Travelers seem to fall into two camps on this issue. Some worry about it and try to avoid the mosquito coil smoke; others dismiss the health concern, considering the smoky coils a prudent precaution to thwart insects and the serious diseases they may harbor, most notably, dengue fever and malaria.
According to a study by UC Riverside scientists, many mosquito coils – most notably those manufactured in Asia – often contain up to one percent BCME (which stands for bis[cloromethyl]ether, a chemical associated with the breakdown of S-2). BCME has been described as “the most potent lung cancer chemical ever discovered.” And lung cancer is just about the most deadly cancer known. In one Chinese factory where mosquito coils were manufactured, a large fraction of employees were dead within five years of starting their jobs. The cause? Lung cancer.
By contrast, no study of cigarettes has ever found tobacco smoke to pose any where near such a high risk. Put it this way: there is no comparison between cigarettes and mosquito coils. Another study -- one that only considered the amount of "small particulate matter" present in mosquito coil smoke (it did not investigate BCME question) -- found the coils to be about 100 times more hazardous to human health than tobacco smoke.
It is illegal to sell mosquito coils in the United States that contain BCME. Nevertheless, Chinese-made mosquito coils that contain BCME have penetrated the US market in recent years.
What to do about the risks associated with mosquito bites; the very real threat of contracting insect-born diseases like dengue and malaria? Mosquito bites can and should be prevented by each individual taking some basic personal precautions:
- In the evenings or wherever mosquitoes are prevalent during the day, keep your body covered in light-colored clothing and spray insect repellent onto exposed extremities.
- At night either sleep under a mosquito net, stay in room with well sealed mosquito screens, or sleep in an air-conditioned room.
- Remember: malaria-bearing mosquitoes strike in the evening and at night. Dengue-carrying mosquitoes can strike at any time.
In many situations, it seems likely that the reality of mosquito-borne diseases (Mulla et al. 2001) may dominate determination of hypothetical risk:benefit ratios for mosquito insecticides delivered using devices such as coils. However, if BCME were an important environmental contaminant resulting from burning mosquito coils containing S-2, it would be impossible to maintain use given the well-established carcinogenicity of BCME in humans.Translation: the risks associated with BCME are so incredibly high that even the contribution mosquito coils make towards stemming the world’s worst tropical diseases would not seem to outweigh the hazard.
My conclusion: Mosquito coil smoke is highly toxic to humans and should be avoided.