L.A. County’s seasonally adjusted unemployment rate shot up to 10.5 percent in January the highest rate in 16 years as thousands of trade and retail jobs were lost amid the deepening recession, according to figures released Friday.

About 521,000 county residents reported being out of work last month, driving the unemployment rate up from 5.9 percent in January 2008 and 9.2 percent in December, according to the Employment Development Department.

Brad Kemp, a former EDD analyst who is now director of regional research at L.A.’s Beacon Economics, cautions that the 10.5 percent jobless rate likely will be revised downward next month as the state receives more information, noting that December’s rate originally was a higher 9.9 percent.

Trade, transportation and utility companies shed 39,900 jobs compared with a year ago. Retail trade took the biggest hit within that group, down 21,900 jobs. Many of those jobs were the result of Mervyn’s department store chain going out of business, but other retailers also reduced staff.

“When you look at individual sectors, what we’re seeing is in line with how the local economy has reacted as these waves of economic imbalance pass through,” Kemp said. “First we saw the housing imbalance, then the financial imbalance and now we’re seeing the consumer imbalance.”

Manufacturing was the second worst-hit industry, down 26,500 jobs. Also hard hit was the information sector: The publishing industry alone lost 2,300 jobs, mostly due to downsizing at companies including the L.A. Times and L.A. Daily News.

A bright spot: educational and health posted the largest year-over-year employment gains, adding 9,800 jobs.Government also added 7,200 jobs.

Statewide, more than one in 10 workers were unemployed in January. California’s 10.1 percent jobless rate was also the highest since 1983.