Final answer:
Efflorescence is not merely a cosmetic issue; it indicates that water is present in material, which can cause structural damage and health risks due to mold.
Step-by-step explanation:
The statement "Efflorescence is a cosmetic issue only" is false. Efflorescence is a condition where water-soluble salts come to the surface of porous materials, such as concrete, brick, or stone, and then evaporate, leaving a powdery residue. While it primarily poses aesthetic concerns, efflorescence can indicate deeper issues. It is often a sign that water is moving through a material, which can lead to potential structural damage due to erosion or freeze-thaw cycles. Moreover, the presence of water can lead to mold growth, which poses health risks.