Heavy Metal Poisoning: Lead

U.S. Agency for Toxic Substances and Disease Registry lists toxic substances according to their prevalence and the severity of their toxicity and lead is in number one position. Recently the development of K-X-ray fluorescence (KXRF) instruments has made it possible to measure bone lead levels (which, in turn, reflect cumulative exposure over many years, as opposed to blood lead levels, which reflect recent exposure). High bone lead levels measured by KXRF are associated with increased risk of hypertension in both men and women. High maternal bone lead levels were found to cause lower birth weight, head circumference, birth length, and lower neurodevelopmental performance in children by age 2.   

Sources of lead poisoning:  Manufacturing of auto batteries, ceramics, fishing weights, lead crystal, demolition of lead-painted houses and bridges; stained glass making, soldering, environmental exposure to paint chips, plumbing, firing ranges (from bullet dust), food or water from lead pipes are the main sources of lead poisoning.  Contaminated herbal remedies, candies and exposure to the combustion of leaded fuels also contribute to the lead poisoning.

Lead can be absorbed through ingestion or inhalation and organic lead (e.g., tetraethyl lead) is absorbed through skin. In blood lead is concentrated in RBCs. Distributed in soft tissue, with ½ life of about 30 days. 15% of lead is sequestered in bone with ½ life of more than 20 years. Lead is excreted mainly in urine, but also appears in other fluids including breast milk.

 Toxicity: Acute poisoning with blood lead levels (BPb) of more than 60–80 µg/100ml can cause impaired neurotransmission and neuronal cell death, which lead to central and peripheral nervous system effects. If blood lead level is more than 80 µg/100ml it can cause acute encephalopathy with convulsions, coma, and death. 

Subclinical exposure of lead in children (BPb 25–60 µg/100ml) is associated with anemia, mental retardation, language deficit, motor function, balance, behavior, hearing, and school performance. Impairment of IQ can occur at even lower levels.

In adults, chronic subclinical exposures (BPb 40 µg/100ml) are associated with an increased risk of anemia, demyelinating peripheral neuropathy (mainly motor), and impairments of reaction time, hypertension, and ECG conduction delays. Chronic renal failure, diminished sperm counts and spontaneous abortions in females is seen.

Related Posts Plugin for WordPress, Blogger...