The damaging effects of diesel fuel pollution go beyond a synergistic role in asthma development. Exposure to a combination of microscopic diesel fuel particles among people with high blood cholesterol (i.e., low-density lipoprotein, LDL or "bad cholesterol") increases the risk for both heart attack and stroke above levels found among those exposed to only one of these health risks. According to André Nel, Chief of Nanomedicine at the David Geffen School of Medicine at UCLA, "When you add one plus one, it normally totals two... But we found that adding diesel particles to cholesterol fats equals three. Their combination creates a dangerous synergy that wreaks cardiovascular havoc far beyond what's caused by the diesel or cholesterol alone." Experimentation revealed that the two mechanisms worked in tandem to stimulate genes that promote cell inflammation, a primary risk for hardening and blockage of blood vessels (atherosclerosis) and, as narrowed arteries collect cholesterol deposits and trigger blood clots, for heart attacks and strokes as well.