Ohio State University Extension Fact Sheet

Community Development

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Lead

CDFS-193-97

Lead was first smelted in approximately 4000 B.C. as a byproduct of silver processing. As galena (lead sulfide), this metal can be smelted at relatively low temperatures. The same sulfur, however, makes this material toxic. History suggests that along with the valuable uses of lead for weapons, containers, and other items, the toxicity of lead was also known. Some believe, for example, that the fall of the Roman Empire was based in part on the common use of lead for drinking vessels. Native Americans conscripted as miners by the Spanish also suffered from lead exposure. This fact sheet will explore what lead is, why it is used in products, the environmental health impact of lead, and what you can do to avoid lead poisoning.

What is lead?

Lead is a heavy, soft, toxic, gray-blue metal present in some insecticides, auto exhaust, industrial emissions, and a variety of products. For example, lead is found in automotive and storage batteries and is used in the manufacture of paint, enamel, ink, glass, rubber, ceramics, and chemicals. Lead is also used as an antiknock additive in gasoline. Lead is commonly found in older pipes, brass faucets, or pipes with soldered fittings. Many imported canned goods also have lead soldering. Some glazes for ceramic dishes or cookware use lead because it adds brilliance to the glaze. "White lead," the chemical equation of which is Pb(OH)2 . 2 PbCO2, is one of the oldest pigments known. Until the 1940s, this pigment was used in paints for homes and public buildings; after the 1940s, the lead was replaced with titanium dioxide.

In the human body, lead inactivates the sulfhydryl (SH) groups of enzymes necessary for the synthesis of heme, which is the oxygen-carrying pigment in the blood. Lead may also interfere with other metabolic systems of cells.

How does lead enter the environment?

Lead released into the environment makes its way into the air, soils, and water. Lead can remain in the environment as dust indefinitely. The lead in fuels contribute to air pollution, especially in urban areas. Soils near highways, freeways, and smelting facilities have higher levels of lead than soils in other areas because of their exposure to lead dust, which accumulates over time. Plants exposed to lead can absorb the metal dust through their leaves. Plants can also take up minimal amounts of lead from the soil.

How does lead enter the human body?

There are two pathways by which lead can enter the human body: 1) ingestion and 2) inhalation. Ingestion of lead dust can come through many exposures. However, only a small percentage (between 5 and 10 percent) of the ingested lead passes from the intestinal tract into the bloodstream. For children, the percentage is slightly higher. Foods exposed to lead can be a source of ingested lead, although scrubbing foods before eating them eliminates nearly all the dust. Drinking water that has passed through older lead pipes or lead solders can carry traces of lead. The ingestion of lead by children is a major health concern. Children playing around soils with higher levels of lead will ingest some of the lead dust through activities such as sticking fingers their in their mouths and even eating soils. Again, the exposure level from such activity is slight except in contaminated areas. For children, the greatest source of ingested lead may be through eating paint chips in older homes or apartments.

Even though lead was removed from paints in the 1940s, an estimated 50 million houses and apartments still contain lead paint. Peeling and chipping paint can release lead dust. The peeling paint chips have a sweet taste that appeals to many children. First described in the U.S. in 1914, pica is an abnormal craving for paint chips that develops as a child first tastes, then begins to crave, the paint chips. Ingestion of lead paint chips can result in an intake 100 times the safe daily load for an adult. At such a level, severe lead poisoning can occur.

The second way lead dust can enter the body is through inhalation of gas, paint fumes, or soldering fumes. Even though most lead has been removed from gasoline, nearly 98 percent of airborne lead is from gasoline emissions. Although inhaled lead comprises a much smaller portion of exposure than ingested lead, between 30 and 50 percent of inhaled lead enters the bloodstream. Inhalation is also a concern in occupational exposure areas; OSHA standards are set to minimize risk of exposure within occupational settings such as shops where lead solder is used.

How does a toxic level of lead affect the human body?

In the body, lead can affect hematologic (blood), renal, neuromuscular, gastrointestinal, central nervous, and reproductive systems. At lower levels of exposure, lead poisoning leads to hyperirritability, poor memory, and sluggishness. At high levels, mental retardation, epileptic convulsions, coma, and even death may occur. Except at high levels, lead toxicity is believed to be reversible, excluding late renal and some central nervous system effects. Lead affects the body in these systems by interfering with blood cell formation.

Children are of special concern regarding lead poisoning for three major reasons. First, children have a higher basal metabolic rate, which affects the absorption and metabolism of toxicants. Second, children have a different breathing zone than most adults in that they are closer to the ground or floor where lead is deposited. Third, children have rapid growth and differentiation of cells. Because the nervous systems of children are still developing and their body masses are relatively small, lead concentrations have a greater impact on children than on most adults. Various health care providers, including pediatric and family practitioners, regard lead poisoning as a major threat to the health and well-being of children.

Several tests enable health care providers to determine lead levels in the body, the most common being a blood test. Lead poisoning is often treated by removing lead from the body using chelating agents. Chelation therapy involves prescribing penicillamine, which binds with lead at a molecular level and is excreted from the body through normal body cleansing processes.

What can an individual do?

As a society, many steps have already been taken to reduce the emission of lead into the ecosystem. Standards for the removal of lead from gasoline, controls within production processes, and similar actions have resulted in a 95 percent reduction in lead emissions since 1974. In water and in paint, industrial changes have resulted in fewer sources of lead exposure, particularly in new construction or reconstruction. Within the home, you can undertake the following measures to better understand potential lead exposures and remedies:

• For lead in water, first check plumbing to see if lead pipes or solders are used. If they are, four levels of action are possible, which are described below. You can also have your water tested for lead levels; contact your local health department about this option and about recommendations based on the findings of lead, if any exists, in your water.
  1. In the mornings, flush the pipes by running cold water through them for at least thirty seconds to remove any water that sat in the pipes overnight. Whenever possible, use cold water, as hot water is more likely to cause any lead to leach.
  2. Consider using bottled water for ice cubes, cooking, brushing teeth, and the like-- especially for small children.
  3. Manufacturers make various claims about the ability of home distillation systems to remove lead from water at the tap. Ask your local health department to run a test and recommend a system appropriate for your home.
  4. If possible and appropriate, replace lead pipes with PVC pipes, which do not require solder, or copper pipes fitted with lead-free solder.
• Inspect the paint within buildings constructed prior to 1950 (or buildings that may have been painted using paint dating from the 1940s or before). If there are places where the paint is peeling, rubbing (such as on window jambs), or chipping, consider repair. Remember that the best option is often the simplest--seal the old paint under a well-applied and well-maintained new paint. If more intensive repair is needed, wear a dust mask and other protective coverings and remove the loose paint. Try not to create additional dust unless you are able to contain and vent the dust. Using a spackle compound, cover the area, then repaint.
• Lead is still used safely for various glazes in earthenware not intended for food storage or serving. Most of these products are clearly marked at purchase. If you have any doubt about glazed products you own, do not use these earthenware containers for food storage or serving.
• Take individual responsibility for producing less auto exhaust--walk or bicycle whenever possible rather than driving.

Lead is a natural element in the ecosystem. Through human activity, we concentrate lead in ways that, if it enters the human body in large enough amounts, is detrimental to health. Knowing more about lead and its use can help each of us and all of us improve our lives.