Concept:
Pharmaceutical pollutants may enter water, soil, and the environment.
Step 1: Antibiotic residues in the environment expose microorganisms to low drug levels.
Step 2: This creates selection pressure.
Step 3: Resistant microorganisms survive and multiply.
Step 4: Hence, antimicrobial resistance is a major concern.
\[
\boxed{\text{Development of antimicrobial resistance}}
\]