Been wondering how much risky mortgages could cost bondholders? Mark Zandi, an economist at Moody's, set a price tag of $225 billion in losses, according to today's Wall Street Journal (subscription required). By his calculations, there are $2.45 trillion (yes that's trillions) in especially risky mortgages outstanding. He includes subprimes, interest-only loans and mortgages that exceed Fannie Mae lending limits of $417,000 in his figures. Bondholders would be hit hard by these losses because the value of the bonds they hold are based on the value of the mortgage securities and their underlying mortgages.

Problems continue to mount with subprime mortgages. In August subprime mortgages that were more than 60 days behind topped 20%, according to First American Loan Performance. That's up from 18.7% in July and 17.1% in June. Yesterday I wrote about how foreclosures are breaking all records and doubling in many parts of the country. The nationwide foreclosure rate is now one in every 196 households. Nevada is hit hardest with 1 in every 61 households facing foreclosure.

Many money market and mutual funds hold the bonds in question. If your fund holds mortgage-backed securities that are not guaranteed by the government (such as Fannie Mae or Freddie Mac), you could be taking on more risk than you planned to take. Money market funds have historically paid $1 for $1, but if the fund you hold does take loses you may get back less than your principal balance because your fund may not be insured by the FDIC. Be sure you understand the risks you are taking with your money market and mutual funds. It's only a matter of time before these mortgage write-downs impact your holdings.

Lita Epstein has written more than 20 books including "Pocket Idiot's Guide to Investing in Mutual Funds" and "The 250 Questions You Should Ask to Avoid Foreclosure."