1. INTRODUCTION

Specifications for impurities and contaminants are critical quality attributes of dietary ingredients and dietary supplements because they have the potential to affect the safety and stability of dietary supplements. Impurities and contaminants include substances that can appear in dietary ingredients and supplements through various routes. They can occur naturally as a result of their presence in the ground, water, or air in the location from which materials are sourced or be introduced inadvertently as part of a product’s synthesis, cultivation, harvest, extraction, or manufacturing. The fact that dietary supplement products and ingredients often stem from multiple and/or inhomogeneous sources, both domestic and nondomestic, increases concerns for quality control, particularly regarding impurities and contaminants.