On Tuesday, National Nurses United (NNU), the nation's largest union of registered nurses, joined a growing chorus of voices opposing the Keystone XL pipeline.

The group said their opposition was rooted in health concerns: from processing of the tar sands the pipeline would carry, from potential spills, and from the multitude of health impacts from climate change, which the tar sands industry exacerbates.

"Nurses care for patients every day who struggle with health crises aggravated by environmental pollution in its many forms," stated NNU Co-President Deborah Burger, RN. "As a society we need to reduce the effects of environmental factors, including climate change, that are making people sick, and endangering the future for our children. That’s why we oppose the Keystone XL pipeline."

"Our leaders should be focused on finding safe, sustainable energy that would also help stem the increase in environmental pollution and climate change," said Burger.

"The health of our world depends on it."