Environmental exposure to lead can cause life-impairing if not deadly consequences. Lead is a metal that can harm humans and the environment and is present in many pollutants and consumer goods. Many of the controversial issues surrounding lead exposure relate to scientific disagreement over the extent and severity of exposure. Other controversies relate to political disagreements over who is exposed, when to test for lead exposure, and who will pay for diagnosis and treatment.
I. What Is Lead?
II. Lead Exposure in the U.S. Population
What Is Lead?
Lead is essentially a mineral. Minerals are formed by hot solutions working their way up from deep below the earth’s rocky crust and crystallizing as they cool near the surface. From early history to the present, lead mining has been part of human culture. Lead has been a key component in cosmetic decoration as a pigment; a spermicide for informal birth control; a sweet-and-sour condiment popular for seasoning and adulterating food; a wine preservative for stopping fermentation or disguising inferior vintages; the malleable and inexpensive ingredient in pewter cups, plates, pitchers, pots and pans, and other household artifacts; the basic component of lead coins; and the material of children’s toys. Most important of all was lead’s suitability for making inexpensive and reliable water pipes. Lead pipes are still used in many parts of the world and are still present in the United States. Lead pipes kept the Roman Empire supplied with water. From then until now lead has been part of our society.
Human exposure to lead is a serious public health problem. Lead adversely affects the nervous, hematopoietic, endocrine, renal, and reproductive systems of the body. Of particular concern are the effects of relatively low levels of lead exposure on the cognitive development of children. Since the 1970s, federal environmental regulations and abatement efforts have mainly focused on reducing the amount of lead in gasoline, paint, and soldered cans. In addition, some federal programs have supported screening for lead poisoning in children by state and local health departments and physicians as well as lead abatement in housing. Currently, lead exposure usually results from lead in deteriorating household paint, lead at the workplace, lead used in hobbies, lead in some folk medicines and cosmetics, lead in children’s toys, and lead in crystal or ceramic containers that leaches into water or food.
Lead Exposure in the U.S. Population
Since the late 1970s, the extent of lead exposure in the U.S. population has been assessed by the National Health and Nutrition Examination Surveys (NHANES). These national surveys have measured blood lead levels (BPbs) of tens of thousands of children and adults and assessed the extent of lead exposure in the civilian population by age, sex, race/ethnicity, income, and degree of urbanization. The surveys have demonstrated an overall decline in BPbs since the 1970s, but they also have shown that a large number of children continue to have elevated BPbs (10 mg/dL). The U.S. EPA claims that owing to environmental regulations, airborne lead amounts have decreased by 90 percent from 1980 to 2005.
Sociodemographic factors associated with higher blood lead levels in children were non-Hispanic black race/ethnicity, low income, and residence in older housing. The prevalence of elevated blood lead levels was 21.9 percent among non-Hispanic black children living in homes built before 1946 and 16.4 percent among children in low-income families who lived in homes built before 1946. Overall, blood lead levels continue to decline in the U.S. population. The disproportionate impact on urban people of color makes it an environmental justice issue, although lead can work its way through ecosystems and affect other groups downwind or downstream.
Lead is a highly toxic metal that was used for many years in products found in and around our homes, schools, and workplaces. Lead can cause a range of health effects, from behavioral problems and learning disabilities to seizures and death. Children six years old and under are most at risk because their bodies are growing quickly.
The EPA is playing a major role in addressing these residential lead hazards. In 1978, there were some 3 to 4 million children with elevated blood lead levels in the United States. By 2002, that number had dropped to 310,000 children, and it continues to decline. Since the 1980s, the EPA has phased out lead in gasoline, reduced lead in drinking water and industrial air pollution, and banned or limited lead used in consumer products, including residential paint. States and cities have set up some programs to identify and treat lead-poisoned children and to rehabilitate deteriorated housing. Parents have greatly helped to reduce their children’s lead exposure by eliminating lead in their homes, having their children’s blood lead levels checked, and learning about the risks of lead for children.
Some population groups continue to be at disproportionately high risk for elevated lead exposure. In general, these are people with low income, people of non-Hispanic black race, and people who live in older housing. Residence in a central city with a population of more than a million people was also found to be a risk factor for lead exposure.
These high-risk population groups are important to recognize for targeting of public health efforts in lead-poisoning prevention. Leaded paint, especially in older homes, is a continuing source of lead exposure. In the United States, approximately 83 percent of privately owned housing units and 86 percent of public housing units built before 1980 contain some lead-based paint. Commercial and industrial structures often have much more lead paint. Bridges are often repainted, and this uses large amounts of lead paint. The areas under the bridges are often contaminated with lead. If the area under a bridge is land, the lead accumulates on the ground and in the dirt. Many bridges of this type are older and in urban areas. Between 5 and 15 million homes contain paint that has deteriorated to the point of being a health hazard. Lead hazard control and abatement costs are highly variable, depending on the extent of the intervention, existing market conditions, type of housing, and associated housing rehabilitation work. Because of the high cost of abatement, the scarcity of adequately trained lead-abatement professionals, and the absence (until 1995) of federal guidelines for implementing less costly methods of containing the hazard of leaded paint, residential lead paint–abatement efforts have focused on homes in which there is a resident child with an elevated BPb rather than on those that have the potential to expose a child to lead. Similarly, publicly funded lead-poisoning prevention programs have focused on screening children to identify those who already have elevated BPbs, so that they may receive interventions, rather than on preventing future lead exposure among children without elevated levels. This is an issue in the public health arena. At least some of the adverse health effects that occur even at relatively low levels of lead may be irreversible. Efforts to prevent lead exposure through screening are important to ensure that children with elevated BPbs receive prompt and effective interventions designed to reduce further lead exposure and minimize health consequences. These types of programs are not consistently well funded.
One source of lead in many countries is vehicle emissions. In the United States these emissions are much lower because lead-free gasoline is used in cars. However, other airborne vehicle emissions, as from diesel, may have a detrimental effect on children. In urban areas near congested roads, exposure to lead via air may be a large vector.
A controversial issue is whether ambient air quality standards are adequate to protect the health of children. Currently a few state environmental agencies are working to identify toxic air contaminants that may cause infants and children to be especially susceptible to risks. In many cases, children may have greater exposure to airborne pollutants than do adults. Children are often more susceptible to the health effects of air pollution because their immune systems and developing organs are still growing. Lead that is inhaled is more easily lodged in the fast-growing bones of children. In a child, it may take less exposure to airborne lead to initiate an asthma attack or other breathing ailment owing to the smaller size and greater sensitivity of the child’s developing respiratory system.
As a pervasive material in civilization, lead is ubiquitous. Lead in the water pipes and drinking vessels may have poisoned the people of Rome and contributed to its downfall. Lead still remains in plumbing systems throughout the United States. In Washington, D.C., some of the leaded sewer and water pipes dead end. This means that there is no way to flush them clear of corrosive wastes and debris. This increases the rate of corrosion of these pipes and leaches lead into the water. When the pipe breaks, it may slowly seep lead-contaminated water into the surrounding ground. Such ground can be anywhere the pipe is found, near a road, river, school, factory, or any place connected to or near the break. This is a matter of great concern in chemically polluted older communities and can develop into a land-use issue or an issue around the environmental permits that may be necessary. Refining methods to assess health risks from lead that may exist at proposed and existing school sites is under way. Because lead is found in so many places where vulnerable populations exist, from children’s toys to hospitals, controversy around lead exposure and cleanup will increase.
The disposal of lead as hazardous waste is also a controversial issue. Demolition of lead-contaminated houses, factories, and infrastructure creates hazardous waste. If burned in an incinerator, the lead could be spread in the air as particulate matter. The disposal of this type of toxic ash can also become a controversy. If the lead-contaminated structure simply stays in place, the lead can affect the soil and nearby water. The reluctance to expend the resources necessary to protect the most exposed people from lead contamination ensures a continuing controversy. This controversy may not necessarily diminish even as science removes uncertainty about lead contamination.
Robert William Collin
- Casas, Jose S., and Jose Sordo, eds., Lead: Chemistry, Analytical Aspects, Environmental Impact, and Health Effects. Boston: Elsevier, 2006.
- Millstone, Erik, Lead and Public Health: The Dangers for Children. Washington, DC: Taylor and Francis, 1997.
- Moore, Colleen F., Silent Scourge: Children, Pollution, and Why Scientists Disagree. New York: Oxford University Press, 2003.
- Troesken, Werner, The Great Lead Water Pipe Disaster. Cambridge, MA: MIT Press, 2006.