(Reuters) - Since the attacks of September 11, 2001, the United States has added at least $3.7 trillion to its national debt for war and homeland security spending, and at least 236,500 people have been killed, most of them civilians, according to the "Costs of War" study by the Watson Institute for International Studies at Brown University in Rhode Island.

The study, first published in June, was updated on September 4 with new death toll estimates based on data from the first half of 2011. The dollar figures were unchanged from June.

The September 11 attacks themselves killed 2,995 people and caused an estimated $50 billion to $100 billion in damage.

Here are figures on the toll since then.

FINANCIAL TOLL:

* Congressional war appropriations to Pentagon since 2001: $1.3 trillion

* Additions to Pentagon base budget: $362 billion to $652 billion

* Interest on Pentagon war appropriations: $185 billion

* Veterans' medical claims and disability: $33 billion

* War-related international aid: $74 billion

* Additions to Homeland Security base spending: $401 billion

* Projected obligations for veterans care to 2050: $589 billion to $934 billion

* Social costs to veterans and military families to date: $295 billion to $400 billion

Future spending requests:

* 2012 Pentagon war spending: $118 billion

* 2012 foreign aid: $12 billion

* 2013-2015 projected war spending: $168 billion

* 2016-2020 projected war spending: $155 billion

ESTIMATED TOTAL: $3.7 trillion to $4.4 trillion

Additional interest payments to 2020: $1 trillion

DEATH TOLL:

Total low estimate: 236,500

Total high estimate: 261,700

DEATH TOLL ESTIMATES BY WAR ZONE:

Afghanistan: 30,400 to 45,600

Iraq: 171,000

Pakistan: 35,000 to 45,000

Yemen: 105

DEATH TOLL ESTIMATES BY CATEGORY:

U.S. military: 6,226 (4,477 in Iraq, 1,749 in Afghanistan)

U.S. contractors: 2,300

Other allied troops: 1,192

Iraqi civilians: 126,000

Iraqi security forces: 10,100

Iraqi army during U.S. invasion: 10,000

Iraqi insurgents: 19,000

Afghan civilians: 12,423 to 14,701

Afghan security forces: 5,138 to 8,000

Afghan insurgents: 10,000 to 20,000

Journalists and media workers: 170

Humanitarian workers: 279

(Reporting by Daniel Trotta; Editing by Michelle Nichols and Will Dunham)