What must be marked on syringes containing blood to indicate potential hazards?

Syringes containing blood must be marked with "Biohazard" to indicate potential hazards associated with handling them. This label communicates the presence of biological materials that could pose a risk to health, specifically in situations where exposure can lead to infections or other medical concerns. The biohazard symbol is universally recognized and alerts healthcare and laboratory personnel to the potential for exposure to infectious agents.

While alternative terms like "Biological hazard" and "Contaminated material" convey similar meanings, "Biohazard" is the standardized term commonly used in safety protocols and regulations, making it the correct choice for labeling such hazardous materials. "Hazardous waste" is also a relevant term but is more general and relates to waste disposal rather than the immediate risks associated with the handling of blood-containing syringes. Thus, using "Biohazard" is essential for proper identification and safety practices in medical and laboratory environments.