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The health and economic effects of lead exposure may be 6-7 times higher than previously estimated, according to a report in The Lancet Planetary Health.

The report found that the magnitude of environmental risk from lead exposure is similar to that of fine-particulate air pollution and exceeds risks associated with unsafe drinking and household-use water.

The researchers were looking for IQ loss among children under 5, heart disease deaths and the lifetime economic impacts of both.

The study

Bjorn Larsen, an analyst at the World Bank, who led the study, used established risk estimates for blood-lead levels from the Global Burden of Disease Study 2019 (GBD).

According to Larsen, the average IQ loss in low- to medium-income families during the five-year observational period — 5.9 points per child — was 80% higher than previous estimates.

Based on an income reduction of about 2% per lost IQ point, Larsen estimated the lifetime income loss at 11.8%.

This translates to an annual global income loss of $2.4 trillion, or 1.6% of global gross domestic product (GDP). As a share of GDP, the burden was highest in low-income countries and lowest in high-income countries.

Since lead exposure is a risk factor for heart disease Larsen used GBD data to calculate the effects of lifetime lead exposure on cardiovascular deaths. He estimated that lead exposure caused 5.5 million cardiovascular deaths globally in 2019.

In its original analysis, GBD had estimated just 0.85 million deaths.

As many as 5 million global deaths (90.2%) occurred in low- and middle-income countries, and 93.1% of those were in modest households in upper-middle-income countries.

Costs associated with these deaths were $4.6 trillion, but the uncertainty in this calculation was large. Low- and middle-income countries accounted for 54% of global cardiovascular deaths.

The estimated cost equaled 5.3% of global GDP in 2019, but no pattern emerged linking relative cost burdens to a country’s economic ranking.

Together, the cost of IQ loss plus cardiovascular deaths was $6.0 trillion, or about 6.9% of global GDP.

Real-world exposures

High lead exposure has no immediate, obvious symptoms, which is why so many cases go undiagnosed until the damage is done.

The average blood lead level for U.S. adults in 2017 was 0.855 micrograms per deciliter. Levels above 3.5 micrograms — the upper 2.5% of exposure levels — trigger concern, especially for pregnant women. The Centers for Disease Control and Prevention uses that figure as the reference cutoff for recommending periodic testing or treatment.

However, exposure varies widely across geographic areas and demographics.

According to one 2021 study, more than half of children tested in Washington, D.C., had lead in their blood and 1.9% had levels above 5.0 micrograms per deciliter.

Among children in low/middle-income countries, 47% have blood lead levels above 5 micrograms per deciliter, and 28% are above 10 micrograms, which was within the range of an earlier report.

By contrast, just 5% of children in high-income countries had blood lead levels above 5 micrograms per deciliter, and only 1% came in above 10 micrograms.

In 1970, New York City became the first jurisdiction in the U.S. to ban lead paint. By 1978, the ban went nationwide. Yet lead paint continues to pose health risks. Although the bans prohibited lead-based paint sales they could not address lead paint in pre-1978 buildings (Figure 1).

While covering lead-based paint with a coat of non-lead paint is safe, renovations that involve sanding, cutting or demolition of lead-painted walls, doors, shelves, etc. generate lead dust that spreads throughout a home and may accumulate to dangerous levels. Since children engage in hand-to-mouth activities, household sources of lead put them at high risk.

Percentage of homes with lead paint by construction year. 87 percent of homes built before 1940 still contain lead-based paint. This number drops to 69% for homes built between 1940 to 1959 and 24% 1960 to 1977 construction. Credit: U.S. Environmental Protection Agency.

The U.S. began phasing out leaded gasoline in 1973 and finally banned leaded gas additives for passenger cars in 1996.

The health and economic benefits of lead-free gasoline have been substantial. As average blood lead levels have fallen by 90% or more since the ban, 1.2 million premature deaths (including 125,000 children) have been avoided. IQs have risen, violent crime has fallen, and the world’s economy has avoided the loss of $2.4 trillion, or 4% of global GDP, per year.

Lower lead exposure-associated healthcare costs are responsible for most of this economic benefit.

Yet despite bans on the two major sources of lead exposure, children may still be vulnerable through contact with jewelry, toys and cosmetics, or through contaminated drinking water, soil, spices or foods.

Testing and treatment

Lead levels are measured by analyzing blood from a vein or through a finger prick, but results from venous blood tend to be more accurate. Home swab kits are available for surfaces or objects, while test strips estimate lead concentrations in liquids, including beverages.

Blood- and instrument-based testing is available only through a healthcare provider.

Patients with harmful lead concentrations may take supplements or drugs to help the body eliminate it. Very high levels may be treated through chelation therapy, a blood purification process involving either oral or intravenous drugs.

Regardless of the diagnosis and treatment, the first step in treating high blood lead levels is to remove or avoid the exposure source.

For millennia lead overexposure has been linked to hallucinations and severe mental problems. Writing to a friend in 1786, Benjamin Franklin described the health effects of lead exposure in distillery workers and lamented society’s reluctance to recognize this risk.

Exposure to lead through drinking vessels has even been blamed for the erratic behavior of Roman emperors, which may have led to the fall of the Roman Empire.

Lead exposure is associated with nervous system damage, hearing loss and speech problems resulting in lower IQ and delayed childhood development.

Blood levels below 10 micrograms per deciliter raise kidney-stressing blood pressure, which unrelieved, may progress to chronic and often irreversible kidney lead poisoning.

Lead exposure has also been linked to anemia, low vitamin D levels, endocrine disruption, low bone density and a host of heart issues.

Toxicology studies in animals and humans have prompted the World Health Organization’s International Agency for Research on Cancer to designate lead as a “probable” human carcinogen, and the U.S. Environmental Protection Agency to conclude: “a causal relationship is likely to exist between Pb [lead] exposure and cancer.”