It wouldn’t be an Aussie summer without the persistent buzz of the pesky mozzie, but are the mosquito coils we use to fend them off actually working? And do they present an even bigger health risk than being bitten?
Mozzie coils and sticks were traditionally made from pyrethrum paste, a natural extract from the pyrethrum daisy, which is a fast-acting knockdown insecticide.
Today, our mosquito coils typically contain pyrethroid insecticides, which are synthetic (man-made) versions of the natural plant extract, or plant-derived substances such as citronella.
While today’s mosquito coils are cheap, portable and generally effective at reducing mosquito bites, they may not actually reduce the risks of mosquito-borne diseases such as malaria, Dengue fever and Ross River virus disease.
Cameron Webb, a clinical lecture from the University of Sydney, explained in a piece for The Conversation that “mosquito coils work in one of two ways. Those that contain insecticides will kill (or at least “knock down”) mosquitoes while those that contain aromatic substances (such as citronella) will repel mosquitoes or inhibit the likelihood they’ll bite.”
The problem, he wrote, is less nuisance-biting by mosquitoes is good, “but when there is a risk of disease, you need to stop all mosquito bites.”
And that risk of disease is on the rise, with Australia having seen record-breaking epidemics of both Ross River virus disease and Dengue in recent years.
Malaria remains a big problem as well. The World Health Organisation’s World Malaria Report 2017 indicated that progress in the success of global malaria control had stalled. In 2016, there were an estimated 216 million cases of malaria worldwide, with some 445,000 deaths.
While the vast majority of malaria-related deaths happened outside Australia, the risk of mosquito-borne diseases here cannot be underestimated.
Webb noted that “a review of 15 previously published studies showed there’s no evidence burning insecticide-containing mosquito coils prevented malaria. Similar studies indicate there’s no strong evidence that routine burning of mosquito coils prevents Dengue risk either.
The other growing concern with mosquito coils, Webb said, was about the potential health risks posed by their burnt remains.
He cited a study that estimated “the particulate matter produced from burning one mosquito coil was equivalent to burning 75-137 cigarettes.”
“This amount of exposure poses a health risk but there is a lack of clear evidence that the long-term exposure to mosquito coil smoke increases the risk of more serious health impacts, such as lung cancer,” Webb wrote.
“In the face of this uncertainty, the key message should be to avoid prolonged exposure, especially in enclosed spaces.”
So should we use mozzie coils or not?
Webb concluded that while there is evidence to suggest that burning a mosquito coil will assist in reducing mosquito bites, they “should be used judiciously,” adding that “ssing them in combination with topical insect repellents probably provides the best protection.”