The greatest hazards to health are contaminants caused by:

• A. Microorganisms
• B. Chemicals
• C. Pests
• D. Radiation

Answer: (A)

Microorganisms pose the greatest health hazard among common contaminants because they cause infectious diseases that can spread quickly and affect many people. Bacteria, viruses, and parasites can contaminate water, food, surfaces, and air, leading to outbreaks and illness with relatively small amounts of exposure. This makes prevention—through proper sanitation, clean water, safe food handling, handwashing, vaccination, and infection-control practices—especially impactful in protecting health.

Chemicals, pests, and radiation can also threaten health, but their risks are often more controllable through regulation, pest management, shielding, and limiting exposure. In many settings, the rapid transmission and potential for large outbreaks driven by microorganisms elevate their status as the most significant health hazard.