David Oswald, RMIT University; Erica Kuligowski, RMIT University, and Kate Nguyen, RMIT UniversityThe collapse of the World Trade Center has been subject to intense public scrutiny over the 20 years since the centre’s twin towers were struck by aircraft hijacked by terrorists. Both collapsed within two hours of impact, prompting several investigations and spawning a variety of conspiracy theories.
Construction on the World Trade Center 1 (the North Tower) and World Trade Center 2 (the South Tower) began in the 1960s. They were constructed from steel and concrete, using a design that was groundbreaking at the time. Most high-rise buildings since have used a similar structure.
FEMA’s report was published in 2002. This was followed by the National Institute of Standards and Technology’s three-year investigation, funded by the US Federal Government and published in 2005.
Some conspiracy theorists seized on the fact the NIST investigation was funded by the federal government — believing the government itself had caused the twin towers’ collapse, or was aware it would happen and deliberately didn’t act.
While there have been critics of both reports (and the investigations behind them weren’t flawless) — their explanation for the buildings’ collapse is widely accepted. They conclude it was not caused by direct impact by the aircraft, or the use of explosives, but by fires that burned inside the buildings after impact.
Why did the towers collapse as they did?
Some have questioned why the buildings did not “topple over” after being struck side-on by aircraft. But the answer becomes clear once you consider the details.
Aircraft are made from lightweight materials, such as aluminium. If you compare the mass of an aircraft with that of a skyscraper more than 400 metres tall and built from steel and concrete, it makes sense the building would not topple over.
The towers would have been more than 1,000 times the mass of the aircraft, and designed to resist steady wind loads more than 30 times the aircrafts’ weight.
That said, the aircraft did dislodge fireproofing material within the towers, which was coated on the steel columns and on the steel floor trusses (underneath the concrete slab). The lack of fireproofing left the steel unprotected.
As such, the impact also structurally damaged the supporting steel columns. When a few columns become damaged, the load they carry is transferred to other columns. This is why both towers withstood the initial impacts and didn’t collapse immediately.
This fact also spawned one of the most common conspiracy theories surrounding 9/11: that a bomb or explosives must have been detonated somewhere within the buildings.
These theories have developed from video footage showing the towers rapidly collapsing downwards some time after impact, similar to a controlled demolition. But it is possible for them to have collapsed this way without explosives.
It was fire that caused this. And this fire is believed to have come from the burning of remaining aircraft fuel.
According to the FEMA report, fire within the buildings caused thermal expansion of the floors in a horizontal and outwards direction, pushing against the rigid steel columns, which then deflected to an extent but resisted further movement.
With the columns resisting movement there was nowhere else for the concrete floors to expand. This led to an increased buildup of stress in the sagging floors, until the floor framing and connections gave in.
The floors’ failure pulled the columns back inwards, eventually leading to them buckling, and the floors collapsing. The collapsing floors then fell on more floors below, leading to a progressive collapse.
This explanation, documented in the official reports, is widely accepted by experts as the cause of the twin towers’ collapse. It is understood the South Tower collapsed sooner because it suffered more damage from the initial aircraft impact, which also dislodged more fireproofing material.
The debris from the collapse of the North Tower set at least ten floors alight in the nearby World Trade Center 7, or “Building 7”, which also collapsed about seven hours later.
While there are different theories regarding how the progressive collapse of Building 7 was initiated, there is consensus among investigators fire was the primary cause of failure.
Both official reports made a range of fire safety recommendations for other high-rise buildings, including to improve evacuation and emergency response. In 2007, the National Institute of Standards and Technology also published a best practice guide recommending risk-reducing solutions for progressive collapse.
What does this mean for high-rise buildings?
Before 9/11, progressive collapse was not well understood by engineers. The disaster highlighted the importance of having a “global view” of fire safety for a building, as opposed to focusing on individual elements.
There have since been changes to building codes and standards on improving the structural performance of buildings on fire, as well as opportunities to escape (such as added stairwell requirements).
At the same time, the collapse of the twin towers demonstrated the very real dangers of fire in high-rise buildings. In the decades since the World Trade Center was designed, buildings have become taller and more complex, as societies demand sustainable and cost-effective housing in large cities.
Some 86 of the current 100 tallest buildings in the world were built since 9/11. This has coincided with a significant increase in building façade fires globally, which have gone up sevenfold over the past three decades.
This increase can be partly attributed to the wide use of flammable cladding. It is marketed as an innovative, cost-effective and sustainable material, yet it has shown significant shortcomings in terms of fire safety, as witnessed in the 2017 Grenfell Disaster.
The Grenfell fire (and similar cladding fires) are proof fire safety in tall buildings is still a problem. And as structures get taller and more complex, with new and innovative designs and materials, questions around fire safety will only become more difficult to answer.
The events of 9/11 may have been challenging to foresee, but the fires that led to the towers’ collapse could have been better prepared for.
David Oswald, Senior Lecturer in Construction, RMIT University; Erica Kuligowski, Vice-Chancellor’s Senior Research Fellow, RMIT University, and Kate Nguyen, Senior Lecturer, ARC DECRA Fellow and Victoria Fellow, RMIT University
Rebecca Ananian-Welsh, The University of Queensland and Keiran Hardy, Griffith UniversityAustralia is a long way from New York and Washington DC, but the September 11 terror attacks had a profound impact on our country.
In Afghanistan and Iraq, we became embroiled in decades-long insurgencies. At home, the attacks had enduring impacts on our legal system. Before 9/11 Australia had zero national counter-terrorism laws. Now, we have 92 of them, amounting to more than 5,000 pages of rules, powers and offences.
These laws have reshaped ideas about criminal responsibility, set us apart from our closest allies, and strengthened a troubling culture of secrecy.
But have they made us safer?
No other nation can match the volume of Australia’s counter-terrorism laws. Their sheer scope is staggering. They include:
- control orders, which allow courts to impose a wide range of restrictions and obligations on people to prevent future wrongdoing. They can mandate curfews, limits on phone or internet usage and electronic monitoring
- preventative detention orders, which allow police to detain people secretly for up to two weeks, either to prevent an attack or protect evidence relating to a recent one
- mandatory retention of all Australians’ metadata for two years and access by enforcement agencies without a warrant
- a power for the home affairs minister to strip dual citizens involved in terrorism of their Australian citizenship.
Many of these schemes are unprecedented in Australian law, outstripping even our historical wartime powers.
Toronto University law professor Kent Roach, one of the world’s leading experts on counter-terrorism laws, has labelled Australia’s approach “hyper-legislation”. This refers not only to the vast scope and number of laws, but also the speed with which they were passed.
On average, it took around two and half days in the House of Representatives and two days in the Senate for each law to be approved. Those are very generous figures — they count the days bills were introduced into parliament, even if they weren’t debated. The speed was fastest under the Howard government, when a new counter-terrorism law was passed on average every 6.7 weeks. But the trend has continued.
A ‘pre-crime’ approach
Counter-terrorism laws in Australia and elsewhere have reoriented the criminal justice system. Under wide-ranging offences, people can be imprisoned for harms they may cause in the future, rather than harms they have caused in the past.
The legislation is designed to bite early, long before the preparatory acts mature into circumstances of deadly or dangerous consequence for the community.
This offence and many others trigger criminal responsibility much earlier than the ordinary criminal law (for example, it has never been a crime to prepare a murder or robbery).
Even tougher than our allies
Australia looked closely to the United Kingdom when designing our first counter-terrorism laws. On top of our close legal and political ties, this was because the UK had already enacted counter-terrorism laws—based on previous emergency powers for Northern Ireland — before 9/11.
In the years since, our laws have become more extreme, setting us apart from the UK and the rest of our “Five Eyes” partners, the United States, Canada, and New Zealand. Not only have “tough on terror” policies played well with voters here, Australia does not have a bill of rights. This means the government has been able to enact counter-terrorism laws that would not be possible elsewhere.
One example of this is the mandatory retention of all Australians’ telecommunications metadata for two years. The European Court of Human Rights held that blanket retention for that time period infringed the basic right to privacy.
Other powers, such as preventative detention orders, would simply not be possible in countries with constitutional protection for human rights. The Council of Australian Governments’ (COAG) 2013 review of counter-terrorism legislation reported preventative detention orders were more likely to be seen in “discredited totalitarian regimes”.
‘The world’s most secretive democracy’
Australia’s counter-terrorism laws enable and entrench these high levels of secrecy. It is a crime to mention basic details about the use of many counter-terrorism powers — or even the mere fact they were used.
Sweeping espionage laws, overhauled in 2018, make it a crime to possess or receive national security information where the information would be made available to a foreign government or company (including through publication in the media). The definition of “national security” is exceptionally broad, extending to anything about Australia’s political and economic relations with other countries.
These offences pose a serious risk to journalists and whistleblowers who act in the public interest. Criminal trials for these offences can be also held in secret, undermining open justice and the right to a fair trial.
Are we any safer?
Undoubtedly, some counter-terrorism laws have enhanced Australia’s national security. But others have little, or no, proven effectiveness, despite their impact on fundamental rights.
For example, in 2012, former Independent National Security Legislation Monitor, Bret Walker SC, found control orders were
not effective, not appropriate and not necessary.
This finding was based on classified submissions by police and security agencies. Despite this, in response to Islamic State, the federal government expanded the grounds for issuing control orders, and allowed them to be imposed on children as young as 14.
These controversial powers might even harm our security over the long-term.
Australia’s Muslim communities have felt targeted by “aggressive” counter-terrorism powers. This leads to lower levels of trust and makes communities less likely to cooperate with police. It also undermines the community cohesion that countering violent extremism programs are trying to build.
Undermining human rights to prevent terrorism can also fuel the grievances that lead to radicalisation and recruitment. Back in 2004, a United Nations panel reported terrorist recruitment thrives when human rights and democracy are lacking.
Ultimately, to reduce terrorism over the long-term, governments need to support greater investments and research into countering violent extremism and deradicalisation programs. This is equally true for Islamist and right-wing terrorism.
Security, but at what cost?
Over the past two decades, evolving terror threats have exposed gaps in our laws that needed to be filled. But many of the laws we ended up with go beyond what is needed to prevent terrorism effectively. They also undermine core values and principles such as the rights to liberty, freedom of speech and freedom of the press.
These values must not be lost in the pursuit of national security. Indeed, upholding them is an essential part of any counter-terrorism strategy.
These lessons have been known for a long time. As then UN secretary-general Kofi Annan said in 2005, when remembering victims of terrorism since 9/11:
compromising human rights cannot serve the struggle against terrorism. On the contrary, it facilitates achievement of the terrorist’s objective.
Erin Smith, Edith Cowan University; Brigid Larkin, Edith Cowan University, and Lisa Holmes, Edith Cowan UniversityEmergency workers and clean-up crew are among 9/11 responders still suffering significant health issues 20 years after the terrorist attacks.
By March 2021, some 80,785 of these responders had enrolled in the World Trade Center Health Program, which was set up after the attacks to monitor their health and treat them.
Now our published research, which is based on examining these health records, shows the range of physical and mental health issues responders still face.
Breathing problems, cancer, mental illness
We found 45% of responders in the health program have aerodigestive illness (conditions that affect the airways and upper digestive tract). A total of 16% have cancer and another 16% have mental health illness. Just under 40% of responders with health issues are aged 45-64; 83% are male.
Our analysis shows 3,439 of responders in the health program are now dead — far more than the 412 first responders who died on the day of the attacks.
Respiratory and upper digestive tract disorders are the number one cause of death (34%), ahead of cancer (30%) and mental health issues (15%).
Deaths attributed to these three factors, as well as musculoskeletal and acute traumatic injuries, have increased six-fold since the start of 2016.
An ongoing battle
The number of responders enrolling in the health program with emerging health issues rises each year. More than 16,000 responders have enrolled in the past five years.
Cancer is up 185% over the past five years, with leukaemia emerging as particularly common, overtaking colon and bladder cancer in the rankings.
This equates to an increase of 175% in leukaemia cases over a five-year period, which is not surprising. There is a proven link between benzene exposure and acute myeloid leukaemia. Benzene is found in jet fuel, one of the toxic exposures at the World Trade Center. And acute myeloid leukaemia is one of the main types of leukaemia reported not only by responders, but by residents of lower Manhattan, who also have higher-than-normal rates.
Prostate cancer is also common, increasing 181% since 2016. Although this fits with the age profile of many of the health program’s participants, some responders are developing an aggressive, fast-growing form of prostate cancer.
Inhaling the toxic dust at the World Trade Center site may trigger a cascading series of cellular events, increasing the number of inflammatory T-cells (a type of immune cell) in some of the responders. This increased inflammation may eventually lead to prostate cancer.
There may also be a significant link between greater exposure at the World Trade Center and a higher risk of long-term cardiovascular disease (disease affecting the heart and blood vessels). Firefighters who responded to the World Trade Center on the morning of the attacks were 44% more likely to develop cardiovascular disease than those who arrived the next day.
The mental health effects
Despite 20 years having passed, PTSD is a growing problem for responders. Almost half of all responders report they need ongoing mental health care for a range of mental health issues including PTSD, anxiety, depression and survivor guilt.
Researchers have also found brain scans of some responders indicate the onset of early-stage dementia. This is consistent with previous work noting cognitive impairment among responders occurs at about twice the rate of people 10-20 years older.
COVID-19 and other emerging threats
Even among responders who have not been infected, the pandemic has exacerbated one of the key conditions caused by search and rescue, and recovery after terrorist attacks — PTSD.
More than 100 responders have died due to complications from the virus, which has also exacerbated other responders’ PTSD symptoms.
The number of responders with cancers associated with asbestos exposure at the World Trade Center is expected to rise in coming years. This is because mesothelioma (a type of cancer caused by asbestos) usually takes 20-50 years to develop.
As of 2016, at least 352 responders had been diagnosed with the lung condition asbestosis, and at least 444 had been diagnosed with another lung condition, pulmonary fibrosis. Exposure to asbestos and other fibres in the toxic dust may have contributed.
Our research involved analysing data from existing databases. So we cannot make direct links between exposure at the World Trade Center site, length of time there, and the risk of illness.
Differences in age, sex, ethnicity, smoking status and other factors between responders and non-responders should also be considered.
Increased rates of some cancers in some responders may also be associated with heightened surveillance rather than an increase in disease.
Nevertheless, we are now beginning to understand the long-term effects of responding to the 9/11 terrorist attacks. Exposure is still having both a physical and mental health impact and it’s likely responders are still developing illnesses related to their exposures.
Ongoing monitoring of responders’ health remains a priority, especially considering the looming threat of new asbestos-related cancers.
Erin Smith, Associate Professor in Disaster and Emergency Response, School of Medical and Health Sciences, Edith Cowan University; Brigid Larkin, PhD candidate, Edith Cowan University, and Lisa Holmes, Lecturer, Paramedical Science, School of Medical and Health Sciences, Edith Cowan University