Lead: A Global Health Problem

One of the major US public health victories in recent decades was to get the lead out of gasoline and paint, and also to (mostly) shift away from lead in pipes that carried water–such that when lead is detected in the water supply in places like Flint, Michigan, or Jackson, Mississippi, it’s rightfully a scandal, and typically linked to the use of badly outdated pipes. But dealing with sources of lead exposure around the world is very much a slow-motion work in progress. Rachel Silverman Bonnifield and Rory Todd discuss the issue in “Opportunities for the G7 to Address the Global Crisis of Lead Poisoning in the 21st Century: A Rapid Stocktaking Report” (Center for Global Development, 2023).

They set the stage in this way (footnotes and references to figures omitted):

Lead poisoning is responsible for an estimated 900,000 deaths per year, more than from malaria (620,000) and nearly as many as from HIV/AIDS (954,000). It affects almost every system of the body, including the gastrointestinal tract, the kidneys, and the reproductive organs, but has particularly adverse effects on cardiovascular health. According to the World Health Organization (WHO), it is responsible for nearly half of all global deaths from known chemical exposures.

Despite this massive burden, the greater part of the harm caused by lead may come not through its effects on physical health, but its effect on neurological development in young children. The cognitive effects of lead poisoning on brain development are permanent, and most severe when lead exposure occurs between the prenatal period to the age of around 6 or 7. Even low-level lead exposure at this age has been conclusively shown to cause lifelong detriments to cognitive ability; though evidence is less definitive, there is also a very strong and compelling literature which links lead exposure to anti-social/violent behavior, attention deficits, and various mental disorders. An estimated 800 million children—nearly one in three globally, an estimated 99 percent of whom live in low- and middle-income countries (LMICs)—have blood lead levels (BLL) above 5 micrograms per deciliter (μg/dL), which the WHO uses as a threshold for recommending clinical intervention to mitigate neurotoxic effects. Effects on cognitive development have been demonstrated in BLLs significantly below this …

What are some of main vectors through which people, especially in low- and middle-income countries, are exposed to lead? The first one discussed is recycling of lead-acid batteries:

While lead has a number of industrial applications, at least 80 percent now goes into the production of lead-acid batteries. … Manual destruction of batteries without protective equipment, uncontrolled smelting, and dumping of waste into waterways and soils are common. Studies show high blood lead levels in children living near lead battery manufacturing and recycling facilities and in workers, and high levels of airborne lead in battery facilities and acute exposure to workers and their families.

The market price of lead has roughly doubled in the last 20 years, as has global mining of lead (which is typically accompanied by extraction of zinc, but also other metals). There are some recent graphic examples. A lead mine in Zambia “led to universal lead poisoning among 90,000 local children.” A gold-mining operation in Nigeria “led to the deaths of more than 400 children from acute lead poisoning in the space of six months in 2010, as a result of workers grinding ores within villages.” Such lead pollution often continues to affect the local environment for decades after the mine is closed.

Perhaps the most unexpected source of lead poisoning is via lead that is added to spices, which are then shipped around the world.

[A]n increasing body of evidence points to lead-adulterated spices as a significant driver of widespread lead poisoning, particularly in South and Central Asia. For turmeric and other spices with bright yellow/orange colors, lead chromate is typically added during the polishing stage to increase pigmentation and reduce polishing time (which also increases the weight of the final product); the bright pigmentation characteristic of lead chromate is considered a sign of high quality, and adulteration therefore allows producers to command a higher price point for their products. Lead may also be inadvertently introduced in smaller concentrations to a broader range of spices—for example oregano, thyme, ginger, or paprika—via contaminated soil, airborne pollution, or cross-contamination at a factory, though this is likely to be a relatively small part of the overall problem.

Via global supply chains, contaminated spices can drive lead poisoning far beyond their countries of origin … In the US, where roughly 95 percent of spices are imported,91 a Consumer Reports investigation found detectable levels of lead or other heavy metals in one third of sampled spices. In New York City, investigations of elevated blood lead levels frequently identify lead adulteration in spices purchased abroad as a likely source, with the highest concentrations of lead found in spices from the countries Georgia, Bangladesh, Pakistan, Nepal, and Morocco …

Lead in paint is an ongoing issue as well.

Despite their danger being established for decades, lead paints remain legal in the majority of countries, and are widely used for residential coatings and decorative purposes in most LMICs [low- and middle-income countries], and for industrial purposes in many high-income countries. Lead additives are primarily in solvent-based paints, and may be added to paint to improve durability, drying capacity, and corrosion prevention, as well as in the form of pigments—especially lead chromate—to enhance color. It can cause occupational exposure as workers inhale dust during manufacture, application, and removal, or exposing their families through take-home contamination. Children are exposed primarily through ingestion of chips and dust, which can occur throughout the life cycle, but may be exacerbated as paint ages as well as during application and removal. Lead paint is an avoidable source of exposure, and there are safe and cost-effective alternatives to lead additives …

Cookware can be another source of lead exposure, especially when lead-based glazed are used on ceramics.

Lead-glazed ceramics are popular in central Mexico, where they are primarily produced by indigenous communities, and are commonly used in restaurants for cooking and serving. They have been identified as a primary cause of elevated blood lead levels in the country,127 where 22 percent of children aged 1 to 4 years have blood lead levels above 5 μg/dL. But they are also used elsewhere in Latin America, North Africa, and South Asia, and may be a significant source of exposure. … More recently, aluminum pots and other cookware produced from scrap metal—used by poor families in LMICs across all regions—have been found to frequently contain lead and other heavy metals …

There are other examples. The cosmetic called Kohl was traditionally made with lead. “While safe, lead-free substitutes exist, traditional leaded Kohl—with up to 98 percent lead content—is still common across the world, and frequently found in G7 member states … Lead is also found in other consumer goods, particularly toys and jewelry. Use of lead in toys is typically to add pigment/color, including via lead paint on surfaces and lead pigment in crayons, sidewalk chalk, and other art supplies …”

The immediate health effects of lead exposure are grim. The long-term effects on child development are worse.