Lead is a gray metal, soft and malleable, present naturally in the earth’s crust. Its widespread use has had a great impact on the environmental pollution and, consequently, a considerable increase in its exposure to the population that has generated serious public health problems.
Lead poisoning is a health problem that deserves adequate attention from all sectors of society, especially because the effects on children occur with lower concentrations of lead than in adults. The immediate effects of lead are neurological, but poisoning in childhood can originate later kidney problems, high blood pressure, and reproductive problems.
What Are The Early Signs Of Lead Poisoning?
The concentration of lead in the blood promotes particular clinical manifestations where the progression of damage in infants begins with lower concentrations than in adults. Acute lead poisoning manifests with renal failure, encephalopathy, and gastrointestinal symptoms. In chronic lead poisoning, which is more frequent, the hematopoietic, nervous, gastrointestinal and reproductive systems are compromised. Several patients with lead poisoning report the signs of abdominal pain, asthenia, irritability, and constipation; in some cases, it can be observed the “Burton border or sulphide line”, this is a violet or blackish border located in the nearest part of the gum with respect to the teeth.
-In a situation of high lead poisoning, peripheral polyneuropathy (it consists of a dysfunction of a part of the nervous system) may occur affecting the upper limbs.
-Acute lead poisoning occurs after respiratory exposure at high concentrations, with encephalopathy (brain dysfunction syndrome), kidney failure and gastrointestinal symptoms. The chronic toxicity is the most frequent and manifests with multisystemic commitment: hematopoietic, nervous system, gastrointestinal, kidney and reproductive system.
-Patients go to health services for signs of abdominal pain, asthenia (generalized feeling of fatigue, physical and mental weakness), headache, irritability, difficulty in the concentration and constipation, among others. Abdominal pain is characterized by pain attacks with abdominal defense, in fact, some patients have been operated on with a diagnosis of acute abdomen, and pain may give way with abdomen pressure.
-Workers exposed for a long time and without personal protection measures can present signs of peripheral polyneuropathy, which affects predominantly the upper limbs. Plumbic encephalopathy, characterized by sensory disorder and seizures occurs in patients with blood lead greater than 100 mg/dL.
-Spinal anomaly, anal atresia, heart disease, esophageal fistula, renal anomalies and limb abnormalities have been described in a newborn of a mother with high blood pressure during the first quarter of pregnancy.
Toxicokinetics of Lead Poisoning
Lead poisoning can adversely affect the nervous, immune, reproductive and cardiovascular systems. Absorption depends on gastrointestinal transit, nutritional status and age; it occurs mainly through the respiratory and gastrointestinal systems; it is greater if there are deficiencies of iron or calcium, in diets rich in fats and during childhood (when it is 40 to 50%, while in adulthood it is 10%). After absorption, 99% is retained in the blood between 30 and 35 days; during the next 4 to 6 weeks it is dispersed to other sites such as liver, kidney, bone marrow and central nervous system. After 1 to 2 months it diffuses to the bones where it is inert and non-toxic.
The average life of lead in brain tissue is approximately 2 years and in bones; it persists for 20 to 30 years, where it can be mobilized in situations such as pregnancy, hyperthyroidism and advanced age. It has been reported its ability to cross the placenta and the blood-brain barrier, so it is considered that damages neurocognitive function in babies and small children generating behavioral problems, decreased IQ and learning.
Finally, the lead that is incorporated into the body is excreted in urine (90%) and in less quantity in bile, skin, hair, nails, sweat and breast milk.
Diagnosis of Lead Poisoning
The diagnosis of lead poisoning is usually difficult because the clinical presentation is subtle and the symptoms are non-specific. It is usually done by blood lead measurements and zinc-protoporphyrin concentrations. The Center for Disease Prevention and Control of the United States (CDC) recommends professional intervention at higher concentrations of 5 μg/dL and 10 μg/dL of lead in blood in children and adults, respectively.
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