Remember those time bombs called derivatives which threatened to economically blow up the world in 2008? Not only were they never really regulated, they are back with a vengeance. A new report, by the Comptroller of the Currency, on Bank Trading and Derivatives Activities, Q2 2011, shows derivatives have increased 11.6% from one year ago to a U.S. holdings of $249 trillion dollars.

Five large commercial banks represent 96% of the total banking industry notional amounts and 86% of industry net current credit exposure.

According to DealBook, those banks are, pretty much the same banks who were given massive bail outs via TARP. BoA especially is already in trouble due to their Countrywide holdings. 99% of all derivatives are held by just 25 banks.

The nation’s four biggest banks — JPMorgan Chase, Citigroup, Bank of America and Goldman Sachs — are the biggest players, holding roughly 95 percent of the industry’s total exposure to derivatives. JPMorgan, which holds the most among commercial banks, carries some $78 trillion worth of derivatives on its books, according to the report. Citi is next on the list, with $56 trillion, up from $54 trillion in the first quarter.

Seeking Alpha has a good explanation of how the actual loss risks are much less than the frightening $249 trillion dollar amount.