Lead (Pb)

Lead is an environmental contaminant. It is a heavy metal found in excess in leaded gasoline, pre-1980s paints, metallurgical facilities, battery and radiator manufacturing, tobacco smoke ^{(WHO 2012)}, shooting ranges ^{(Laidlaw 2017, Gelbert 2009)}, ceramic glaze, stained glass and tinted glass. Some cosmetics (kohl or surma made with galena), herbal teas, game meat, and cooking ceramics can increase exposure to the metal. The main sources of lead exposure are occupational and home renovation work. ^{(Fletcher 1999)}

It serves no useful function in the body and tends to accumulate in the skeletal structures of the body. It accumulates in blood and soft tissues for a month and in bone for decades. It is removed from bone in periods such as pregnancy and breastfeeding, increasing its concentration in blood years after exposure. It has cardiovascular and respiratory toxicity and, especially in children, neurological damage. Absorption by the respiratory route is 50% and by the digestive route does not reach 10%.

Although it is recognized that the ideal maximum level of lead would be 0, acceptable levels are: 50 (CDC 2016) - 150 (INSHT 2024) micrograms (µg)/m3 of TLV-TWA (Threshold Limit Value – Time-Weighted Average), 10 µg/L of water and 5 µg/L of breast milk. ^{(WHO 1989)}

In the blood of unexposed persons there should be no more than 3.5 µg/dL ^{(CDC 2024)}. Above 5 µg/dL in plasma an environmental assessment is recommended (AAP 2021). Exposed workers of childbearing age with blood lead levels greater than 30 µg/dL should be removed from exposure. Pregnant or breastfeeding workers should be protected from lead exposure. ^{(European Commission 1992)}

In terms of occupational risk for nursing mothers ^{(INSHT 2024, EC Regulation 2008)}, the safety data sheet for lead contains the hazard phrase H373 (ant. R33): “May cause damage to organs through prolonged or repeated exposure”, and the nursing mother should therefore be removed from her workplace. According to current European regulations ^{(EC Regulation 2008)}, when a product is carcinogenic and/or mutagenic, working nursing mothers should not be exposed to mixtures, whether of solids, liquids or gases, with concentration limits higher than 0.3%.

Mother should not breastfeed if mother contaminated or intoxicated or with blood lead level greater than 40 µg/dL (Mother 2022, Schreck 2016, ACOG 2012-2016, Lawrence 2013) and also should not breastfeed if she should be treated with a chelator (mobilization of lead from bone).

All infants born to mothers with blood lead levels greater than or equal to 5 mcg/dL should have their blood lead levels measured at birth. ^{(Schreck 2016)}

Infants with a blood lead level less than 10 µg/dL can continue breastfeeding. ^{(AAP 2021)}

In published work, lead levels in artificial formulas were higher than levels in breast milk ^{(Walker 1980)}. Commercial infant formulas from China contained an average of between 1.6 and 2.5 μg/kg of lead with a range of 0.4 to 5.75. ^{(Su 2020)}