Blood Lead Unit Converter
Blood Lead Unit Converter
Convert blood lead between µg/dL, µg/L, µmol/L and nmol/L, and read the result against the CDC reference value and the standard action levels.
Blood Lead converter
Mass ⇄ molarBlood lead 4 µg/dL
Formula and conversion factor
µg/dL = µmol/L ÷ 0.04826
µg/L = µg/dL × 10 · nmol/L = µmol/L × 1000
- 0.04826
- derived from the atomic weight of lead, 207.2
- venous vs capillary
- capillary samples are prone to contamination from skin lead and read falsely high; any raised capillary result needs venous confirmation
- bone burden
- blood lead reflects recent exposure and the exchangeable pool; over 90% of the adult body burden sits in bone and is released slowly
Worked example
Blood lead 4 µg/dL
4 × 0.04826 = 0.193 µmol/L
= 40 µg/L = 193.1 nmol/L
Above the CDC child reference value of 3.5 µg/dL but below the adult reference value of 5 — the same result flags differently depending on which population is selected
Action levels in both units
| µg/dL | µmol/L | Significance |
|---|---|---|
| 3.5 | 0.169 | CDC blood lead reference value for children — the 97.5th centile of US children aged 1–5 years |
| 5 | 0.241 | Commonly used adult reference value; above this, review occupational and environmental exposure |
| 20 | 0.965 | Substantial exposure in a child — urgent source identification and close follow-up |
| 45 | 2.172 | Chelation generally considered in children |
| 70 | 3.378 | Medical emergency — risk of encephalopathy; inpatient chelation |
Unit conversions
| From | To | Multiply by |
|---|---|---|
| µg/dL | µmol/L | 0.04826 |
| µmol/L | µg/dL | 20.72 |
| µg/dL | µg/L | 10 |
| µmol/L | nmol/L | 1,000 |
Reading a blood lead result, and what it does not tell you
Blood lead in µg/dL is converted to µmol/L by multiplying by 0.04826, a factor that comes directly from the atomic weight of lead, 207.2. µg/L is simply µg/dL multiplied by ten, and nmol/L is µmol/L multiplied by a thousand. The unit mix is a genuine source of error: a result of 4 µg/dL and one of 4 µmol/L differ by a factor of roughly twenty, and the latter would be a life-threatening concentration.
The most important point about the numbers is what they are not. The CDC blood lead reference value of 3.5 µg/dL, lowered from 5 µg/dL in 2021, is set at the 97.5th centile of the distribution in US children aged 1 to 5 years. It identifies the most exposed 2.5% of children so that they can be followed up; it is a statistical marker that moves as population exposure falls. No safe blood lead concentration has been identified, and measurable cognitive effects have been demonstrated below 5 µg/dL, so a child under the reference value has not been shown to be unharmed.
A blood lead concentration reflects recent exposure and the exchangeable pool rather than the total body burden. More than 90% of the adult burden is stored in bone, with a half-life measured in decades, and it is mobilised slowly back into blood during periods of increased bone turnover — notably pregnancy, lactation, immobilisation, hyperthyroidism and osteoporosis. A woman with a historic exposure can therefore have a rising blood lead in pregnancy with no current source at all, and the mobilised lead crosses the placenta. Pre-analytical error matters too: capillary sampling picks up lead from skin and reads falsely high, so a raised fingerprick result needs venous confirmation before anything else happens.
Treatment follows from all of this. Chelation is reserved for high concentrations — generally considered in children at around 45 µg/dL and mandatory with encephalopathy — and it lowers the blood level without reversing neurodevelopmental harm already done; the randomised succimer trial in children with moderately raised levels showed no cognitive benefit. Identifying and removing the exposure source, whether housing paint, contaminated soil, water pipes, imported cosmetics or spices, occupational dust or a hobby such as shooting or stained glass, is the intervention that changes outcome.
Frequently asked questions
How do I convert blood lead from µg/dL to µmol/L?
Multiply by 0.04826, derived from the atomic weight of lead, 207.2. A blood lead of 4 µg/dL is 0.193 µmol/L. To go the other way, multiply µmol/L by 20.72.
What is the CDC blood lead reference value?
3.5 µg/dL (0.169 µmol/L) for children, lowered from 5 µg/dL in 2021. It is the 97.5th centile of the distribution in US children aged 1 to 5 years, so it identifies the most exposed 2.5%.
Is a blood lead below the reference value safe?
No safe blood lead concentration has been identified. The reference value is a statistical marker of the most exposed children, not a threshold below which lead causes no harm, and cognitive effects have been demonstrated below 5 µg/dL.
Does a normal blood lead exclude past lead exposure?
No. Blood lead reflects recent exposure and the exchangeable pool. More than 90% of the body burden is stored in bone with a half-life of decades, and is released slowly, particularly in pregnancy, lactation and other states of increased bone turnover.
When is chelation used for lead poisoning?
It is reserved for high concentrations — generally considered in children at around 45 µg/dL, and urgently with encephalopathy at 70 µg/dL or above. It lowers the blood level but does not reverse neurodevelopmental harm, so removing the exposure source is what matters.
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References
- Centers for Disease Control and Prevention. Blood Lead Reference Value. Atlanta, GA: CDC.
- Advisory Committee on Childhood Lead Poisoning Prevention. Low Level Lead Exposure Harms Children: A Renewed Call for Primary Prevention. Atlanta, GA: CDC; 2012.
- Kosnett MJ, Wedeen RP, Rothenberg SJ, et al. Recommendations for medical management of adult lead exposure. Environ Health Perspect. 2007;115(3):463–471.