Monocrotophos is a chemical that is banned in 46 countries and is easily available in India.
This chemical is so toxic that just a dose as light as the weight of 5 grains of rice can be fatal. But in Maharashtra's cotton belt, it is a popular pesticide. And many brands can be easily bought off the shelf.
Traces of this pesticide were found in the mid-day meal that killed 23 children in Chhapra, Bihar.
Although its use for edible crops is banned, in the Vidarbha region of Maharashtra, it is easily available and widely used in cash crops as well as edible varieties.
Dr Vijay Chandak, a wholesaler, says that monocrotophos is also used to keep "insects away from chillies, vegetables and even citrus fruits like sweet lime (mausmi)".
In 2009, the United Nations had urged India to consider a ban on monocrotophos. However, these warnings were just ignored.
In the heart of Lucknow, at many stores, pesticides containing small and large quantities of monocrotophos can be easily bought. A five litre bottle can cost Rs 2,700. A 100 millilitre bottle costs just Rs 65.
Shopkeepers say that during the mango harvest season in orchards in and around Lucknow, they sell thousands of litres of monocrotophos as it's a potent insecticide.
On the outskirts of Lucknow, in Mohanlalganj, paddy farmers these days are using butachlor, a type of herbicide.
We find some used cans of butachlor in the house of a farmer, Ram Krishna.
These may not be as lethal as monocrotophos, which killed the children in Bihar, but it still is a dangerous substance to have in the house, where Ram Krishna is raising three children.
Experts suggest that perhaps the best way to prevent poisoning is to force companies to take back used containers of these pesticides, which is the norm in most developed countries.
Krishnan Gopal, a health researcher with Toxics Watch, who recently visited the ground of this tragedy, Gandaman village in Chhapra says, "With pesticides, responsibility does not end with the seller and the buyer. The main responsibility for safe use of pesticides lies with the manufacturers who ideally should be taking back these used containers and government should make laws to make it legally binding."
But as long as these pesticides continue to be openly sold, and the reuse of their containers remains a common domestic practice, they will always pose a serious threat to rural households across the country.