Lethal gambit

WITH the ministry of health and familywelfare ready to launch a major offensive against malaria from June 1, thecountry is in for another dose of one ofthe most toxic chemicals known tohumans: dichlorodiphenyl trichloroethane (DDT). Health minister SaleemSherwani recently announced the setting up of a special committee to monitor measures to eradicate malaria.

Despite the ban on use of benzenehexachloride (BHC) in agriculture andfor vector control, the use of chemicalslike DDT is still widely prevalent in public health services. According to an estimate, about 10,000 metric tonnes Of DDTis produced annually in India for vectorcontrol. Before the ban, DDT and BHCrepresented 70 per cent of the totalpesticides consumed in the country.Of this, 80 per cent of the DDT and 40per cent of the BHC was used to control breeding of mosquitoes underthe National Malaria EradicationProgramme (NMEP). BHC was onlyrecently withdrawn from use.

The World Health Organization(WHO) has termed DDT as a Class moderately hazardous pesticide'.According to Health Hazards ofPesticides and its Management, aVoluntary Health Association ofIndia (VHAI) publication, the possibleeffects of DDT include cancer, ill-effectson reproductive health and liver damage. It has also been proved that DDT isnon-biodegradable, is passed on throughthe food chain, and accumulates in bodyfat. In fact, DDT has been found in significant and sometimes dangerous levels in mother's milk. Contact with clothesmade from plant fibres containingresidues of DDT can also introduce thechemical into the body. During theSomoza regime in Nicaragua, heavyapplications of DDT on cotton resultedin contamination of human breast milk:in urban areas, the chemical was foundin mothers' milk at levels 42-45 timesabove the WHO's 'safe' level.

Yet DDT continues to be used indiscriminately in India. Says SanjoySengupta of the VHAI, "DDT enters thefood chain through air, soil and water.We should discourage the use of suchchemicals."

Anomalies are rampant even in theagricultural sector. It is alleged that inspite of the ban on Use of DDT in agriculture, it is still being used by farmers since it is easily available in the market.As Sengupta points out, "Laying down alaw does not automatically restrict useof a toxic pesticide.'

Insecticides and chemical larvicideswith a long life have been the mainstayof the malaria control programme. DDT,BHC and malathion are the main pesticides used under the NMEP. Syntheticpyrethroids like allethrin and lambdacyhalothrin, not considered as harmfulas organochlorides, have also been usedin vector control. But tests have shownthat even synthetic pyrethroids havesome toxic effects on aquatic life. Safe,traditional and alternative methods tocurb malaria have been given the go-by.

Before DDT arrived on the scene,people across the world used variousmethods to curb malaria includingdraining swamps, covering pools ofstanding water with oil and installationof screens in residences. These techniques were highly effective, reducingmortality due to malaria substantially.

Alternative methods include use ofpotent larvicidal agents and fish thatcontrol the breeding of mosquitoes. Forexample, strains of Bacillus sphaericusremain toxic for mosquito larvae for sixto nine months and have a lethality of 90per cent, according to researchers inThailand. In Pondicherry, India, speciesof fish such as Gambusia affinis andAplocheilus blochii have been foundto reduce breeding of anophelesmosquitoes in wells from 32.8 percent to one per cent in a month.

In view of the well-known advantages of biological control methods,Sengupta avers that it is better to goin for "a proper mix of environmental management and the use of biological pesticides". But with the government loath to do away with DDT, achemical banned as far back 1972 inthe us, the killer pesticide continuesto stalk urban and rural India.