Lead Poisoning

What is lead? It is an element with the symbol Pb (latin plumbum) in the heavy metal family with atomic number 82 and is a soft, malleable metal. It has practical applications and is used in many common products. For example batteries, pipes, as shields in radiology, ammunition, and even pencils for writing. It is also used in alloys and other products. It has been used in ancient times in the Roman and Greek empires as well as in Asia for weapons and even the arts such as glass making, glazes, and enamals.

Where is lead found? Lead is in the environment and can be found in the soil, paint in old buildings , in water pipes which can affect drinking water, and may even contaminate some foods such as canned food, certain manufacturing plants, and mines. It can also be released into the air and be inhaled. It may end up contaminating the soil. Once the industrial revolution started the manufacturing process and especially mining has led to increased release of lead into the environment. The health effects were observed and recorded in the 1800’s in France and England where lead poisoning occurred in some miners. A century later another culprit was leaded gasoline. With the change to unleaded gasoline the average blood level of lead dropped by 78%. Over the years other sources such as lead in the paint of old houses was noted. When canned food was initially invented some lead had leached into the food. Again manufacturing processes have changed to minimize lead in these products. With an aging infrastructure the most recent concern had been with old lead pipes that contaminate the water supply. Flint Michigan has been in the headlines for comtamination of their water supply due to old lead pipes. People and the drinking water have been tested with some falling within the acceptable range and some with much higher levels. Recently Virginia tech has analyzed some 250 samples and found that 45% of samples had over 5pp billion. Some had excess of 100ppb and in one case over 1000ppb. This was a random sample and did not target the most at risk homes.

How does it effect human health? Lead is poisonous to the body if injested (through contaminated food or water or even by injesting soil or paint particles) or inhaled from manufacturing/mining processes. It may even be absorbed thru the skin although this is less common. At high enough levels lead can damage all organs especially the nervous system, the kidneys, and the blood cells. It can also be incorporated into bone in place of calcium. In the body lead can inhibit an enzyme needed to incorporate iron into hemoglobin and leads to a microcytic anemia. The acceptable blood levels are 10ug/dl although this is still much higher then found in people in many rural nonindustrialized areas. At very high levels when the patient experiences neurological symptoms and organ damage, a chelating agent EDTA is used. This can bind to lead and causes it to be excreted in the urine. In growing children chronic exposure is of particular concern because of the growing central nervous system. So prevention, awareness, testing, and changing the environment (ie removing old paint and replacing old lead pipes) can lead to long term solutions.

Lead levels: Lowest reported lead levels of people today in remote regions of the southern and northern hemispheres (0.78 ug/dl and 3.20 ug/dl respectively). In high population industrial areas 64.5% to 99.5% had lead levels >10ug/dl. The world health organization has set a level as 10 ug/dl as acceptable. As an example 116 children near an automobile battery recycling plant in Haina, near Santo Domingo, Dominican Republic were poisoned by lead. The mean blood lead level at that time was 71 µg/dl with a minimum of 9 µg/dl and a maximum of 234 µg/dl. Within the US many states test children age 1-5 that are at high risk and are funded by the CDC in order to track data and monitor. Overall there has been a significant decline in the number of cases with elevated lead levels by 40%-90% over the last 15 years.

In any case there are many things in the environment that effect us and our health. Except in the case of long term exposure at moderate to high levels of lead, it seems more reasonable that a multifactorial cause is likely the reason in the lower IQ’s at lead levels <10ug/dl.

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