Below are citations and abstracts to 5 published studies on the health impacts of smoke from mosquito coils. Entries are arranged by publication date.
1: Inhal Toxicol. 2009 Aug;21(10):837-48.
Particles emitted from indoor combustion sources: size distribution measurement and chemical analysis.
Roy AA, Baxla SP, Gupta T, Bandyopadhyaya R, Tripathi SN.
Department of Civil Engineering, Environmental Engineering Programme, Indian Institute of Technology Kanpur, Kanpur, India.
This study is primarily focused toward measuring the particle size distribution and chemical analysis of particulate matter that originates from combustion sources typically found in Indian urban homes. Four such sources were selected: cigarette, incense stick, mosquito coil, and dhoop, the latter being actually a thick form of incense stick. Altogether, seven of the most popular brands available in the Indian market were tested. Particle size distribution in the smoke was measured using a scanning mobility particle sizer, using both long and nano forms of differential mobility analyzer (DMA), with readings averaged from four to six runs. The measurable particle size range of the nano DMA was 4.6 nm to 157.8 nm, whereas that of the long DMA was 15.7 nm to 637.8 nm. Therefore, readings obtained from the long and the nano DMA were compared for different brands as well as for different sources. An overlap was seen in the readings in the common range of measurement. The lowest value of peak concentration was seen for one brand of incense stick (0.9 x 10(6) cm(-3)), whereas the highest (7.1 x 10(6) cm(-3)) was seen for the dhoop. Generally, these sources showed a peak between 140 and 170 nm; however, 2 incense stick brands showed peaks at 79 nm and 89 nm. The dhoop showed results much different from the rest of the sources, with a mode at around 240 nm. Chemical analysis in terms of three heavy metals (cadmium, zinc, and lead) was performed using graphite tube atomizer and flame-atomic absorption spectrophotometer. Calculations were made to assess the expected cancer and noncancer risks, using published toxicity potentials for these three heavy metals. Our calculations revealed that all the sources showed lead concentrations much below the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) level. One of the two mosquito coil brands (M(2)) showed cadmium concentrations two times higher than the California Environmental Protection Agency (Cal EPA) reference exposure level (REL). The latter also showed the highest carcinogenic risks of 350 people per million population. The amount of zinc obtained from the sources, however, was found to be quite below the standard limits, implying no risk in terms of zinc.
2: J Epidemiol. 2008;18(1):19-25.
Exposure to mosquito coil smoke may be a risk factor for lung cancer in Taiwan.
Chen SC, Wong RH, Shiu LJ, Chiou MC, Lee H.
Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan.
BACKGROUND: About 50% of lung cancer deaths in Taiwan are not related to cigarette smoking. Environmental exposure may play a role in lung cancer risk. Taiwanese households frequently burn mosquito coil at home to repel mosquitoes. The aim of this hospital-based case-control study was to determine whether exposure to mosquito coil smoke is a risk for lung cancer.
METHODS: Questionnaires were administered to 147 primary lung cancer patients and 400 potential controls to ascertain demographic data, occupation, lifestyle data, indoor environmental exposures (including habits of cigarette smoking, cooking methods, incense burning at home, and exposure to mosquito coil smoke ), as well as family history of cancer and detailed medical history.
RESULTS: Mosquito coil smoke exposure was more frequent in lung cancer patients than controls (38.1% vs.17.8%; p<0.01). Risk of lung cancer was significantly higher in frequent burners of mosquito coils (more than 3 times [days] per week) than nonburners (adjusted odds ratio = 3.78; 95% confidence interval: 1.55-6.90). Those who seldom burned mosquito coils (less than 3 times per week) also had a significantly higher risk of lung cancer (adjusted odds ratio = 2.67; 95% confidence interval: 1.60-4.50).
CONCLUSION: Exposure to mosquito coil smoke may be a risk factor for development of lung cancer.
3: J Appl Toxicol. 2006 May-Jun;26(3):279-92.
Mosquito coil smoke inhalation toxicity. Part II: subchronic nose-only inhalation study in eats.
Pauluhn J, Mohr U.
Institute of Toxicology, Bayer HealthCare, Wuppertal, Germany. juergen.pauluhn@bayerhealthcare.com
This paper addresses the results of a subchronic inhalation study in rats exposed to the smoke of burning mosquito coils manufactured in Indonesia. The objective of the study was a comparative assessment of different mosquito coils, including a blank coil, utilizing the OECD No. 413 testing paradigm, however, with the
focus on hazard identification at a single maximum tolerated exposure concentration rather than concentration-response. Groups of rats were nose-only exposed 6 h a day, 5 days a week for 13 weeks to an average particulate concentration of 30 mg m(-3) from either blank coils or coils that contain the insecticidal ingredient transfluthrin. Nose-only air-exposed rats served as a control. A range of markers of exposure have been characterized to define the most critical exposure metrics with regard to total suspended particulate matter (TSP) and potentially noxious volatile products of combustion. During the course of the exposure period the smoke-exposed rats showed clinical signs suggestive of acute upper respiratory tract sensory irritation. Body weights were mildly affected in the male rats, but food and water consumption were indistinguishable amongst the groups. Carboxyhemoglobin concentrations were approximately 11% throughout the exposure period in smoke exposed rats. Hematology, clinical pathology and urinalysis as well as the analysis of organ weights and histopathology of extrapulmonary organs and the lung did not reveal any evidence of adverse systemic or local effects, whereas in the anterior region of the nasal passages, and to some extent also in the larynx, irritant-related changes typical for water-soluble upper respiratory irritants were found. Markers of pulmonary inflammation or increased phagocytosis and lysosomal activity in bronchoalveolar lavage were indistinguishable amongst the groups. gamma-Glutamyltranspeptidase was significantly increased in the smoke exposure groups, which is taken as
indirect evidence of an adaptive upregulation of the pulmonary antioxidant glutathione. In rats exposed to mosquito coil smoke containing transfluthrin, a somewhat increased frequency of alveolar macrophages with foamy appearance was identified through cytodifferentiation but not histopathology compared with the blank coil. From the specific staining of intracellular phospholipids, the notion is supported that this equivocal finding is probably related to an increased uptake of modified pulmonary surfactant rather than increased engulfment of insoluble particulate matter since pigmentation or clustering or intra-alveolar cells did not occur. The results of this subchronic inhalation study support the conclusion that smoke from burning mosquito coils in concentrations high enough to elicit acute upper respiratory tract irritation due to the presence of common wood-combustion products (such as aliphatic aldehydes) did not cause any adverse
effect in the lower respiratory tract or any other extrapulmonary organ. The most critical mode of action is related to acute and readily perceivable sensory irritation. The concentration tested was estimated to be well above that occurring under more realistic exposure conditions. Therefore, overnight exposure to the smoke from burning mosquito coils (manufactured in Indonesia) is unlikely to be associated with any unreasonable health risk.
4: J Appl Toxicol. 2006 May-Jun;26(3):269-78.
Mosquito coil smoke inhalation toxicity. Part I: validation of test approach and acute inhalation toxicity.
Pauluhn J.
Institute of Toxicology, Bayer HealthCare, Wuppertal, Germany. juergen.pauluhn@bayerhealthcare.com
Burning mosquito coils indoors to repel mosquitoes is a common practice in many households in tropical countries. The evaluation and assessment of the inhalation toxicity of smoke emitted from mosquito coils appear to be particularly challenging due to the complex nature of this type of exposure atmosphere. The potential health implications of the gases, volatile agents and particulate matter emitted from burning coils or incense have frequently been addressed; however, state-of-the-art inhalation toxicity studies are scarce. The focus of this paper was comparatively to evaluate and assess the appropriateness and practical constraints of the whole-body versus the nose-only mode of exposure for inhalation toxicity studies with burning mosquito coils. With regard to the controlled exposure of laboratory animals to complex smoke atmospheres the nose-only mode of exposure had distinct advantages over the whole-body exposure,
which included a rapid attainment of the inhalation chamber steady state, minimization of particle coagulation and uncontrolled adsorption of condensate onto the chamber surfaces. While in whole-body chambers a different kinetic behaviour of volatile and particulate constituents was found which caused
inhomogeneous, i.e. artificially enriched atmospheres with volatile components at the expense of aerosols, the nose-only mode of exposure provided maximum exposure intensities without losses of the particulate phase of the exposure atmosphere. Collectively, the results obtained support the conclusion that the dynamic
nose-only mode of exposure is experimentally superior to the quasistatic whole-body exposure mode which provides the least control over exposure atmospheres and the outcome highly contingent on selected experimental factors. Acute inhalation toxicity studies in rats suggest that the most critical metrics of exposure are apparently related to (semi)volatile upper respiratory tract sensory irritants, whilst the asphyxic component, carbon monoxide, plays a role only at overtly irritant exposure levels. However, this study was conducted at exposure concentrations much higher than encountered by people in residential settings and the effects observed under these conditions may not be relevant to hazards from exposures at common use levels. Neither an acute 8 h exposure of rats nor the 1 h sensory irritation study in mice and rats provided experimental evidence that irritant particle-related effects had occurred in the lower respiratory tract. In summary, the protocols devised evaluate and assess the acute inhalation toxicity of mosquito coil smoke demonstrating that the nose-only mode of exposure of rats to the smoke of mosquito coils is suitable to assess the toxic potency of different coils. The nose-only mode has clear advantages over the whole-body exposure mode. The inhalation studies conducted show unequivocally that acute toxic effects are difficult to produce with this type of product even under rigorous testing conditions.
5: Environ Health Perspect. 2003 Sep;111(12):1454-60.
Mosquito coil emissions and health implications.
Liu W, Zhang J, Hashim JH, Jalaludin J, Hashim Z, Goldstein BD.
Joint Graduate Program in Exposure Measurement and Assessment, University of Medicine and Dentistry of New Jersey (UMDNJ) and Rutgers University, 170 Frelinghuysen Road, Piscataway, NJ 08854, USA.
Burning mosquito coils indoors generates smoke that can control mosquitoes effectively. This practice is currently used in numerous households in Asia, Africa, and South America. However, the smoke may contain pollutants of health concern. We conducted the present study to characterize the emissions from four common brands of mosquito coils from China and two common brands from Malaysia. We used mass balance equations to determine emission rates of fine particles (particulate matter < 2.5 microm in diameter; PM(2.5)), polycyclic aromatic hydrocarbons (PAHs), aldehydes, and ketones. Having applied these measured
emission rates to predict indoor concentrations under realistic room conditions, we found that pollutant concentrations resulting from burning mosquito coils could substantially exceed health-based air quality standards or guidelines. Under the same combustion conditions, the tested Malaysian mosquito coils generated more measured pollutants than did the tested Chinese mosquito coils. We also identified a large suite of volatile organic compounds, including carcinogens and suspected carcinogens, in the coil smoke. In a set of experiments conducted in a room, we examined the size distribution of particulate matter contained in the coil smoke and found that the particles were ultrafine and fine. The findings from the present study suggest that exposure to the smoke of mosquito coils similar to the tested ones can pose significant acute and chronic health risks. For example, burning one mosquito coil would release the same amount of PM(2.5) mass as burning 75-137 cigarettes. The emission of formaldehyde from burning one coil can be as high as that released from burning 51 cigarettes.
