CUPERTINO (AP) — Union organizers are hoping to add security guards at Apple’s campus to their ranks in the latest push by organized labor in Silicon Valley.

United Service Workers West, an arm of the Service Employees International Union, is concerned about the guards’ ability to make ends meet given the high cost of living in the San Francisco Bay Area, a spokesman for United Service Workers West, Alfredo Fletes, told the San Jose Mercury News.

The guards are employed by Security Industry Specialists, which has a contract with Apple Inc.

Fletes said a survey of Security Industry Specialists’ job postings in Silicon Valley last year indicated that a large share of the positions were part-time.

“Even if (SIS) does pay above-average wages, we worry that the instability of the hours and the high turnover rate is really impeding workers from obtaining a better way of life,” he said.

A call to the company Wednesday was not immediately returned. On its website, it says its guards are some of the highest-paid security officers in the industry and have benefit packages that exceed those offered by competitors.

The unionization push comes as bus drivers with Facebook Inc.’s shuttle bus contractor, Loop Transportation, voted last week to join the Teamsters Local 853. Advocates say they want to narrow the wide gap between the perks and wages technology workers receive and those given to the contract workers who provide vital services.

They are calling on technology companies such as Apple to get involved.

In a letter this month, the Rev. Jesse Jackson urged Apple CEO Tim Cook to stand up for service workers, the Mercury News reported. Jackson and his Rainbow PUSH coalition recently put pressure on technology companies to release demographic data about their workforces.

“Part of the narrative of their firm is equitable and first-class leadership,” Jackson told the newspaper about Apple. “As they grow at such a rapid pace, they should have world-class working conditions for their workers from the bottom up.”