of sites assessed, and the parameters under study.

The articles analysed clearly showed that certain aspects contribute to the correct management of IAQ and, consequently, to its improvement, namely: (i) the correct design, management and maintenance of infrastructures and equipment, namely filtration systems and heating, ventilation and air conditioning systems; (ii) the appropriate selection of building and renovation materials; (iii) the choice of disinfection and cleaning chemicals; (iv) adequate review of the various procedures carried out in hospitals in order to avoid/mitigate unnecessary contaminant emissions; (v) monitoring of physicochemical and thermal comfort parameters. It is also important to note that the aspects identified should be redefined and planned, where applicable, considering the analysis of the data obtained and the most up-to-date research and scientific knowledge.

It would be extremely important to carry out further studies in this area in order to establish monitoring programmes, particularly for other pollutants that are important for the protection of human health, such as ultrafine particles or pollutants of secondary origin. In fact, the assessment of this type of contaminant in the indoor air of healthcare facilities, which is by nature already rich in numerous chemical species, is an important area for future research.

These themes are fundamental and promising guidelines for preserving and improving indoor air quality in healthcare units, particularly in hospitals, ensuring that environmental parameters do not reach concentrations that could jeopardise the health not only of healthcare professionals and other healthcare workers, but also of patients/users.

Indoor Air Quality management should also be a priority concern for the government, healthcare units managers, technical managers and professionals working in the field of Occupational Health and Public Health, who should join forces to adopt public policies, technical standards, appropriate procedures and frequent monitoring of physicochemical and microbiological parameters. This is the only way to guarantee safe and healthy hospital environments that promote the principles of quality and humanized healthcare.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary Material 1 (150KB, docx)

Acknowledgements

This research was supported by the FP-I3ID– Fernando Pessoa Institute for Research, Innovation and Development, 4249-004 Porto, Portugal.

Abbreviations

X2

Chi-square Test

CFA

Confirmatory Factor Analysis

CH 2 O

Formaldehyde

CO

Carbon monoxide

CO 2

Carbon dioxide

DHC

Descending Hierarchical Classification

HVAC

Heating, Ventilation and Air Conditioning

IAQ

Indoor Air Quality

NO 2

Nitrogen dioxide

O 3

Ozone

PM

Particulate matter

PRISMA

Preferred Reporting Items for Systematic Reviews and Meta-Analyses

RQ

Research Question

SJR

Scimago Journal & Country Rank

SO 2

Sulphur dioxide

TVOC

Total Volatile Organic Compounds

VOC

Volatile Organic Compounds

Author contributions

AL: Conceptualization, methodology, formal analysis and writing– original draft preparation; AF and NB: writing– review and editing. All authors have read and agreed to the published version of the manuscript.

Funding

The authors did not receive specific funding for this work.

Data availability

The authors of this article declare that all the data generated and analyzed during the systematic review are fully included in the submitted article and in the supplementary materials (Supplementary Materials_V2). These supplementary materials contain the complete list of references included in the review, as well as a table summarizing the main information extracted from the studies analyzed (including authors, year of publication, title, journal, quartile, H index, country, type of health unit and parameters evaluated). Supplementary material may be published together with the article or made available by the journal in its own repository, in accordance with its editorial policies.A data availability statement duly signed by the corresponding author of the article “Systematic review of the literature on indoor air quality in healthcare facilities and its effects on health” has been attached in the “Related files” field.The following information was also included in the “Availability of data and materials” section of the manuscript:“All data produced and analyzed during this study are included in this article, as well as in the supplementary materials attached to the article.These supplementary materials contain the complete list of references included in the review, as well as a table summarizing the main information extracted from the studies analyzed (including authors, year of publication, title, journal, quartile, H index, country, type of health unit, and parameters evaluated).”

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

  • 1.Zaman SU, Yesmin M, Pavel MRS, Jeba F, Salam A. Indoor air quality indicators and toxicity potential at the hospitals’ environment in Dhaka. Bangladesh Environ Sci Pollution Res. 2021;28(28):37727–40. [DOI] [PubMed] [Google Scholar]
  • 2.Manisalidis I, Stavropoulou E, Stavropoulos A, Bezirtzoglou E. Environmental and health impacts of air pollution: A review. Front Public Health. 2020;8. [DOI] [PMC free article] [PubMed]
  • 3.Cocâr¸tăcocâr¸tă DM, Prodana M, Demetrescu I, Elena P, Lungu M, Didilescu AC. sustainability Indoor Air Pollution with Fine Particles and Implications for Workers’ Health in Dental Offices: A Brief Review. 2021 10.3390/su13020599
  • 4.Mannan M, Al-Ghamdi SG. Indoor air quality in buildings: A comprehensive review on the factors influencing air pollution in residential and commercial structure. Int J Environ Res Public Health. 2021;18(6):3276. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Ferreira A, Barros N. COVID-19 and lockdown: the potential impact of residential indoor air quality on the health of teleworkers. Int J Environ Res Public Health. 2022;19(10):6079. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 6.Shaw D, Carslaw N. INCHEM-Py: an open source Python box model for indoor air chemistry. J Open Source Softw. 2021;6(63):3224. [Google Scholar]
  • 7.Lee HJ, Lee KH, Kim DK. Evaluation and comparison of the indoor air quality in different areas of the hospital. Medicine. 2020;99(52):e23942. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Palmisani J, Di Gilio A, Viana M, de Gennaro G, Ferro A. Indoor air quality evaluation in oncology units at two European hospitals: Low-cost sensors for tvocs, PM2.5 and CO2 real-time monitoring. Build Environ. 2021;205:108237. [Google Scholar]
  • 9.Kim JB, Prunicki M, Haddad F, Dant C, Sampath V, Patel R et al. Cumulative lifetime burden of cardiovascular disease from early exposure to air pollution. J Am Heart Assoc. 2020;9(6). [DOI] [PMC free article] [PubMed]
  • 10.Rastgeldi Doğan T. Investigation of indoor air quality in a hospital: A case study from şanlıurfa, Turkey. Doğal Afetler Ve Çevre Dergisi. 2019;5(1):101–9. [Google Scholar]
  • 11.Veysi R, Heibati B, Jahangiri M, Kumar P, Latif MT, Karimi A. Indoor air quality-induced respiratory symptoms of a hospital staff in Iran. Environ Monit Assess. 2019;191(2). [DOI] [PubMed]
  • 12.Zhou Y, Yang G. A predictive model of indoor PM2.5 considering occupancy level in a hospital outpatient hall. Sci Total Environ. 2022;844. [DOI] [PubMed]
  • 13.Rufo JC, Annesi-Maesano I, Carreiro-Martins P, Moreira A, Sousa AC, Pastorinho MR et al. Issue 2 - Update on adverse respiratory effects of indoor air pollution part 1): indoor air pollution and respiratory diseases: A general update and a Portuguese perspective. Pulmonology. 2023. [DOI] [PubMed]
  • 14.Suzuki N, Nakaoka H, Hanazato M, Nakayama Y, Tsumura K, Takaya K, et al. Indoor air quality analysis of newly built houses. Int J Environ Res Public Health. 2019;16(21):4142. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 15.Albahar S, Li J, Al-Zoughool M, Al-Hemoud A, Gasana J, Aldashti H, et al. Air pollution and respiratory hospital admissions in kuwait: the epidemiological applicability of predicted PM2.5 in arid regions. Int J Environ Res Public Health. 2022;19(10):5998. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 16.Kalender-Smajlović S, Kukec A, Dovjak M. The problem of indoor environmental quality at a general Slovenian hospital and its contribution to sick Building syndrome. Build Environ. 2022;214.
  • 17.Seng KT, Shen LC, Ling NS, Chin SP, Xin TJ, En TK, et al. Comparative study on the indoor air quality in critical areas of hospitals in Malaysia. Nat Environ Pollution Technol. 2023;22(2):921–7. [Google Scholar]
  • 18.Yau YH, Phuah KS. Indoor air quality study in four Malaysian hospitals for centralized and non-centralized ACMV systems. Air Qual Atmos Health. 2023;16(2):375–90. [Google Scholar]
  • 19.Surawattanasakul V, Sirikul W, Sapbamrer R, Wangsan K, Panumasvivat J, Assavanopakun P, et al. Respiratory symptoms and skin sick Building syndrome among office workers at university hospital, Chiang mai, thailand: associations with indoor air quality, AIRMED project. Int J Environ Res Public Health. 2022;19(17):10850. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.Fonseca A, Abreu I, Guerreiro MJ, Barros N. Indoor Air Quality in Healthcare Units—A Systematic Literature Review Focusing Recent Research. Vol. 14, Sustainability. (Switzerland). MDPI; 2022.
  • 21.Baudet A, Baurès E, Blanchard O, Le Cann P, Gangneux JP, Florentin A. Indoor carbon dioxide, fine particulate matter and total volatile organic compounds in private healthcare and elderly care facilities. Toxics. 2022;10(3). [DOI] [PMC free article] [PubMed]
  • 22.Shajahan A, Culp CH, Williamson B. Effects of indoor environmental parameters related to Building heating, ventilation, and air conditioning systems on patients’ medical outcomes: A review of scientific research on hospital Buildings. Indoor Air. Volume 29. John Wiley and Sons Inc; 2019. pp. 161–76. [DOI] [PMC free article] [PubMed]
  • 23.Fonseca A, Abreu I, Guerreiro MJ, Abreu C, Silva R, Barros N. Indoor air quality and sustainability management-Case study in three Portuguese healthcare units. Sustain (Switzerland). 2019;11(1).
  • 24.Tranfield D, Denyer D, Smart P. Towards a methodology for developing Evidence-Informed management knowledge by means of systematic review. Br J Manag. 2003;14(3):207–22. [Google Scholar]
  • 25.Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. Int J Surg. 2021;88. [DOI] [PubMed]
  • 26.Scimago J. & Country Rank [Internet]. [cited 2024 May 18]. Available from: https://www.scimagojr.com/
  • 27.Mendeley. Mendeley [Internet]. [cited 2024 Mar 26]. Available from: https://www.mendeley.com/?interaction_required=true
  • 28.IRaMuTeQ [Internet]. [cited 2024 Jun 25]. Available from: http://www.iramuteq.org/
  • 29.Mazieri MR, Quoniam LM, Reymond D, Cunha KCT. Use of IRaMuTeQ for content analysis based on descending hierarchical classification and correspondence factor analysis. Revista Brasileira De Mark. 2022;21(5):1978–2048. [Google Scholar]
  • 30.Reinert M. Alceste Une méthodologie d’analyse des Données textuelles et Une application: Aurelia de Gerard de nerval. Bull Sociol Methodology/Bulletin De Méthodologie Sociologique. 1990;26(1):24–54. [Google Scholar]
  • 31.Sousa YSO. O Uso do software iramuteq: fundamentos de lexicometria Para pesquisas qualitativas. Estudos E Pesquisas Em Psicologia. 2021;21(4):1541–60. [Google Scholar]
  • 32.de Souza MAR, Wall ML, Thuler AC, de Lowen MC, Peres IMV. The use of IRAMUTEQ software for data analysis in qualitative research. Revista Da Escola De Enfermagem Da USP. 2018;52:0. [DOI] [PubMed] [Google Scholar]
  • 33.Baqer NS, Mohammed HA, Albahri AS. Development of a real-time monitoring and detection indoor air quality system for intensive care unit and emergency department. Signa Vitae. 2023;19(1):77–92. [Google Scholar]
  • 34.Tang H, Li C, Ding J. Field study of indoor environment quality in an open atrium with ETFE membrane in a healthcare facility. 2019; Available from: 10.1051/e3sconf/2019111020
  • 35.Uz Zaman S, Yesmin M, Riad Sarkar Pavel M, Jeba F, Salam A. Indoor air quality indicators and toxicity potential at the hospitals’ environment in Dhaka, Bangladesh. 2021; Available from: 10.1007/s11356-021-13162-8 [DOI] [PubMed]
  • 36.Haleem A, Al-Obaidy AH, Haleem S. Air quality assessment of some selected hospitals within Baghdad City. Eng Technol J. 2019;37(1 C):59–63. [Google Scholar]
  • 37.Bang CS, Lee K, Yang YJ, Baik GH. Ambient air pollution in Gastrointestinal endoscopy unit. Surg Endosc. 2020;34(9):3795–804. [DOI] [PubMed] [Google Scholar]
  • 38.Zhang S, Song K, Ban Q, Gong P, Li R, Peng Z. Indoor air quality and smoking control in healthcare environments in Northern China. Sustain (Switzerland). 2023;15(5).
  • 39.Boonphikham N, Singhakant C, Kanchanasuta S, Patthanaissaranukool W, Prechthai T. Indoor air quality in public health centers: A case study of public health centers located on main and secondary roadsides, Bangkok. Environ Nat Resour J. 2022.
  • 40.Naser, Hamed H, Haddabi A, Mubarak M, Saadi A, Ramaswamy M et al. A study on indoor air quality in major hospitals in Sultanate of Oman. 2023.
  • 41.Deiana G, Dettori M, Masia MD, Spano AL, Piana A, Arghittu A et al. Monitoring radon levels in hospital environments. Findings of a preliminary study in the university hospital of sassari, Italy. Environ - MDPI. 2021;8(4).
  • 42.Afra A, Mollaei Pardeh M, Saki H, Farhadi M, Geravandi S, Mehrabi P, et al. Anesthetic toxic isoflurane and health risk assessment in the operation room in abadan, Iran during 2018. Clin Epidemiol Glob Health. 2020;8(1):251–6. [Google Scholar]
  • 43.Chang PK, Chuang HH, Hsiao TC, Chuang HC, Chen PC. Investigating the invisible threat: an exploration of air exchange rates and ultrafine particle dynamics in hospital operating rooms. Build Environ. 2023;245.
  • 44.Wang H, Feng D, He Y, Jin X, Fu S. Comprehensive interventions to reduce occupational hazards among medical staff in the pathology department of five primary hospitals. BMC Public Health. 2023;23(1). [DOI] [PMC free article] [PubMed]
  • 45.Yao J, Zhong J, Yang N. Indoor air quality test and air distribution CFD simulation in hospital consulting room. Int J Low-Carbon Technol. 2022;17:33–7. [Google Scholar]
  • 46.Nguyen PDM, Martinussen N, Mallach G, Ebrahimi G, Jones K, Zimmerman N, et al. Using low-cost sensors to assess fine particulate matter infiltration (Pm2.5) during a wildfire smoke episode at a large inpatient healthcare facility. Int J Environ Res Public Health. 2021;18:18. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 47.Rahayu EP, Saam Z, Sukendi S, Afandi D. The factors of affect indoor air quality inpatient at private hospital, pekanbaru, Indonesia. Open Access Maced J Med Sci. 2019;7(13):2208–12. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 48.Alfa MT, Öztürk A. Perceived indoor environmental quality of hospital wards and patients’ outcomes: A study of a general hospital, minna, Nigeria. Appl Ecol Environ Res. 2019;17(4):8235–59. [Google Scholar]
  • 49.Guo K, Qian H, Ye J, Sun F, Zhuge Y, Wang S et al. Assessment of airborne bacteria and fungi in different-type buildings in nanjing, a hot summer and cold winter moist Chinese City. Build Environ. 2021;205.
  • 50.Fu Y, Liu S, Guo W, He Q, Chen W, Ruan G et al. Inhalation exposure assessment techniques on ventilation Dilution of infectious respiratory particles in a retrofitted hospital lung function room. Build Environ. 2023;242.
  • 51.Nimra A, Ali Z, Nasir zaheer A, Tyrrel S, Sidra S. Characterization of indoor air quality in relation to ventilation practices in hospitals of lahore, Pakistan. Sains Malays. 2021;50(6):1609–20. [Google Scholar]
  • 52.Zhou Y, Yang G. Real-time monitoring of pollutants in occupied indoor environments: A pilot study of a hospital in China. J Building Eng. 2022;59.
  • 53.Rautiainen P, Hyttinen M, Ruokolainen J, Saarinen P, Timonen J, Pasanen P. Indoor air-related symptoms and volatile organic compounds in materials and air in the hospital environment. Int J Environ Health Res. 2019;29(5):479–88. [DOI] [PubMed] [Google Scholar]
  • 54.Chamseddine A, Alameddine I, Hatzopoulou M, El-Fadel M. Seasonal variation of air quality in hospitals with indoor–outdoor correlations. Build Environ. 2019;148:689–700. [Google Scholar]
  • 55.Riveron TP, Wilde MJ, Ibrahim W, Carr L, Monks PS, Greening NJ et al. Characterisation of volatile organic compounds in hospital indoor air and exposure health risk determination. Build Environ. 2023;242.
  • 56.Lee HJ, Lee KH, Kim DK. Evaluation and comparison of the indoor air quality in different areas of the hospital. Med (United States). 2020;99:52. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 57.Colas A, Baudet A, Cann P, Le, Blanchard O, Gangneux JP, Baurès E et al. Quantitative health risk assessment of the chronic inhalation of chemical compounds in healthcare and elderly care facilities. Toxics. 2022;10(3). [DOI] [PMC free article] [PubMed]
  • 58.Guo M, Zhou M, Wei S, Peng J, Wang Q, Wang L et al. Particle removal effectiveness of portable air purifiers in aged-care centers and the impact on the health of older people. Energy Build. 2021;250.
  • 59.Ramli A, Shamsudin SB, Lim JF, Lim MC. Occupational formaldehyde exposure and the health symptoms among histopathology laboratory workers in North Borneo. Pertanika J Sci Technol. 2023;31(5):2413–26. [Google Scholar]
  • 60.Farhadi F, Khakzand M, Altan H, Chahardoli S. IAQ in CCU units: an experimental and numerical investigation based on the outlet air height (case study: Namazi hospital, Shiraz). Int J Vent. 2023.
  • 61.Kangarlou MB, Fatemi F, Dehdashti A, Iravani H, Saleh E. Occupational health risk assessment of airborne formaldehyde in medical laboratories. Environ Sci Pollut Res. 2023;30(17):50392–401. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplementary Material 1 (150KB, docx)

Data Availability Statement

The authors of this article declare that all the data generated and analyzed during the systematic review are fully included in the submitted article and in the supplementary materials (Supplementary Materials_V2). These supplementary materials contain the complete list of references included in the review, as well as a table summarizing the main information extracted from the studies analyzed (including authors, year of publication, title, journal, quartile, H index, country, type of health unit and parameters evaluated). Supplementary material may be published together with the article or made available by the journal in its own repository, in accordance with its editorial policies.A data availability statement duly signed by the corresponding author of the article “Systematic review of the literature on indoor air quality in healthcare facilities and its effects on health” has been attached in the “Related files” field.The following information was also included in the “Availability of data and materials” section of the manuscript:“All data produced and analyzed during this study are included in this article, as well as in the supplementary materials attached to the article.These supplementary materials contain the complete list of references included in the review, as well as a table summarizing the main information extracted from the studies analyzed (including authors, year of publication, title, journal, quartile, H index, country, type of health unit, and parameters evaluated).”

Articles from BMC Public Health are provided here courtesy of BMC

RESOURCES