How Does Lead Affect the Human Body?

In children, exposure to lead has been associated with lower school performance, prolonged reaction intervals and decreased hand-eye coordination. The physiological immaturity of fetuses and infants (up to 3 years) increases the risk that lead will enter the central nervous system, which can result in permanent neurological or behavioral disturbances.

Lead can affect almost all the organs and systems, being the first manifestations in the neurological system, then lead poising causes serious consequences in the cardiovascular, renal and reproductive system as it were described above. It is worth mentioning that the absence of symptoms in the patient does not exclude lead poisoning.

Neurological problems can occur even in individuals with blood lead levels considered safe (<10 μg / dL). Individuals without symptoms, especially children, can have neurological damage. In children, acute exposure to high doses of lead can cause encephalopathy, with the presence of ataxia (difficulty coordinating movements), seizures, hyperirritability, coma and death. Several studies in children refer to different blood levels of lead associated with encephalopathy, but a level ≥70 μg / dL indicates a high risk of developing the complication. This level is associated with neurological damage or long-term behavioral disturbances, although the child still does not have symptoms and signs of encephalopathy.

Some studies show that, for every 10 μg / dL of blood lead increase, the intelligence quotient drops from 4 to 7 points. Exposure to lead is also associated with other neuropsychological problems, decreased attention with hyperactivity, deafness, and disturbances of the balance and peripheral nerves. Some of these defects persist into adulthood.

Individuals exposed to lead as adults may have the same complications as children, but at higher blood lead levels. For example, encephalopathy can occur with 460 μg / dL.

The precursor symptoms of encephalopathy include drowsiness, irritability, decreased attention and memory, and the presence of tremors, which can occur with lower levels of lead in the blood. In clinical reality, symptoms and signs do not necessarily occur in an expected way; some symptoms occur at lower levels, others at higher levels. There are other symptoms that can occur at levels of 40 to 120 μg / dL; these include decreased libido, manual dexterity, ability to understand, reaction interval, visual motor activity, intelligence quotient, memory and concentration. This person may also present with depression, headaches, changes in mood, headaches, dizziness, fatigue, impotence, irritability, lethargy, nervousness, general malaise and weakness. In addition, problems of postural balance and alterations of the peripheral nerves are described. Workers exposed to high levels of lead show paralysis of the radial nerve, due to decreased nerve conduction and muscle weakness.

The severity of lead exposure is directly related to the effects on the kidney. Severe exposure for a brief period is associated with reversible alterations of proximal tubular function, glycosuria, aminoaciduria, hyperphosphaturia (presence of glucose, amino acids and elevated levels of phosphate in urine). However, continuous or repeated exposures can lead to chronic nephropathy (interstitial nephritis), which is generally irreversible.

The presence of lead decreases the production of the heme nucleus, which affects the body’s ability to produce hemoglobin. It is estimated that a blood lead level of 50 μg / dL in adults with occupational exposure and around 40 μg / dL in children represents the anemia threshold, although other studies in children suggest a lower threshold (25 μg / dL).

High blood pressure is related to several risk factors; these factors include age, body weight, diet and physical activity. Lead exposure may be another factor that contributes to the development of hypertension. Although exposure to low or moderate levels of lead (blood level <30 μg / dL) shows only a minimal relationship, higher levels, generally related to occupational contacts, increase the risk of high blood pressure and cerebrovascular disease.

Exposure to lead causes a decrease in the total count and an increase in the proportion of abnormal sperm. The effects begin with levels of around 40 μg/dL. Chronic exposure, apart from the effect of acute exposure, also decreases the concentration, total count and motility of the sperm. The duration of these harmful effects is unknown after the exposure to lead ceases.