Kate Mara, Sophia Bush Get Eco-Friendly at H&M's Conscious Collection Event

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Kate Mara, left, and Sophia Bush

Emmy Rossum, Camilla Belle and Amber Valetta also turned out for the retailer's launch party of its stylish sustainable line.

On Wednesday night, H&M proved that you don’t have to sacrifice style for the environment with the celebration of their third Conscious Exclusive collection. Decked in the line's eco-friendly threads, guests including, Sophia Bush, Kate Mara, Emmy Rossum and Camilla Belle, showed up to West Hollywood's Eveleigh restaurant to support the launch, alongside the face of the line and special guest, Amber Valetta, and hosts Alexia Niedzielski and Elizabeth von Guttman of sustainable fashion magazine Ever Manifesto.

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Bush was in especially good spirits, following the day's news that her NBC show, Chicago PD, had just been picked up for a second season. "I said, 'I'm going out and I'm not wearing pants!'" joked the actress, recalling her reaction upon hearing the announcement, which prompted her decision to sport the line's white lace dress with an overlay collar for the evening.

Valetta, who sported a sleek new cropped 'do, wore a naturally-tanned organic leather top paired with organic silk pants from the collection in support of the launch. "It's awesome that there's a major global brand that's affordable and pushing this movement," said the model, who launched the socially responsible online fashion platform Master and Muse in 2013. "It's absolutely necessary."

She also offered a few of her own day-to-day, environmentally friendly fashion tips. "Reuse something," she urged. "I just took a vintage piece, and changed the hem and added a slit to the front, so it looked sexier and new."