Widespread fogging may do more harm than good
With mosquito-borne diseases such as dengue and Zika on the rise, the control of the mosquito population is more than ever the responsibility of every Singaporean resident. In this regard, I agree with the call for heftier penalties for those who fail to fulfil their part in the fight against such diseases (“Impose more severe penalties for those found to be breeding mosquitoes”; Sept 2).
But I strongly disagree with the call for more intensified open-air fogging on many grounds (“Intensify fogging to cover whole of affected areas”; Sept 1).
Over the years, the National Environment Agency (NEA) has gradually moved away from large-scale open-area fogging and there are many arguments that support such decisions.
First, fogging is only moderately effective in the control of the mosquito population. For each adult mosquito killed, many more larvae in the water remain unaffected. Reducing the number of larvae is a more effective measure, which means that oiling achieves better results than fogging.
Second, the pesticides used in vector control are neurotoxins and have been linked to adverse effects in humans. Many of these chemicals were originally designed as nerve gasses in chemical warfare; however, much lower levels of the chemicals are used in pesticides.
Exposure to neurotoxins, even in low quantities, is also associated with numbness of the lips and tongue, nausea, headaches and respiratory problems. For these reasons, many countries have banned open-air fogging completely.
Third, fogging is also toxic to other insects, such as butterflies and bees. The National Parks Board is planting more plants that host butterflies in an attempt to increase their population numbers, and these beautiful insects are particularly sensitive to pesticides. When bee populations are greatly affected by pesticidies, global food production could be affected because of the lack of pollination.
Pesticides are also harmful to many other animals, including those that are natural predators of mosquitoes. Most pesticides used in fogging are toxic to fish, which are very important for the eradication of mosquito larvae. Frogs, geckos and birds, which also eat mosquitoes, could also be affected by pesticides.
In fact, according to the European Union classification system, most of the chemicals used in pest control are classified as “Harmful (Xn)” and “Dangerous for the environment (N)”.
Taken together, oiling and the eradication of breeding grounds in personal living spaces are much more effective tools in the fight against dengue and Zika than widespread fogging is.
The responsibility for eliminating breeding grounds in one’s own home and garden, while reporting possible breeding sites in public spaces to the relevant authorities, lies with everybody. We all need to play our part to keep the diseases at bay.