On Aug. 5, Deutsche Bank raised eyebrows across the country when it said 48 percent of all Americans holding mortgages — 25 million households — could be underwater by early 2011. The San Diego metro area was projected to hit the 51 percent underwater mark.

But First American CoreLogic said last week that the problem is improving, not worsening, nationally. The proportion of properties likely to be underwater dropped from 32.5 percent in March to 32.2 percent in June.

The San Diego-area figure was placed at 42.6 percent, 39th-highest among 207 metro areas studied and 12th among the 51 areas in the study with population over 1 million people.

The company estimated the aggregate value of underwater homes in the San Diego area at $91.8 billion. Los Angeles ranked first with more than $310 billion in underwater home values.

The suits are being watched locally and nationally because, if successful, they would provide strength to advocates and litigators struggling to make lenders accountable for “toxic’’ mortgage loans that have pushed millions of Americans into foreclosure.

Guy Cecala, publisher of the Maryland-based industry newsletter Inside Mortgage Finance, said a growing number of lawsuits against lenders are like those filed by smokers who claimed cigarette companies knew their products were cancerous.