Lead Poisoning

Mr. Thompson brings his 2 year old son to the clinic for a routine exam. As part of your examination you perform a blood lead level. The level comes back at 22ug/dL. How would you proceed with this case?

Introduction

The above case is not an uncommon one, particularly in the Chicagoland area, and it is important for the pediatrician to routine screen for lead toxicity as it can be asymptomatic. 

A normal lead level is 0. However, considering that lead is ubiquitous in an industrialized society, we all have some lead in our bodies. An acceptable lead level is less than 5 ug/dL.

The most important thing to do in this case is to ask about how the child was exposed to lead.

 

Possible sources of lead are:

  1. Lead in dirt (seeped in from when gasoline was leaded), with exposure via touching dirt with hands and putting hands in mouth, eating dirt, etc.
  2. Lean in pain chips from pre-WW II
  3. Lead in dust. Increased possibility if renovation is being done or there is tearing down of old buildings. 
  4. Lead-contaminated clothing from the workplace
  5. Improperly glazed pottery - lead can be etched out by acid materials like orange juice.  This type of pottery is common in Latin America.

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  1. Lead in water, canned goods, lead batteries, gasoline.
  2. Sniffing of gasoline by adolescents
  3. Lead in retained bullets.

Children are at higher risk for lead poisoning than adults for several reasons. They absorb a higher proportion of ingested lead, distribute more of it to water-soluble reservoirs in soft tissues rather than bone, have an immature blood–brain barrier resulting in increased penetration of lead into the central nervous system, and have developing body systems (blood, bone, immune, kidney, brain, and nervous system) that are more susceptible to injury at the cellular level.

Children are more likely to have iron deficiency, a comorbidity of lead poisoning, that enhances lead’s absorption, changes its kinetics, and works synergistically to increase the vulnerability of children to developmental delays.

 

Risk of Lead Exposure:

  1. Lives in or regularly visit house built before 1960 with peeling paint chips
  2. Lives in or regularly visit house built before 1960 that has recently undergone renovation
  3. Sibling or playmate has recently been diagnosed with high lead level
  4. Family member who works with or has a hobby with lead
  5. Live near an active lead smelter or battery burning recycling plant.

The incidence of lead encephalopathy is lower now than in the 1970's due to the removal of lead from gasoline. The incidence of lead poisoning is still a problem especially in areas that have old deteriorating housing with peeling paint that contains lead. Also, home rehabbing has led to lots of dust that has been contaminated with lead. This dust can then be breathed in by children.

 

Questions to ask parents and patients

Although it is clinic policy to screen all children between the ages of six months and six years who live within the City of Chicago (see below), the following questions are useful for identifying children at risk for lead exposure living in lower risk regions.  In the case of a confirmed lead exposure, these questions may also help to identify the source of the exposure.

Question:

To determine if…

When was your house/apartment/condo built?

Lead paint was not banned until the end of 1977.

Do you live close to a highway or an industrial plant?

Although leaded gasoline has been banned in the US since 1995, pollution from cars using leaded fuel was a major source of soil contamination.  Soil contamination from automotive and industrial sources remains prevalent.

Is your child from a foreign country?

Many developing countries (notably those with large refugee populations) have not yet banned leaded gasoline, the main source of environmental lead.

Have you traveled to Mexico, Central or South America or Asia?

Cosmetics, pottery, and home remedies high in lead are very common in the Americas outside of the US and Canada (EBLL prevalence of >7%) and the Pacific Rim.

Does anyone work with lead in the home, especially hobbies involving antiques?

Jewelry making, automotive repair, antiques, plumbing, stained glass work are anecdotally associated with in-home lead exposure.  The older the lead component, the more likely it is to generate dust.

How often does your child put things in his mouth?

Although pica (eating of non-food items) is a rather rare cause of lead exposure, as part of normal development children exhibit hand-to-mouth behaviors that place them at risk for ingesting paint chips or lead dust.

 

In Illinois, particularly the Chicagoland area, lead exposure is an ongoing pediatric public health concern.  Nationwide, of the more than 3 million children tested annually, approximately 1% will test positive for an elevated blood lead level (EBLL, defined previously as a blood lead level greater than 10 mcg/dL, and now greater than 5 mcg/dL).  By comparison, in Illinois 3.5% of children tested positive in 2007 (the most recent data available).  While this represents a six-fold decrease since 1997, it is nonetheless a rate surpassed only by Vermont (4.3%), with Pennsylvania (3%) and Rhode Island (2.3%) as the only other states with rates above 2%.  Furthermore, while under-testing remains a concern nationwide (12.7% of children < 6 years are tested), in Illinois under-testing is particularly acute (9.4%) despite the increased risk of exposure.

As a result of this need, and Illinois state law (see below) blood lead testing represents an underutilized screening tool that should be considered in every patient, and should be routinely done in anyone with risk factors as well as anyone living in Chicago at regular intervals (9 months, 15 months, 2 years and yearly until 6)

 

Diagnosis of Lead Intoxication

  1. Known exposure
  2. History of pica
  3. X-rays may show lead chips in the abdomen - indicative of recent pica 

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  1. "Lead lines" on bone radiographs- increased calcification at the metaphyseal plate of long bones- are not diagnostic

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  1. Lead level from venous puncture (NOT capillary as lead can be on the hands and show a false positive)

 

There is no direct correlation between lead level and symptoms. Encephalopathy may be preceded by behavioral changes, vomiting, and abdominal pain. With encephalopathy, there is persistent vomiting, papilledema, seizures, ataxia, and coma. The effect of chronic lower levels on neurodevelopment are controversial, but there is significant concern to warrant intervention and treatment at lower levels. There is some evidence that lower levels may affect behavior, school performance, IQ, and hyperactivity.

 

Effects of Lead Exposure and Poisoning

Like other heavy metals, lead is a cumulative poison that affects patients through either chronic exposure or acutely following exposure to exceptionally high amounts.  It has a broad spectrum of effects that may be easily overlooked, particularly in chronic exposure, that can nonetheless be debilitating over time, particularly in the case of the developing child.

Lead is distributed between the blood, soft tissue (including the central nervous system), and primarily the skeletal tissue. Exposure affects many different organ systems, most notably the CNS, skeleton, and hematopoiesis.

System

Effects

Findings

CNS (children)

Developmental delay

Loss of milestones

Encephalopathy (even seizures)

Typically asymptomatic

Paucity or absence of speech

Decreased concentration, short-term memory, fine motor skills

Peripheral nervous system (adults)

Neuropathy

Decreased motor strength

Decreased sensation

Hematologic

Sideroblastic anemia

Ringed sideroblasts with basophilic stippling

Musculoskeletal

Reduced growth potential

“Bright line” on long-bone radiographs (deposition in the growth plate)

Gingival lead lines (very low sensitivity)

Gastrointestinal

Nausea and vomiting

Colic (intermittent abdominal cramping)

Lack of specific findings pointing to an alternative intraabdominal diagnosis

Renal

Interstitial nephritis

Predisposition to gout

 

 

Even in case of acute exposure to potentially lethal quantities of lead, the presenting symptoms are typically non-specific: seizures, tingling or numbness, paralysis, and colic. Therefore, the timely diagnosis and treatment of lead poisoning requires an alert and attentive physician (see below).

 

Treatment

Treatment of lead depends upon the severity of the exposure and the status of the patient.  In the otherwise healthy child, the most important treatment is removal from exposure.   Given that lead was nearly ubiquitous in paints and automotive fuels until the late 20th century, and given that environmental contamination persists for years to decades, identification of the source of exposure and its removal can be an extensive process.

To prevent further exposure, education in hand-washing and food preparation, careful monitoring of oral intake, the consumption of strictly bottled water, and even relocation may be necessary until the contamination can be removed.  In the absence of specific organ damage (10‑19 mcg/dL), serial blood lead levels are sufficient to ensure resolution. At higher levels of exposure (20‑45 mcg/dL) especially in the setting of neurodevelopmental delay, anemia, or other organ damage, additional testing and appropriate specialist referral may be necessary.

At high levels of exposure (≥45 mcg/dL, urgently for 70 mcg/dL or greater) or in acute cases, abdominal radiography is often advised to rule out particulate ingestion that may require whole bowel irrigation.  These patients warrant a complete head-to-toe physical to search for signs of organ damage, and chelation therapy should be initiated.  Chelation therapy uses the binding of lead by EDTA to remove the toxin from the serum.  This will quickly reduce blood levels, although in chronic exposure, the bone acts as a depot and will continue to release lead into the circulation for some time, even after exposure has been ended.

 

To summarize:

  1. 0-3ug/dL- no intervention
  2. 4-25ug/dL- environmental survey, notification of Chicago Public Health, careful follow up
  3. > 25ug/dL- chelation therapy should be considered in addition to above measures
  4. >70ug/dL - hospitalize and chelate with BAL and EDTA, in addition to above measures
  5. If there are paint chips present on an abdominal film, cathartics may be useful.
  6. Try to remove child from the source. This is often difficult to achieve.  There are resources for families needing assistance in paying for this if they are homeowners, as well as resources for renters, click on the link below:

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Chelating Agents

  1. DMSA (succimer) Chemet. It may be given orally. Binds with lead and is excreted through the kidneys. There is a rebound effect after cessation of therapy. It is given for 19 days and LFT's must be checked. It may cause nausea and vomiting secondary to its smell. It may be better to give with pop or juice. Useful for levels < 70ug/dL
  2. BAL
  3. Ca EDTA
  4. Penicillamine

It is important to recheck the lead level. A venous blood sample must be used because of possible contamination of finger sticks.  In the above case the child should be called back and the level should be repeated in one month. Also, possible exposures should be discussed not only in the home but in other areas where the child spends time (e.g. baby-sitter's and relatives' homes). You should also ask about other sibs, parents’ occupations, previous treatment of other family members, condition of house and whether there had been recent renovations. If the repeat level is still greater than 5 g/dL, the Board of Health should be notified to inspect the home. 

Poison Control is a great resource for helping determine which chelation agent to use, when to recheck levels, or restart chelation.  Click on the link below for more information.

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Commonly asked questions

  • What regulations are in place to prevent lead poisoning?

The laws and regulations are highly variable from state to state, with differing levels of efficacy.  The overarching law is Residential Lead-Based Paint Hazard Reduction Act of 1992 of Title X requiring the disclosure of lead-based paint in residential buildings by the owner to any lessee or buyer.

With regards to inspection and clean-up, although the Department of Housing and Urban Development maintains some regulations, the majority of regulation is at the state level.  In Illinois, the only requirement for inspection and ablation (if lead paint is found) is for the immediate housing unit and common areas, even though other units in the building are also likely to be contaminated.  It is important to encourage the patients to contact neighbors as they are at risk as well, and their units also present a potential source of re-exposure for the patient.

Click on the link below for resources relating to Chicago.

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  • How often should my child be tested for lead?

For Chicago residents, current laws and health policies dictate that all children ages 9 months to six years should be tested annually.  Regulations vary from state-to-state and no specific consensus exists.  However, the minimum testing recommended for asymptomatic patients as recommended by the American Academy of Pediatricians and required by Medicaid (though not routinely enforced) is 2 screenings, once at one year of age, and again at two years of age.

The American Academy of Family Physicians following the United States Preventative Services Task Force guidelines does not currently recommend screening in the general population unless a high risk for exposure is suspected. USPSTF grades the level of evidence a category “I”, concluding that evidence is insufficient to recommend for or against routine screening for elevated blood lead levels in asymptomatic children who are at increased risk.

  • Does water fluoridation increase the risk and rate of lead exposure?

The concerns regarding fluoridation and lead exposure generally stem from opposition to water fluoridation in general.  Several studies in the past have attempted to show a relationship between fluorine and lead, and have found no such link exists.  As an aside, the view that lead pipes caused the fall of the Roman Empire, while logical, has been similarly discredited.

 

  • Your patient tests positive for an EBLL now what?  Reporting and Counseling

It is policy (and Illinois law) that results greater than 5 be reported to the Department of Public Health, and the patient should be referred to back to their primary care physician or a health clinic with laboratory capabilities. 

By referring the patient to the Department of Public Health, they assist with identifying and eliminating the source of exposure.

Returning to the principle that eliminating exposure is the primary treatment for most patients, patients and parents should be counseled in the importance of:

  • Relocation, even if temporarily (rarely practical)
  • Basic handwashing in breaking the cycle of exposure
  • Monitoring for paint chips and dust in the home, and mouthing behaviors in children
  • Follow-up with a primary physician and public authorities

Follow-up is the most critical component of any response plan as relocation or ablation (profession cleaning or repair) are the only modalities proven to reduce blood lead levels in children.

 

CPS and WIC Testing Requirements

Under the Illinois Lead Poisoning Prevention Act, physicians are expected to administer a lead test annually to all children 9 months (15 months, 2 years and annual until six years of age) for those  “who are determined to reside in an area defined as high risk by the Department [of Public Health of the State of Illinois]”.  All of Chicago has been defined as high risk by the Department. although CPS only requires lead testing for children entering preschool or kindergarten up to age six.  To help define WIC eligibility, the USDA has created a series of “nutritional risk criteria” which include anemia and lead exposure.  Individual states determine which of these criteria to apply, with Illinois requiring screening for both.

 

Because of prevalence, risk, Illinois public policy and law, and WIC requirements, it is policy to administer an annual lead test to all children between the ages of 9 months to six years requesting a routine physical exam or believed to be at risk for lead exposure.

 

For More Information:

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Illinois Revised Statutes, Chapter 410, Paragraph 45
“Lead Poisoning Prevention Act”

 

References

  1. Chandran, Latha, and Rosa Cataldo. Lead poisoning: basics and new developments. Pediatrics in Review 31.10 (2010): 399-406.
  2. Laraque, Danielle, and Leonardo Trasande. Lead Poisoning Successes and 21st Century Challenges. Pediatrics in Review 26.12 (2005): 435-443.
  3. Markowitz,Morri Lead Poisoning Pediatrics in Review October 2000
  4. Rogan W, Dietrich K, et al. The Effect Of Chelation Therapy with Succicmer on Neuropsychological Development in Children Exposed to Lead NEJM Vol 344 No. 19 May 10, 2001 Pg 1421
  5. Canfield R. et al. Intellectual Impairment in Children with Blood Lead Concentrations below 10 ug per Deciliter. NEJM 348:16 pg 1517. April 17, 2003
  6. Dietrich K.N. Effect of Chelation Theray on Neuropsychological Development.  Pediatrics July 2004
  7. American Academy of Pediatrics Policy Statement, Lead Exposure in Children: Prevention, Detection, and Management.  Pediatrics Oct. 2005
  8. Laraque D. and Trasande L. Lead Poisoning: Success and 21st Century Challenges.  Pediatrics in Review December 2005
  9. Binns H et al. Interpreting and Managing Blood Lead Levels of Less than 10 in Children and Reducing Childhood Exposure to Lead: Recommendations of the Center for Disease Control and Prevention Advisory Committee on Lead Poisoning Prevention.  Pediatrics Nov 2007
  10. MMWR August 2012 Lead in Drinking Water and Human Blood Lead Levels in the United States
  11. American Academy of Pediatrics, Committee on Environmental Health. “Lead Exposure in Children: Prevention, Detection, and Management.”  Pediatrics, 2005; 116(4):1036-1046.

 

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