Expansion of renewable sources should appreciably improve the health of the 700,000 U.S. workers employed in the energy sector. That's according to an assessment published recently in the Journal of the American Medical Association.

For the study, researchers at the Medical College of Wisconsin in Milwaukee examined the human health risks associated with traditional fossil fuels such as coal, oil and natural gas relative to renewable energy sources such as wind, solar and biomass.

Wind and solar appeared to pose less risk of workplace injury and death than traditional fossil-fuel industries, study authors say. That's because the dangerous energy-extraction phase is minimized or eliminated in wind or solar energy production, the researchers explain.

Biomass - comprised of biofuels, organic waste and wood derived fuels - currently accounts for more than half of U.S. energy-renewable consumption and doesn't appear to offer a significant safety benefit to U.S. workers relative to fossil fuels, the report concluded.