Lead poisoning

DEFINITION: A condition caused by high levels of lead in the blood. This major preventable environmental health problem is found in both children and adults, but more frequently in children.

ALSO KNOWN AS: Saturnism, plumbism, painter’s colic

ANATOMY OR SYSTEM AFFECTED: Brain, circulatory system, endocrine system, musculoskeletal system, nervous system, reproductive system

Causes and Symptoms

Lead poisoning is a major, preventable environmental health problem. Elevated lead levels in adults can increase blood pressure and cause fertility problems, nerve disorders, arthralgia, and problems with memory and concentration. Very high blood lead levels of seventy micrograms per deciliter can cause devastating health consequences, including seizures and other neurological symptoms, abdominal pain, developmental delays, attention deficit, hyperactivity, behavior disorders, hearing loss, anemia, coma, and death. Children under the age of seven are at high risk for harm because their brains and nervous systems are still maturing. Blood lead levels as low as ten micrograms per deciliter are associated with harmful effects on children’s ability to learn.

Lead exposure in adults is usually a result of jobs in painting, welding and smelting, the manufacturing of car batteries, and other occupations involving lead. Children can be exposed to lead in many ways. Sources of exposure include soils contaminated by automobile exhaust, lead-based paint, and environmental contaminants released by industrial processes that use or produce lead-containing materials. Contributors to childhood lead exposure also include lead-contaminated containers, food, dust, soil, air, and water; toys contaminated with lead paint; lead-containing ceramics and hobby supplies; parental transfer from lead-rich occupational environments; and traditional medicines such as azarcon and greta.

Deteriorating lead-based paint in older homes is the most important source of lead exposure in children. In the United States, lead-based paint was banned from residential use in 1978, but families living in homes built before this time (especially before 1960) are at elevated risk. Lead-based paint dust, often generated during home renovation, is the most common form of exposure. Swallowing lead-based paint dust through normal hand-to-mouth activity and chewing directly on painted surfaces are major methods of lead ingestion. Children are often attracted to lead paint because of its sweet taste.

Upon entering the human body, inorganic lead is not metabolized but is directly absorbed, distributed, and excreted. The rate at which lead is absorbed depends on its chemical and physical form and on the physiologic characteristics of the exposed person. Once in the blood, lead is distributed among three compartments: the blood; soft tissue zones, such as the kidneys, bone marrow, liver, and brain; and mineralizing tissues, such as bones and teeth. For lead poisoning to take place, major acute exposures to lead need not occur. The body accumulates lead and releases it slowly; therefore, even small doses over time can be toxic. It is the total body accumulation of lead that is related to the risk of adverse effects. Whether lead enters the body through inhalation or ingestion, the biologic effects are the same—interference with normal cell function and with certain physiologic processes.

By and large, children show a greater sensitivity to the effects of lead than adults. Parents working in lead-related industries not only may inhale lead dust and lead oxide fumes but also may eat, drink, and smoke in or near contaminated areas, increasing the probability of lead ingestion and subsequent transfer to their children. Since lead readily crosses the placenta, the fetus is at risk. Fetal exposure can cause potentially adverse neurological effects in utero and during postnatal development. (Some pregnant women may also suffer from a condition called pica, where they feel compelled to eat things like paint, further increasing risk.) The incomplete development of the blood-brain barrier in very young children, up to thirty-six months of age, increases the risk of the entry of lead into the developing nervous system, which can result in prolonged neurobehavioral disorders. Children absorb and retain more lead in proportion to their weight than adults. Young children also show a greater prevalence of iron deficiency, a condition that can increase the gastrointestinal absorption of lead.

Symptoms of lead poisoning and lead intoxication vary because of differences in individual susceptibility, and the severity of symptoms increases with increased exposure. Symptoms of mild lead toxicity include abdominal discomfort, fatigue, muscle pain, or paresthesia. Moderate toxicity is indicated by arthralgia, tremor, fatigue, difficulty concentrating, headache, abdominal pain, vomiting, weight loss, and constipation. Severe toxicity symptoms include paresis or paralysis, encephalopathy, seizures, severe abdominal cramps, hearing loss, changes in consciousness, and coma.

Treatment and Therapy

If a child is suspected of having lead poisoning, laboratory tests are necessary to evaluate lead intoxication levels. Laboratory techniques defining lead toxicity include blood lead level screening, erythrocyte protoporphyrin (EP) and zinc protoporphyrin (ZPP) screening, creatinine, urinalysis, and hematocrit and tests with peripheral smear. The Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) recommend that all children living in high-risk neighborhoods or conditions should have their blood levels tested regularly until the age of five.

The for suspected lead poisoning cases includes special attention to hematologic, cardiovascular, gastrointestinal, and renal systems. Any neurological or behavioral changes are considered significant indicators. In addition, severe and prolonged lead poisoning may be indicated by a purplish line on the gums. A complete interview and medical evaluation of a suspected lead poisoning patient includes a full workup and medical history. Clues to potential exposure vectors can be obtained by discussing family and occupational history, use of traditional medicines, remodeling activities, hobbies, table and cookware, drinking water, nutrition, proximity to industry or waste sites, and the physical condition and age of the patient’s residence, school, and/or daycare facility.

The treatment and management of lead poisoning first involves the separation of the patient from the source of lead. After a diagnosis of lead poisoning is made, local environmental health officials should be contacted to determine the lead source and what remediation action is necessary for its control. This may include testing a home's paint and water for lead, as well as identifying hobbies such as making stained glass, soldering electrical devices, or fishing with lead-containing sinkers, all of which can expose children to lead poisoning. A diet high in calcium and iron may help to decrease the absorption of lead.

The US Centers for Disease Control and Prevention (CDC) recommends that children with blood lead levels of 45 micrograms per deciliter or greater should be referred for chelation therapy immediately. However, chelation should be used with caution. Several drugs are capable of binding or chelating lead, depleting both soft and hard (skeletal) tissues of lead and reducing its acute toxicity. All these drugs have potential side effects and must be used with caution. The most commonly used chelating agent is calcium disodium edetic acid, but several other agents are available.

Prevention and Remediation

Toxic exposure to lead remains a problem in the twenty-first century. According to the World Health Organization (WHO), lead accounts for almost half of all chemical exposure–related deaths annually worldwide, as well as a significant portion of the global burden of health issues, including 30 percent of idiopathic intellectual disability, 4.6 percent of cardiovascular disease, and 3 percent of chronic kidney disease. In response, many governments and other authorities have undertaken initiatives to reduce the risk of lead exposure and increase awareness of the problem. Notably, the WHO and the United Nations Environment Programme (UNEP) formed the Global Alliance to Eliminate Lead Paint in 2011 as a voluntary international collaboration effort. Several US government organizations, including the Environmental Protection Agency (EPA) and the US Agency for International Development (USAID), have been involved in the alliance.

In the United States and other developed countries, the issue is most acute for children living in older housing in low-income areas. In the US, the issue of lead poisoning drew much public attention in the late 2010s, after approximately one hundred thousand people in Flint, Michigan, including thousands of children, were exposed to dangerously high levels of lead in drinking water beginning in 2014. Many of the exposed children suffered irreversible damage such as hearing loss and learning disabilities. The situation in Flint was declared a federal emergency in 2016 and highlighted the ongoing problem of lead exposure despite longstanding abatement efforts.

Health experts agree that the primary method of preventing lead poisoning is removal of environmental hazards that lead to exposure. Examples include deleading older homes and municipal replacement of lead water pipes. Many jurisdictions have longstanding legislation intended to limit lead in the environment, such as the US phaseout of leaded gasoline in the 1980s. However, regulations such as deleading rules in residential buildings often require private assessment and compliance, which can make implementation more challenging. Some developing countries also lack strict regulation of lead paint and other products containing lead, which can present difficulties not only in those countries but also internationally due to globalization.

Secondary prevention of lead poisoning involves proper blood testing and referral for follow-up care. Irregularity in testing requirements presents a major obstacle in many areas. For example, lead testing is not mandated in the US and many states do not have testing programs at all. Of the states that do test for lead, many do not report the results to the CDC, and the lack of strong statistical data further complicates efforts to address the problem.

Bibliography

Denworth, Lydia. Toxic Truth: A Scientist, a Doctor, and the Battle over Lead. Beacon, 2009.

"EPA International Cooperation on Lead Pollution." United States Environmental Protection Agency, 2 Feb. 2024, www.epa.gov/international-cooperation/epa-international-cooperation-lead-pollution. Accessed 24 May 2024.

Fliesler, Nancy. “Lead Exposure Still a Problem for Some Children.” Boston Children's Answers, 27 Sept. 2021, answers.childrenshospital.org/lead-exposure. Accessed 25 July 2023.

"Global Alliance to Eliminate Lead Paint." UN Environment Programme, www.unep.org/topics/chemicals-and-pollution-action/pollution-and-health/heavy-metals/global-alliance-eliminate. Accessed 24 May 2024.

Goldstein, Inge F., and Martin Goldstein. How Much Risk? A Guide to Understanding Environmental Health Hazards. Oxford UP, 2002.

Grandjean, Philippe. Only One Chance: How Environmental Pollution Impairs Brain Development—And How to Protect the Brains of the Next Generation. Oxford UP, 2013.

Kessel, Irene, and John T. O’Connor. Getting the Lead Out: The Complete Resource on How to Prevent and Cope with Lead Poisoning. Rev. ed. Perseus, 2001.

Korfmacher, Katrina S., and Michael L. Hanley. "Are Local Laws the Key to Ending Childhood Lead Poisoning?" Journal of Health Politics, Policy and Law 38.4 (2013): 757–813. Print.

Landrigan, Philip J., and Ruth Ann Etzel. Textbook of Children's Environmental Health. Oxford UP, 2014.

"Lead Poisoning." Mayo Clinic, 21 Jan. 2022, www.mayoclinic.org/diseases-conditions/lead-poisoning/symptoms-causes/syc-20354717. Accessed 24 May 2024.

"Lead Poisoning." World Health Organization, 11 Aug. 2023, www.who.int/news-room/fact-sheets/detail/lead-poisoning-and-health. Accessed 24 May 2024.

Morgan, Monroe T. Environmental Health. 3rd ed. Thomson, 2003.

"Preventing Childhood Lead Poisoning." US Centers for Disease Control and Prevention, www.cdc.gov/lead-prevention/prevention/index.html. Accessed 24 May 2024.

Schmidt, Charles W. "Unsafe Harbor? Elevated Blood Lead Levels in Refugee Children." Environmental Health Perspectives 121.6 (2013): A190–95.

Vivier, Patrick, et al. "The Important Health Impact of Where a Child Lives: Neighborhood Characteristics and the Burden of Lead Poisoning." Maternal and Child Health Journal 15.8 (2011): 1195–1202.

Warren, Christian. Brush with Death: A Social History of Lead Poisoning. Johns Hopkins UP, 2001.