Although the hazard has been recognized since ancient times, lead exposures high enough to produce poisoning are still common in the United States, as well as the rest of the industrialized world. Amounts of lead high enough to produce signs and symptoms of poisoning have been found in common consumer products such as foods, beverages (especially wines), cosmetics, medicines, etc., up until the last half of the 20th century in the United States. In many other countries lead contamination of foods and beverages continues to be extremely high with numerous cases of overt poisoning identified yearly.

Throughout this century, occupational lead exposures have resulted in the most severe cases among adults. For example, in the early 1900 occupational exposures in the United States were so high that only numbers of cases of poisonings resulting in death were maintained. During the period 1900-1933 over 3,400 deaths from lead poisoning were reported in the United States, with more than 1,200 deaths reported in England and Wales.

Lead poisoning damages a number of organ systems including the nervous system, the blood- forming system, the kidney and the reproductive system. Both adults and children are affected by lead exposure. For a number of reasons, that we will discuss, the developing nervous system of the infant before birth and early in life is extremely susceptible to the effects of lead.

In this discussion of the adverse health effects of lead, we will look at: how people are exposed to lead; the types of adverse health effects produced by lead; which age groups are most likely to be affected by lead, and other factors that influence whether or not a person will become ill from exposure to lead-based paint. The scientific literature on this topic is very extensive.

Dust can have thousands of parts per million lead by weight. Studies of children living in high-lead areas showed that when the child's hands were cleaned using "wet wipes" each cleaning removed 20 to 30 pg lead. Lead dusts are a very important exposure pathway. For children it is the most important pathway. Thus, it is very important not to leave lead- containing dust in the area being abated. It is also very important for lead not to be carried home from the worksite.

How Lead Exposure Occurs

• Inhalation

If lead-based paint removal is performed by a method that produces lead fumes (heating) or by a method that produces fine inhalable lead particles (sanding or grinding) lead from these processes can be inhaled. Fume or dust control is needed for processes that generate these hazards.

When very fine particles or vapors of lead are inhaled with air they act like fumes and can get into the upper airways and the lungs. Larger particles are cleared from the upper airways, swallowed, and absorbed in the gastrointestinal tract. Smaller particles enter the lungs and are absorbed by the lung. In normal adults 30-50% of inhaled lead is retained. The amount of lead that is absorbed depends on the size of the particle of lead. Of the very fine particles that reach the lowest part of the lungs, a very high amount is absorbed. Vapors or fumes of lead caused by heating lead (for example, with heat guns) are almost entirely absorbed by the lungs. Research is not yet clear whether children absorb more of the inhaled lead than adults.

When a person is in an environment that contains lead, she/he can transfer lead into body tissues through eating or breathing fine particles of lead. Eating, or ingestion, is the major route of exposure of both children and adults to lead. Breathing, or inhalation, of extremely fine particles of lead or lead vapor is typically not a major route of lead exposure for children or adults. However, if lead-based paint removal is being done by a method that heats the painted surface (as with a torch or heat gun), lead from the surface is vaporized and can be inhaled. This is one of the reasons why lead-removal methods that use heat to blister or torch the painted surface are either not recommended or are not allowed in some localities.

• Ingestion

After lead particles from dust or chips of paint are ingested, swallowed, and dissolved by stomach acids, the gastrointestinal tract absorbs part of the lead that was ingested. In tile same way nutrients from foods are taken into the blood, lead can be taken into the blood and other body organs. For adults, about 5-15% of the ingested lead is absorbed. Young children absorb much more of the ingested lead, typically 40-50%.

The amount of ingested lead absorbed also depends on the size of the particle. Generally the smaller the particle, the higher the absorption rate. Fine dusts generated from sanding or grinding of lead-based paint are absorbed more than the same amount of lead in the form of flakes of paint. In addition, fine dust is, in many ways, less noticeable to a child or an adult than are flakes or chips of paint, and therefore more easily ingested. This difference in the amount of lead that is absorbed is one of several reasons why young children are harmed more by lead than are adults.

When people do not eat much food, or are low in some nutrients, the body absorbs more of the ingested lead. This happens because the body is trying to absorb the "good" things it needs and grabs the lead also. Lead exposed workers (lead abatement workers, remodeling/renovation workers, etc.) can ingest lead if they smoke or eat without first thoroughly washing their hands and face.

When a person is in an environment which contains lead from chipping, powdering or peeling paint or other sources, the individual can transfer lead into body tissues through eating or breathing fine particles of lead. This problem is especially severe among very young children, especially toddlers under two-years of age. Among children in this age group, exploring their world by placing their hands, toys and other objects in their mouths is entirely normal. However, in a high-lead environment this normal activity can cause terrible effects on the child's health, particularly the central nervous system.

Many young children not only place in their mouths things that are not food, but may also swallow small objects. "Pica" is the term used when the child does this a lot. Pica can be for non-food objects that may or may not be high in lead. For example, very young children may swallow paper, crayons, and cigarette ashes. These are not particularly high in lead.

However, if young children swallow chips or flakes of high-lead paint for several weeks, the effects can be terrible.

 Based on reports by their mothers or other primary care-givers, approximately 10% of children under three years-of-age swallow non-food    objects. As children get older they don't do this as much. The frequent occurrence of mouthing behavior or pica among very young children is an additional reason why this age group is particularly likely to have lead poisoning.