Human emissions of the potentially harmful trace metal vanadium into Earth's atmosphere have spiked sharply since the start of the 21st century due in large part to industry's growing use of heavy oils, tar sands, bitumen and petroleum coke for energy, a new Duke study finds. These emissions now exceed those from all natural sources combined. Growing evidence suggests exposure to vanadium-rich aerosols can impair respiratory functions and exacerbate conditions such as asthma or COPD.