Book excerpt: This book presents an integrated and holistic discussion on cadmium, lead and mercury toxicity in aquatic environments, expanding general concepts on chemical speciation effects and exploring specific environmental toxicological issues, exposure routes, and bioanalytical approaches for their determination and assessments on their intracellular deleterious effects. It contains worldwide and regional aspects on cadmium, lead and mercury occurrence, fate, and toxicity, addressing key environmental exposure and health risk concerns to both humans and aquatic organisms. Our book is of interest to anyone conducting research in the broad fields of oceanography, geochemistry, ecotoxicology, and environmental and public health.