Incense use and respiratory tract carcinomas: a prospective cohort study

Recommended approaches for screening and early detection of lung cancer in the Middle East and Africa (MEA) region: a consensus statement

Background

The prevalence of lung cancer in the Middle East and Africa (MEA) region has steadily increased in recent years and is generally associated with a poor prognosis due to the late detection of most of the cases. We explored the factors leading to delayed diagnoses, as well as the challenges and gaps in the early screening, detection, and referral framework for lung cancer in the MEA.

Methods

A steering committee meeting was convened in October 2022, attended by a panel of ten key external experts in the field of oncology from the Kingdom of Saudi Arabia, United Arab Emirates, South Africa, Egypt, Lebanon, Jordan, and Turkey, who critically and extensively analyzed the current unmet needs and challenges in the screening and early diagnosis of lung cancer in the region.

Results

As per the experts' opinion, lack of awareness about disease symptoms, misdiagnosis, limited screening initiatives, and late referral to specialists were the primary reasons for delayed diagnoses emphasizing the need for national-level lung cancer screening programs in the MEA region. Screening guidelines recommend low-dose computerized tomography (LDCT) for lung cancer screening in patients with a high risk of malignancy. However, high cost and lack of awareness among the public as well as healthcare providers prevented the judicious use of LDCT in the MEA region. Well-established screening and referral guidelines were available in only a few of the MEA countries and needed to be implemented in others to identify suspected cases early and provide timely intervention thus improving patient outcomes.

Conclusions

There is a great need for large-scale screening programs, preferably integrated with tobacco-control programs and awareness programs for physicians and patients, which may facilitate higher adherence to lung cancer screening and improve survival outcomes.

Characteristics of fine particles from incense burning at temple premises of Kathmandu Valley, Nepal

The impact of incense burning on ambient air quality was investigated by measuring the concentrations of fine particles (PM2.5), elemental carbon (EC), organic carbon (OC), and their oxidative potential (OP) at three temple premises in Kathmandu Valley, Nepal. These temples, namely, Bajrabarahi, Bagalamukhi, and Bhadrakali, are located in three distinct environments: forest, residential, and roadside, respectively. During the incense burning event days, the PM2.5 concentration at Bhadrakali (431.4 μgm-3) was significantly higher than that measured at the Bagalamukhi (135.2 μgm-3) and Bajrabarahi (84.7 μgm-3) temple premises. This observation is consistent with the fact that Bhadrakali Temple had the highest intensity of incense burning. Additionally, the temple premises were also influenced by vehicular emissions from transportation facilities. Carbonaceous aerosols significantly increased during incense burning events, indicating that incense burning contributes significantly to the formation of primary and secondary OC. Moreover, the OP of PM2.5 during the incense burning event days was higher compared to non-event days (p < 0.05), suggesting an elevated health risk due to the increased concentration and toxicity of fine particles. These findings highlight the substantial impact of incense burning on air quality in temple premises, emphasizing the need to implement effective strategies to mitigate the associated health risks.

Effects of Particulate Matter Exposure on the Eustachian Tube and Middle Ear Mucosa of Rats

OBJECTIVES

Particulate matter (PM) is a risk factor for various diseases. Recent studies have established an association between otitis media (OM) and PM exposure. To confirm this relationship, we developed a novel exposure model designed to control the concentration of PM, and we observed the effects of PM exposure on the Eustachian tube (ET) and middle ear mucosa of rats.

METHODS

Forty healthy, 10-week-old, male Sprague-Dawley rats were divided into 3-day, 7-day, 14-day exposure, and control groups (each, n=10). The rats were exposed to incense smoke as the PM source for 3 hours per day. After exposure, bilateral ETs and mastoid bullae were harvested, and histopathological findings were compared using microscopy and transmission electron microscopy (TEM). The expression levels of interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and vascular endothelial growth factor (VEGF) in the middle ear mucosa of each group were compared using real-time reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

In the ET mucosa of the exposure group, the goblet cell count significantly increased after PM exposure (P=0.032). In the middle ear mucosa, subepithelial space thickening, increased angio-capillary tissue, and inflammatory cell infiltration were observed. Moreover, the thickness of the middle ear mucosa in the exposure groups increased compared to the control group (P<0.01). The TEM findings showed PM particles on the surface of the ET and middle ear mucosa, and RT-PCR revealed that messenger RNA (mRNA) expression of IL-1β significantly increased in the 3-day and 7-day exposure groups compared to the control group (P=0.035). VEGF expression significantly increased in the 7-day exposure group compared to the control and 3-day exposure groups (P<0.01).

CONCLUSION

The ET and middle ear mucosa of rats showed histopathologic changes after acute exposure to PM that directly reached the ET and middle ear mucosa. Therefore, acute exposure to PM may play a role in the development of OM.

Chronic exposure to indoor air pollutants in association with attention-deficit/hyperactivity disorder symptoms in Chinese schoolchildren: A cross-sectional study

BACKGROUND

While increasing studies confirmed the adverse effects of indoor air pollution (IAP) on cardiopulmonary systems, less is known about the impact of IAP on child's brain.

OBJECTIVE

To explore the associations between multiple indoor air pollutants exposures and attention-deficit/hyperactivity disorder (ADHD) symptoms in Chinese schoolchildren.

METHODS

We invited 8630 individuals aged 6-12 years from an ongoing school-based cohort study across Guangzhou from April to May 2019. There are 7495 and 7245 children were respectively evaluated on the parent- and teacher-rated Conner's Rating Scale-Revised, and 7087 children were assessed on both versions. Indoor air pollutants exposures including cooking oil fumes, incense burning, home renovation, and secondhand smoke, were measured using a questionnaire reported by parents and children, and further converted into an index. Generalized linear mixed-effects models were performed to evaluate the associations between indoor air pollutants exposures and ADHD index and the presence of ADHD symptoms.

RESULTS

As reported by parents, 321 (4.3%) children had ADHD symptoms. Each of the four pollutants was positively associated with higher ADHD index and higher odds of ADHD symptoms. Children exposed to 1, 2, and ≥ 3 types of indoor air pollutants had higher ADHD index and higher odds of ADHD symptoms than those non-exposed children. For parent-reported ADHD symptoms, the odds ratios ranged from 1.24 [95% confidence interval (CI): 0.92-1.67] to 2.73 (95% CI: 1.86-4.01). These associations were consistent in parent- and teacher-reported ADHD symptoms, and the combination of both.

CONCLUSION

Indoor air pollutants exposures were positively associated with higher prevalence of children's ADHD symptoms assessed by whether parents or teachers.

Development and application of the Ames test using a direct-exposure module: The assessment of mutagenicity of incense and sidestream cigarette smoke

We had previously developed an improved Ames module to directly determine the mutagenicity of gaseous formaldehyde (HCHO) and toluene without liquid extraction. This study further evaluated the suitability and sensitivity of this module on whole and real polluted air samples. For this, two common brands of stick incense (A and B) and cigarettes (A and B) were harvested, and various types of incense smoke (IS) and sidestream cigarette smoke (SCS) samples were generated by lighting 3, 6, 12, 24, 30, or 36 incense sticks, and by lighting 1, 2, or 3 cigarettes, respectively, in an acrylic box. CO₂ , CO, total volatile organic compound (TVOC), PM_1.0, and HCHO concentrations in the air samples were determined, and all air samples did not partially fit the requirements of the air quality standards. The smoke samples were then directly exposed to TA100 for 10, 20, 30, or 60 min in our exposure module. Exposure to IS (brand A) for 30 to 60 min and exposure to IS (brand B) for 60 min led to statistically (p < 0.05) weak (below the twofold rule) but dose-dependent mutagenic activities either with or without metabolic activation. Furthermore, a short-term exposure (10-60 min) to SCS (brands A and B) displayed statistically significant (p < 0.05) direct-acting, indirect-acting, time- and dose-dependent mutagenic activities. Furthermore, our data also support that the liver S9 enzyme could enhance the mutagenic activities in most IS and SCS samples. This study confirmed that the modified Ames module can be applied to directly detect the mutagenic activities of real polluted air samples.

Association between household incense burning and executive function in Chinese children

Incense burning is common in Asia including China. Research investigating the association between household incense burning and children's neurodevelopment is scarce. We aimed to examine this association in Chinese children. In 2019, we randomly enrolled 8293 children aged 6-12 years from 5 elementary schools in Guangzhou, southern China. Information on duration and frequency of household incense burning was collected using a questionnaire. Children's executive function was evaluated using the parental report of the Behavioral Rating Inventory of Executive Function. A general linear model was used to assess the associations between incense burning and executive function. Children who occasionally and frequently exposed to incense burning exhibited worse performance on executive function. For example, frequent incense burning was associated with increases in behavioral regulation index (BRI) of 1.77 (95%CI: 0.97, 2.58) points and metacognition index (MI) of 1.40 (95%CI: 0.60, 2.20) points, compared to never incense burning group. Parental smoking and household income were significant modifiers of the associations, with the stronger associations were observed in children having smoking parent(s) and poorer household income. The findings suggest that household incense burning was associated with poorer executive function, especially in children whose parent(s) were smokers and in those with low household income.

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.

Indoor Air Pollution Increases the Risk of Lung Cancer

(1) Background: Cooking and burning incense are important sources of indoor air pollutants. No studies have provided biological evidence of air pollutants in the lungs to support this association. Analysis of pleural fluid may be used to measure the internal exposure dose of air pollutants in the lung. The objective of this study was to provide biological evidence of indoor air pollutants and estimate their risk of lung cancer. (2) Methods: We analyzed 14 common air pollutants in the pleural fluid of 39 cases of lung adenocarcinoma and 40 nonmalignant controls by gas chromatography-mass spectrometry. (3) Results: When we excluded the current smokers and adjusted for age, the adjusted odds ratios (ORs) were 2.22 (95% confidence interval CI = 0.77-6.44) for habitual cooking at home and 3.05 (95% CI = 1.06-8.84) for indoor incense burning. In females, the adjusted ORs were 5.39 (95% CI = 1.11-26.20) for habitual cooking at home and 6.01 (95% CI = 1.14-31.66) for indoor incense burning. In pleural fluid, the most important exposure biomarkers for lung cancer were naphthalene, ethylbenzene, and o-xylene. (4) Conclusions: Habitual cooking and indoor incense burning increased the risk of lung adenocarcinoma.

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.

Predicting environmental risk factors in relation to health outcomes among school children from Romania using random forest model - An analysis of data from the SINPHONIE project

BACKGROUND

Few studies have simultaneously assessed the health impact of school and home environmental factors on children, since handling multiple highly correlated environmental variables is challenging. In this study, we examined indoor home and school environments in relation to health outcomes using machine learning methods and logistic regression.

METHODS

We used the data collected by the SINPHONIE (Schools Indoor Pollution and Health: Observatory Network in Europe) project in Romania, a multicenter European research study that collected comprehensive information on school and home environments, health symptoms in children, smoking, and school policies. The health outcomes were categorized as: any health symptoms, asthma, allergy and flu-like symptoms. Both logistic regression and random forest (RF) methods were used to predict the four categories of health outcomes, and the methods prediction performance was compared.

RESULTS

The RF method we employed for analysis showed that common risk factors for the investigated categories of health outcomes, included: environmental tobacco smoke (ETS), dampness in the indoor school environment, male gender, air freshener use, residence located in proximity of traffic (<200 m), stressful schoolwork, and classroom noise (contributions ranged from 7.91% to 23.12%). Specificity, accuracy and area under the curve (AUC) values for most outcomes were higher when using RF compared to logistic regression, while sensitivity was similar in both methods.

CONCLUSION

This study suggests that ETS, dampness in the indoor school environment, use of air fresheners, living in proximity to traffic (<200 m) and noise are common environmental risk factors for the investigated health outcomes. RF pointed out better predictive values, sensitivity and accuracy compared to logistic regression.

Residence characteristics and risk of nasopharyngeal carcinoma in southern China: A population-based case-control study

OBJECTIVES

Given the role of exposures related to residence in the development of nasopharyngeal carcinoma (NPC) has not been well explored, present study aims to investigate the magnitude and pattern of associations for NPC with lifelong residential exposures.

MATERIALS AND METHODS

We carried out a multi-center, population-based case-control study with 2533 incident NPC cases and 2597 randomly selected population controls in southern China between 2010 and 2014. We performed multivariate logistic regression to estimate odds ratios (ORs) with 95% confidence intervals (CIs) for the risk of NPC associated with residential exposures.

RESULTS

Compared with those living in a building over lifetime, risk of NPC was higher for individuals living in a cottage (OR: 1.56; 95% CI: 1.34-1.81) or in a boat (3.87; 2.07-7.21). NPC risk was also increased in individuals using wood (1.34; 1.03-1.75), coal (1.70; 1.17-2.47), or kerosene (3.58; 1.75-7.36) vs. using gas/electricity as cooking fuel; using well water (1.57; 1.34-1.83), river water (1.80; 1.47-2.21), or spring/pond/stream water (2.03; 1.70-2.41) vs. tap water for source of drinking water; living in houses with smaller-sized vs. larger windows in the bedroom (3.08; 2.46-3.86), hall (1.89; 1.55-2.31) or kitchen (1.67; 1.34-2.08); and increasing exposure to cooking smoke [(1.53; 1.20-1.94) for high exposure)] or burned incense [(1.59; 1.31-1.95) for daily use)]. Weighted Cox regression analysis corroborated these results.

CONCLUSION

Poorer residential conditions and household air pollution are associated with an increased risk of NPC. Large-scale studies in other populations or longitudinal studies are warranted to further corroborate these findings.

Associations between household incense burning and delayed motor development among preterm infants modified by gestational age and maternal educational status

BACKGROUND

Household incense burning is a common ritual behavior in the Asia-Pacific region but has been associated with inferior developmental outcomes in term infants. We aimed to examine these associations among preterm infants.

METHODS

Information from 1190 mother-infant pairs during 6- and 18-month follow-up to the Taiwan Birth Cohort Study was examined for associations between household incense burning exposure and infant neurodevelopmental milestone achievement using multivariable Cox proportional hazard model with propensity score weighting, along with stratified, sensitivity, and decomposition analysis.

RESULTS

Household incense burning exposure was associated with delayed gross motor milestone achievement among all preterm infants according to the Cox model and after propensity score weighting. Meanwhile, associations for delayed development were found in gross motor domain milestones among late preterm infants, while fine motor domain delay was found among other preterm infants. Furthermore, the associations between household incense burning status and gross motor milestone delays were attenuated by the interaction between higher education level and household incense burning exposure status.

CONCLUSIONS

Household incense burning exposure was associated with delays, and the motor domains affected differed according to degree of prematurity. These associations were modified by the attenuation upon higher maternal educational status and exposure status interaction.

The Evolving Epidemiology of Nasopharyngeal Carcinoma

BACKGROUND

The epidemiology of nasopharyngeal carcinoma (NPC) has long been a source of fascination due to the malignancy's striking geographic distribution, the involvement of the oncogenic Epstein-Barr virus (EBV), the unique association with intake of Chinese-style salt-preserved fish, and etiologic heterogeneity by histologic subtype.

METHODS

This review summarizes the current epidemiologic literature on NPC, highlighting recent results from our population-based case-control study in southern China.

RESULTS

Findings from our case-control study provide new insight into the epidemiology of NPC, including a diminished role of Chinese-style salt-preserved fish, a profound impact of EBV genetic sequence variation, modest positive associations with passive smoking and household air pollution, and possible effects of oral health and the oral microbiome. Recent findings from other studies include a protective association with infectious mononucleosis, suggesting a causal role of early EBV infection; familial risk conferred by shared genetic variation in the host antibody-mediated immune response to EBV infection; and an unclear association with occupational exposure to formaldehyde.

CONCLUSIONS

To shed further light on the interplay of environmental, genetic, and viral causes of NPC, large pooled studies must accumulate sufficient cases with detailed exposure data.

IMPACT

New epidemiologic findings have reshaped the causal model for NPC.

Contributions of burning incense on indoor air pollution levels and on the health status of patients with chronic obstructive pulmonary disease

Background

Among Buddhist or Taoist Taiwanese residents, burning incense is a common source of indoor particulate matter (PM), including PM₁₀ and PM_2.5, and can adversely affect the health status of patients with chronic obstructive pulmonary diseases (COPD). However, few studies have focused on the effects of intermittent burning of incense on PM concentration levels and the health status of patients with COPD. This correlational cohort study aimed to investigate the association between burning incense exposure duration, indoor air pollution levels, and lung function in patients with COPD in Taiwan.

Methods

We assessed 18 outpatients at seven time points with moderate-to-severe COPD using the COPD Assessment Test (CAT), and lung function tests. PM level changes were assessed at seven intervals using generalized estimating equations.

Results

Participants were primarily male (84%), with a mean age of 72.1 (standard deviation (SD)  ± 9.3) years, and with a mean COPD duration of 3.7 (SD  ± 3.1) years. Both PM₁₀ and PM_2.5 levels were the same as the background levels 1 h after incense burning. Burning incense may not influence lung function or symptom severity in patients with COPD in a short-time period. Air quality returned to baseline levels 1 h after burning incense.

Conclusion

Patients with COPD should avoid staying in rooms where incense is burnt, for up to 1 h. The small sample size and short study period may have influenced our results. Future longitudinal studies with larger sample sizes and long-term follow-ups are recommended.

Green Worship: The Effects of Devotional and Behavioral Factors on Adopting Electronic Incense Products in Religious Practices

The Buddhist tradition of incense burning has been practiced in many Asian countries. Prior studies have indicated that frequent exposure to incense smoke is linked to carcinogen-related health issues. However, widespread acceptance of health-friendly electronic incense and rituals remains limited. Based on theories of religious perceptions and health behavior, the present study aims to identify the factors which influence the acceptance of electronic incense burning in religious practices. A between-subjects (105 Buddhist participants) experiment was designed to compare the effects of different incense burners on religiosity, worship intention, perceived self-efficacy, health-promotion intention, and its underlying mechanism. Our results imply that Buddhists tend to show similar religiosity and worship intention in three different scenarios, namely, the usage of a traditional incense burner, an electronic incense burner, and an electronic burner attached with a doctrine reminder. Buddhists also tend to have a higher perceived self-efficacy and higher health-promotion intention when exposed to electronic incense scenarios (either with or without the attached doctrine reminder). The perceived self-efficacy was found to mediate the effect of the incense burning on health-promotion intention. Important implications for public policies are also discussed.

Long-term incense use and the risk of end-stage renal disease among Chinese in Singapore: the Singapore Chinese health study

BACKGROUND

Experimental studies have shown that exposure to incense burning may have deleterious effects on kidney function and architecture. However, the association between chronic exposure to incense smoke and risk of end-stage renal disease (ESRD) has not been reported in epidemiologic studies.

METHODS

We investigated this association in the Singapore Chinese Health Study, a prospective population-based cohort of 63,257 Chinese men and women of 45-74 years of age in Singapore during recruitment from 1993 to 1998. Information on the practice of incense burning at home, diet, lifestyle and medical history was collected at baseline interviews. ESRD cases were identified through linkage with the nationwide Singapore Renal Registry through 2015. We used Cox proportional hazards regression analysis to estimate hazard ratio (HR) and 95% confidence interval (CI) of ESRD associated with domestic incense burning.

RESULTS

Among cohort participants, 76.9% were current incense users. After an average 17.5 years of follow-up, there were 1217 incident ESRD cases. Compared to never users, the multivariable-adjusted HR for ESRD risk was 1.05 (95% CI, 0.80 to 1.38) for former users and 1.26 (95% CI, 1.02 to1.57) for current users of incense. In analysis by daily or non-daily use and duration, the increased ESRD risk was observed in daily users who had used incense for > 20 years; HR was 1.25 (95% CI, 1.07 to 1.46). Conversely, the risk was not increased in those who did not use incense daily or who had used daily but for ≤20 years.

CONCLUSIONS

Our findings demonstrate that long-term daily exposure to domestic incense burning could be associated with a higher risk of ESRD in the general population.

Incense burning smoke sensitizes lung cancer cells to EGFR TKI by inducing AREG expression

Incense burning is common in Asian countries due to the religious beliefs. Environmental exposure to incense burning smoke is a potential risk factor for tumor development and progression of non-small cell lung cancer (NSCLC). Eastern Asia ethnic origin is strongly associated the clinical benefits of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in NSCLC patients. However, the impact of the oriental custom of incense burning on the cancer progression and the EGFR TKI-sensitivity of NSCLC remains unclear. Our results showed that long-term exposure to incense burning extract (IBE) increases the cellular proliferation with S phase accumulation and the motility activity of NSCLCs. Interestingly, IBE enhances EGFR signaling activity without affecting its genetic status, and increases the cellular sensitivity of NSCLC cell lines to EGFR TKIs. Auramine, a yellow dye for making incense sticks, was identified as a residual composition in the burning incense smoke, and showed similar EGFR TKI-sensitizing effects. Furthermore, IBE or auramine transcriptionally induce EGFR ligand amphiregulin (AREG) expression for the enhancement of EGFR activity. Neutralization of AREG reduced the viability of IBE-treated cells. These results indicated that exposure to incent smoke may enhance NSCLC progression and their sensitivity to EGFR TKIs through increasing their oncogenic addiction to AREG-induced EGFR signaling.

Environmental and Life-Style Related Risk Factors for Sinonasal and Nasopharyngeal Malignancies among a Prospective Cohort in Jos, Nigeria

Background

Worldwide evidence indicates that environmental and life-style related factors are associated with increased risk for cancers in the head and neck region. We aim to study the association between these risk factors and cancers in the sinonasal and nasopharyngeal regions in our environment.

Methods

Longitudinal prospective cohort study at the Jos University Teaching Hospital, Jos, Nigeria. Risk exposures were classified based on the International Agency for the Research on Cancer (IARC) classification of suspected carcinogens. Associations between variables were analyzed using logistic regression.

Results

We studied 44 patients with malignancies in nasopharynx (n= 24; 54.5%) and sinonasal regions (n= 20; 45.5%). Male to female ratio is 1.9:1 and mean age is 45.2 years. Alcohol was the commonest risk factor in males (n= 19; 43.2%) while cooking wood fumes were the commonest in females (n= 14; 31.8%) which was associated with increased risk for malignancies for all sites, showing ten times risk in nasal cancers (OR= 9.67; 95% CI 1.87- 9.88; p= 0.01). Tobacco was associated with elevated risk of malignancies in the nasomaxillary and nasal regions. Other risks were herbicides, pesticides, and chemical fertilizers in farmers.

Conclusion

The significant risk exposures in females were cooking wood fumes and alcohol, tobacco, and exposure to agricultural chemicals in males. Life-style modification and environmental changes to ensure clean air in Nigeria are essential to reduce risks.

Household incense burning and infant gross motor development: Results from the Taiwan Birth Cohort Study

BACKGROUND

Air pollution from biomass burning were associated with neurodevelopmental deceleration, but limited studies concerned about the effect of indoor biomass burning. Incense burning is a common household ritual practice in Taiwan, while past studies mainly focused on birth weight and allergic disease.

OBJECTIVES

We aimed to find the association between incense burning exposure and children's neurodevelopment.

METHODS

In Taiwan Birth Cohort Study (TBCS), a nationwide representative birth cohort study, children were assessed upon home interview with structured questionnaires upon six and eighteen months old. Multivariate logistic and Cox proportional hazard regression adjusting confounding factors were applied to explore the odds ratio (OR) and hazard ratio (HR) between household incense burning exposure and caregiver-reported neurodevelopment milestones.

RESULTS

In this study, 15,310 term singletons were included, and household incense burning was associated with delay in gross motor neurodevelopment milestone, such as walking with support (Occasional incense burning: OR = 1.26, 95% confidence interval (CI): 1.08 to 1.47, HR = 1.07, 95% CI: 1.03 to 1.11; persistent incense burning: OR = 1.44, 95% CI: 1.22 to 1.69, HR = 1.11, 95% CI: 1.07 to 1.16) and walking steadily (Occasional incense burning: OR = 1.14, 95% CI: 0.98 to 1.32, HR = 1.07, 95% CI: 1.03 to 1.11, persistent incense burning: OR = 1.24, 95% CI: 1.06 to 1.45, HR = 1.09, 95% CI: 1.04 to 1.13).

CONCLUSIONS

Our study suggested household incense burning exposure was associated with delay in gross motor neurodevelopmental milestones. Further research is warranted to elucidate the possible mechanism and causal relationship.

Incense Smoke and Increasing Carotid Intima Media Thickness: A Cross-Sectional Study of the Thai-Vietnamese Community

Incense burning, a source of household indoor air pollution, is possible to effect on cardiovascular system. Our study sought to examine the association of long-term exposure to household incense smoke with increased carotid intima-media thickness (CIMT). A cross-sectional study was conducted 132 adults aged ≥35 years. Participants were stratified into 3 groups by their long-term household incense use; nonexposed group, non-daily exposed group, and daily exposed group. A combined mean CIMT (mean difference = 0.04 mm; P < .01) and combined maximum CIMT (mean difference = 0.09 mm; P < .01) in the daily exposed group had greater than the nonexposed group. The mean CIMT and maximum CIMT of the left common carotid artery in the daily exposed group was significantly greater than the nonexposed group ( P < .01). These findings suggest that incense burning inside the house may be a risk factor for cardiovascular disease morbidity and mortality.

Associations between maternal exposure to incense burning and blood pressure during pregnancy

Incense burning is a popular practice in Asian and Arabic countries. Previous studies show that incense burning was associated with increased risks of adverse outcomes among non-pregnant population. However, very few studies explored its health effects among pregnant women, who are more susceptible to environmental stressor. We aimed to examine the association between incense burning at home and hypertensive disorders as well as blood pressure levels during pregnancy, using data from 10,563 pregnant women recruited in Born in Guangzhou Cohort Study, China between January 2013 and December 2015. Information on frequency and duration of exposure to incense burning were collected at early and late pregnancy using questionnaire. Data on outcome variables, including hypertensive disorders diagnosis and blood pressure levels at the final antenatal visit before delivery, were extracted from medical records. We used Poisson regression model and general linear model to examine the associations between incense exposure and the outcomes. We found incense use at early pregnancy was not significantly associated with outcomes. Pregnant women who frequently smelled the incense burning at late pregnancy was associated with higher risk of hypertensive disorders (relative risk, 1.84; 95% confidence interval, 1.14-2.98) and higher levels of blood pressure (1.6mmHg increase of systolic blood pressure; 95% confidence interval, 0.4-2.8mmHg) before delivery, compared to those did not burn incense. These associations tended to more evident among women without active and passive smoking. We did not observe significant dose-response relationship between exposure duration and the risk of hypertensive disorders. We firstly reported exposure to incense burning was associated with the risk of hypertensive disorders and blood pressure levels during pregnancy. Given hypertensive disorders in pregnancy are well-established risk factors for a variety of adverse outcomes and the incense burning is a modifiable factor, our finding may have important public health significance.

The Association of Domestic Incense Burning with Hypertension and Blood Pressure in Guangdong, China

Domestic incense burning is a common activity in China. Although it generates serious air pollution and has been linked to various health outcomes, it remains unknown whether it is associated with blood pressure and hypertension. A community-based survey including 1153 hypertensive subjects and 4432 normotensive participants in Guangdong (China) was used to examine this question. Two-level logistic regression was used to estimate the odds ratio (OR) and 95% confidence interval (CI). The analyses showed that, compared with non-users, OR of hypertension was 1.24 (95% CI: 1.03–1.50) for users, and 1.37 (95% CI: 1.04–1.80) for daily users with a clear dose-response relationship. The estimated increases in systolic and diastolic blood pressures were 1.02 mmHg (95% CI: 0.06–1.99) and 1.26 mmHg (95% CI: 0.69–1.83) for users, 0.67 mmHg (95% CI: −0.35–1.68) and 1.25 mmHg (95% CI: 0.66–1.85) for occasional users, and 2.09 mmHg (95% CI: 0.79–3.39) and 1.28 mmHg (95% CI: 0.52–2.05) for daily users, respectively. The results remained after adjusting for potential confounders and more pronounced associations were found among females. This study suggests that domestic incense burning may increase the risk of hypertension and blood pressure in the study population, and women are more vulnerable to these effects than men.

Incense Burning during Pregnancy and Birth Weight and Head Circumference among Term Births: The Taiwan Birth Cohort Study

BACKGROUND

Incense burning for rituals or religious purposes is an important tradition in many countries. However, incense smoke contains particulate matter and gas products such as carbon monoxide, sulfur, and nitrogen dioxide, which are potentially harmful to health.

OBJECTIVES

We analyzed the relationship between prenatal incense burning and birth weight and head circumference at birth using the Taiwan Birth Cohort Study. We also analyzed whether the associations varied by sex and along the distribution of birth outcomes.

METHODS

We performed ordinary least squares (OLS) and quantile regressions analysis on a sample of 15,773 term births (> 37 gestational weeks; 8,216 boys and 7,557 girls) in Taiwan in 2005. The associations were estimated separately for boys and girls as well as for the population as a whole. We controlled extensively for factors that may be correlated with incense burning and birth weight and head circumference, such as parental religion, demographics, and health characteristics, as well as pregnancy-related variables.

RESULTS

Findings from fully adjusted OLS regressions indicated that exposure to incense was associated with lower birth weight in boys (-18 g; 95% CI: -36, -0.94) but not girls (1 g; 95% CI: -17, 19; interaction p-value = 0.31). Associations with head circumference were negative for boys (-0.95 mm; 95% CI: -1.8, -0.16) and girls (-0.71 mm; 95% CI: -1.5, 0.11; interaction p-values = 0.73). Quantile regression results suggested that the negative associations were larger among the lower quantiles of birth outcomes.

CONCLUSIONS

OLS regressions showed that prenatal incense burning was associated with lower birth weight for boys and smaller head circumference for boys and girls. The associations were more pronounced among the lower quantiles of birth outcomes. Further research is necessary to confirm whether incense burning has differential effects by sex.

CITATION

Chen LY, Ho C. 2016. Incense burning during pregnancy and birth weight and head circumference among term births: The Taiwan Birth Cohort Study. Environ Health Perspect 124:1487-1492; http://dx.doi.org/10.1289/ehp.1509922.

Measurements of VOC/SVOC emission factors from burning incenses in an environmental test chamber: influence of temperature, relative humidity, and air exchange rate

This study investigates the influence of three environmental indoor parameters (i.e., temperature, relative humidity, and air exchange rate) on the emission of 13 volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) during incense burning. Experiments have been carried out using an environmental test chamber. Statistical results from a classical two-level full factorial design highlight the predominant effect of ventilation on emission factors. The higher the ventilation, the higher the emission factor. Moreover, thanks to these results, an estimation of the concentration range for the compounds under study can be calculated and allows a quick look of indoor pollution induced by incense combustion. Carcinogenic substances (i.e., benzene, benzo(a)pyrene, and formaldehyde) produced from the incense combustion would be predicted in typical living indoors conditions to reach instantaneous concentration levels close to or higher than air quality exposure threshold values.

Domestic incense use and lung cancer in Asia: a review

While there is strong evidence for the association between household air pollution and lung cancer among non-smoking women, the association between domestic incense use and lung cancer risk has been inconsistent. We conducted a systematic review of PubMed articles authored between 1969 and August 25, 2015 before performing a manual review of each study, and found a total of seven published studies on this topic. Most of the studies are case-control in design and did not further stratify by sex and smoking status. Of the seven studies, three reported positive associations, three reported null associations and one study found a negative association between incense use and lung cancer. Only one study reported estimates for non-smoking women. Future studies should be larger in sample size, stratify by both sex and smoking status in their analyses, and collect more detailed information on incense use in order to facilitate the understanding of the association between domestic incense use and lung cancer risk among non-smoking women in Asia.

Household inhalants exposure and nasopharyngeal carcinoma risk: a large-scale case-control study in Guangdong, China

BACKGROUND

Epidemiological studies show that cigarette smoking increase the risk of nasopharyngeal carcinoma (NPC), however, whether other common, potentially adverse household inhalants increase NPC risk remains uncertain.

METHODS

We conducted a large case-control study to explore the effects of household inhalants, such as incense, mosquito coil, cooking fumes, and wood combustion, on NPC risk. We recruited 1,845 cases and 2,275 controls from Guangdong province, a high-risk area for NPC in China, to obtain the demographic data and relevant exposure information through face-to-face interviews.

RESULTS

We found that incense burning was associated with NPC risk by comparing frequent incense use with never using incense [OR and 95% confidence interval (CI) = 1.73, (1.43, 2.09)]. Wood fuel use was also associated with NPC risk compared with non-wood fire use [OR and 95% CI = 1.95, (1.65, 2.31)]. More intriguingly, we observed a significant addictive interaction between frequent incense burning and heavy cigarette smoking on NPC risk [synergistic index (SI) = 1.67; 95% CI: 1.01, 2.76]. We also found a significant joint effect between wood fuel use and NPC family history for NPC risk (SI = 1.77; 95% CI: 1.06, 2.96). However, neither mosquito oil nor cooking fumes were associated with NPC risk.

CONCLUSIONS

Our study shows that incense smoke is not only the potential independent risk factor but also co-contributes with cigarette smoking to NPC risk. Moreover, wood combustion is another potential environmental risk factor and exerts a joint effect with NPC family history on NPC.

Nasopharyngeal Carcinoma in Oman: A Descriptive Analysis

OBJECTIVES

We sought to analyze all cases of nasopharyngeal carcinomas (NPC) in Oman to determine the most common clinical presentation, whether it is associated with certain tribes in Oman, and its distribution in different regions of the country. We also looked at the histopathological diagnosis, treatment modality, recurrence, and metastasis.

METHODS

This retrospective chart analysis was performed using the data of all patients with NPC who presented to the Al Nahdha Hospital (the main tertiary hospital of head and neck surgery in Oman) from January 2003 until August 2011.

RESULTS

Twenty-six cases of NPC were included in the final study population. Muscat (the capital city of Oman) had the highest number of cases followed by the Ash Sharqiyah, Al-Batinah, and Dhofar regions. The largest number of cases were found in the Al-Balushi tribe. Cases had a bimodal distribution within two age groups (20-30 years and 50-60 years). Follow-up ranged between six months and seven years.

CONCLUSION

Neck mass and nasal symptoms were the most common presentations of NPC in Oman. Further studies, with a larger sample size are required in order to support our results.

Ultrastructural changes, increased oxidative stress, inflammation, and altered cardiac hypertrophic gene expressions in heart tissues of rats exposed to incense smoke

Incense smoke exposure has recently been linked to cardiovascular disease risk, heart rate variability, and endothelial dysfunction. To test the possible underlying mechanisms, oxidative stress, and inflammatory markers, gene expressions of cardiac hypertrophic and xenobiotic-metabolizing enzymes and ultrastructural changes were measured, respectively, using standard, ELISA-based, real-time PCR, and transmission electron microscope procedures in heart tissues of Wistar rats after chronically exposing to Arabian incense. Malondialdehyde, tumor necrosis alpha (TNF)-α, and IL-4 levels were significantly increased, while catalase and glutathione levels were significantly declined in incense smoke-exposed rats. Incense smoke exposure also resulted in a significant increase in atrial natriuretic peptide, brain natriuretic peptide, β-myosin heavy chain, CYP1A1 and CYP1A2 messenger RNAs (mRNAs). Rats exposed to incense smoke displayed marked ultrastructural changes in heart muscle with distinct cardiac hypertrophy, which correlated with the augmented hypertrophic gene expression as well as markers of cardiac damage including creatine kinase-myocardial bound (CK-MB) and lactate dehydrogenase (LDH). Increased oxidative stress, inflammation, altered cardiac hypertrophic gene expression, tissue damage, and architectural changes in the heart may collectively contribute to increased cardiovascular disease risk in individuals exposed to incense smoke. Increased gene expressions of CYP1A1 and CYP1A2 may be instrumental in the incense smoke-induced oxidative stress and inflammation. Thus, incense smoke can be considered as a potential environmental pollutant and its long-term exposure may negatively impact human health.

A health risk assessment of Arabian incense (Bakhour) smoke in the United Arab Emirates

Burning Arabian incense (Bakhour) is a common practice in the Middle East and Arabian Gulf. Although the incense generates large amounts of chemicals and air pollutants, little is known with regard to the nature of these chemicals and their potential health risks. The aim of this study is to provide a comprehensive characterization of the chemical constituents emitted in Bakhour smoke, and subsequently to examine the associated health implications of these components. Thermo-gravimetric analysis was used to investigate the presence and the thermal profile of volatile organic compounds in three different samples of Bakhour smoke. Thermal desorption-gas chromatography-mass spectrometry was then applied to isolate all the volatile and semi-volatile compounds present in the Bakhour smoke samples. Using a spectral library and an extensive literature search, all organic compounds detected were analyzed for potential health risks. A total of 859 compounds were emitted from burning the different Bakhour samples. The novel finding of this research shows that 42 detected compounds are suspected/known carcinogens, 20 are known to have toxic effects, and at least 200 compounds are known irritants to the eyes, skin, respiratory and digestive tracts, as reported in human and/or animal studies. Our study suggests that inhaled Bakhour smoke contains a substantial number of adverse compounds, which are known to be detrimental to human health. Moreover, the evidence presented shows that incense burning is a significant source of environmental pollution; with the potential of significant health concerns particularly with long term exposure. As the majority of the compounds detected have no reported clinical data, there is an urgent need for significant research in this field.

Acute effects of inhaling Oud incense on voice of Saudi adults

BACKGROUND AND OBJECTIVES

Like in most of the Arab countries, incense burning, including Oud, is widely used in Saudi Arabia. The widespread effects of the Oud incense on voice have not been examined. Thus, the aim of this study was to examine the short-term effects of Oud incense on laryngeal symptoms and voice acoustics in normal Saudi adults.

DESIGN AND SETTINGS

A prospective study that has been carried out at King Abdulaziz University Hospital between July 2012 and Jan 2014.

MATERIALS AND METHODS

Study subjects were recruited on a volunteer basis. A total of 72 adults (44.4% males and 55.6 % females), were exposed to Oud incense smoke for 5 minutes while sitting 1 m away from an electrical sensor in a closed room. Symptom and acoustic voice analyses were performed pre-exposure and immediately post-exposure.

RESULTS

A total of 27.8% of the subjects reported throat and voice symptoms after 5 minutes of exposure. Some frequency-related acoustic measures increased in male and female subjects after exposure to Oud incense. However, the difference between the pre- and post-exposure measures was not statistically significant.

CONCLUSION

One third of the study subjects reported voice-related symptoms following exposure to Oud incense. Despite the absence of statistical significant difference, some frequency-based acoustic parameters increased following exposure to Oud incense smoke.

Incense use and cardiovascular mortality among Chinese in Singapore: the Singapore Chinese Health Study

BACKGROUND

Incense burning is common in many parts of the world. Although it is perceived that particulate matter from incense smoke is deleterious to health, there is no epidemiologic evidence linking domestic exposure to cardiovascular mortality.

OBJECTIVE

We examined the association between exposure to incense burning and cardiovascular mortality in the Singapore Chinese Health Study.

METHODS

We enrolled a total of 63,257 Singapore Chinese 45-74 years of age during 1993-1998. All participants were interviewed in person to collect information about lifestyle behaviors, including the practice of burning incense at home. We identified cardiovascular deaths via record linkage with the nationwide death registry through 31 December 2011.

RESULTS

In this cohort, 76.9% were current incense users, and most of the current users (89.9%) had burned incense daily for ≥ 20 years. Relative to noncurrent users, current users had a 12% higher risk of cardiovascular mortality [multivariable adjusted hazard ratio (HR) = 1.12; 95% CI: 1.04, 1.20]. The HR was 1.19 (95% CI: 1.03, 1.37) for mortality due to stroke and 1.10 (95% CI: 1.00, 1.21) for mortality due to coronary heart disease. The association between current incense use and cardiovascular mortality appeared to be limited to participants without a history of cardiovascular disease at baseline (HR = 1.16; 95% CI: 1.07, 1.26) but not linked to those with a history (HR = 1.00; 95% CI: 0.86, 1.17). In addition, the association was stronger in never-smokers (HR = 1.12; 95% CI: 1.02, 1.23) and former smokers (HR = 1.19; 95% CI: 1.00, 1.42) than in current smokers (HR = 1.05; 95% CI: 0.91, 1.22).

CONCLUSIONS

Long-term exposure to incense burning in the home environment was associated with an increased risk of cardiovascular mortality in the study population.

Domestic incense burning and nasopharyngeal carcinoma: a case-control study in Hong Kong Chinese

Incense burning is a powerful producer of carcinogens and has been considered as a risk factor for nasopharyngeal carcinoma (NPC). We conducted a case-control study and case-only analyses to investigate the effect of incense burning and its interaction with genetic background on NPC risk among Hong Kong Chinese. Between June 2010 and December 2012, we recruited 352 incident cases of NPC and 410 controls. We collected information on lifelong practice of domestic incense burning via interviews and genotyped 80 single nucleotide polymorphisms (SNPs) in DNA repair genes. We observed an increased NPC risk associated with daily burning in women [Adjusted OR = 2.49, 95% confidence interval (CI): 1.33, 4.66] but not in men. The adjusted OR for daily burning with poor ventilation was 2.08 (95% CI: 1.02, 4.24), while that with good ventilation was 1.35 (95% CI: 0.92, 1.98). Interactions between 2 SNPs (rs2074517 and rs4771436) and incense burning were significantly associated with NPC risk and tended to have a SNP exposure-response effect. Evidence for gene-environment interactions supported the knowledge that NPC is a multi-factorial disease resulting from the joint effects of environmental exposures and inherited susceptibility.

Long lived gamma emitting radionuclides in incense

A study of long-lived gamma emitters in incense was performed. The incense samples originated from seven different countries, and the investigated radionuclides were Ra, Ra, and K. Gamma spectroscopy revealed the presence of all three investigated radionuclides in all samples. Interestingly, the activity concentrations revealed a clear bimodal distribution that distinguished samples that were natural incense from others that were processed incense. The activity concentrations in the latter group were found to be one order of magnitude greater than in the former group. Consequently, the estimated annual effective dose from the latter group was one order of magnitude higher than that of the former group. Nonetheless, the doses from both groups were found to be some three orders of magnitude less than the average worldwide exposure to inhaled natural radionuclides. This finding suggests the radiological safety of incense for the investigated radionuclides.

Deaths and medical visits attributable to environmental pollution in the United Arab Emirates

Background

This study estimates the potential health gains achievable in the United Arab Emirates (UAE) with improved controls on environmental pollution. The UAE is an emerging economy in which population health risks have shifted rapidly from infectious diseases to chronic conditions observed in developed nations. The UAE government commissioned this work as part of an environmental health strategic planning project intended to address this shift in the nature of the country’s disease burden.

Methods and Findings

We assessed the burden of disease attributable to six environmental exposure routes outdoor air, indoor air, drinking water, coastal water, occupational environments, and climate change. For every exposure route, we integrated UAE environmental monitoring and public health data in a spatially resolved Monte Carlo simulation model to estimate the annual disease burden attributable to selected pollutants. The assessment included the entire UAE population (4.5 million for the year of analysis). The study found that outdoor air pollution was the leading contributor to mortality, with 651 attributable deaths (95% confidence interval [CI] 143–1,440), or 7.3% of all deaths. Indoor air pollution and occupational exposures were the second and third leading contributors to mortality, with 153 (95% CI 85–216) and 46 attributable deaths (95% CI 26–72), respectively. The leading contributor to health-care facility visits was drinking water pollution, to which 46,600 (95% CI 15,300–61,400) health-care facility visits were attributed (about 15% of the visits for all the diseases considered in this study). Major study limitations included (1) a lack of information needed to translate health-care facility visits to quality-adjusted-life-year estimates and (2) insufficient spatial coverage of environmental data.

Conclusions

Based on international comparisons, the UAE’s environmental disease burden is low for all factors except outdoor air pollution. From a public health perspective, reducing pollutant emissions to outdoor air should be a high priority for the UAE’s environmental agencies.

A case-referent study of lung cancer and incense smoke, smoking, and residential radon in Chinese men

BACKGROUND

Burning incense generates large amounts of air pollutants, many of which are confirmed or suspected human lung carcinogens.

OBJECTIVES

We conducted a population-based case-referent study to examine the effect of incense smoke exposure on lung cancer risk among Chinese males and explored the joint effect of cigarette smoking and exposure to residential radon.

METHODS

We recruited 1,208 male lung cancer incident cases and 1,069 community referents from 2004 to 2006 and estimated their lifetime exposures to incense smoke and other residential indoor air pollutants based on self-reported information collected during interviews. We performed unconditional multivariable logistic regression analysis to estimate the odds ratio (OR) for lung cancer associated with exposure to incense smoke after adjusting for possible confounders. We conducted stratified analyses by smoking status and exposures to incense burning and residential radon and explored the potential additive-scale interactions.

RESULTS

We observed an association between incense exposure and lung cancer that was limited primarily to smokers. Cigarette smoking and high cumulative incense exposure at home appeared to have a synergistic effect on lung cancer (compared with never-smokers who never used incense, the OR for lung cancer for smokers who used incense ≥ 60 day-years = 5.00; 95% confidence interval: 3.34, 7.51). Power was limited, but we also found preliminary evidence suggesting that radon exposure may increase risk among smokers using incense.

CONCLUSION

Our study suggests that exposure to incense smoke in the home may increase the risk of lung cancer among smokers and that exposure to radon may further increase risk.

Soot-driven reactive oxygen species formation from incense burning

This study investigated the effects of reactive oxygen species (ROS) generated as a function of the physicochemistry of incense particulate matter (IPM), diesel exhaust particles (DEP) and carbon black (CB). Microscopical and elemental analyses were used to determine particle morphology and inorganic compounds. ROS was determined using the reactive dye, Dichlorodihydrofluorescin (DCFH), and the Plasmid Scission Assay (PSA), which determine DNA damage. Two common types of soot were observed within IPM, including nano-soot and micro-soot, whereas DEP and CB mainly consisted of nano-soot. These PM were capable of causing oxidative stress in a dose-dependent manner, especially IPM and DEP. A dose of IPM (36.6-102.3μg/ml) was capable of causing 50% oxidative DNA damage. ROS formation was positively correlated to smaller nano-soot aggregates and bulk metallic compounds, particularly Cu. These observations have important implications for respiratory health given that inflammation has been recognised as an important factor in the development of lung injury/diseases by oxidative stress. This study supports the view that ROS formation by combustion-derived PM is related to PM physicochemistry, and also provides new data for IPM.

Lung cancer in Chinese women: evidence for an interaction between tobacco smoking and exposure to inhalants in the indoor environment

BACKGROUND

Epidemiologic data suggest that Chinese women have a high incidence of lung cancer in relation to their smoking prevalence. In addition to active tobacco smoke exposure, other sources of fumes and airborne particles in the indoor environment, such as cooking and burning of incense and mosquito coils, have been considered potential risk factors for lung cancer.

OBJECTIVES

We used a case-control study to explore effects of inhalants from combustion sources common in the domestic environment on lung cancer and their modification by active tobacco smoking.

METHODS

We analyzed 703 primary lung cancer cases and 1,578 controls. Data on demographic background and relevant exposures were obtained by face-to-face interviews in the hospital.

RESULTS

We observed a positive relationship with daily exposure to incense or mosquito coils and to cooking fumes only among smokers, and no association among lifetime nonsmokers. Interactions between smoking and frequency of cooking, or exposure to incense or mosquito coils were statistically significant and consistent with synergistic effects on lung cancer. The odds ratio (OR) comparing smokers without daily incense or mosquito coil exposure with nonsmokers without daily exposure was 2.80 [95% confidence interval (CI), 1.86-4.21], whereas the OR comparing smokers with daily exposure to the same referent group was 4.61 (95% CI, 3.41-6.24). In contrast, daily exposure to incense or mosquito coils was not associated with lung cancer among nonsmokers (OR = 0.91; 95% CI, 0.72-1.16). We observed the same pattern of associations for smokers without (OR = 2.31; 95% CI, 1.52-3.51) and with (OR = 4.50; 95% CI, 3.21-6.30) daily cooking exposure compared with nonsmokers, with no evidence of an association with daily cooking exposure among nonsmokers.

CONCLUSION

Our results suggest that active tobacco smoking not only is an important risk factor for development of lung cancer, but also may cause smokers to be more susceptible to the risk-enhancing effects of other inhalants.

Challenge assay: A functional biomarker for exposure-induced DNA repair deficiency and for risk of cancer

A variety of biomarkers have been used to monitor exposed populations to determine potential health hazards from their exposure to environmental toxic agents. However, the majority of these biomarkers have been focused onto the identification of biological damage from the exposure. Therefore, there is a need to develop functional biomarkers that can identify exposure-induced functional deficiencies. More importantly, these deficiencies should be positioned along pathways that are responsible for the development of specific diseases. One of such pathways belongs to the extensive and complex DNA-repair machinery. The machinery thus becomes a large target for damage from environmental toxic agents. The hypothesis is that damage to any component of a repair pathway will interfere with the pathway-specific repair activities. Therefore, when cells from exposed populations are challenged with a DNA-damaging agent in vitro, the in vivo exposure-induced repair deficiency will be dramatically amplified and the deficiency will be detectable in a challenge assay as increased chromosome aberrations, micronuclei or un-repaired DNA strand breaks. The challenge assay has been used in different laboratories to show that a variety of exposed populations (with exposure to air pollutants, arsenic, benzene, butadiene, cigarette smoke, incense smoke, lead, mercury, pesticides, uranium or xylene but not to low concentrations of air pollutants or butadiene) expressed abnormal challenge response. The predicted health consequences of some of these studies have also been validated. Therefore, the challenge assay is a useful functional biomarker for population studies. Details of the challenge assay and its application will be presented in this review.

Effects of incense smoke on human lymphocyte DNA

Incense burning is common in Southeast Asia, where it is a traditional and ceremonial practice in deity worship and paying respect to ancestors. However, incense emissions are an important source of indoor air pollution in Asia, and may induce health problems to those exposed. In this in vitro study the effects of incense emissions on human DNA were investigated using the comet assay. Particulates in smoke from six kinds of incense were trapped in saline or ethanol and human lymphocytes were exposed under controlled conditions. Results showed that DNA damage, including strand breaks, was induced by both aqueous and ethanolic extracts of two samples. The ethanolic extract of one sample induced DNA damage, while no significant DNA damage was found in the remaining three samples. The mechanisms underlying DNA damage induced by incense emissions were also investigated. Catalase (CAT), sodium azide, and superoxide dismutase (SOD) were co-incubated with extract, which exerted significant DNA damaging effects. Results showed that CAT with or without SOD diminished DNA damage, whereas sodium azide did not seem able to reduce DNA damage. Data indicate there are potential adverse health effects of such exposure, particularly for temple workers.