Indoor incense burning impacts cognitive functions and brain functional connectivity in community older adults

Association between cooking with solid fuels and depressive symptoms among middle-aged and older adults in China: The mediating effect of the residential environment

BACKGROUND

Depression is a common issue among elderly people in both developing and developed countries. Existing research indicates that cooking with solid fuels has a negative impact on the mental health of middle-aged and elderly people (aged 45 and older). However, the potential role of the residential environment in this process is not yet clear. Clarifying this issue may help identify effective interventions to improve public health for elderly people. This study aimed to explore the association between cooking with solid fuels and depressive symptoms, as well as the potential mediating role of the residential environment in this relationship.

METHOD

This study utilized cross-sectional data from the China Health and Retirement Longitudinal Study (CHARLS) for 2020, involving approximately 19,000 respondents aged 45 years and older. Propensity score matching (PSM) was used to explore the association between cooking with solid fuels and depressive symptoms. Additionally, a range of potential covariates were adjusted, and the Sobel test was applied to assess the potential mediating effect of the residential environment on this relationship.

RESULTS

According to the fully adjusted model, cooking with solid fuels was significantly associated with an increased risk of depressive symptoms in middle-aged and older adults (β = 0.315, P < 0.001), and this finding was confirmed through robustness tests using different propensity score matching methods. Heterogeneity analysis revealed that this association was particularly significant among men (β = 0.318, P < 0.001), those aged 60-74 (β = 0.347, P < 0.001), and individuals with a middle school education (β = 0.353, P < 0.001). Mediation effect analysis revealed that indoor cleanliness (β = 0.0090, P < 0.001), indoor broadband coverage (β = 0.0077, P < 0.001), and the installation of indoor air purifiers (β = 0.0010, P < 0.1) mediated the relationships between cooking with solid fuels and depressive symptoms.

CONCLUSION

Given the growing attention given to improving indoor environments and enhancing mental health, the findings of this paper highlight that improving indoor cleanliness, increasing broadband coverage indoors, and installing air purifiers can effectively intervene in and prevent depressive symptoms caused by cooking with solid fuels.

Increase of the indoor concentration of volatile organic compounds after the use of incense and scented candle in studio apartments determined using passive sampling

Burning incenses and scented candles may provide harmful chemicals. Although many studies have evaluated volatile organic chemicals emitted by their use and related health risks, extension of our understanding for guiding appropriate use under various use conditions is necessary. In this study, emission characteristics of commercial incenses and scented candles were evaluated in a laboratory chamber using real-time measurement and the time-weighted average exposure concentrations of monoaromatic compounds and monoterpenes were assessed using passive samplers while volunteers living in a studio apartment use them. After burning incense, the average levels of benzene increased from 1.4 to 100 μg m-3. The presence of a wood core in commercial incense products was the main cause of high benzene emission by burning them although the increase in benzene was also influenced by factors such as the brand of the products, the number of incense sticks burned, the duration of each burning session, and ventilation period. Electrical warming of scented candles increased the levels of monoterpenes by factors of 16-30 on average. Considering the emission characteristics found in this study, exposure to benzene and monoterpenes could be mitigated by cautious use of those products in residential areas.

Association of Exposure to Indoor Air Pollution with Unhealthy Symptoms among Middle-aged and Older Adults in India: Evidence from a Large-scale Survey

Background

The usage of solid cooking fuels is widely prevalent in low and middle-income countries, including India, and contributes to indoor air pollution (IAP), which has detrimental health effects. Moreover, time spent inside the house increases as people age. In this context, the present study tried to understand the association between exposure to indoor air pollution and unhealthy symptoms, including shortness of breath, dizziness, headache, fatigue, wheezing, and cough among middle-aged and older adults in India.

Methods

We extracted the unit-level individual data (N = 63 790) from the Longitudinal Aging Study in India (LASI)-Wave 1 (2017-2018). The statistical analyses used were Chi-square test and binary logistic regression, which estimated the odds ratio to identify the determinants of the unhealthy symptoms.

Results

The odds of shortness of breath (adjusted OR: 1.14, 99% CI: 1.05-1.23), dizziness (adjusted OR: 1.28, 99% CI: 1.21-1.35), fatigue (adjusted OR: 1.32, 99% CI: 1.26-1.39), wheezing (adjusted OR: 1.30, 99% CI: 1.19-1.42), and cough (adjusted OR: 1.36, 99% CI: 1.27-1.45) were higher among individuals from households where solid cooking fuels was used. Similarly, the odds of shortness of breath, headache, wheezing, and cough were higher among individuals with a household member who smoked inside the house. The results indicated that the odds of shortness of breath, headache, and cough were significantly lower among participants exposed to incense use.

Conclusion

Based on the results of this study, we suggest developing programs to combat the sources of indoor air pollution and the associated unhealthy symptoms, especially in rural settings. It is also important to bring awareness and practice clean fuel usage at individual and community levels to improve population health.

Study on the Relationship between Cerebral Blood Perfusion, Neuronal Cytokines and Cognitive Function in Patients with Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a common neurodegenerative disorder characterized by the progressive emergence of multiple cognitive deficits. Early diagnosis is of great significance for the intervention and treatment of AD. The objective of this study is to explore the relationship between cerebral blood perfusion, neuronal cytokines and cognitive function in patients with AD.

METHODS

AD patients admitted to the 903 Hospital of the People's Liberation Army Joint Logistics Support Force from June 2020 to January 2023 were retrospectively selected as the study objects, and 65 healthy people who underwent physical examination during the same period were included in the control group. Subjects in both groups underwent 3.0 T magnetic resonance imaging (MRI) to observe their cerebral blood perfusion parameters. The level of cognitive function in both groups was assessed using the Montreal Cognitive Assessment (MoCA). Venous blood was collected from both groups, and the serum levels of brain-derived neuronal factor (BDNF) and glial cell-derived neurotrophic factor (GDNF) were measured by enzyme-linked immunosorbent assay (ELISA). The correlation of serum BDNF and GDNF levels with cerebral blood perfusion parameters and MoCA score in the AD group was analyzed using Spearman analysis.

RESULTS

The cerebral blood flow signal intensity of the left frontal lobe, right frontal lobe, left temporal lobe, right temporal lobe, left parietal lobe, right parietal lobe, left occipital lobe, and right occipital lobe of the observation group was significantly lower than that of the control group (p < 0.001). The visuospatial, executive functions, naming, attention, language function, abstract generalization ability, memory ability, orientation, and total MoCA scale scores were significantly lower than those of the control group (p < 0.001). The serum levels of BDNF and GDNF in the observation group were significantly lower than those in the control group (p < 0.001). The results of Spearman analysis showed that cerebral blood perfusion parameters of the left frontal lobe, right frontal lobe, left temporal lobe, right temporal lobe, left parietal lobe, right parietal lobe, left occipital lobe, and right occipital lobe were positively correlated with cognitive function scores in AD patients, serum BDNF and GDNF levels were positively correlated with cognitive function scores in AD patients, and the correlation was statistically significant (p < 0.05).

CONCLUSION

In AD patients, blood perfusion parameters and serum BDNF and GDNF levels were significantly lower than those of healthy people. Cerebral blood perfusion parameters of the left frontal lobe, right frontal lobe, left temporal lobe, right temporal lobe, left parietal lobe, right parietal lobe, left occipital lobe, and right occipital lobe, and BDNF and GDNF levels were positively correlated with cognitive function scores in AD patients.

Characterizing PM2.5 Emissions and Temporal Evolution of Organic Composition from Incense Burning in a California Residence

The chemical composition of incense-generated organic aerosol in residential indoor air has received limited attention in Western literature. In this study, we conducted incense burning experiments in a single-family California residence during vacancy. We report the chemical composition of organic fine particulate matter (PM2.5), associated emission factors (EFs), and gas-particle phase partitioning for indoor semivolatile organic compounds (SVOCs). Speciated organic PM2.5 measurements were made using two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC×GC-HR-ToF-MS) and semivolatile thermal desorption aerosol gas chromatography (SV-TAG). Organic PM2.5 EFs ranged from 7 to 31 mg g-1 for burned incense and were largely comprised of polar and oxygenated species, with high abundance of biomass-burning tracers such as levoglucosan. Differences in PM2.5 EFs and chemical profiles were observed in relation to the type of incense burned. Nine indoor SVOCs considered to originate from sources other than incense combustion were enhanced during incense events. Time-resolved concentrations of these SVOCs correlated well with PM2.5 mass (R2 > 0.75), suggesting that low-volatility SVOCs such as bis(2-ethylhexyl)phthalate and butyl benzyl phthalate partitioned to incense-generated PM2.5. Both direct emissions and enhanced partitioning of low-volatility indoor SVOCs to incense-generated PM2.5 can influence inhalation exposures during and after indoor incense use.

Indoor air pollution and cognitive function among older adults in India: a multiple mediation approach through depression and sleep disorders

BACKGROUND

Studies across multiple countries reveal that depression and sleep disorders can lead to cognitive decline. This study aims to speculate on the effect of different sources of indoor air pollution on cognition and to explore the mediation effect of depression and sleep disorders on cognition when exposed to indoor air pollution. We hypothesize that an older adult experiences higher cognitive decline from indoor pollution when mediated by depression and sleep disorders.

METHODS

We use data from Longitudinal Aging Study in India (LASI), 2017-2018, and employ a multiple mediation model to understand the relationship between indoor air pollution and cognition through sleep disorders and depression while adjusting for possible confounders. Sensitivity analysis was applied to see the effect of different sources of indoor pollution (cooking fuel, indoor smoke products, and secondhand smoke) on cognitive performance.

RESULTS

The effect of three sources of indoor pollutants on cognition increased when combined, indicating stronger cognitive decline. Unclean cooking practices, indoor smoke (from incense sticks and mosquito coils), and secondhand smoke were strongly associated with sleep disorders and depression among older adults. Indoor air pollution was negatively associated with cognitive health (β= -0.38) while positively associated with depression (β= 0.18) and sleep disorders (β= 0.038) acting as mediators. Sensitivity analysis explained 45% variability while adjusting for confounders.

CONCLUSION

The study lays a foundation for future investigations into the nexus of indoor pollution and mental health. It is essential to formulate policies to reduce exposure to varying sources of indoor air pollutants and improve screening for mental health services as a public health priority.

Particulate organic emissions from incense-burning smoke: Chemical compositions and emission characteristics

Incense burning is a common practice in Asian cultures, releasing hazardous particulate organics. Inhaling incense smoke can result in adverse health effects, yet the molecular compositions of incense-burning organics have not been well investigated due to the lack of measurement of intermediate-volatility and semi-volatile organic compounds (I/SVOCs). To elucidate the detailed emission profile of incense-burning particles, we conducted a non-target measurement of organics emitted from incense combustion. Quartz filters were utilized to trap particles, and organics were analyzed by a comprehensive two-dimensional gas chromatography-mass spectrometer (GC × GC-MS) coupled with a thermal desorption system (TDS). To deal with the complex data obtained by GC × GC-MS, homologs are identified mainly by the combination of selected ion chromatograms (SICs) and retention indexes. SICs of 58, 60, 74, 91, and 97 were utilized to identify 2-ketones, acids, fatty acid methyl esters, fatty acid phenylmethyl esters, and alcohols, respectively. Phenolic compounds contribute the most to emission factors (EFs) among all chemical classes, taking up 24.5 % ± 6.5 % of the total EF (96.1 ± 43.1 μg g-1). These compounds are largely derived from the thermal degradation of lignin. Biomarkers like sugars (mainly levoglucosan), hopanes, and sterols are extensively detected in incense combustion fumes. Incense materials play a more important role in shaping emission profiles than incense forms. Our study provides a detailed emission profile of particulate organics emitted from incense burning across the full-volatility range, which can be used in the health risk assessments. The data processing procedure in this work could also benefit those with less experience in non-target analysis, especially GC × GC-MS data processing.

Exposure to incense burning, biomarkers, and the physical health of temple workers in Taiwan

Incense burning releases heavy particulate matter (PM) and nitrogen dioxide (NO2), known to have adverse effects on human health. Long-term exposure to PM and NO2 increases inflammatory cytokine levels and can induce respiratory diseases. This study examined the association between incense burning exposure and the health status, especially inflammatory biomarkers, of temple workers and volunteers in Taiwan. The longitudinal observational study compared adult temple workers and volunteers, with long-term incense burning exposure, to residents from outpatient clinics in the Chiayi area. Forced expiratory volume in 1 s (FEV1) and serum and exhaled breath condensate (EBC) cytokines were assessed. Nonparametric Mann-Whitney U tests were used to compare cytokine levels of the exposure and control groups during the cold and hot weather seasons. FEV1 was significantly more diminished in the exposed group than in the control group during the cold season. Exposure status was associated with greater hot-cold seasonal differences in serum interleukins (IL)-1β (regression coefficient (B) = 6.6, 95% confidence interval (CI) = 5.0 to 8.3, p < .001), IL17-A (B = 2.4, 95% CI = 0.3 to 4.5, p = .03), and plasminogen activator inhibitor [PAI]-1 (B = 5.4, 95% CI = 1.5 to 9.3, p = .009). After adjusting for confounders, the groups' serum levels of IL-1β, IL-17A, and PAI-1 significantly differed. EBC cytokines did not show significant differences. Elevated levels of IL-1β, IL17-A, and PAI-1 have been associated with various autoinflammatory syndromes and diseases. Given the cultural significance of incense burning, culturally sensitive interventions, including education, policy development, and program implementation, are crucial to protect individuals' health, especially temple workers, from the adverse effects of exposure, addressing the manufacture, importation, and sale of incense.

Tanshinone IIA suppresses burning incense-induced oxidative stress and inflammatory pathways in astrocytes

The burning incense (BI) behavior could be widely observed in Asia families. Incense sticks are often believed to be made from natural herbs and powders, and to have minimal impact on human health; however, there is limited research to support this claim. The current study aimed to identify the components of BI within the particulate matter 2.5 µm (PM_2.5) range and explore if BI has bio-toxicity effects on rat astrocytes (CTX-TNA2). The study also examined the protective effects and underlying molecular mechanisms of tanshinone IIA, a primary lipid-soluble compound found in the herb danshen (Salvia miltiorrhiza Bunge), which has been shown to benefit the central nervous system. Results showed that despite the differences in BI components compared to the atmospheric particulate matter (PM) standards, BI still had a bio-toxicity on astrocytes. BI exposure caused early and late apoptosis, reactive oxygen species (ROS) production, MAPKs (JNK, p38, and ERK), and Akt signaling activation, and inflammation-related proteins (cPLA2, COX-2, HO-1, and MMP-9) increases. Our results further exhibit that the tanshinone IIA pre-treatment could significantly avoid the BI-induced apoptosis and inflammatory signals on rat astrocytes. These findings suggest that BI exposure may cause oxidative stress in rat astrocytes and increase inflammation-related proteins and support the potential of tanshinone IIA as a candidate for preventing BI-related adverse health effects.

Lifetime air pollution exposure, cognitive deficits, and brain imaging outcomes: A systematic review

As the amount of air pollution and human exposure has increased, the effects on human health have become an important public health issue. A field of growing interest is how air pollution exposure affects brain structure and function underlying cognitive deficits and if structural and connectivity changes mediate the relationship between the two. We conducted a systematic review to examine the literature on air pollution, brain structure and connectivity, and cognition studies. Eleven studies matched our inclusion criteria and were included in the qualitative analysis. Results suggest significant associations between air pollution and decreased volumes of specific brain structures, cortical thickness and surface area such as in the prefrontal cortex and temporal lobe, as well as the weakening of functional connectivity pathways, largely the Default Mode (DMN) and Frontal Parietal (FPN) networks, as detected by fMRI. Associations between air pollution and cognitive outcomes were found in most of the studies (n = 9), though some studies showed stronger associations than others. For children & adolescents, these deficiencies largely involved heavy reasoning, problem solving, and logic. For young and middle-aged adults, the associations were mostly seen for executive function and visuospatial cognitive domains. To our knowledge, this is the first systematic review to consolidate findings on the associations among air pollution, brain structure, and cognitive function. In the future, it will be important to conduct further longitudinal studies that follow children who have been exposed at a young age and examine associations with brain structure and cognition throughout adulthood.

Risk of cognitive impairment from exposure to incense smoke

Incense is aromatic biotic material that releases fragrant smoke when burned. We aim to investigate the cognition risks from incense smoke. We obtained data from Taiwan Biobank in community. Cognition function was assessed by mini-mental state examination (MMSE). There were 978 participants in our study, including incense exposure (N = 131) and without incense exposure (N = 847). MMSE scores and registration sub-scores were lowered in incense exposure group than the other group. Incense exposure is one of the independent risk factors for cognitive decline in MMSE and registration sub-scores after adjusting confounding factors We concluded the risk of cognitive impairment, with predominant in registration in healthy individuals with incense exposure in community.

Brief diesel exhaust exposure acutely impairs functional brain connectivity in humans: a randomized controlled crossover study

BACKGROUND

While it is known that exposure to traffic-related air pollution causes an enormous global toll on human health, neurobiological underpinnings therein remain elusive. The study addresses this gap in knowledge.

METHODS

We performed the first controlled human exposure study using functional MRI with an efficient order-randomized double-blind crossover study of diesel exhaust (DE) and control (filtered air; FA) in 25 healthy adults (14 males, 11 females; 19-49 years old; no withdrawals). Analyses were carried out using a mixed effects model in FLAME. Z (Gaussianised T/F) statistic images were thresholded non-parametrically using clusters determined by Z > 2.3 and a (corrected) cluster significance threshold of p = 0.05.

RESULTS

All 25 adults went through the exposures and functional MRI imaging were collected. Exposure to DE yielded a decrease in functional connectivity compared to exposure to FA, shown through the comparison of DE and FA in post-exposure measurement of functional connectivity.

CONCLUSION

We observed short-term pollution-attributable decrements in default mode network functional connectivity. Decrements in brain connectivity causes many detrimental effects to the human body so this finding should guide policy change in air pollution exposure regulation.

TRIAL REGISTRATION

University of British Columbia Clinical Research Ethics Board (# H12-03025), Vancouver Coastal Health Ethics Board (# V12-03025), and Health Canada's Research Ethics Board (# 2012-0040).

Household air pollution and cognitive health among Indian older adults: Evidence from LASI

BACKGROUND

Previous shreds of evidence have suggested that ambient air pollution is negatively associated with cognitive health among older adults, but whether indoor air pollutants such as cooking fuel, tobacco smoke, and incense burning exposure affect the cognitive score is unknown, especially in limited-resource areas.

METHOD

The study has utilized the recently released data from the Longitudinal Ageing Study of India (LASI), Wave 1, conducted from 2017 to 2018. A total of 63,883 (≥45 years) older adults were considered for the analysis. Descriptive statistics, bivariate analysis and ordinary least squares regression were employed in the study.

RESULTS

The estimated mean cognitive score was 25.4 and the percentage of solid fuel users was 45.6 in India. The cognitive score gap between the two groups was more remarkable in Tamil Nadu (clean fuels: 29.7; solid fuels: 23.9). A significant cognitive score gap was observed for all indoor air pollutants, i.e., cooking fuel (clean: 29.7 and solid fuels: 23.9), exposure to tobacco smoke (not exposed: 25.7 and exposed: 24.4), and exposure to daily incense burning (not exposed: 25.9 and exposed: 24.8). The unadjusted model found that a one-unit increase of using charcoal/lignite/coal reduces the cognitive score by 5 (95% CI: -5.36, -4.61). A similar effect of exposure to tobacco smoke (β = -0.79, 95% CI: -0.89, -0.68) and incense burning (β = -0.28, 95% CI: -0.30, -0.26) was explored in the study. After adjusting socioeconomic and demographic characteristics, indoor air pollution was found to be a significant determinant of cognitive health.

CONCLUSIONS

The study has identified exposure to indoor air pollution as a risk factor for cognitive impairment among older adults. Therefore, we suggest an urgent need of promoting existing schemes like the Pradhan Mantri Ujjwala Yojana and creating awareness about the adverse effects of indoor air pollutants for a better future.

Association between Long-Term Air Pollution, Chronic Traffic Noise, and Resting-State Functional Connectivity in the 1000BRAINS Study

BACKGROUND

Older adults show a high variability in cognitive performance that cannot be explained by aging alone. Although research has linked air pollution and noise to cognitive impairment and structural brain alterations, the potential impact of air pollution and noise on functional brain organization is unknown.

OBJECTIVE

This study examined the associations between long-term air pollution and traffic noise with measures of functional brain organization in older adults. We hypothesize that exposures to high air pollution and noise levels are associated with age-like changes in functional brain organization, shown by less segregated brain networks.

METHODS

Data from 574 participants (44.1% female, 56-85 years of age) in the German 1000BRAINS study (2011-2015) were analyzed. Exposure to particulate matter (PM10, PM2.5, and PM2.5 absorbance), accumulation mode particle number (PNAM), and nitrogen dioxide (NO2) was estimated applying land-use regression and chemistry transport models. Noise exposures were assessed as weighted 24-h (Lden) and nighttime (Lnight) means. Functional brain organization of seven established brain networks (visual, sensorimotor, dorsal and ventral attention, limbic, frontoparietal and default network) was assessed using resting-state functional brain imaging data. To assess functional brain organization, we determined the degree of segregation between networks by comparing the strength of functional connections within and between networks. We estimated associations between air pollution and noise exposure with network segregation, applying multiple linear regression models adjusted for age, sex, socioeconomic status, and lifestyle variables.

RESULTS

Overall, small associations of high exposures with lesser segregated networks were visible. For the sensorimotor networks, we observed small associations between high air pollution and noise and lower network segregation, which had a similar effect size as a 1-y increase in age [e.g., in sensorimotor network, -0.006 (95% CI: -0.021, 0.009) per 0.3 ×10-5/m increase in PM2.5 absorbance and -0.004 (95% CI: -0.006, -0.002) per 1-y age increase].

CONCLUSION

High exposure to air pollution and noise was associated with less segregated functional brain networks. https://doi.org/10.1289/EHP9737.

Stable C and N isotopes of PM2.5 and size-segregated particles emitted from incense stick and cigarette burning

This work measured the δ¹³C and δ¹⁵N signatures in PM_2.5 and size-segregated particles emitted from incense stick and cigarette burning in different brands or nicotine contents for pollution source identification indoors. Three popular brands of incense stick and cigarette were selected for experiments. A personal environmental monitoring sampler and a Sioutas cascade impactor were used to collect PM_2.5 and size-segregated particles, respectively, for isotopic signatures analyses. Our data showed that both δ¹³C and δ¹⁵N values were heavier from incense stick burning (δ¹³C: 27.3 ± 0.5; δ¹⁵N: 8.63 ± 1.35) than cigarette (δ¹³C: 28.5 ± 0.2; δ¹⁵N: 4.15 ± 0.69). The scatter plots of δ¹³C and TC/PM_2.5 and of δ¹⁵N and TN/PM_2.5 can be applied to distinguish particle pollution sources and assess the influence of cigarette burning to PM_2.5 according to different nicotine contents. The δ¹³C values in size-segregated particles were similar to incense stick or cigarette burning; the δ¹³C values in PM_2.5 were significantly higher than those in size-segregated particles. However, the nitrogen amount was too low in most of the size-segregated particles to analyze δ¹⁵N from incense stick and cigarette burning. These results suggest that the δ¹³C signatures on PM_2.5 cannot represent the isotopic characteristics of size-segregated particles and δ¹⁵N has limitation for pollution source identification of different particle sizes.

Transcutaneous Electrical Acupoint Stimulation Ameliorates Cognitive Function through PINK1/Parkin Mediated Mitophagy in VD Rats

In this study, we investigated whether transcutaneous electrical acupoint stimulation (TEAS) could improve cognitive function in VD rats by regulating PINK1/Parkin-mediated mitophagy. VD rat model was prepared by modified 2-vessel occlusion (2-VO) and randomly divided into four groups: Sham group (Sham), Model group (Model), TEAS group (TEAS), and TEAS + 3-MA group (T +3 -MA). In the T +3 -MA group, autophagy inhibitor (3-MA) was injected into the lateral ventricle. After modeling, Y maze (YM), new object recognition test (NORT), Morris water maze (MWM), immunofluorescence, and Western blot were used to observe the effects of TEAS on VD rats. Behavioral experiments revealed that TEAS effectively improved the learning and memory ability of VD rats. Immunofluorescence results showed that TEAS could upregulate LC3 expression. Western blot results showed that TEAS upregulated the expression of PINK1, Parkin, and LC3-II, and downregulated the expression of LC3-I and p62 in VD rats. T +3 -MA group shows the opposite trend to TEAS group. This study demonstrates that TEAS ameliorates cognitive function through PINK1/Parkin-mediated mitophagy in VD rats.

Health and Environmental Risks of Incense Smoke: Mechanistic Insights and Cumulative Evidence

Incense burning is practiced alongside many sacred rituals across different regions of the world. Invariable constituents of incense brands are 21% (by weight) herbal and wood powder, 33% bamboo stick, 35% fragrance material, and 11% adhesive powder. Major incense-combustion outputs include particulate matter (PM), volatile organic content, and polyaromatic hydrocarbons. The relative toxicity of these products is an implicit function of particle size and incomplete combustion, which in turn vary for a specific incense brand. Lately, the attention given to the Air Quality Index by international regulatory bodies has created concern about mounting PM toxicity. The uncharacteristically small physical dimensions of these entities complicates their detection, and with no effect of gravity PM fractions rapidly contribute to oxidative stress, enhancing random biochemical reactions upon being inhaled. Incense burning generates four times the PM extent (45 mg•g⁻¹) of cigarettes (~10 mg•g⁻¹). Several poisonous gases, such as CO, CO₂, NO₂, and SO₂, and the unavoidable challenge of disposing of the burnt incense ash further add to the toxicity. Taken together, these issues demonstrate that incense burning warrants prompt attention. The aim of this article is to highlight the toxicity of incense-combustion materials on the environment and human health. This discussion could be significant in framing future policy regarding ecofriendly incense manufacture and reduced usage.

The Adverse Impact of Incense Smoke on Human Health: From Mechanisms to Implications

Incense burning is a very popular activity in daily life among many parts all over the world. A growing body of both epidemiological and experimental evidences has reported the negative effects of incense use on human well-being, posing a potential threat at public significance. This work is a comprehensive review that covers the latest findings regarding the adverse impact of incense smoke on our health, providing a panoramic visualization ranging from mechanisms to implications. The toxicities of incense smoke come directly from its harmful constituents and deposition capacity in the body. Besides, reactive oxygen species-driven oxidative stress and associated inflammation seem to be plausible underlying mechanisms, eliciting various unfavorable responses. Although our current knowledge remains many gaps, this issue still has some important implications.

Human health-risk assessment based on chronic exposure to the carbonyl compounds and metals emitted by burning incense at temples

Health effects resulting from the smoke of carbonyl compounds (aldehydes and ketones) and metal-containing incense particles at temples during incense burning periods were evaluated at temple A (without incense reduction activities) and B (with incense reduction activities), Nantou County, in 2018. The predominant size fractions of particles were PM₁, PM_1-2.5, and PM_2.5-10 at both temples. The total particle mass at temple A was approximately 1.1 times that of temple B due to incense reduction at temple B. The most abundant metal elements in all particle size fractions at both temples were Fe, Al, and Zn. Metal species of incense smoke are divided into three groups by hierarchical cluster analysis and heatmaps, showing higher metal contents in groups PM₁, PM_18-10, and PM_18-2.5 at temple A. In contrast, higher metal contents were observed in PM_18-10 and PM_2.5-1 at temple B. Most of the carbonyl species were formaldehyde and acetaldehyde, released during incense burning periods, with concentrations ranging from 6.20 to 13.05 μg/m³ at both temples. The total deposited fluxes of particle-bound metals at temples A and B were determined to be 83.00% and 84.82% using the International Commission on Radiological Protection (ICRP) model. Health-risk assessments revealed that the risk values of metals and carbonyls were above recommended guidelines (10^-6) at temple A. Since worshippers and staff are exposed to incense burning environments with poor ventilation over a long period, these toxic organic compounds and metals increase health risks in the respiratory tract. Therefore, incense reduction is important to achieve healthy temple environments.

Exposition of respiratory ailments from trace metals concentrations in incenses

Selected trace metals of importance in different incense before and after the smoldering process were assessed based on the recent respiratory ailments. Marketed perfumed and non-perfumed incense from different countries was separately analyzed using an Inductive coupled Plasma-Mass Spectroscopy (ICP-MS). A particulate analyzer measured the dispersed particulates (PM_2.5) in the indoor environment. The analysis revealed higher mean metals concentrations in the smoldered perfumed incense (1.98 µg g^-1) than in the non-smoldered and non-perfumed incense (0.59 µg g^-1). Pilot-scale experiments included the smoke dispersed in different sized-rooms, and the distance between the inhaler and the smoldering incense. Simultaneously, a questionnaire distributed to 300 residents from six sampling areas revealed the exposure of incense to human health. This study indicated significant attributes on (a) the room size and incense volume, (b) the permissible inmate's number in a room, (c) the distance between the inmate vicinity and the point of smoldering incense, (d) selectivity of incense, besides the outdoor environmental influence. Furthermore, this study revealed the various categories of respiratory ailments in residents in relation to the frequency of burning incense, prolonged smoke exposure, and the impact of burners although, earlier beneficial effects of incenses were evidenced. This study recommends preventive measures to human respiratory ailments from smoldering incense.

Association between solid fuel use and cognitive decline among middle-aged and elderly Chinese adults: a longitudinal study

This study was conducted to investigate (1) the association between solid fuel use for cooking and cognitive function; (2) the moderating effects of gender and residential area on cognitive scores among solid fuel users; and (3) the effects of solid fuel use on cognitive decline among different gender and age subgroups in 2011–2018. A total of 5140 Chinese middle-aged and elderly participants were successfully followed for 7 years (2011–2018). Solid fuel use was self-reported as using solid fuel for cooking at home, and cognitive function was assessed by 4 parts: episodic memory, time orientation, numerical ability and picture drawing. After adjusting for covariates, solid fuel users had lower cognitive scores, and the moderation effects of gender and residence on cognitive function were significant among the solid fuel users. In addition, compared with the group of clean fuel users, solid fuel users had a faster decline rate of cognitive function among the subgroups of female and elderly people.

AD Resemblance Atrophy Index as a Diagnostic Biomarker for Alzheimer's Disease: A Retrospective Clinical and Biological Validation

BACKGROUND

Magnetic resonance imaging (MRI) provides objective information about brain structural atrophy in patients with Alzheimer's disease (AD). This multi-structural atrophic information, when integrated as a single differential index, has the potential to further elevate the accuracy of AD identification from normal control (NC) compared to the conventional structure volumetric index.

OBJECTIVE

We herein investigated the performance of such an MRI-derived AD index, AD-Resemblance Atrophy Index (AD-RAI), as a neuroimaging biomarker in clinical scenario.

METHOD

Fifty AD patients (19 with the Amyloid, Tau, Neurodegeneration (ATN) results assessed in cerebrospinal fluid) and 50 age- and gender-matched NC (19 with ATN results assessed using positron emission tomography) were recruited in this study. MRI-based imaging biomarkers, i.e., AD-RAI, were quantified using AccuBrain®. The accuracy, sensitivity, specificity, and area under the ROC curve (AUC) of these MRI-based imaging biomarkers were evaluated with the diagnosis result according to clinical criteria for all subjects and ATN biological markers for the subgroup.

RESULTS

In the whole groups of AD and NC subjects, the accuracy of AD-RAI was 91%, sensitivity and specificity were 88% and 96%, respectively, and the AUC was 92%. In the subgroup of 19 AD and 19 NC with ATN results, AD-RAI results matched completely with ATN classification. AD-RAI outperforms the volume of any single brain structure measured.

CONCLUSION

The finding supports the hypothesis that MRI-derived composite AD-RAI is a more accurate imaging biomarker than individual brain structure volumetry in the identification of AD from NC in the clinical scenario.