Causes and Symptoms
Lead poisoning is a major, preventable environmental health problem. Elevated lead levels in adults can increase blood pressure and cause fertility problems, nerve disorders, arthralgia, and problems with memory and concentration. Children under the age of six are at high risk for harm because their brains and nervous systems are still maturing. Blood lead levels as low as 10 micrograms per deciliter are associated with harmful effects on children’s ability to learn. Very high blood lead levels of 70 micrograms per deciliter can cause devastating health consequences, including seizures and other neurological symptoms, abdominal pain, developmental delays, attention deficit, hyperactivity, behavior disorders, hearing loss, anemia, coma, and death.
Children can be exposed to lead in many ways. Sources of exposure include automobile exhaust, lead-based paint, and environmental contaminants released by industrial processes that use or produce lead-containing materials. Contributors to childhood lead exposure also include lead-contaminated containers, food, dust, soil, air, and water; toys contaminated with lead paint; lead-containing ceramics and hobby supplies; substance abuse such as gasoline sniffing; parental transfer from lead-rich occupational environments; and traditional medicines such as azarcon and greta. Deteriorating lead-based paint in older homes is the most important source of lead exposure in children (many homes built prior to 1960 contain some lead-based paint). Swallowing lead-based paint dust through normal hand-to-mouth activity and chewing directly on painted surfaces are major methods of lead ingestion. Children are often attracted to lead paint because of its sweet taste. Lead-based paint in homes, however, was banned from residential use in 1978, but families living in homes built before this time (especially before 1960) are at risk. Lead exposure in adults is usually a result of jobs in house painting, welding and smelting, the manufacturing of car batteries, and other occupations involving lead.
Upon entering the human body, inorganic lead is not metabolized but is directly absorbed, distributed, and excreted. The rate at which lead is absorbed depends on its chemical and physical form and on the physiologic characteristics of the exposed person. Once in the blood, lead is distributed among three compartments: the blood; soft tissue zones such as the kidneys, bone marrow, liver, and brain; and mineralizing tissues such as bones and teeth. For lead poisoning to take place, major acute exposures to lead need not occur. The body accumulates lead and releases it slowly; therefore, even small doses over time can be toxic. It is the total body accumulation of lead that is related to the risk of adverse effects. Whether lead enters the body through inhalation or ingestion, the biologic effects are the same—interference with normal cell function and with certain physiologic processes.
By and large, children show a greater sensitivity to the effects of lead than do adults. Parents working in lead-related industries not only may inhale lead dust and lead oxide fumes but also may eat, drink, and smoke in or near contaminated areas, increasing the probability of lead ingestion and subsequent transfer to their children. Since lead readily crosses the placenta, the fetus is at risk. Fetal exposure can cause potentially adverse neurological effects in utero and during postnatal development. The incomplete development of the blood-brain barrier in very young children, up to thirty-six months of age, increases the risk of the entry of lead into the developing nervous system, which can result in prolonged neurobehavioral disorders. Children absorb and retain more lead in proportion to their weight than do adults. Young children also show a greater prevalence of iron deficiency, a condition that can increase the gastrointestinal absorption of lead.
Symptoms of lead poisoning and lead intoxication vary because of differences in individual susceptibility, and the severity of symptoms increases with increased exposure. Symptoms of mild lead toxicity include abdominal discomfort, fatigue, muscle pain, or paresthesia. Moderate toxicity is indicated by arthralgia, tremor, fatigue, difficulty concentrating, headache, abdominal pain, vomiting, weight loss, and constipation. Severe toxicity symptoms include paresis or paralysis, encephalopathy, seizures, severe abdominal cramps, hearing loss, changes in consciousness, and coma.
Treatment and Therapy
If a child is suspected of having lead poisoning, laboratory tests are necessary to evaluate lead intoxication levels. Laboratory techniques defining lead toxicity include blood lead level screening, erythrocyte protoporphyrin (EP) and zinc protoporphyrin (ZPP) screening, creatinine, urinalysis, and hematocrit and hemoglobin tests with peripheral smear. The Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) recommend that all children living in high-risk neighborhoods or conditions should have their blood levels tested regularly until the age of five.
The physical examination for suspected lead poisoning cases includes special attention to hematologic, cardiovascular, gastrointestinal, and renal systems. Any neurological or behavioral changes are considered significant indicators. In addition, severe and prolonged lead poisoning may be indicated by a purplish line on the gums. A complete interview and medical evaluation of a suspected lead poisoning patient includes a full workup and medical history. Clues to potential exposure vectors can be obtained by discussing family and occupational history, use of traditional medicines, remodeling activities, hobbies, table and cookware, drinking water source, nutrition, proximity to industry or waste sites, and the physical condition and age of the patient’s residence, school, and/or day -are facility.
The treatment and management of lead poisoning first involves the separation of the patient from the source of lead. After a diagnosis of lead poisoning is made, local environmental health officials should be contacted to determine the lead source and what remediation action is necessary for its control. This may include testing a home's paint and water for lead, as well as identifying hobbies such as making stained glass, soldering electrical devices, fishing with lead-containing sinkers, all of which can expose children to lead poisoning. A diet high in calcium and iron may help to decrease the absorption of lead.
The Centers for Disease Control and Prevention recommends that children with blood lead levels of 45 micrograms per deciliter or greater should be referred for chelation therapy immediately. However, chelation should be used with caution. Several drugs are capable of binding or chelating lead, depleting both soft and hard (skeletal) tissues of lead and reducing its acute toxicity. All these drugs have potential side effects and must be used with caution. The most commonly used chelating agent is calcium disodium edetic acid, but several other agents are available.
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