1 Substance abuse. Abuse of drugs and alcohol can contribute to panic disorder.  Major life stress. Stressful events and major life transitions, such as the death of a loved one, can sometimes trigger panic attacks, which can potentially recur and go on to become panic disorder.
Zero emission refers to an engine, motor, process, or other energy source, that emits no waste products that pollutes the environment or disrupts the climate. Contents.
Is it possible for vehicles powered by hydrogen fuel cells to reduce the pollution in the air? FREDERIC J. BROWN/AFP/Getty Images One of the most important benefits of a hydrogen economy is that fuel cells are nonpolluting. No carbon emissions are produced when electricity is generated in a fuel cell. A hydrogen fuel cell produces two byproducts -- heat and water. If every vehicle on the road were powered by a hydrogen fuel cell, the familiar clouds of smog that hang over many U.S. cities, most of which comes from vehicle exhaust, would largely disappear.