A prestigious, multibillion-rupee project to build a neutrino observatory under a mountain in southern India has run aground, with politicians and activists raising fears of radioactivity and water pollution.

The India-based Neutrino Observatory (INO), a collaboration between seven scientific research institutions in the country, was set up to study atmospheric neutrinos — elusive fundamental particles created when cosmic rays strike the Earth’s atmosphere.

The 15-billion-rupee (Dh868 million) project has had a slow start.

Initial discussions began 14 years ago in 2001, planning continued through 2009, a final site in Tamil Nadu was allocated in 2012, government funding was granted last year, and in January, the project received final approval by prime minister Narendra Modi’s administration.

However, opponents of the project have insisted that it will wreck forests inear to the site in the district of Theni, and that construction will ruin groundwater supplies.

One NGO, the Kerala-based Society of Science Environment and Ethics, has also claimed that the INO is a cover for India-US atomic experiments, and that a stream of neutrinos beamed to Theni from Chicago’s Fermilab could have radioactive substances potentially hazardous to Indian villagers.

The scientists involved in the project reject the claims and say the project will release no radioactivity at all, and that it will cause minimal pollution.

In March, a bench of the Madras high court barred any work from proceeding on the INO until the Tamil Nadu Pollution Control Board issued a report about the project.

The report has yet to be completed, leaving scientists frustrated and anxious about the future of their project.

Building the observatory under a mountain is crucial to the project’s success, said Naba Mondal, a scientist at the Tata Institute of Fundamental Research (TIFR) in Mumbai.

Since atmospheric neutrinos have such high energies, “experiments have to be set up under rock coverage”, he added. Rock that is a kilometre or more thick acts as a filter, blocking lower energy particles but allowing neutrinos to zip through.

In fact, India’s earlier set of neutrino experiments which began in 1965, were conducted at depths of between two and three kilometres in a gold mine in Kolar, Karnataka. The experiments ran until 1992, when the government shut down the mine because its gold output was becoming commercially unviable.

V Narasimham, a physicist who worked in the Kolar lab, said he and his TIFR colleagues assembled a 300-ton neutrino spotter underground.

“It was a competitive world. We were in a race with some South African scientists to be the first in the world to detect atmospheric neutrinos,” Mr Narasimham said.

Although the South African team was the first to pick up these neutrinos, the Indian scientists beat them to publication.

The INO will feature a neutrino spotting machine weighing 50,000 tons — the weight of a battleship. It will consist of massive magnetised plates of iron, and sandwiched between these plates will be roughly 30,000 particle detectors.

This is a more complex machine than the one in Kolar, as it is designed to answer more complicated questions, Mr Mondal said.

Even before the science had begun, the scientists faced a different sort of challenge — allaying people’s fears.

D Indumathi, a particle physicist at the Institute of Mathematical Sciences in Chennai, said that the INO had already been shifted once from another site in Tamil Nadu due to environmental concerns.

The new site, according to a government report in 2011, would face only “notional” forest clearance.

“No forest land is expected to be occupied, since both the tunnels and laboratories are underground,” the report said.

Despite this, Ms Indumathi said, she and other scientists conducted outreach programmes in Theni.

“Some people were afraid about whether the mountain would fall down if we tunnelled through it, others were confused about atoms and neutrinos,” she said. “Some people even had very simple questions: ‘You’ll fence off the area, so our goats won’t be able to graze in the mountains.’”

Through town-hall meetings, pamphlets and informal interactions, the scientists obtained the consent of most of the people who lived in the area, she said.

Some residents, however, continue to be mobilised by the Marumalarchi Dravida Munnetra Kazhagam (MDMK), a state political party headed by V Gopalsamy, who petitioned against the INO at the Madras high court saying that it posed a threat to groundwater and could “affect the livelihoods of five southern districts of the state”.

But Ms Indumathi is confident that the INO will not be a threat to the region. She also rejected the rumour that the INO will work with neutrinos beamed out from Fermilab.

“Even if there was such a beam of neutrinos — which is not the case — you’d need to be exposed it continuously for 100 million years to even equal the sort of radioactivity you’re exposed to in one normal year,” she said.

“A project that should be seen only on its own merits is being questioned along obscurantist, misleading, fear-mongering lines,” she said. “That is really a tragedy.”