NEW DELHI (REUTERS) - His hands protected by torn orange gloves, Dalbira Singh has a grim job scraping waste from train toilets from the tracks at New Delhi's Hazrat Nizamuddin station, a few minutes from Prime Minister Narendra Modi's office.
Like an estimated 1 million other Indians, Mr Singh does the work because he was born into a low caste. His parents did the same work before him. "This is a disgusting job but no one will give me another. I am destined to be a toilet-cleaning man," Mr Singh said this week, picking up soiled sanitary towels and diapers before wiping the tracks with a cloth soaked in cleaning chemicals.
But Mr Modi, like Mahatma Gandhi, wants to change things so not only those born to a low caste work to keep India clean.
On Thursday, a holiday for Gandhi's birthday, Mr Modi launched the Swachh Bharat Abhiyan, or Clean India Mission, to modernise sanitation within five years.
He starting by trying to change attitudes and he set an example by taking a broom and sweeping up rubbish in a Delhi neighbourhood occupied by members of the Valmiki caste, whose lot in life is traditionally "manual scavenging", a euphemism for clearing other people's faeces.
"Often we assume the job of cleaning up belongs to safai karmacharis and don't bother to clean," Mr Modi said referring to cleaners. "Don't we all of have a duty to clean the country?" To drive home his point, he ordered government workers including his ministers came to work on Thursday to sweep offices and clean toilets.
India's fast-growing towns and cities are littered with rubbish. Most rivers and lakes are polluted with sewage and industrial effluents.
Education will be vital if Mr Modi is to change age-old attitudes towards hygiene and purity, and he will have to finish Gandhi's bid to free India's "untouchable" low castes. "Modi will have to deal with society's failure to liberate the Dalits (low caste people) from the demeaning profession if he wants India to be as clean as Singapore," said Pravin Panchal, a researcher at the Environmental Sanitation Institute think-tank.
Less than a third of India's 1.2 billion people have access to sanitation and more than 186,000 children under five die every year from diarrhoeal diseases caused by unsafe water and poor sanitation, according to the charity WaterAid.
The United Nations said in May half of India's people defecate outside - putting people at risk of cholera, diarrhoea, dysentery, hepatitis A and typhoid.
The resulting diseases and deaths, mostly among the poor, cause major losses. The World Bank in 2006 estimated that India was losing 6.4 percent of gross domestic product annually because of poor sanitation.
Mr Modi wants every home and school to have access to a toilet by 2019, in time for the 150th anniversary of Gandhi's birth.
To be successful, he will have to banish the widespread belief in the countryside that it is unclean to defecate inside and that only Dalits should deal with excrement.
U.S. group Human Rights Watch, in a report in August, documented cases of authorities recruiting people from low castes to clean open defecation grounds. The group found people were often coerced into do the work with threats of reprisals.
The practice is most common in small-town India, where people from castes still considered "untouchable" clean waste from toilets which do not have modern flush systems.
Caste-based discrimination was banned in India in 1955, but Dalits face prejudice in every sector from education to employment.
In just one example this week, the Dalit chief minister of Bihar state, Jitan Ram Manjhi, said he was told a temple in the state was "purified" after he visited it last month.