A review of the biological toxicity effects of Ammonia exposure

Abstract

Ammonia exposure is a significant environmental concern, as it can enter the human body through multiple exposure routes, including the atmosphere, water sources, and the food chain, posing a multidimensional threat to public health. This review first describes the sources of ammonia exposure and its direct and long-term effects on human health, including respiratory diseases, the risk of gastrointestinal cancer, and liver toxicity from water eutrophication. Physiologically, the urea cycle in the liver and intestinal microorganisms mainly converts ammonia into relatively non-toxic compounds. However, when liver function is impaired, elevated blood ammonia can induce hyperammonemia, accompanied by intestinal microbiota imbalance. Existing treatments, such as drugs and dialysis, are limited by long cycles and high costs. In recent years, fecal microbiota transplantation based on engineered bacteria has shown potential therapeutic promise. Finally, we discuss the ammonia metabolism mechanisms and key enzyme systems of autotrophic and heterotrophic ammonia-oxidizing bacteria, and then talk about using these genes for therapeutic intervention. This review first elaborates on the effects of ammonia exposure on various aspects of the human body, then discuss the physiological aspects of intestinal microbiota disorder caused by elevated blood ammonia under impaired liver function.