Problems for Discussion - 3 -Lead

Lead is found widely in the environment. It is extensively used in industry and has been historically used in older paint products and in gasoline. Additionally, lead has been used as both an intentional and unintentional additive to traditional and herbal medications. Around the home, lead may be found in older home water piping, as a metal used in cookware and other utensils and in crockery. Finally, lead may also be a component in various hobbies and crafts (eg pottery glazing, lead light production, soldering) As a result, lead may be persistent or unrecognised and unknowingly present in the environment both domestically and in the workplace. Chronic exposure to lead is particularly concerning in the paediatric population as neurologic impairment in a developing nervous system may result at significantly lower levels than in adults.

The management of lead exposure requires careful history taking to ascertain the source of the exposure and may include visits to the home or workplace to determine how to limit further exposure. Indications for chelation in lead poisoning vary with age and the presence of signs of toxicity. Controversy still exists as to the appropriate indications for chelation, particularly in the paediatric population, and how effective this may be in reducing mild neurologic impairment. Finally, the recommended blood lead level threshold for the development of lead-related developmental impairment in children has been falling.

• Understand the circumstances in which lead toxicity may occur.
• Understand why children are more at risk of lead poisoning.
• Discuss the target organs and clinical effects of lead poisoning.
• Outline the general approach to the management of elevated lead levels and lead poisoning.
• Compare the values of various different chelating agents used in lead poisoning.
• Discuss the role of chelation therapy in asymptomatic paediatric lead poisoning.

1. WikiTox Lead
2. Emedicine Lead
3. Mudipalli A Lead hepatotoxicity & potential health effects.Indian J Med Res. 2007 Dec;126(6):518-27 (fulltext)
4. Cunningham G.Lead–toxicology and assessment in general practice.Aust Fam Physician. 2007 Dec;36(12):1011-3 (fulltext)
5. Riddell TJ, Solon O, Quimbo SA, Tan CM, Butrick E, Peabody JW.Elevated blood-lead levels among children living in the rural Philippines.Bull World Health Organ. 2007 Sep;85(9):674-80 (fulltext)
6. Miranda ML, Kim D, Galeano MA, Paul CJ, Hull AP, Morgan SP. The relationship between early childhood blood lead levels and performance on end-of-grade tests.Environ Health Perspect. 2007 Aug;115(8):1242-7 (fulltext)
7. Kosnett MJ, Wedeen RP, Rothenberg SJ, Hipkins KL, Materna BL, Schwartz BS, Hu H, Woolf A.Recommendations for medical management of adult lead exposure.Environ Health Perspect. 2007 Mar;115(3):463-71 (fulltext)
8. Dona A, Dourakis S, Papadimitropoulos B, et al. Flour contamination as a source of lead intoxication. Clin Toxicol. 1999;37:109-12.
9. Rojas-Marcos I, Gorriz M, Santafosta E, et al. Cerebellar oedema and sideroblastic anaemia. Lancet. 2002;360:2046.
10. Campbell C, Osterhoudt KC. Prevention of childhood lead poisoning. Curr Opin Pediatr. 2000;12:428-37.
11. Rogan WJ, Dietrich KN, Ware JH, et al. The effect of chelation therapy with succimer on neuropsychological development in children exposed to lead. N Eng J Med. 2001;344:1421-6.(fulltext)
12. Kalia K, Flora SJ. Strategies for safe and effective therapeutic measures for chronic arsenic and lead poisoning. J Occup Health. 2005 Jan;47(1):1-21 (fulltext)

A 3-year-old Australian-born Vietnamese boy is referred to your toxicology unit for assessment of lead poisoning after his LMO performed a finger-prick lead test that was elevated at 37 mg/dL (1.78 mmol/L). He has previously been well with normal development. The patient has an older male sibling with a diagnosis of attention deficit disorder.

His height and weight are plotted on the 25th-centile for age. Exam reveals a healthy looking child with a normal physical and neurologic exam for age.

1. Outline what further information you would like to elicit from the child’s parents to help make a risk assessment?
2. Are you aware of any data on the pharmacokinetics of lead?
3. What are the limitations of finger-stick blood level estimations?
4. What further investigations would you recommend and how may these investigations aid in your assessment of this child?
5. The child’s parents have heard of medication that could be taken orally to ‘get rid of the lead’. What medications are available for oral chelation in lead poisoning?
6. The appropriate level for chelation in children with elevated blood lead levels is a topic of constant debate among toxicologists and paediatricians as seen in some of the references cited. What are the indications for chelation in childhood lead poisoning? Is it possible to make concrete recommendations based on the current knowledge available?

A 56-year-old radiator mechanic is referred to you by an occupational physician for assessment of an elevated blood lead level. He has complained of headaches and poor concentration for about 2 months. Past history reveals hypertension treated with ramipril.

On examination: HR85 bpm, BP 150/84, Temp 36 deg C, GCS 15, pupils equal and reactive, fundoscopy normal. Cardiovascular, respiratory and gastrointestinal examinations are all normal. Neurological exam: no focal signs, normal power and coordination, generally brisk reflexes and down-going plantar responses. His mini-mental state score is 29/30.

Hb 112 g/L, WCC 8.0, plts 234. Na 146, K 4.3, Ur 8.0, Cr 130, LFTs: GGT 98 otherwise ‘normal’. Whole blood lead level is 69 µg/dL (3.3 mmol/L).

1. What further history would you like to elicit regarding this patient?
2. What are the potential occupational sources of lead for this patient?
3. What investigations might be useful to assess this man further?
4. What are the indications for chelation in a case of adult lead poisoning?
5. Should this patient receive chelation therapy? If yes, which agents should be used and how should they be administered?
6. How may the occupational physician be of benefit in this case?