Lead Levels in the USA Among Childbearing and Breastfeeding Women
by Anne Eglash MD, IBCLC, FABM
According to a new report from the US National Health and Nutrition Examination Survey, lead levels among adults in the USA have declined from 1976 to 2016. This is mainly due to a decrease in environmental exposure to lead from sources such as leaded gasoline, paint, plumbing fixtures, toys and other products. Lead exposure is generally low for adults in the USA, but there are approximately 500,000 women still being exposed to lead at levels that may harm their developing fetuses or breastfeeding infants. In addition, women with significant lead levels have a higher risk for miscarriage, gestational high blood pressure, and preterm delivery. Fetal exposure is associated with intrauterine growth retardation, decreased postnatal growth, and adverse neurodevelopmental outcomes.
Women at highest risk of lead exposure include foreign-born recent immigrants, eating lead-contaminated objects such as old paint chips, smoking or exposure to second hand smoke, people who renovate older homes, living near a smelter or a hazardous waste site. According to the authors of this week’s report, these are risk factors associated with poverty, being an individual of color, and social injustice.
- Mothers store lead in their bones, and the stored lead is more likely to move into the blood stream during pregnancy and into the breastmilk during lactation.
- Maternal lead exposure one decade before pregnancy increases the risk of a significant blood and breastmilk lead level during pregnancy and lactation.
- The ban on lead paint in the USA occurred in 1990. Prior to 1990, paint used in homes may be a source of lead contamination.
- Over 90% of lead contamination among adults is from imported spices.
- The American College of Obstetrics and Gynecology recommends that providers ask pregnant women about their risks for lead exposure, and perform blood testing if risk factors are identified.
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Lead can adversely affect maternal and child health across a wide range of exposures; developing fetuses and breastfeeding infants may be particularly vulnerable. We describe the distribution of blood lead levels (BLLs) in U.S. women of childbearing age and associations with sociodemographic, reproductive, smoking, and housing characteristics over a 40-y period.
Data from the National Health and Nutrition Examination Survey (NHANES) II, NHANES III Phase I and Phase II, and 1999–2016 continuous NHANES were used to describe the distribution of BLLs (given in micrograms per deciliter; 1μg/dL=0.0483μmol/L) in U.S. women 15–49 years of age between 1976 and 2016. For all women with valid BLLs (n=22,408), geometric mean (GM) BLLs and estimated prevalence of BLLs ≥5μg/dL were calculated overall and by selected demographic characteristics. For NHANES II, estimated prevalence of BLLs ≥10 and ≥20μg/dL were also calculated.
The most recent GM BLLs (2007–2010 and 2011–2016, respectively) were 0.81μg/dL [95% confidence interval (CI): 0.79, 0.84] and 0.61μg/dL (95% CI: 0.59, 0.64). In comparison, GM BLLs in earlier periods (1976–1980, 1988–1991, and 1991–1994) were 10.37μg/dL (95% CI: 9.95, 10.79), 1.85μg/dL (95% CI: 1.75, 1.94), and 1.53μg/dL (95% CI: 1.45, 1.60), respectively. In 2011–2016, 0.7% of women of childbearing age had BLLs ≥5μg/dL, and higher BLLs were associated with older age, other race/ethnicity, birthplace outside the United States, four or more live births, exposure to secondhand tobacco smoke, and ever pregnant or not currently pregnant.
Lead exposure in U.S. women of childbearing age is generally low and has substantially decreased over this 40-y period. However, based on these estimates, there are still at least 500,000 U.S. women being exposed to lead at levels that may harm developing fetuses or breastfeeding infants. Identifying high-risk women who are or intend to become pregnant remains an important public health issue.
The US ban on lead in residential paint was enacted in 1978, so residential house paint purchased in the US after 1978 has been lead free. Over 90% of lead exposure in the US is now from occupational sources, such as art materials, construction sites, batteries, old cars, gun ammunition, lead mining, plumbing fixtures, etc.
A major message of this document is that in addition to screening infants for lead exposure during the first 2 years of life (at least), women of child bearing age also need screening to reduce their risk of lead exposure. Despite the fact that overall lead exposure in the USA is much lower in the last 40 years, it is not gone, and there is a subset of women who are still highly exposed to lead. Women in this subset are more likely to be recent immigrants, of color, and have occupational risks.