The results of the survey have been reported in a paper in the latest - February 10- issue of 'Current Science,' the journal of the Indian Academy of Sciences, headquartered in Bangalore, by Mr. V.P. Sharma of the Delhi-based research centre which is a part of the Indian Council of Medical Research (ICMR).

According to the author, the Indian market for various mosquito repellents - coils, mats, lotions and vaporizers - is Rs. 500-600 crores, growing annually at 7 to 10 percent. Almost all of them use synthetic pyrethroids, that is, the allethrin group of compounds or diethyl toluimide (DEET).

The MRC survey carried out by their own personnel, covered both users and medical practitioners in urban and rural areas. Results have revealed that 11.8 per cent of the users of synthetic pyrethroids, across all age groups and both sexes, "complained of a variety of acute toxicity effects either soon after or within a few hours of use of repellents." The most common compliant was breathing problem, followed by eye irritation, often accompanied by bronchial irritation, headache or skin reaction. In 2 cases, persons who did not earlier suffer from asthma, became asthmatic.

Of those using DEET-based cream, 11.4 percent reported skin reaction and itching. Of the 286 doctors covered in the survey, 165 or 57.6 per cent reported acute toxicity following use of repellents. The paper also cites a 1998 report of the Indian Toxicological Research Centre, Lucknow, where serious health consequences of the use of repellents were recorded.

Even those who do not immediately feel any adverse effects may be in long term danger: Mr. Sharma said "although symptoms disappear shortly after withdrawal, those who do not suffer acute toxicity and continue to use these repellents for extended periods may suffer neurotoxic and immunotoxic hazards."

He suggests mosquito nets as safe alternatives or a "neem cream" made up of 5 parts neem oil and 95 parts coconut or mustard oil. Burning neem oil in kerosene is also a safe alternative, he states.

Meanwhile, the Kochi Corporation in Kerala, an area where mosquito is an endemic scourge, has - under directions from the Kerala High Court - recently tried out a novel and cost-effective method of reducing the mosquito population at the larvae stage itself. It has conducted experiments suggested by the retired National Institute of Oceanography (NIO) scientist, Dr. U.K. Gopalan where the salinity of water in canals and stagnant pools - major breeding grounds for the mosquito - is increased by adding sea-water.

The Corporation, in an affidavit submitted last week, has told the High Court that the experiment conducted according to Dr. Gopalan's method was successful and mosquito larvae were found morbid in the canal portions where salinity was increased.

Speaking to this correspondent, the Kochi based Dr. Gopalan said he had confirmed by a series of experiments extending over years, that when the salinity level reaches 30 parts per thousand or PPT (the normal percentage of salt in the sea), mosquito larvae cannot survive beyond 3 hours. Even at lower concentrations of 15 PPT, they are dead in 12 hours. And when the concentration is upped to 60 PPT, the larvae perish within the hour. It was mainly a report in "The Hindu" describing Dr. Gopalan's earlier work that caught the High Court's attention and led to its directions to the civic body, Dr. Gopalan added. It is estimated that the daily sale of mosquito repellents in Kochi alone exceed Rs. 3 lakhs.