deleterious effect of a gradual accumulation of lead in body tissues, as a result of repeated exposure to lead-containing substances.

In the home, the main sources of lead are usually lead-based paint and drinking water (water-supply system) carried through lead pipes; lead-based paints are especially harmful to children who chew on painted toys and furnishings and eat paint peelings from the walls. Industries in which workers encounter lead-containing solids, dusts, or fumes are the petroleum industry, mining and smelting, printing, cutlery and storage-battery manufacture, plumbing and gas fitting, paint and pigment manufacture, and manufacture of ceramics, glass, and ammunition. Other possible sources of lead poisoning include the agricultural use of insecticides containing lead compounds; the spraying of fruits and vegetables may affect the workers and, eventually, the consumers. Constant exposure to the exhaust fumes of motor vehicles powered by fuel containing tetraethyl lead is also suspected of causing lead poisoning, especially in children.

Individual susceptibility to lead poisoning varies widely. Symptoms also vary; they may develop gradually or appear suddenly after chronic exposure. The poison affects the entire body—especially the nervous system, the gastrointestinal tract, and the blood-forming tissues. The victim usually becomes pallid, moody, and irritable and may complain of a metallic taste. Digestion is deranged, the appetite fails, and there may be severe abdominal pain, with spasms of the abdominal muscles (“lead colic”) and constipation. A black line (“lead line”) may appear at the base of the gums. There is often anemia. In later stages, headache, dizziness, confusion, and visual disturbances may be noted. Peripheral nerve involvement results in a paralysis (“lead palsy”) that generally first affects the fingers, hands, and wrists (“wrist drop”). The most serious effects are seen in children under the age of six, in whom brain and nervous system development is still occurring. In these children, even a small amount of lead can result in permanent damage and loss of function of the affected area of the brain. Complications may occur, such as learning disabilities, slowed growth, blindness, and deafness or, in extreme cases, convulsions and coma ending in death. Brain injury may also occur in adults after massive exposure.

The lead in the tissues may be removed gradually with substances such as the calcium salts of ethylene diamine, tetraacetic acid, and penicillamine. A lengthy treatment may be necessary, but recovery is usually complete, except when there is major involvement of the brain structures. Until the last half of the 20th century, damage to the brain caused by lead poisoning ended in death in about 25 percent of the cases; about half of those who survived showed some degree of permanent mental deterioration.