The fourth annual "Arizona's Greenest Workplace Challenge," hosted by green-living advocate and Internet radio host Gina Murphy-Darling, is open for nominations.

Individuals can nominate their own business, their employer or any Arizona company or organization for its efforts to reduce, reuse and recycle in the workplace and provide a healthy environment for employees. 

There will be two winners selected. The Greenest Workplace winner will be chosen by a panel of statewide advocates in the green movement and announced on Sept. 27. A People's Choice Award will be chosen by online voters, and announced the same day.

The Greenest Workplace winner will receive a private tour and lunch for up to 20 employees at the University of Arizona's Biosphere 2, as well as 20 Mrs. Green S'well beverage bottles and 20 Mrs. Green reusable shopping bags. The People's Choice Award winner will get lunch hosted by Whole Foods and 20 Buffalo Exchange gift certificates and 20 gift certificates. 

Previous winners include Golden Eagle Distributors, Inc., and St. Michael's Parish Day School.

To nominate a business, go to before midnight Friday, Sept. 20.