| hazards summary | Lead is a naturally occurring bluish-gray metal found in small amounts in the earth's crust. Lead can be found in all parts of our environment. Much of it comes from human activities including burning fossil fuels, mining, and manufacturing. Lead has many different uses. It is used in the production of batteries, ammunition, metal products (solder and pipes), and devices to shield X-rays. Because of health concerns, lead from gasoline, paints and ceramic products, caulking, and pipe solder has been dramatically reduced in recent years.CDC uses a blood lead reference value (BLRV) of 3.5 micrograms per deciliter (µg/dL) to identify children with higher levels of lead in their blood compared to most children. This level is based on the 97.5th percentile of the blood lead values among U.S. children ages 1–5 years from the 2015–2016 and 2017–2018 National Health and Nutrition Examination Survey cycles. Children with blood lead levels at or above the BLRV represent those at the top 2.5% with the highest blood lead levels. To learn more about CDC’s updated recommendations on children’s blood lead levels, please visit:http://www.cdc.gov/nceh/lead/ACCLPP/blood_lead_levels.htm.Lead is used in the manufacture of batteries, metal products and ammunition. Exposure to lead can occur from breathing contaminated air in or near workplaces that process lead or lead materials, as well as from incidentally ingesting dust or paint chips in houses with lead-based paint. Lead can cause effects on the blood, as well as the nervous, immune, renal and cardiovascular systems. Early childhood and prenatal exposures are associated with slowed cognitive development, learning deficits and other effects. Exposure to high amounts of lead can cause gastrointestinal symptoms, severely damage the brain and kidneys, and may cause reproductive effects. Large doses of some lead compounds have caused cancer in lab animals.At blood lead levels above 900 ug/L (90 ug/dl), poisoning can cause acute lead encephalopathy. Peripheral neuropathy results from levels above 600 ug/L (60 ug/dl). Most reports of lead-related symptoms (fatigue, abdominal pain, and arthralgia) begin at blood levels greater than 600 ug/L. Typical concentrations of lead in surface water in the USA is between 5 and 30 ug/L. Typical intake of lead in the USA is 2 to 9 ug per day from food, water, and beverages. In an analysis of PbB and neurobehavioral test results from 40,000 participants from NHANES III, no statistically significant relationships between blood lead concentration and neurobehavioral test performance were found. . . . Tibia lead, representative of cortical bone, has a residence time of 25 to 30 years and serves as a biomarker of cumulative dose. . . . With additional study, lead in bone could be a viable measure of lead body burden, but at this point in time, the database is insufficient. Heavy lead exposure causes anemia. Lead inhibits hemoglobin synthesis (ALAD and other enzymes), and also shortens lifespan of RBCs with resulting hemolysis. Exposure to high air concentrations of lead can precipitate hemolytic anemia. The anemia of chronic lead toxicity, the primary hematologic effect of lead exposures, is enhanced by shortened red cell survival as well as by inhibition of hemoglobin synthesis. At blood levels above 50-60 ug/dl, suppression of heme synthesis causes anemia. Lead-exposed workers may develop proximal renal tubular damage and progressive renal insufficiency. Lead can produce slight hepatic injury in experimental animals. There is strong positive data associating lead exposure with spontaneous abortions and prematurity in pregnant women, neurological dysfunction in children and decreased sperm counts in men. The OSHA standard requires periodic determination of blood lead in workers exposed at or above action level (30 ug/m3) for more than 30 days per year. About 90% of pre-1940 homes contain lead-based paints, while about 60% of 1960-1979 homes contain significant amounts of lead in paint. The use of lead piping and lead solder in plumbing has been prohibited since 1986. Inorganic lead compounds are probable human carcinogens. Organic lead compounds are not classifiable. In contrast to inorganic lead, organic compounds are absorbed readily through the skin and into the CNS. Trabecular lead (measured in the patella) reflects exposure in the last 10 years, while cortical bone (measured in the mid-tibia) reflects lifetime exposure. Tetraethyl & tetramethyl lead (CAS # 78-00-2 & 75-74-1) are covered separately. |