Effects of exposure to incense smoke associated with impaired lung function and respiratory disease: A Systematic Review

Incense (bakhour) is used by the community through ceremonies, traditional health practices, and aromatherapy. Nevertheless, evidence from experiments and studies of populations suggests that a habit of burning incense makes the lungs work less well. The study investigated the relationship between exposure to incense smoke and impaired lung function and respiratory diseases. Data tracing was carried out systematically by following PRISMA guidelines and establishing inclusion and exclusion criteria for �ltering, selecting, and including articles registered in the PROSPERO database. This study describes respiratory symptoms/ diseases, home use of incense, and lung function measurement.Six articles were included; 6 articles (100%) reported using incense indoors, and �ve (83%) reported using incense outside the home. Respiratory symptoms and diseases caused by exposure to incense sticks are 5 (83%) shortness of breath, 6 (100%) wheezing, asthma, and in�ammation of the lungs, 2 (33%) chronic obstructive pulmonary disease, and 4 (67%) allergic rhinitis. Incense smoke particles decrease lung function based on FVC, FEV, PEFR, and FEF values of 25-75%. The results indicate that smoking incense adversely affects lung function and leads to respiratory diseases. The community and related parties can minimize and conduct education and prevention related to simultaneous incense exposure in the community to reduce the burden of diseases and disorders due to respiratory incense smoke in areas that use it daily.


Introduction
Incense (bakhour) in the community is generally used for the ceremony.In addition, burning incense is used as a traditional health practice to utilize fragrant scents for medicinal purposes called Usada (Hindu-Balinese) and Ayurveda (Hindu-Indian) [1], [2].Burning incense inside and outside homes, places of worship, and other public places has been used for generations, especially in the Asian region [3].It is reported that the global consumption of incense exceeds 200 million tons per year.Therefore, it has considerable health and environmental implications [4].Daily incense burning will continue to contribute to polluting particulates that can degrade the environment and lower the degree of health through decreased respiratory tract function [5], [6].According to several studies, exposure to incense smoke can impair lung organ function and create harmful health effects, considerably raising the risk of respiratory diseases caused by pollution [7], [8].
The constituents contained in incense smoke are considered detrimental to health and the environment [19]- [21].This is caused by carcinogens capable of damaging the human respiratory organs for an extended period with the intensity of routine or frequent exposure [21]- [25].Previous studies that have revealed the clinical effects of incense smoke exposure in experimental animals and humans have not been widely reported, especially those associated with changes in lung function and the mechanisms of the underlying changes.The study aimed to investigate the relationship between exposure to incense smoke and impaired lung function and respiratory diseases by focusing on respiratory disease symptoms, lung function examinations in incense users inside and outside the home, and testing the effects of incense smoke exposure on humans and experimental animals.This review hopes that longterm exposure to incense smoke on the environment and human and animal health and that the preventative actions that can be done to limit the hazards posed, especially for those who use it daily, will be revealed.

Systematic review registration
This systematic review uses the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocol guidelines [26].The study has been listed on the PROSPERO database with the registration number CRD420222988868.

Eligibility criteria
The articles selected in this review are cross-sectional, cohort, observational, and experimental studies.
The feasibility of the article is determined by the researcher independently by reviewing eligible titles and abstracts based on the criteria: (1) animals or humans exposed to incense smoke or direct contact with exposure to incense smoke; (2) exposure to incense smoke is carried out indoors or outdoors; (3) the selected article is included in the original type of article; (4) the year published between 2016-2021 and entered into reputable journals (Scopus and Web of Science).The year range is selected depending on the novelty of the research, and the journal's reputation determines the article's credibility.In this review, the article should discuss exposure to incense smoke, impaired lung function due to incense smoke, damage mechanisms due to incense smoke, content in incense smoke, and other respiratory diseases affected by incense smoke and changes in lung tissue due to inhaling incense smoke.Articles that do not meet the criteria for eligibility, duplicates, discontinued, and irrelevant studies are excluded at this stage.

Sources of information, literature search strategies, and study selection
In this review, we use a trusted database and credible sources to nd articles that t the topic of discussion raised.PubMed (MeSH term) ("exposure incense" AND "Lungs"); ScienceDirect ("exposure incense" AND "Lungs" AND "respiratory disease"); ProQuest ("exposure incense" AND "Lungs" AND "respiratory disease"); Cochrane Library ("exposure incense" AND "respiratory disease"); Emerald and Nature ("exposure incense" AND "lung disease" OR "respiratory disease").All articles could be included and ltered in two eligibility stages.The rst screening stage is assessed by selecting titles and abstracts from articles relevant to a predetermined topic.Furthermore, abstracts that meet the inclusion criteria are included in this review, while those that do not will be excluded.The second stage will be ltered based on the results and discussions on the research topic and will be conducted as a comprehensive and independent analysis as review material.The study exceptions are described in the PRISMA diagram (Figure 1).

Data extraction
Data extraction was carried out independently using each selected article's standard structure and form.The information collected and summarized in each article includes the rst author's name and year of publication, study period (month or years), gender, respiratory symptoms/diseases (Breathlessness, Wheezing, COPD, Asthma, Rhinitis, and Pneumonia), home use of incense (outside and inside), measurement of lung function (FEV1 (%), FVC (L/s), PEFR (L/s), FEF 25-75%), sample size, intervention, design study, and outcome.Three authors carried out the data extraction, and if there was disagreement in some interpretation, it was resolved by deliberation until consensus.

Quality assessment
The quality assessment of the articles in this study was conducted independently by three authors using the Joanna Briggs Institute (JBI) critical assessment checklist for cross-sectional, cohort, observational, and experimental studies (RCT) [26].If disagreements between authors arose, they were resolved through deliberation to reach a consensus.

Data collection and analysis of data
The data collection protocol for this box was approved before starting the analysis and the work project.Bibliographic data results in features and follow-up results are extracted independently.The data was further reconciled to obtain data related to incense smoke exposure on impaired lung function and respiratory diseases in this review.In the selected article, we found a signi cant structural difference.The appeasement of comparisons of each article and the varying size of results resulted in a meta-analysis.However, we presented the results of evidence-based synthesis in a comprehensive and articulated manner in the narrative and summary of the table.

Search results
The literature search in this work returned six original articles that meet the inclusion and exclusion criteria (Table 1).The articles were published between 2016 and 2021.Five articles were on human subjects, whereas one used mice.The process of nding articles, ltering, eligibility, and inclusion following PRISMA diagrams and PICOS Framework can be observed in gure 1.

Study summary
This study included six reports of research ndings on the association between exposure to incense smoke and impaired lung function and respiratory diseases.Incense smoke is known to have a terrible impact on human health, mainly resulting in chronic diseases whose symptoms have been known and felt for a long time.This review obtained studies that used human objects as much as 5 (83.33%) and only used the test animal model 1 (16.67%).The length of time of the study varied from 3, 4, 6, 12, and 24 months.Studies to determine the effects of exposure were dominated by cohort studies 3 (50%), crosssectional studies 2 (33.33%), and experimental studies 1 (16.67%).
Furthermore, the use of incense in the community serves various needs such as a means of worship, a medium of meditation, and traditional medicine based on USADA and Ayurveda in the form of aromatherapy and room fragrance [2], [4], [27].People who use incense in the house reach 100% (6), while the use of incense outside the house is only 5 (83.33%).The high use of incense in the house indicates the ease of polluting particulates carried by air and contained in incense smoke into the human body and causing damage to the respiratory tract, including the lungs.The accumulation of air in the house can reduce lung capacity resulting in respiratory disorders and diseases.
The danger caused by exposure to incense smoke in the room indicates pollutants trapped in the house and will stick to objects in the room [31], [32].Furthermore, the person or individual in the room will inhale the existing constituents, resulting in respiratory disorders and diseases [17], [33].Moreover, a puff of smoke in space can alter the temperature, relative humidity, and air exchange rate.It will accelerate the rate at which carcinogenic chemicals from incense smoke enter the human body [10], [34].Quickly smoke from burning incense into the body through the respiratory tract will produce various symptoms and diseases in the respiratory system.In this study, it was reported that people experienced symptoms of respiratory disorders such as 5 (83%) reported shortness of breath, 6 (100%) experiencing wheezing, asthma, and in ammation of the lungs, 2 (33%) the presence of COPD and 4 (67%) had chronic rhinitis.These results show a risk of being affected by incense smoke to impaired lung function and respiratory diseases both indoors and outdoors [16], [35], [36].This study reported that smoke from burning incense harms respiratory tract health, mainly resulting in impaired lung function [27], [29].Table 2 displays a decline in lung function based on FVC, FEV, PEFR, and FEF 25-75%.In addition, incense smoke particles with a tiny size of < 1 μm decrease the value of FEV1 and FVC in lung function.This can cause clogged airways and increase in ammation in the bronchi and alveoli due to the lung's capacity to receive oxygen, presented in table 2.

Incense smoke pollutants in reducing lung capacity and inducing respiratory disease
The lungs become a very vital organ for human life.Exposure to pollutants with high intensity can cause disruption, damage, and failure of respiratory system function [17].Incense smoke has small particles and ash that can harm human health and signi cantly change lung organs' shape and function [27], [31].
Several studies indicate that incense smoke can irritate the airway, increase in ammation in the lung organs, decrease oxygen intake into the lungs as a result of alveolar thickening and necrosis in the bronchi, and trigger cytokine and chemokine expression in the epithelium of the airway, resulting in a decrease in lung function and respiratory diseases [18].Research conducted by Zhang et al. [28] involving 4,041 children in 27 elementary schools exposed to incense smoke continuously showed that exposure to incense smoke adversely affected lung function by reducing work power and improving symptoms of respiratory diseases.Incense burning smoke is 1.39 times higher risk of causing bronchitis in boys (OR = 1.39).Exposure to smoke is the risk of causing bronchiolitis 1.72 higher in girls (OR = 1.72) and wheezing, and asthma is 1.49 higher in all treatment groups (OR = 1.49).This indicates that exposure to incense smoke is toxic to the lung organs, especially the bronchi and alveoli, and decreases pulmonary function, triggering the disease.Studies on the high risk of disease in one gender are not explained openly and explicitly.However, the odds ratio (OR) value indicates that exposure to incense smoke is associated with lower lung function.
The use of incense in the house is a greater risk of smoke being inhaled into the body through the respiratory tract.Tran et al. [34] revealed that exposure to incense smoke increases particulate matter concentrations 2.5 (PM 2.5 ) indoors by 120% more than those who do not use it.The frequency of using incense with high intensity (daily) is at risk of 61.6% higher than using incense sometimes.In addition, daily use of incense had an 18.5% higher risk of increased particulate matter concentrations.This happens because incense smoke particles are microscopic and easily in and out of the respiratory tract; houses that have poor ventilation can accelerate in ammatory processes in the lung organs and decrease pulmonary function and cause respiratory diseases [30], [35], [37].Another study revealed that people who grow incensed 2-4 times daily indoors result in incense smoke containing carbon monoxide concentration in the lungs, subsequently interacting with in ammatory cells and exacerbating chronic respiratory conditions that cause asthma, COPD, rhinitis, and pneumonia [12].
Decreased lung function and increased respiratory diseases are closely related to the content of pollutants contained in incense smoke [9].Burned incense releases toxic compounds that cannot directly degrade the environment [9], [11].Burning incense for various purposes produces exhaust gases from imperfect combustion.Carbon monoxide content has been reported to cause poisoning from long-term use of incense that can damage the alveoli organs and reduce lung function and capacity [12].
Symptoms of CO gas poisoning in incense smoke are shortness of breath, vomiting, and headaches [37].Furthermore, particulate matter (PM 1, 2.5, 10 ) in incense smoke can worsen respiratory diseases, damage tissues, and be concentrated in the lungs resulting in necrosis and impaired lung function [14].The condensed concentration of sulfur dioxide and nitrogen dioxide in the lungs induces in ammation, the release of the bronchi, and modi cations to the pulmonary system's defenses, resulting in a signi cant risk of necrosis, hyperresponsiveness (AHR), and impaired bronchial epithelial barrier function.In addition, VOCs and PAHs found in incense smoke have been associated with asthma exacerbations, irritation of the barrier epithelium, rhinitis, decreased oxygen absorption capacity to the lungs, and alveolar obstruction [13], [38].Exposure to incense smoke induces respiratory diseases including wheezing, asthma, COPD, shortness of breath, chest tightness, lung in ammation, and rhinitis [16], [18], [30].Figure 2 brie y explains incense smoke can hurt lung function and cause respiratory diseases.

Conclusion
Six articles published between 2016 and 2021 discuss the impact of incense smoke inhalation, which is linked to impaired lung function and respiratory diseases.There is a high risk of respiratory disease and capacity associated with the short-and long-term usage of incense at home and everywhere else.Incense burning does not signi cantly affect lung function.Epidemiological studies reveal that Nitrogen dioxide, Carbon monoxide, Sulfur dioxide, Hydrogen Sul de, Particulate Matter, Ozone, Total Suspended Particulate, VOCs, and PAHs are the main constituents responsible for the decreased function, capacity, and structure of the lungs associated with a decrease of FVC, FEV, PEFR, and FEF values of 25-75%.Exposure to incense smoke causes various respiratory diseases: wheezing, asthma, COPD, shortness of breath, chest tightness, lung in ammation, and rhinitis.In the future, an in-depth study is needed regarding exposure and the impact caused by the habit of burning incense on changes in the lungs' capacity, function, and ability to minimize the occurrence of respiratory diseases.A brief mechanism of exposure to incense smoke decreases lung function

Figure 1 Process
Figure 1

Table 1 .
Summary of evidence and studies on the effects of exposure to incense smoke ExperimentalThe effect of a single exposure to IS on airway function obtained exposure to IS increases AHR, which is reflected by the

Table 2 .
Lung capacity measurements are associated with respiratory disease caused by