Mortgage purchases and issuance at government-sponsored enterprise (GSE) Freddie Mac fell to nearly $28.4bn, from $30.9bn in June -- bringing the year-to-date totally to $207.4bn so far in 2010.

Refinance-loan purchase and guarantee volume at Freddie fell to $18.1bn in July, from $19.1bn in June, according to the firm's monthly volume summary (download here). The aggregate unpaid principal balance of the GSE's mortgage-related investments decreased by $13.6bn.

Additionally, the total guaranteed Participation Certificates (PCs) and structured securities issued fell at a 4.4% annualized rate in July.

The GSE's total mortgage portfolio continued to decline at an annualized rate of 3.9%. Freddie Mac has not seen positive annualized growth since April.

The GSE's single-family delinquency rate decreased to 3.89% in July, while its multifamily delinquency rate increased 2 basis points to 0.3%, from 0.28% in June.

Freddie's 120-plus-day delinquencies remained flat at 0.2% in July for fixed-rate mortgages (FRM) and dropped slightly to 0.98% for adjustable-rate mortgages (ARM), down 1 basis point from the previous month.

Mortgage loans 90-days delinquent dropped for both FRMs and ARMs; down to 0.31% and 1.24%, respectively.

The Mortgage Bankers Association released its quarterly index tracking national delinquency rates today. According to the report, delinquent prime FRMs account for 4.75% of all mortgage loans and prime ARMs account for 9.3%.

Write to Christine Ricciardi.

Disclosure: The author holds no relevant investments.