The US-EPA regulates mosquito coils sold in the US and does not approve coils that contain a chemical called “S2” (octachlorodipropyl ether) that acts as a pyrethroid synerist in mosquito coils. S2 is not allowed in the US but is used as an ingredient in some mosquito coil products manufactured and sold in Asia. S2 can produce a degredation product (BCME) which is carcinogenic and can cause lung cancer. Studies* have found higher incidence of unusual lung cancers in workers involved in manufacture of mosquito coils. Although sales of products containing S2 are not permitted in the US, some of the products containing S2 may be obtained through online sales or other means. These products are still marketed in other countries with less strict rules than the US. It is best practice to limit exposure to such products. For mosquito deterrence, a repellent applied to the skin can be a safer alternative to chemicals that might be inhaled.
*JIE ZHANG, HUI‐WEI QI, YU‐PING SUN, HUI‐KANG XIE and CAI‐CUN ZHOU. 2015. Mosquito coil exposure associated with small cell lung cancer: A report of three cases. Oncology Letters.