Why 9/11 still casts a shadow over America

As relatives gather at Ground Zero, wrangles drag on over a memorial museum – and the death toll among emergency workers continues to rise

America will pause again today to remember the victims of the attacks on lower Manhattan and the Pentagon 11 years ago, against a backdrop of recriminations over delays in finishing a museum at Ground Zero and with the pomp of last year's 10th anniversary largely absent.

Vice President Joe Biden will visit Shanksville, Pennsylvania, where United 93 came down after passengers overwhelmed hijackers who had intended to crash the plane into the Capitol or the White House. President Barack Obama will attend services of remembrance in Washington and at the Pentagon.

As relatives of the dead stream into Ground Zero for a ceremony starting with a moment of silence at 8.45am – the time the first of the two jets struck the Twin Towers – many will be reflecting not just on the pain of remembrance but also on the renewed political wrangling that has slowed redevelopment of the site. For the first time, no politicians have been invited to speak.

Progress has been made at the site. A new park, with a pair of huge square wells with water cascading down their sides, that forms the heart of a memorial space was opened a year ago and has attracted 4.5 million visitors already. One World Trade Centre, which will become the tallest building in America, is due to be completed next year, as well as 4 World Trade Centre, on the other side of the park. Less edifying, however, is a stand-off between the Port Authority of New York and New Jersey, which owns the land and is headed by the governors of the two states, and the National September 11 Memorial and Museum Foundation, which is led by New York Mayor Michael Bloomberg.

The dispute has halted construction since December. The museum was meant to open to the public today; at this rate it may not even be ready for the 12th anniversary.

Curators say they are still busy gathering exhibits and artefacts for the museum on the assumption that the deadlock between the two parties over money – each side says the other owes them more than $100m in construction costs – will be resolved. "We're gathering photos from victims' family members, badges and equipment from first responders, items like that," said spokesman Michael Frazier.

Further sobering the atmosphere today will be new reports of illness and death among emergency workers who were deployed after the collapse of the Twin Towers and who were exposed to toxic and carcinogenic substances. Only a week ago, the New York City Fire Department added five more names to the roster of 55 former firemen who have died from illnesses related to 9/11.

"We're burying guys left and right," said Nancy Carbone, executive director of Friends of Firefighters, a Brooklyn-based charity. "This is an ongoing epidemic." The emergence of difference kinds of cancer as a cause of death among those who were at Ground Zero has complicated efforts to distribute money from a $2.7bn federal fund for those suffering medical effects.

The memorial park in Shanksville has also seen steady visitor traffic. As in New York, however, the site is still a work in progress. A visitors' centre is due to open next spring and new walkways and tree plantings are planned for a year later.