In the past, lead was used in paints, gasoline, water pipes, and other household products, such as the solder used in canned food. Although these uses have been limited in the U.S., lead is still used in many products and industrial processes both in the U.S. and around the world. Housing built prior to 1978 is likely to contain lead-based paint and lead-contaminated household dust, especially if the house was built prior to 1950. Soil surrounding these houses may also be contaminated with lead.
Children less than 6 years of age are the most likely to be exposed to lead because of their increased hand-to-mouth behavior and high absorption rates. The lead gets into their bodies by their ingesting lead dust or paint chips, inhaling dust, mouthing or chewing items that contain lead or have been contaminated by lead, and/or by eating contaminated food or water. Adult lead exposure is usually related to occupational or recreational (hobby) exposure. Children of those who work with lead may also become exposed when lead contamination is brought home on the work clothes of their parents.
How is the sample collected for testing?Blood is drawn from a vein in the arm. Sometimes, blood is collected by fingerstick for infants and children. If test results from a fingerstick are abnormal, a venous blood draw should be ordered to confirm the results.
Is any test preparation needed to ensure the quality of the sample?No test preparation is needed.
How is it used?The lead test is used to evaluate the concentration of lead in the blood at the time the sample was collected. The blood lead test is used to screen for exposure to harmful levels of lead. It may also be ordered to monitor the effectiveness of treatment and to confirm that lead levels are decreasing over time.
Lead concentrations are monitored at the local level following State and National standards. The Centers for Disease Control and Prevention (CDC), the American Academy of Pediatricians (AAP), and a variety of other organizations make recommendations regarding screening children for lead exposure. Testing recommendations and the definition of what is an abnormal blood lead level have changed significantly over the past 45 years. In 1991, the CDC concluded that previous levels were not low enough, and in 1997 the blood lead level of concern for children was decreased from 25 micrograms per deciliter to 10 micrograms per deciliter.
Blood lead is monitored in workers whose environment contains lead. It is used to evaluate chronic lead exposure and recent lead exposure. Sometimes, a zinc protoporphyrin (ZPP) test is also ordered. The ZPP is increased when lead begins to affect red blood cell production. It is not sensitive enough to use as a screening tool for children, but it may be ordered to help evaluate average lead exposure in adults over the last several weeks.
When is it ordered?For screening children:
The CDC released guidelines for testing children for lead in 1997 and guidelines for managing children found to have elevated blood lead levels in 2002. They recommend that each state develop a plan to detect children who may have been exposed to lead. The CDC and the AAP recommend that, at a minimum, screening be offered to:
- Every Medicaid-eligible child and those children whose families are part of an assistance program; these children should be screened at age 1 and again at 2 years of age.
- At risk children 3-6 years of age who have not been previously tested.
- Children who live in or regularly visit a house or apartment built before 1950, or before 1978 if the dwelling has been/or is undergoing renovation or remodeling.
- Children with a playmate or sibling who has or did have lead poisoning.
People should check with their local health department regarding lead screening guidelines specific to the risks in their area.
The CDC and AAP recommend that children of parents who work with lead be considered for screening, and that immigrant, refugee, and other foreign-born children be tested when they enter the United States.
Managing children with elevated blood levels:
Since fingerstick samples can be contaminated during collection of the specimen, an initial elevated result obtained by a fingerstick sample should be repeated with a venous test for confirmation, usually within a week to a month after the first test. Follow-up testing is then used to monitor the persistence of an elevated blood lead test and is recommended whenever a child’s blood lead level is higher than 10 micrograms per deciliter. Those with persistent lead levels above 15-19 micrograms per deciliter (remain elevated for 3 months or more) and those with initial tests greater than 20 micrograms per deciliter should have their home surroundings evaluated to determine the source of the lead exposure.
For screening adults:
Blood lead tests may be ordered to screen people in the workplace if lead contamination is a possibility. Family members also may be screened because lead can be carried home on clothing. This testing conforms to federal and state laws for occupational exposure.
There is not yet a national guideline for blood lead screening in adults as there is for children. The clinical cut-off values for elevated blood lead currently vary from state to state. According to the CDC's Adult Blood Lead Surveillance program (ABLES), a national health objective is to reduce all blood levels in adults to less than or equal to 25 micrograms per deciliter.
Adults who work in industries known for lead exposure, such as smelter facilities, lead plating, auto repair, and construction, should be screened for lead exposure. Adults who have hobbies that involve lead-based paints, ceramics, or gasoline also should be tested. For a list of hobbies that may expose someone to potentially high levels of lead, go to Lead Poisoning.
The Occupational Safety and Health Administration (OSHA) has developed rules for monitoring for lead in the workplace. OSHA requires that employee blood monitoring programs be triggered by the results found in an initial air monitoring program. If a worker has an initial blood lead test result of more than 40 micrograms per deciliter, for example, testing should be done every two months until two consecutives lead tests show a blood lead level below micrograms per deciliter. Higher levels call for closer monitoring.
For both children and adults, lead testing may be ordered when a person's symptoms suggest potential lead poisoning. These symptoms are non-specific and may include fatigue, changes in mood, nausea, prolonged stomach distress, headache, tremors, weight loss, peripheral neuropathy, anemia, reproductive failure, encephalopathy, memory loss, seizures, and coma. Many children have no symptoms at the time of the exposure, but potentially permanent damage can still be occurring. Testing for lead exposure should be considered in children presenting with growth failure, anemia, sleep problems, hearing loss, or speech, language or attention deficits.
What does the test result mean?The higher the test result, the more lead is in the blood. However, the amount of lead in the blood does not necessarily reflect the total amount of lead in the body. This is because lead travels from the lungs and intestinal tract to the blood and organs, and then is gradually removed from the blood and organs and stored in tissues such as bones and teeth. The danger that a particular lead level represents depends on the age and health of the person, the amount of lead they are exposed to, and the amount of time that they are exposed to elevated lead levels.
Exposure to lead is not healthy for anyone, but children are more vulnerable to its effects. The national health goal is to have every child's blood lead level below 10 micrograms per deciliter by the year 2010. Any test results above this level trigger management and monitoring. Recent studies suggest that there may not be any safe lead level for children, that even below 10 micrograms per deciliter, some children will have cognitive impairment. If further studies support this, then the recommended lead levels may be lowered again in the future.
For non-pregnant adults, a level below 25 micrograms per deciliter is generally considered to be acceptable. If a worker has levels above 45 micrograms per deciliter, he must be removed from lead exposure until his blood lead level drops below 40 micrograms per deciliter. Removal may also be recommended if he is symptomatic at any level below 70 micrograms per deciliter. Because lead will pass through the blood to an unborn child, pregnant women need to limit their exposure to lead to maintain a blood level below 10 micrograms per deciliter and as close to zero as possible to protect the developing fetus.
Most experts agree that a child with a lead level greater than 45 micrograms per deciliter should be treated with succimer in the hospital unless the patient is encephalopathic. Any lead level greater than 70 micrograms per deciliter, whether in a child or an adult, should be considered a medical emergency.
Any child who has an elevated blood lead level needs to have their home or other environment evaluated. Other people at the residence should be tested as well. Without the elimination or reduction of the source of the exposure - a lead hazard in the environment - the elevated lead level will likely recur.
Is there anything else I should know?Poisoning with lead is more harmful for children, whose brains and other organs are still developing. Adults tend to recover from lead ingestion better than children. Children who may be at risk should be screened as soon as possible.
Lead interferes with the absorption of iron. Children with raised blood lead concentrations should be tested for iron defiency.
Each person eliminates lead differently. Thus, laboratory tests are just one part of the picture in lead poisoning cases. Careful monitoring with medical examinations is needed.
Physicians should be aware that cultural practices and folk remedies, including soil ingestion, can increase a person’s risk of lead exposure. Folk remedies prepared by newly immigrated populations from Southeast Asia are particularly known as possible sources of lead. Other potential lead sources include imported foods, candy, cosmetics, costume jewelry, brass keys, and toys or household items containing or painted with lead.
Quais produtos no Brasil ainda contém chumbo, além de tinta e cerâmica?
Alguns produtos ainda contêm chumbo entre eles: baterias de carro, soldas, alguns canos, munições, telhados, tintas industriais, alguns PVC, vinil e plásticos, objetos em latão, incluindo chaves, bijuteria e materiais de blindagem de raios-X.
Como as pessoas ficam expostas? Tocar esses produtos é suficiente para elevar meus níveis sanguíneos?
Apenas segurar um objeto de chumbo nas mãos não vai intoxicá-lo. O chumbo está mais presente como componente inorgânico e não atravessa a pele. No entanto, a inalação ou ingestão de poeira com chumbo pode intoxicá-lo. Situações em que poderiam ocorrer intoxicação por chumbo seriam:
- tocar superfícies cobertas por poeira de chumbo e então levar poeira para a boca com os dedos, alimento ou brinquedos
- quando uma criança toca as janelas de uma casa construída antes de 1978 com a boca ou dedos e depois engole poeira de chumbo ou lascas chumbo
- ingestão de chumbo na jardinagem de solo contaminado em torno de fundação de uma casa antiga ou garagem, ou em solo contaminado com gasolina com chumbo ao longo de estradas antigas, ou ambientes industriais abandonados
- engolir bala de chumbo (munições de arma de fogo), peso de cortina, ou um brinquedo de chumbo e não expeli-lo pelo sistema digestório
- inalar gases de queimadas de madeiras pintadas com chumbo ou caixas de baterias em lareiras domésticas
Quais profissões podem levar à exposição ao chumbo?
Alguns trabalhos que colocam as pessoas e seus familiares em risco de exposição ao chumbo incluem:
- Fusão de chumbo
- Solda de aço
- Reconstrução de pontes
- Instrutores e pessoal da limpeza de zonas de tiro
- Reformas e restauros de casas antigas
- Trabalho de fundição
- Reciclagem de sucata
- Fabricação de vitrais
- Uso de esmalte de chumbo em cerâmica
- Tingimento metálico
- Reparo de automóveis
- Soldador de cabos
Existem maneiras de me proteger e à minha família da exposição ao chumbo?
- Lave as mãos e os brinquedos da criança com frequência para reduzir a contaminação por poeira de chumbo
- Evite usar remédios que contenham chumbo
- Mantenha seus filhos (e mulheres grávidas) longe dos perigos do chumbo e das áreas durante a reforma ou restauro de construções
- Não deixe as crianças colocarem objetos que não são brinquedos próprios na boca, incluindo chaves, joias ou terra
Existem maneiras de me proteger e à minha família da exposição ao chumbo se eu trabalho em uma região de risco?
Sim. Se você trabalha em uma região de potencial risco à exposição de poeira ou gases de chumbo:
- Lave as mãos antes de comer, beber ou fumar
- Coma, beba ou fume em áreas livres da poeira e gases de chumbo
- Mantenha suas roupas de rua em um local limpo; trocar roupas e sapatos antes de trabalhar com o chumbo
- Tome banho imediatamente após trabalhar com chumbo, antes de ir para casa
- Lave suas roupas de trabalho no local de trabalho ou separadamente das outras roupas