Following Sunday morning services, 27 people attended a church social where coffee, baked goods, and sandwiches were served. Within 15–60 minutes, 13 people developed vomiting and abdominal discomfort, accompanied over the next several hours by nonbloody diarrhea. Within 12 hours, seven of these individuals were hospitalized with ongoing gastrointestinal symptoms, hypotension, and anion gap metabolic acidosis. Fluid resuscitation and pressors were accompanied by adequate urine output. What diagnoses should be considered? What tests should be conducted, and what therapy should be considered?
Some metals such as iron are essential for life, whereas others such as lead are present in all organisms but serve no useful biologic purpose. Some of the oldest diseases of humans can be traced to heavy metal poisoning associated with metal mining, refining, and use. Even with the present recognition of the hazards of heavy metals, the incidence of intoxication remains significant, and the need for preventive strategies and effective therapy remains high. Toxic heavy metals interfere with the function of essential cations, cause enzyme inhibition, generate oxidative stress, alter gene expression, and perturb cell signaling. As a result, multisystem signs and symptoms are a hallmark of heavy metal intoxication.
When intoxication occurs, chelator molecules (from chela “claw”), or their in vivo biotransformation products, may be used to bind the metal and facilitate its excretion from the body. Chelator drugs are discussed in the second part of this chapter.
TOXICOLOGY OF HEAVY METALS
Lead poisoning is one of the oldest occupational and environmental diseases in the world. Despite its recognized hazards, lead continues to have widespread commercial application, including production of storage batteries (nearly 90% of US consumption), ammunition, metal alloys, solder, glass, plastics, pigments, and ceramics. Corrosion of lead plumbing in older buildings or supply lines may increase the lead concentration of tap water. Environmental lead exposure, ubiquitous by virtue of the anthropogenic distribution of lead to air, water, and food, has declined considerably in the last three decades as a result of the elimination of lead as an additive in gasoline, as well as diminished contact with lead-based paint and other lead-containing consumer products, such as lead solder in cans used as food containers. Legislation in the United States in 2011 further reduced the maximum permissible lead content of children’s products to 100 ppm. Lead continues to be used in some formulations of aviation gasoline for piston-engine aircraft. The presence of lead in certain folk medicines (eg, the Mexican remedies azarcon and greta, and certain Ayurvedic preparations) and in cosmetics (eg, kohl utilized around the eyes in certain African and Asian communities) has contributed to lead exposure to children and adults. Although public health measures, together with improved workplace conditions, have decreased the incidence of serious overt lead poisoning, there remains considerable concern over the effects of low-level lead exposure. Extensive evidence indicates that low levels ...