The march, launched on Wednesday, is the second by survivors and victims in two years.
 
Compensation calls
 
In 2006, marchers camped on Delhi's pavement for weeks before getting assurances from Manmohan Singh, India's prime minister, that he would look into their demands for compensation and clean-up of the toxic waste.
 
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Victims of a toxic legacy

Protesters say the government has since protected chemical companies rather than uphold its promises, and are calling for an independent body to be set-up to assist the disaster victims.
 
"We want a commission on Bhopal and we want this mess gone," Leela Bhai, a survivor, told Al Jazeera.
 
The disaster occurred on December 3, 1984, when a storage tank at the Union Carbide India pesticide plant in Bhopal spewed deadly methyl isocyanate gas into the air, killing more than 3,500 slum dwellers immediately.
 
"I remember the night of the gas leak like it was yesterday," Leela said. "As we fled the city, there were bodies lying everywhere, bodies like dead insects."
 
The toll has since climbed to more than 15,000, the government says.
 
But activists say the number of fatalities is double that and that up to 5,000 tonnes of toxic chemicals have leached into soil and water from the plant site, causing tens of thousands to be chronically ill.
 
Health problems
 
According to local doctors, the majority of those seeking medical care in Bhopal are survivors of the leak suffering from chronic respiratory ailments, but children born long after the accident are also having problems.
 
The march route

Mohammad Ali Qaiser, a Bhopal doctor, said "congenital deformities such as cleft palate, cleft lip and, of course, head circumference - sometimes very big or sometimes very low - and mental retardation" were common.
 
The Indian government acknowledges it has been slow to address the issue adequately.
 
Arjun Singh, the Indian human resources minister, told Al Jazeera: "You know justice is not that quick. More [important] than justice is the aid that they require, the rehabilitation and taking care of their medicines and everything.
 
"I think that should be expedited."
 
With approximately 700km left on their trek to Delhi, victims are counting on the march to have a better outcome than that of two years ago.
 
"Things will be different," Dhingra said. "We have already started the dialogue with the ministry of chemicals and they've been very receptive."
 
"And there's going to be tremendous international pressure."
 
The survivors want US giant Dow Chemical, which took over Union Carbide in 1999, to pay for the clean-up and health damages. They are also demanding that clean water is supplied.
 
Dow, however, says all liabilities were settled in 1989 when Union Carbide paid $470m.