Why are low-density lipoproteins (ldl) considered unhealthy?

Blood LDL Level: LDL is a particle that carries cholesterol in the blood. Increased numbers of circulating LDL particles drive their entry into the walls of arteries where they promote and accelerate atherosclerosis (hardening of the arteries), and subsequently increase risk for heart attack, stroke and premature death. Lowering LDL can reduce this risk.