Labor organizers with the Teamsters union announced Monday that they're holding an election to unionize Bay Area drivers who work for Google Express, the shopping service that delivers everything from toothpaste to televisions purchased by online consumers. The union is seeking to represent about 140 Google Express drivers and warehouse workers employed by Adecco, a temp agency that provides most of the delivery service's staff. "Workers are required to sign short-term employment agreements with Adecco that limit them to two years before the company lets them go," the Teamsters Local Union 853 said in a press release announcing the vote.