Lead is a naturally occurring metal that has been used extensively throughout history. Its usage is traced right back to ancient history. High exposure to lead, particularly in young children, is associated with health complications. Lead poisoning is not a new phenomenon. Reports of lead poisoning from water pipes and wine containers date back to Roman times.
Most of the lead absorbed into the body is accumulated in the bone. Some is distributed in the blood and soft tissues around the body. Lead can interfere with hematopoiesis, leading to the reduced synthesis of heme and the increased production of toxic products such as aminolevulinic acid and protoporphyrin. The lead tends to remain in the body for several months, and is slowly excreted by the renal system over an extended period of time. This can result in chronic health effects such as:
- Mental retardation
- Intellectual impairment
- Delayed or impaired growth
- Behavioral problems
- Loss of appetite
- Poor coordination and school performance.
In severe cases or acute toxicity, the symptoms may include abdominal pain, nausea, vomiting, seizure or coma.
Children are more susceptible to the effects of lead poisoning than adults for a range of reasons:
- Infants, toddlers and young children are more likely to put objects in their mouth, which can increase the consumption of lead from dust and soil on the objects.
- Additionally, the tolerable upper intake is smaller for children than adults, so they are more susceptible to the adverse effects of high doses.
Although both organic and inorganic lead has the potential to cause lead toxicity, inorganic lead is the most common offender.
Exposure to lead may occur through ingestion, inhalation or absorption across the skin. In children, a common cause of lead poisoning is ingestion of lead from putting objects in their mouth. The absorption of lead depends on several factors including the solubility of the form of lead ingested, the particle size, the presence of other nutritional deficiencies, and the diet of the child.
Early in the twentieth century, lead paint in home environments was suggested as a common cause of lead poisoning in children. However, this was not confirmed until several decades later. Eventually, lead was banned from US household paints in 1978. As a result, exposure to deteriorating paint from houses painted before 1978 accounts for the majority of exposure to lead in childhood. Other sources of lead exposure include cosmetics, jewelry, batteries, cement, canned food and farming equipment.
Possible sources of lead exposure in children may include:
- Soil and dust
- Tobacco smoke
- Glazed pottery
- Lead piping, solder or crystal
A blood test to determine the blood lead levels (BLLs) is used to monitor for lead intoxication, make a diagnosis and guide the treatment plan.
The Centers for Disease Control and Prevention (CDC) has established that the upper reference interval value for BLL is >5µg/dL. Anything above this is a reason for concern in children younger than 5 years of age. However, it should be stressed that there is no safe level for BLL. In other words, some children with a BLL <5µg/dL may still experience the effects of lead toxicity.
The best way to prevent lead poisoning in children is to reduce their exposure to possible sources of lead.
There are also several ways to reduce the absorption of lead from the environment. Lead is more easily absorbed into the body in an acidic environment with a small particle size. Thus fine lead dust leads to higher lead levels than paint chips.
An adequate nutritional intake is also essential to help prevent lead poisoning. A deficiency in iron, calcium, zinc, copper or protein may lead to greater absorption of lead. Conversely, a high intake of fats can increase lead absorption. Some vegetables such as leafy greens may have a protective effect, as they appear to increase the elimination of lead from the body.
Research data indicates that the prevalence of elevated BLLs in children in the industrialized world is on the decline. However, lead poisoning in children remains a common health threat that is largely preventable with simple environmental interventions. In fact, it is estimated that more than 4 million households in the United States have children that are currently being exposed to high lead levels. Approximately 500,000 children are estimated to have a BLL greater than 5µg/dL.