How soon after exposure is Lead detectable in my child’s blood? What is the “half-life” of Lead in the bloodstream? How long does Lead stay in the body?

Here’s a link from the CDC with some info on this topic

A quote from the above-linked article: “Lead is cleared from the blood and soft tissues with a half-life of 1 to 2 months and more slowly from the skeleton, with a half-life of years to decades.”

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#1.) How soon after exposure is Lead detectable in my child’s blood?

Lead is detectable in the blood immediately upon exposure in most cases. Lead “bio-mimics” Calcium — because Lead is “misidentified” as Calcium-like by certain metabolic processes. So, much the same way your body begins to process dietary Calcium the moment it enters your digestive system via your mouth, the body immediately begins to try to “utilize” Lead (with both inhalation and ingestion pathways) by substituting it for Calcium and storing it in place of Calcium in the body — in the brain, organs, and bones. This is the pathway by which Lead causes damage to normally Calcium-dense structures – like the tissues of the brain, bones, teeth, and organs. When the body substitutes Lead for structurally & neurologically/electrically critical Calcium, the body cannot function properly.

In my experience, many pediatricians and poison control center representatives are not up on the current science that demonstrates that Lead shows up in the blood immediately. I saw this (again) firsthand at the beginning of the CoviD Pandemic (early 2020)… A mama contacted me because her baby had swallowed some Lead pellets from inside a maraca. Poison control told her “not to worry”! I told her to rush to the Emergency Room and get an immediate Blood Lead Level (BLL) test. ER docs were also reluctant to administer the BLL test, but did so — and within a few hours of her child swallowing the pellets his BLL was registering 7.0 (µg/dL). 

In conclusion: If you suspect an acute exposure, it is never “too soon” to get tested. It is also good to get tested right away because you want to be able to estimate what the highest exposure level was, so you can have a sense of the likely scope of possible impacts. Following an acute exposure, Blood Lead levels will start going down fairly quickly, too (if the source of exposure has been fully removed) and – while it is impossible to determine with certainty precisely what the peak levels might have been  – if you don’t test right away, you may never know anything meaningful at all about the approximate highest BLL as a result of a specific-event acute exposure.

#2.) What is the “half-life” of Lead in blood?

Chart below is the progression of my son Avi’s Blood Lead Level
over the two years after he was poisoned. Continue reading below the chart.

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My children were acutely poisoned in early August, 2005. Avi was not tested until November 4, 2005 (about 3 months after his exposure) – so we will likely never know how high his BLL was initially – but based on the scientific understanding of the half-life of Lead in the blood (which is a theory that does not often play out in practical real-world applications) – we can guess…  

The theoretical “half-life” of Lead in the blood (following an acute exposure) is understood by the medical community to be 30 to 45 days. Again, this is a theoretical construct — as one can only normally demonstrate this if the source of exposure is:

1.  known & specific (clearly-identified & likely incident related)
2.  subsequently completely/fully removed 

(Meeting both of these conditions is not always possible.)

In the case of the little boy above (who swallowed the maraca pellets – a specific-event acute exposure),  the source was both specifically known, and removed fully. In the case of a child who is living in a Lead-painted house without remediation, identifying all primary exposure sources (especially for chronic / persistent low level exposure) is less clear-cut, and thus knowing if the source of exposure has been fully removed (without constant thorough testing of both the home and the child) can also be more challenging.

Theory vs. Reality – Lower Levels

In practice (vs. theory), when children’s Blood Lead Levels get below a BLL 5.0, it seems that the remaining BLL points tend to come down more slowly (much more slowly than being reduced by half every 30 to 45 days) even if the source of exposure is fully removed. You can see a clear example of this when looking at the progression of my son Avi’s Blood Lead Levels from November 2005 through March 2007 – on the chart above. It took nearly seven months (from August 23 to March 12th the following year) for Avi’s BLL to reduce from a BLL of 6.0 to a BLL of 4.0 even though he was fully removed from the source of his exposure during that period of time [we had moved to a new construction townhome in April of 2006 and did not move again until April 2007.]

Given my sons’ initial exposure was a specific-event acute exposure (it occurred over just a couple of days], and given we know the pathway of exposure (inhalation of Lead-containing fumes caused by the burning of Lead paint), AND because we know the approximate date for the onset of severe / acute symptomatic expression of their exposure (in retrospect, we know this – as they became instantly quite sick when the torch burning of the paint was started by the workmen in early August 2005), one might theoretically extrapolate the following:

• Tested 11/4/2005, BLL 16.0
• 30 days earlier (10/5/2005), likely/possibly in the neighborhood of BLL 32.0
• 30 days earlier (9/5/2005), likely/possibly in the neighborhood of BLL 64.0
• Initial poisoning – early August 2005 – possible approximate BLL at initial exposure: 128.0

So while we cannot know for sure that Avi’s BLL was in fact initially a 128 – it makes sense as a hypothetical extrapolation, given observed typical “half-life” trajectories, AND both the acute incidental nature of his exposure, and the extreme/dramatic symptoms he experienced from the moment (we later determined) he had been poisoned, and in the months following his poisoning.

For an alternate scenario, let’s discuss a baby with a hypothetical BLL of 7.0:

In theory, the following progression might be expected – if the child is removed fully from the source:

• Date of testing: 7.0
• 30 days later (theoretical minimum half-life): baby might be down to a 3.5
• 30 days later: baby might be down to a 1.75
• 30 days later: baby might be down to a 0.875 (or “less than 1 microgram of Lead per deciliter of Blood.)

This is why, when a parent comes to me excited that their baby has dropped from a BLL of 7.0 to a BLL of (for example) 3.0 six months after the initial testing, I have concerns that there is possibly still a persistent chronic low-level exposure source impacting that kiddo (or that their low level BLL now is a “remainder” from a previously higher level – yet not known/ not tested for  – exposure at a younger age.)

Separating “theory” from practical reality

Again – looking at the progression of my own children’s BLL’s, the half-life theory does not always play out. In my experience working with families, a failure of the half-life theory is especially likely to be observed when there has been a higher-level acute exposure, in a very young, rapidly-growing baby (with consequent high cellular turnover) – which can result in Lead levels fluctuating and not reducing quickly (even with complete removal of the child from a known source) — as relatively high amounts Lead [absorbed with an initial acute exposure] may be released back into the bloodstream from tissues and organs and bones as the child grows.

It is also for this reason (the possible potential for Lead that has been stored in their body to be released & recirculated) that non-medically supervised chelation (including food-based chelation and other non-medical interventions) is quite controversial.

#3.) How long does Lead stay in the body?

Well, Dr. Lanphear said it best in my film: “Ninety percent of the Lead that you have ever been exposed to is likely still in your body”. The half-life of Lead in tissue and bones is much longer than that of Lead in the bloodstream and the main mechanism through which a Blood Lead Level gradually comes down is that – rather than being eliminated – the Lead in the bloodstream is actually absorbed by the tissue, organs and bones in the place of Calcium over time…. so in most cases, when a child’s Blood Lead Level goes down, that does not mean that the Lead has left their body. Lead continues to accumulate in tissue and bones throughout your lifetime, with every exposure to any amount of Lead you encounter in your environment — and then is sometimes released back into the bloodstream with high cellular turnover events (like pregnancy, menopause and traumatic physical injury (e.g. a bone fracture).

It is for this reason (that most of the Lead you have been exposed to in your life will stay in your body) that primary prevention of childhood Lead-poisoning is key. This is also the reason we do ourselves a disservice if we do not at least try to eliminate all possible sources of bioavailable Lead from our lives — Leaded dishes; Leaded toys, old Lead-painted doors, windows, siding, or other architectural components, stained glass, Leaded crystal; Leaded brass; old Leaded solder; Leaded sports equipment (Leaded bullets; Leaded fishing weights; uncoated Lead diving weights, etc.) – with widely-available, affordable safer alternatives, there is no reason to have these things in our lives, and the more Lead-exposure sources we can remove from our lives, the healthier we will be long-term.

As always, thank you for reading and for sharing Lead Safe Mama posts. Your sharing of this work keeps us doing what we do. Please let me know if you have any follow-up questions to this and I will do my best to answer them personally as soon as I have a moment.

Tamara Rubin
#LeadSafeMama