Limestone choona - the primary source of choona (calcium carbonate) other than mining (limestone) is from marine organisms, i.e. sea shells or kakka . These living shells or marine animals are collected mainly by women from sea shores and backwaters of Kerala. The collection of kakka is a common occupation in the coastal belt of the Arabian Sea covering places like Kollam, Alappuzha and Ernakulam districts. The flesh of the live creatures inside the shells is scooped out and sold for a good price in the meat market, whereas the shells are sold to the choona factories in the region which pick up huge quantities. At these factories the shells are mixed with charcoal and baked in a kiln. The foul smell during baking is because the shells have a thin membrane-like coating. Twenty-four hours later the shells are transformed into ithil – the local name for choona or calcium hydroxide. Choona is mainly utilised as edible lime, an ingredient used in paan, as an insecticide (particularly on tea estates), for whitewashing walls and as a cleaning agent in waste water treatment systems. The lime produced here is used to spread on agricultural fields.