Even though lead is a natural substance, the issue comes down to amount. Even healthy substances are toxic is excess. There is no known physiological need for lead. We can tolerate other metals better, like aluminum, zinc, iron, because our body has requirements for them. But in the case of lead and cadmium, there is no use for them in our bodies. Thus, they are toxic in low amounts.
For those who poo-poo the risks, the following is from the toxic substances risk site (with results documented by research literature) Take a look at the impacts on the brain. I happen to treasure that particular organ and its functions.:
http://www.atsdr.cdc.gov/HEC/CSEM/lead/physiologic_effects.html#nerve
Lead primarily affects the peripheral and central nervous systems, renal function, blood cells, and the metabolism of vitamin D and calcium. Lead can also cause hypertension, reproductive toxicity, and developmental effects.
Lead encephalopathy (damage to the skull and brain) may occur (Kehoe 1961). Precursors of encephalopathy, such as dullness, irritability, poor attention span, muscular tremor, loss of memory, and hallucination, may occur at low levels.
Effects can be manifested as malaise; forgetfulness; irritability; lethargy; impaired concentration; depression and mood changes; increased nervousness; headache; fatigue; impotence; decreased libido; dizziness; weakness; and paresthesia; as well as diminished reaction time, visual motor performance, hand dexterity, IQ scores, and cognitive performance (ATSDR 1999).
Kidney Problems
Lead exposure can lead to renal effects such as Fanconi-like syndromes, chronic nephropathy, and gout.
Many studies show a strong association between lead exposure and renal effects. Acute, high dose lead-induced impairment of proximal tubular function manifests in aminoaciduria, glycosuria, and hyperphosphaturia (a Fanconi-like syndrome); these effects appear to be reversible (ATSDR 1999). However, continued or repetitive exposures can cause a toxic stress on the kidney that, if unrelieved, may develop into chronic and often irreversible lead nephropathy (i.e., interstitial nephritis).
Most lead-associated renal effects or disease are a result of ongoing chronic low levels or current high acute exposure. They can also be attributable to previous chronic lead exposure.
Lead inhibits several enzymes critical to the synthesis of heme, causing a decrease in blood hemoglobin.
Cardiovascular (Hypertension) Effects
· Lead exposure may lead to increased risk for hypertension and the effects of hypertension.
Reproductive Effects
· Evidence suggests an association between lead exposure and certain reproductive and developmental outcomes.
Male Reproductive Effects
Recent reproductive function studies in humans suggest that current (ongoing) occupational exposures may decrease sperm count totals and increase abnormal sperm frequencies (Alexander et al. 1996; Gennart et al. 1992; Lerda 1992; Lin et al. 1996; Telisman et al. 2000).
Ron