There is no precise direct correlation between blood level and clinical manifestations. Children with blood lead levels greater than 100 ug/dl may occasionally appear clinically well, and children with blood lead level 30-35 ug/dL may be symptomatic. The probability of severe symptoms increases with the increase in exposure to lead, and is greater the higher the blood lead level is.
If blood lead levels are low, there may be no obvious symptoms of lead poisoning, although even low levels of lead may alter physiology and impact child development. Studies have shown an increase of blood lead from 10 μg/dL to 20 μg/dL results in an average decrease in IQ of approximately 2 points. That is why it is important to screen young children for lead poisoning.
Symptoms in young children may develop insidiously and may abate spontaneously. The following symptoms may occur:
- Gastrointestinal– anorexia, sporadic vomiting, intermittent abdominal pain (colic) or constipation.
- Central Nervous System– behavior changes, hyperactivity, aggression impulsiveness, irritability, lack of interest in play, lethargy, development delays, reversal in verbalization, loss of motor skills, clumsiness, short attention span or leaning disabilities.
- Hematologic– anemic, pallor
- Cardiovascular– hypertension, bradycardia
- Encephalopathy may occur as toxic damage to the brain progresses - sudden onset of persistent vomiting; sever ataxia (loss of coordination), altered state of consciousness, coma, seizures or massive cerebral edema in younger children. Encaphalopathy rarely occurs in blood lead levels under 100 μg/dL.
- Nonspecific or vague symptoms include abdominal pain, vomiting, constipation, anorexia, headache and fever.