Fogging: Adding to the pollution or a necessary evil?

At a time when we know the PM2.5 in the air is getting worse, it seems there is one more thing that we need to worry about. Of course we know there  are other pollutants in the air - and the Diwali firecrackers are going to make all of this multiplier times worse! But there is one aerosol that we are also injecting into the air, one that we probably need to, to protect ourselves from mosquito-borne diseases like chikanguniya and dengue. Here is one of CFA's founding members' thoughtful viewpoint on fogging. Reprinted by permission by the author.



The billowing white smoke brings relief. It shows we are on the offensive against the dreaded mosquito-borne viral menaces. But should we be a tad bit worried too? This opaque, odorless cloud is not a result of Mother Nature. How many times have you instinctively held your breath as you walked through it? I know I do every time I encounter anti-mosquito fogging. I don’t walk, I rush through it wondering how many more steps to go before I clear the cloud. It is a test of my lung capacity, how long can I hold my breath before the next inhale and exhale?
The clouds from fogging machines are pervasive in New Delhi right now. And rightly so. With cases of chikungunya and dengue skyrocketing – at epidemic proportions this year, we should be happy to see government agencies and neighborhoods taking such a proactive role to reduce mosquito populations.
This misty fog means death to all mosquitos right? Yet I can’t help but worry whatever is in a fog that can kill mosquitos en masse, can’t be good for me, right? And that is the thing with fogging.
What is in it? Will it harm me, my children? And really, how effective is it in killing mosquitos?

Well, experts agree the answers are complex sometimes leading to more questions and unease. First off, it’s fair to say fogging is very, very widely used around the world in developed and developing countries to help combat mosquito populations. But fogging is one step of many that should be taken. The World Health Organization (WHO) recommends an integrated approach to mosquito control to tackle all life stages of the mosquito. Fogging only targets one stage. It paralyzes and kills, sometimes but not always, adult mosquitos. Yet perhaps the biggest advantage of fogging is one of public relations.

Mosquito fogging provides the most visible and ongoing evidence of that a government or community is taking action against the problem. The effectiveness of fogging, though, is limited and short term.

I took a deeper look at mosquito fogging, it’s effectiveness and impact on our health. Here’s what I discovered.

5 Questions Answered on Mosquito Control:
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1. Why isn’t fogging the silver bullet, the best way to tackle mosquitos?

First let’s consider the innovative, adaptive and opportunistic animal at the root of mosquito-borne disease:

The Aedes aegypti mosquito has a complex life cycle. They are container breeders and make full use of the urban setting to breed. Female mosquitos lay their eggs on the wet walls of containers, small or large, with even miniscule amounts of water. Discarded bottle caps, your pet’s water bowl, clogged rain gutters, used tires, discarded rubbish, toilet tanks are all breeding venues for this insect. The eggs can survive for a long time in a dry state, even up to a year!

Once they submerge in water, they hatch and over a very short period of time emerge as a newly formed and biting adult. Then 8-10 days later they are dead. But not before the female mosquitos have dined on human blood, her preferred meal, and produced eggs. Up to 100-200 eggs are produced after every blood meal! She can produce as many as 5 mega batches of eggs that she lays at different locations, smartly ensuring some will survive.

The problem with fogging is it only targets adult mosquitos, not the eggs or larvae. Also, consider the timing and location of fogging. If done midday, it will be less effective than being done at dawn and dusk. Fogging also will not reach the many, many indoor mosquitos who have made their way into our homes, creating whole reproductive ecosystems right under our nose!

2. What’s in the fog?

There is no one easy answer to this. There are many chemical options used in mosquito fogging. At least 10 different chemicals are widely used such as permethrin also known as pyrethroid, piperonyl butoxide (PBO), S-Bioalletrin, melathion, fenthion, BTI, and the banned abroad but widely used in Asia and Africa – DDT, which accumulates and remains in our bodies over years and is very harmful. To make it more complex, the chemicals used in fogging aren’t effective on mosquitos beyond the immediate dispersal. And skilled evolutionary warriors, mosquitos quickly develop resistance to the chemicals used requiring new pesticide variations to be effective!

3. Will fogging harm me, my children, my pets?

Pediatricians and public health agencies say mosquito fogging is safe for human exposure. That said in a contradictory turn, most also advise avoiding exposure all together, remaining inside when fogging occurs with windows and doors closed. Local Delhi pediatricians report increased cases of asthma, allergic reactions, and upper respiratory issues, especially in those more sensitive and prone to respiratory difficulties.

4. What else can be done? How do we get rid of mosquitos?

WHO stresses the urgency in eliminating mosquito breeding sites - that means small and large containers and areas where water collects. As an emergency measure only, fogging is best timed at dawn and dusk when mosquito activity is most intense. Some countries are introducing biological methods to control mosquitos such as mosquito larvae-devouring fish into water sources.

5. What can we do at home?

Prevent and protect! For years, we have slept under mosquito nets. My children love it, comparing their beds to mini forts. If you do not have screens on your window’s consider having them made to allow air circulation without letting these flying predators in. Wear lightweight long sleeve shirts and trousers and use natural anti-mosquito creams. Lastly, be vigilant about your garden, barsati, driveway and colony gardens to ensure these do not have breeding opportunities with standing water containers.

Considering worldwide cases of dengue alone have risen 30-fold compared to 50 years ago, this problem is not going away anytime soon. So be informed and be proactive. If you live in an area that fogs, protect yourself and your family by finding out when community fogging takes place and stay inside with the windows shut during this time. If possible, remain indoors for about 12 hours, possible only when evening fogging takes place perhaps, but at the very least for several hours.

Tina Chadha 
Tina is a founding member of Care For Air. In 2009, she relocated to New Delhi, India. Within her own family, she has felt the impact of India’s air pollution problem. She believes the air we breathe is the ultimate democratizer and that clean air must be accessible to all.

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