The proposed ban on Coke and Pepsi by retail shops in Tamil Nadu started today. The state's traders are batting for local beverage brands, citing concerns about health. The traders and the Left organisations have been campaigning against the two beverage giants for nearly 30 years. Two years ago, a plot allotted for a bottling plant by Coca Cola in Erode district was even cancelled following a huge protest by farmers, who claimed that the plant would siphon off ground water.