Thirty years later, many still bear the scars - they include children with birth and congenital defects and others whose lives have been blighted by chronic illness.
Nazes Afroz travels to Bhopal to meet children born to parents who were exposed to the gas on 3 December 1984 or who were born in the aftermath of the leak.
Aseem Ansari, 15, was born with acute deformities of his facial bones and suffers from chronic weakness, fatigue and frequent nose bleeds. Mother Hanifa Bee has been taking him to hospitals and clinics ever since he was born. He has dropped out of school and works in a furniture factory to help his family financially. He knows little about the gas leak that affected his parents when they were in their youth.
Swati Mishra, 17, was born with partial paralysis of the left side of her body. She suffers from acute weakness and has been visiting hospitals and doctors all her life. Her father was a young boy at the time of the leak but she knows little about the accident. Swati is studying computer administration at a local college and her aim is to find work either at a bank or the railways so she can support her father who has very little income.
Twenty-one-year-old Sheraz Raeen, who was born with severe brain damage, needs constant care. He cannot speak or look after himself. His family sends him to a day-care centre set up by one of the local groups demanding rights for the gas victims. From the time of his birth, his family has been paying for his medical treatment at government hospitals as well as private clinics. Sheraz's full time carer, his mother Firoza Bee, asks: "When will he be categorised as a victim of the gas leak and when will he be paid compensation and get proper medical care?"
Sheraz's younger sister, 17-year-old Gulnar Raeen, was born with a minor defect in her right leg. She also has chronic weakness and breathing difficulties. A school dropout, Gulnar has a vague knowledge of the disaster. She only knows that her parents were affected by a gas leak from the Union Carbide factory.
Both of Faizan Shaikh's parents were affected by the gas leak and he was born with severe problems in his right eye and has been treated for it since his birth. Although the 15-year-old looks healthy, he gets out of breath easily and can't do much physical work. He has dropped out of school and now works as an assistant in a photography studio.
Shaima Shaikh, 15, was born with a minor birth defect in one of her feet. She suffers from chronic fatigue and has frequent headaches and blackouts. Her mother has also suffered acutely from being exposed to the gas since a young age. Shaima has little information about the accident and whatever little she knows, she has heard it from her family.
Asif Shaikh, 29, was born four months after the disaster. His mother, who lived in a slum just a stone's throw away from the factory, was in the final stages of pregnancy when the leak occurred. Mr Shaikh suffers from chronic weakness and has eye and breathing troubles. He can't do much physical labour and hence assists in the family-run flour mill.
Chetna Koli, 21, has heard about the thousands killed and maimed in her slum from her parents who were also victims of the leak. She has also seen photos and films made about the accident. She has chronic eye irritation and suffers from breathlessness. Her 15-year-old brother was born with a tumour on his back and had to undergo surgery three days after birth. After school, she joined a course to be a lab technician and wants a job in a hospital or a clinic so that she can support her father, another gas victim who has a meagre income.
Gas Mohammad was so named because he was born on the morning of 3 December 1984, just hours after the leak. An unusually quiet man, he doesn't communicate much and suffers from severe weakness and breathlessness. Due to poor health, he cannot do work involving manual labour. So, he does odd jobs when he finds them. His aunt, who lives with his family, gave birth to a child exactly a year after the accident but the baby died minutes after he was born.
Gas Mian was also born just hours after the leak killed and maimed tens of thousands of people in his neighbourhood. "Do I look like a 30-year-old man? I look much older. This accident blighted my life," he says when asked about the incident. His seven-year-old son Faran was born with a defective foot. The Mian family still carries the legacy of the accident that ruined the lives of thousands of poor slum dwellers like him.
A poisonous gas leak from the Union Carbide Corporation plant in the central Indian city of Bhopal 30 years ago killed several thousand people and injured more than half a million.