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Lead is a naturally occurring element or base metal that is very dense, malleable, and resists corrosion. It occurs naturally as galena (lead sulphite), white lead (basic lead carbonate), and red lead (lead oxide). Lead has a low melting temperature, and it can be molded or shaped easily, and has been used in a wide variety of construction and industrial applications. Lead was used as a protective coating and roofing material on buildings as early as 5,000 years ago. The ancient Romans used lead to construct water pipes and troughs. More recently, lead has been utilized as an ingredient or component in paints, cosmetics, medical preparations, glass, ammunition, plumbing solder, batteries, gasoline, and solder on food cans. Lead has also been used for sound shielding and as a radiation shield in x-ray and nuclear applications.
Recently, the dangers of lead poisoning have come to the forefront of public attention. Lead poisoning can cause a number of adverse human health effects, but is particularly detrimental to the neurological and intellectual development of children. Lead is a cumulative poison, and repeated exposure can cause a gradual accumulation of lead in the body and directly affect the central nervous system and the kidneys. The primary routes of lead absorption into the human body are inhalation and ingestion. Lead entering the respiratory and digestive systems is released to the blood and distributed throughout the body, it then accumulates in the bones and teeth, where it can remain for many years. Generally speaking, the severity of symptoms is dependant upon the level of exposure.
As a result of past and current industrial uses, lead has become a common environmental contaminant. Lead is an element, it does not breakdown or biodegrade. Environmental concerns over lead poisoning have recently resulted in programs to curtail the use of lead. The phase out of leaded gasoline has contributed to a decline in air lead levels. Concerns over the health effects of lead has resulted in a reduction in the amount of lead in paints, ceramics, caulking and pipe solder, as well as lead solder in food cans. Although progress has been made in reducing lead use and the corresponding exposure, lead continues to be a significant environmental and public health problem.
Lead was used as an octane booster in gasoline for approximately 50 years, and even though the use of leaded gasoline has been significantly reduced, the high levels of lead found in the soil can be attributed to past emissions from internal combustion engines. A similar situation exists regarding lead based paint. Although the use of lead in paints has been dramatically reduced, there is a major concern over the huge amount of lead based paint that was historically applied on virtually all industrial, commercial, and residential projects. Lead was added to make paint durable. At one time the lead content of a paint was marketed as a measure of its quality, the more lead, the better the paint, and prior to 1940 lead content ranged anywhere from 10-70%. Voluntary paint industry standards reduced the lead content to about 1% around 1950, and lead in residential paints was discontinued in 1978. Lead was added to make paint durable, so lead paints were frequently selected for use on kitchens, bathrooms, window and door trim, as well as most exterior applications.
When surfaces that have been previously painted with lead based paints deteriorate, or are otherwise disturbed, the lead pigments can leech out of the paints. This creates a hazard to the environment in the form of lead dust and lead paint flakes that will eventually become dust. Children have been known to ingest lead paint flakes (probably because they have a sweet taste). Many health authorities believe that the primary source of lead poisoning in children is the lead based paints in older housing, and institutions. Adults need to be concerned with occupational exposure to lead. Those who work in construction, demolition, painting industries or in other lead industries or hobbies can be exposed to lead. The clean-up, removal, transportation and disposal of lead materials should be entrusted to professionals.
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