'Fogging harms health, spares larvae'

CSE study says it kills only adult mosquitoes, puts children and elderly at risk

A new study by Centre for Science and Environment says fogging has no impact on mosquito larvae. Instead, it has a harmful effect, especially on children, the elderly and those with respiratory problems.

The mist, which is 95 per cent diesel, is equated with measures taken by Delhi’s civic agencies to fight dengue. But it knocks down only the adult mosquito, and not the larvae that are the source of breeding.

Larvicides, on the other hand, are recognised as an important intervention to prevent large-scale spread of dengue. Targeting adult mosquitoes offers temporary control and that too in limited settings and under ideal conditions, say the experts.

“We looked into the issue when community members approached us and shared their observations and experiences. We found that fogging is ineffective in containing dengue and has a harmful effect on the health of people,” said Chandra Bhushan, Deputy Director General, Centre for Science and Environment (CSE).

For example, in the case of outdoor fogging the mist most often does not attain the required concentration and reach in order to be effective. Preconditions like wind speed and direction as well as air temperature influence the concentration. Indoor fogging, on the other hand, is a challenge due to reluctance of residents to allow it, he said.

The World Health Organisation guidelines on dengue too question the role of fogging. They recognise that fogging has been used by Southeast Asian countries for the past 25 years, but it has not been effective.

Even experts at municipal corporations of Delhi feel that fogging is more about assuring people that some action is being taken.

Health impact
The fogging mix usually contains diesel to the tune of 95 per cent along with an insecticide, mostly malathion.

“This means a vehicle-mounted container typically has 95 liters of diesel which is used up in one round of fogging. Several rounds by the vehicle in a day could mean several hundred litres of diesel per vehicle,” the study said.

Diesel is known to contain carcinogens. Malathion, a class III pesticide is also classified as “slightly hazardous” by  WHO.

Medical experts suggest that direct inhalation of diesel fumes, combined with insecticides, can exacerbate asthma or bronchitis among those with respiratory ailments.

Pregnant women, small children and old people are most susceptible to aggravation. Eye specialists say diesel fumes can cause irritation and itching of skin and eyes. A prolonged exposure could lead to temporary swelling of the cornea.

“Once sprayed, this concoction is not only inhaled but is also absorbed in soil and water. In case of fogging the entire emissions take place in very short time in a particular area,” the study said.

The municipal corporations of south and east Delhi have already spent about Rs 70 lakh on diesel for fogging till Oct 10. 

“Considering the total area of Delhi, the remaining days of the fogging season and the price of diesel, the estimated total diesel use could go over 4.5 lakh litres this year,” Bhushan said.

While it is only the civic agencies which fumigate colonies, this year saw an unusual competition between the political parties. They bought private machines for their respective strongholds, adding to the release of chemicals in air.

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