This is going to be a series of blog posts where I’m going to attempt to teach readers of this blog the stuff that most medical personnel don’t know. Then when you go to your doctor with your concerns, you’ll be in a position to teach them.
The first post in what will hopefully be a series is on blood lead levels.

What does the blood lead level mean?

When you measure the blood lead level, it is a combination of lead in the blood due to lead exposure in the last couple of months and lead released from the bones which is there because of longer-term exposure to lead. It’s called blood lead levels because the lead is measured in whole blood (plasma plus red blood cells).

Shortly after initial exposure to lead, most of the lead in blood is in your red blood cells and only very little in plasma. Red blood cells don’t have a nucleus and don’t have any way of repairing themselves so they eventually wear out after a few months. When that happens, they get broken down and the lead they contained appears in the urine or faeces and the blood lead level drops.

But the fall in blood lead level after exposure is stopped is not due to most of the lead leaving your body, it is only the lead that was in red blood cells. Any other lead that has been taken up by your organs (brain, liver, kidneys, bone) is still there. Lead accumulates in the body as long as there is any exposure.

This is probably the most important point I can make. The blood lead level tells you very little about how much lead you’ve accumulated, it mostly it only indicates more recent exposure to lead, but not entirely.

We need to understand where lead is in the body. You will find lead in the body anywhere where you would find calcium because the body can’t tell the difference between the two elements. You’ll also find lead where there is a lot of sulphur, such as sulphur-enzymes, and you’ll find lead where it has displaced zinc, disabling zinc enzymes.

It’s useful to consider lead in the body as being in compartments or pools because the effects of lead are different. There is the circulatory pool (blood, lymph), the soft tissue pool (kidneys, liver, other organs), the brain pool and the bone pool which is actually 2 pools, trabecular or spongy bone near the joints, and cortical bone, which is the long hard bone. Trabecular bone is rapidly renewed, cortical bone is only slow renewed.

Lead in each of the pools is retained for a different time and often has different effects. Lead is also exchanged between the pools.

I’ll concentrate on bone lead just now, and the other pools will be discussed later

If you have been exposed to lead for a longer period like months or years most of the lead you’ve absorbed and accumulated will be in the bones. In children under 16 up to 75% of the lead in the body is in the bones, in adults it can be up to 95%. It stays there for a long time.

Even if you are only exposed to tiny amount of lead, the natural remodelling process where bone is constantly broken down and rebuilt will result in accumulated lead being released from bone.

It is bone lead being released into the circulation that is responsible for the long-term damage caused by lead. It is bone lead that is released and passed to the foetus during pregnancy, and to the baby by breastfeeding. It is bone lead that can cause the symptoms of acute lead poisoning in leukemia, or dementia-like symptoms in osteoporosis.

Bone lead has to be considered in any treatment strategies concerned with removing lead from the body, and dealing with bone lead is a marathon, not a sprint.

Most medical people don’t understand this and the relationship with blood lead levels. I’ll try and make this clear in the next few posts.