Pesticide Residue Laboratory Department of Entomology, Assam Agricultural University, Jorhat, 785 013.
Plant Protection Department, Tocklai Experimental Station Tea Research Association, Jorhat, 785 008, India
Online published on 3 November, 2011.
Dissipation of synthetic pyrethroid insecticide alphamethrin (1R cis, α S and as Cis, αR enantiomer pair of cypermethrin) residues in tea was studied under field conditions during November, 1991. Tea bushes (31 year old) of mixed clones were treated once with the insecticide at 26.5 and 53 g/ha rates as foliar sprays. Residues of alphamethrin persisted beyond two weeks in green tea shoots. The rate of dissipation of residues followed the first order kinetics with half-life values of 3.5 and 3.8 days for the two application rates, respectively. There was little degradation of these residues during manufacturing of tea as when CTC (curling, tearing and crushing) tea was manufactured on the same day of insecticidal treatment, the residues in the made tea ranged from 6.85 to 10.01 mg/kg. The half-life values in made tea were 3.7 and 3.9 days. About 1.4 to 4.1% of the residues in the made tea could be transferred into liquor when brewed in hot water. The potential daily intake of alphamethrin residues for an average Indian adult through consumption of this contaminated beverage was found to be about 8 μg which is below the acceptable daily intake of 2750 μg per person for cypermethrin.
Alphamethrin, residues, tea, daily intake
