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Serving Western Washington since 1998.
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The Issue: Lead in Coatings.
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Lead was added to paint, varnish, and stains to give them brighter colors and make them more durable. Lead made coatings dry faster, more flexible, brighter, and imparted anti-fugal and antimicrobial qualities. Because the lead was dissolved in oil (linseed oil for instance) the coatings were also water resistant.
Starting in 1978 lead was no longer permitted in coatings used in residential projects in the USA. However it is still found in coatings used on boats and in other settings (traffic paint, bridges, for instance). Deteriorating lead paint can produce dangerous lead levels in household dust and soil, a major cause of chronic lead poisoning. In particular lead-containing coatings found on friction surfaces of windows and doors can pose a significant source of lead dust. Many young children display pica, eating things that are not food. Because the lead in old paints tastes sweet, this makes eating it even more likely. Even a small amount of a lead-containing paint can contain tens or hundreds of milligrams of lead. |
Peeling lead-based paint is an important source of lead dust in the home environment.
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Effects of lead on the human body.
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The list of processes and tissues negatively influenced by lead is quite long.
The human body does not differentiate between lead, which has no known role in our body, and calcium, iron, and zinc, all of which are essential (cofactors) for many different enzyme functions within the body. Lead is implicated in heart problems, asthma, hearing loss, tooth decay, cataracts, kidney damage (including predisposition for gout), high blood pressure and all its associated risks and possibly programmed cell death in brain cells. It interferes in several ways with the formation of heme, a component of hemoglobin, the oxygen-carrying part of red blood cells. In this and other ways it may lead to anemia. Lead reduces sperm count. It leads to reduced birth weight, miscarriage, and prematurity. Because lead passes through the placenta, fetuses can be poisoned in utero. Because it is secreted in breast milk lead levels in nursing mothers and their infants are usually similar. Lead interferes with the binding of neurotransmitters to their receptors, thus blocking proper nerve function, leading to learning and memory problems. Lead causes nerve damage through degeneration of the axon (nerve fiber connecting the nerve cell body to other cells) as well as loss of nerve cells’ myelin (insulating) coating, inhibiting proper nerve propagation. It inhibits synapse formation in the cerebral cortex in children. All of this adds up to: mostly peripheral nerve damage in adults and damage to the (developing) central nervous system in children. Problems associated with lead in young children include anxiety, aggression, learning and developmental disabilities, and reduced IQ, just to name a few. No lower threshold for effects has been determined, meaning there is no safe level of lead exposure. |
 Source: Wikipedia |
Paths of exposure.
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Organic lead is easily absorbed through ingestion (eating) and inhalation (breathing).
A portion of the lead that is ingested or inhaled is stored in various tissues, including blood, bones, and soft tissues. The remainder is excreted, mainly in urine. In adult 94% of absorbed lead is stored in tissues like bones, hair, and teeth, where lead is thought to be less harmful, while in children only 70% of absorbed lead is deposited in a similar way. That means that five times more lead remains in the bloodstream in children, probably contributing to the greater damaging effects of lead in children. The half-life of lead stored in tissues is measured in weeks for blood (about 40 days in men, possibly longer in women and children), months for soft tissues, and 20 – 30 years for bone. Lead in bones is reintroduce into the bloodstream long after the initial exposure is gone, since bone is constantly replaced. Lead is removed from the body very slowly. It is mainly excreted in urine. Smaller amounts of lead are eliminated through the feces, and very small amounts in hair, nails, and sweat. The Center for Disease Control has set the standard elevated blood lead level for adults at 25 µg/dl (a µg –micro gram- is one millionth of a gram) of the whole blood. For children however, the number is set much lower at 10 µg/dl of blood and in 2012 there were recommendations to reduce this to 5 µg/dl, which will still pose a risk. |
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Sources:
Joint EPA – HUD curriculum for Lead Safety for Renovation, Repair, and Painting. Initial Instructor Manual. October 2011: click HERE.
Agency for Toxic Substances and Disease Registry: click HERE.
Center for Disease Control: click HERE.
Wikipedia (20 references) : click HERE.
Joint EPA – HUD curriculum for Lead Safety for Renovation, Repair, and Painting. Initial Instructor Manual. October 2011: click HERE.
Agency for Toxic Substances and Disease Registry: click HERE.
Center for Disease Control: click HERE.
Wikipedia (20 references) : click HERE.