Fogging is ineffective in controlling dengue, says CSE

Fogging knocks down only adult mosquitoes and not the larvae.— File Photo  

The fogging drive carried out by the Delhi Government is ineffective against mosquitoes which are responsible for causing the dengue outbreak, according to the Centre for Science and Environment (CSE).

Fogging is one of the solutions offered by the Delhi health department to control the spread of dengue in the city.

As on October 17, the city has reported over 12,531 dengue cases and 32 deaths. The rise in cases from 778 in August to 6,775 in September and 4,925 by mid-October alone indicates the negligible effect of fogging.

“Working with the community members and as per our observations and experiences we have found that fogging is ineffective in containing dengue and has a harmful effect on the health of people,” said Chandra Bhushan, deputy director general, CSE.

According to the CSE, fogging knocks down only the adult mosquito, and not the larvae that are the source of breeding. Larvicide measures, 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.

“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. Pre-conditions 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/owners in allowing fogging into their premise. Besides the limitation of resources, there are practical limitations in covering all houses/premises across the city,” said a release issued by the green non-government organisation.

The frequency of fogging is another determinant. It is recommended to be repeated after 3-4 days which is far from the reality across the city.

“Unless repeated frequently, fogging cannot control the next batch of adults out of the larvae. This is why, source control through larvicide measures is considered effective,” said Amit Khurana, head of Food Safety and Toxins Programme at CSE.

The release also noted that fogging mix usually contains huge amounts of diesel to the tune of 95 per cent along with an insecticide, mostly Malathion. At times, petrol is also added.

“This means a vehicle-mounted container typically has 95 litres of diesel (is known to contain carcinogens) 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,” said Mr. Bhushan.

Meanwhile, the municipal corporations of south and east Delhi have already spent about Rs.70 lakh on diesel for fogging till Oct 10, 2015.

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. Keeping a 100-day fogging-intensive season, this is about 4,500 litres of diesel per day, which is equivalent to diesel used by over 2,000 cars in a day.

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

The fogging mix usually contains huge amounts of diesel to the tune of 95 per cent along with an insecticide, mostly Malathion. At times, petrol is also added