Field evaluation of biodegradable controlled release formulation of fenthion against Mansonia mosquitos.

Controlled release monolithic formulation of fenthion, an organophosphorus mosquito larvicide, prepared by the physical entrapment of the active agent into biodegradable polymer matrices was evaluated against Mansonia mosquito larvae breeding in hydrophytes infested coconut husk retting ponds. Field evaluation was carried out at two application rates viz, 2.5 and 1.0 ppm. Absolute control of larval breeding was observed for 25 and 17 weeks and over 50% reduction in breeding density was observed for another 3 and 2 weeks for the respective application rates of 2.5 and 1.0 ppm. The bioassay carried out with the water samples collected from the ponds treated at 2.5 ppm against the fourth instar larvae of Mansonia annulifera showed larval mortality of more than 95% for 14 weeks and 80-95% from 15 to 25th week. The concentration of fenthion in the treated ponds was found to vary between 0.006 and 0.095 ppm during the evaluation period.

N-nitrosamines in Indian beers.

Presence of volatile N-nitrosamines in beer and other alcoholic drinks are well documented in developed countries. Analysis of 120 beer samples of various brands/batches showed positivity for N-nitrosodimethylamine (NDMA) in more than 100 samples. The overall mean of 3.6 ppb of NDMA is higher than those currently found in Western countries. Since N-nitrosamines are proven carcinogens in animals at several sites it is necessary to keep their levels of exposure to as low as possible.

A case control study of selenium in cancer.

As selenium has been shown to be a risk modifier of cancer at several sites in a case-control approach, selenium nutriture was studied in oral and oesophageal cancer patients. The mean selenium level in oral cancer patients was 102.6 ng/ml and in oesophageal cancer 103.3 ng/ml, while in the matched controls it was 117.5 and 116.2 ng/ml respectively. Relative risk estimates were 3.16 (P < 0.02) and 16.0 (P < 0.01) in oral and oesophageal cancer patients respectively. The risk appears to increase with selenium levels lower than 115 ng/ml.

Development of environmentally compatible controlled release formulations of a mosquito larvicide.

A new controlled release system of a mosquito larvicide, fenthion has been developed by the chemical modification of sodium carboxymethylcellulose into a hydrophobic gel of copper carboxymethylcellulose. Four formulations having a slab geometry were developed with two concentrations of the larvicide and two extents of cross-linking. The release profile of the larvicide from the formulations was studied under laboratory conditions. The formulation with a cross-linking period for 48 h and a 20 per cent larvicide concentration with respect to the dry weight of the formulation has been found to be stable with a sustained release of the active ingredient for a period of 25 wk. The release profile of the formulation followed zero order release kinetics after three weeks in water. The concentration of fenthion ranged between 0.07 and 0.21 mg/l at the application rate of one slab per five litres of water with an average release rate of 6.38 mg/wk during the period of study.

Development & evaluation of controlled release formulations of DEPA, an insect repellent.

Three controlled release formulations of the insect repellent DEPA (N, N-Diethyl phenylacetamide), Depa-A, Depa-B and Depa-C have been developed and tested on human subjects against Aedes aegypti adult mosquitoes for repellency and the results were compared to those of a solution of DEPA (Depa-0). The increase in the protection time of the formulations, as compared to Depa-0 was compared. Depa-B was found to be effective with a protection time of 7.13 and 6.15 h and percentage increase in protection time of 44.5 and 38.2 at the two application rates of 0.5 and 0.25 mg/cm2 of the repellent. This observation agreed with the studies carried out on the evaporation of the repellent formulations on two models, on adsorbing and nonadsorbing surfaces for the relative adsorption and evaporation by analysing the repellent concentrations, using an infrared spectrophotometer.