Environmental contaminants and intestinal function

The environmental contaminants which have their major effects on the small intestine may be classified into five major categories: (1) bacterial, viral, and parasitic agents, (2) food and plant substances, (3) environmental and industrial products, (4) pharmaceutical agents, and (5) toxic agents whose metabolic effects are dependent on interreaction with intestinal bacterial flora, other physical agents (detergents), human intestinal enzyme deficiency states, and the nutritional state of the host. Bacterial, viral, and parasitic agents are the most important of all such agents, being responsible for significant mortality and morbidity in association with diarrheal diseases of adults and children. Several plant substances ingested as foods have unique effects on the small bowel as well as from contaminants such as fungi on poorly preserved grains and cereals. Environmental and industrial products, in spite of their widespread prevalence in industrial societies as contaminants, are less important unless unexpectedly intense exposure occurs to the intestinal tract. Pharmaceutical agents of several types interreact with the small bowel mucosa causing impairment of transport processes for fluid and electrolytes, amino acid, lipid and sugars as well as vitamins. These interreactions may be dependent on bacterial metabolic activity, association with detergents, mucosal enzyme deficiency state (disaccharidases), and the state of nutrition of the subject.