How lead enters your body
The main ways that human bodies absorb lead are by breathing lead-contaminated air and swallowing lead-contaminated particles. The proportion of lead absorbed depends on several factors including the solubility of the lead contaminant, the size of the lead particles, and the person’s age, sex, and diet. Lead that is absorbed through the lungs, or through the stomach or intestines, is carried in the blood Lead in the blood can move into body tissues and organs. Some lead is stored in bones and teeth. From there it is slowly released back into the blood over years. More lead is released from bones at certain times (e.g. during childhood, pregnancy, breastfeeding, menopause, prolonged bed rest, or in osteoporosis). This means that some lead continues to be released into the blood, long after a person is no longer exposed to lead, and the rate of release can change as the person’s health changes.
How lead leaves your body
Over time most of the lead in the blood is removed from the body by the kidneys via the urine, and some is removed by the liver via the faeces. If a person is exposed to a single ‘dose’ of lead, most of this lead is quickly removed from the body (some may be stored in bone for a short time before being released). If a person is repeatedly or continuously exposed to lead, most of the lead retained by the body is stored in bone, then released over many years after exposure stops.
There is no safe level of lead
While there is no level considered safe, a 5 ug/dL (micrograms per decilitre) level can be used as an indicator to determine unusual exposure that is cause for investigation.
October 2014, Health Minister Lawrence Springborg accepted a recommendation from the Chief Health Officer to reduce the current mandatory blood lead notification level in Queensland from 10 micrograms per decilitre (µg/dL) to 5 µg/dL. Dr Young’s recommendation followed the release in July of the National Health and Medical Research Council’s draft information paper.
The paper, Evidence on the effects of lead on human health, emphasised that although lead was a naturally occurring substance, no evidence existed to show it was necessary to human health. Harmful effects of lead, particularly on infants and children, are likely even at low levels of exposure.
As such, while there was no level considered safe, a 5 µg/dL level in blood could indicate unusual exposure and warrant investigation.