Short Communication
Blood lead levels in children attending a tertiary teaching hospital in Enugu, southeastern Nigeria Emmanuel I. Ugwuja1, Innocent S. I. Ogbu2, Elizabeth A. Umeaku2, Festus C. Otuu2 1
Department of Chemical Pathology, Faculty of Clinical Medicine, Ebonyi State University, Abakaliki, Nigeria, Department of Medical Laboratory Science, College of Medicine, University of Nigeria, Enugu, Nigeria
2
Background: Reports have demonstrated widespread lead contamination of the Enugu environment and the possibility of childhood lead poisoning. Objective: To determine the blood lead levels of children attending University of Nigeria Teaching Hospital, Ituku Ozalla, Enugu, Enugu State. Method: Blood samples from 100 children were analysed for blood lead concentration using an atomic absorption spectrometer. Results: The mean (SD) age was 6.2 (2.13) years (range 1–15) and the mean (SD) blood lead level was 8.7 (5.4) mg/dl (range 0.3–17.7). Thirty-three per cent of the children had blood lead levels .10 mg/dl, which is the United States Center for Disease Prevention and Control action limit, and 36% of the children had blood lead levels of 5–10 mg/dl. Mean (SD) blood lead level in the 6–10-years age group was 11.3 (5.7) mg/dl and 9.4 (4.6) mg/dl in the .10-years age group, which is significantly higher than in the 1–5-years age group [7.5 (5.1) mg/dl, P50.03]. Males had significantly higher mean (SD) blood lead levels than females [9.6 (5.8) vs 6.8 (3.8), P50.03]. Conclusion: One-third of children had blood lead levels .10 mg/dl, particularly older and male children. Blood lead screening should be considered for sick children, and further screening of blood lead levels in children should be undertaken in Enugu and other parts of Nigeria, and efforts made to identify the sources of exposure. Keywords: Blood lead level, Lead poisoning, Screening, Enugu
Introduction Lead poisoning in children is a major health problem worldwide.1 Although Nigeria switched to unleaded gasoline in 2003, other identified sources of lead exposure include flaking house paint, use of traditional medicine, lead-contaminated food and water, and use of unregulated cosmetics.2 The extensive industrial use of lead has also contributed to environmental contamination. The prevalence of children’s elevated blood lead levels (.10 mg/dl) ranged from 34% to 70% in different geographical locations in Nigeria.3–5 In 2010, massive lead poisoning was reported in some villages in the north-central state of Zamfara which claimed the lives of about 355 children,6 particularly in the town of Bagega where an estimated 1500 children were exposed to lead poisoning.7 Well water in Enugu was Correspondence to: E I Ugwuja, Department of Chemical Pathology, Faculty of Clinical Medicine, Ebonyi State University, PMB 053, Abakaliki, Nigeria. Email: [email protected]
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found to be contaminated with lead.8 Lead poisoning in children is defined as blood lead levels (BLL) of .10 mg/dl.9 Lead is toxic to the heart,10 kidneys11,12 and the reproductive and nervous systems.11–14 At blood lead levels .10 mg/dl, there is a high probability of permanent neurological damage1 which manifests as low intelligent quotient (IQ), reduced short-term memory, decreased attention, reading and arithmetic ability, poorer fine motor skills, and impaired emotional regulation and social engagement.14 Exposure to lead during childhood has also been associated with anti-social behaviour later in life.10,15,16 Children absorb ingested lead10 more readily than adults and this may partly explain why the effects of lead are more serious in children than in adults.17 Symptoms of lead poisoning are non-specific and the condition may not be suspected when an exposed child presents to the clinic. The aim of this study was to determine blood lead levels in children attending the Paediatric Out-Patient Department.
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Subjects and Methods Study location The study was conducted in the Paediatric OutPatient Department of the University of Nigeria Teaching Hospital, Ituku Ozalla, Enugu in southeastern Nigeria. Enugu has a population of 722,664. It is located in the Cross River basin and the Benue trough at an elevation of 1000 m. The highlands surrounding Enugu are mostly sandstone and the lowlands are on shale. The average annual rainfall is around 2000 mm.
Blood lead levels in children
Children were allocated to the following age groups: #5 years, 6–10 years and §10 years. The Ethics and Research Committee of the University of Nigeria Teaching Hospital, Ituku Ozalla approved the study protocol.
Statistical analysis The data were analysed for mean and standard deviations, and comparison of means was undertaken using the paired t-test with statistical significance set at P(0.05.
Subjects
Results
Children aged 1–15 years were recruited from the Paediatric Out-Patient Clinic between June and August 2011. The children were attending the hospital for various health problems. During this period, a total of 133 children were seen at the clinic. The aims of the study were explained to the parents, after which their consent was sought. Patients included in the study were those whose parents reside in the Enugu metropolis, who freely gave their consent to participate in the study, those whose health problems were minor, such as malaria, and those attending for a general check-up. Children with major conditions such as seizures, neurological disorders and other symptoms that could be associated with lead toxicity were excluded from the study. A total of 100 children were recruited.
Blood lead levels ranged from 0.3 to 17.7 mg/dl with a mean (SD) of 8.7 (5.4). 33% (33/100) of the children had blood lead levels .10 mg/dl, 36% had levels ranging from 5 to 10 mg/dl and 31% had levels ,5 mg/ dl. Children in the age groups #5, 6–10 and .10 years had mean (SD) blood lead of 7.5 (5.1) mg/dl, 11.3 (5.7) mg/dl and 9.4 (4.6) mg/dl, respectively (Table 1). Blood lead levels were significantly higher in older children (Fig. 1). Males had significantly higher mean (SD) blood lead levels than females [9.6 (5.8) vs 6.8 (3.8) mg/dl, P50.03].
Laboratory methods Venous blood samples were collected into lead-free navy-blue top vacutainer tubes (Becton-Dickinson, Rutherford, NJ, USA) containing sodium heparin and stored at 4uC prior to lead analysis. An atomic absorption spectrophotometer (Bulk Scientific, AVG model 201) equipped with a graphite furnace with a detection limit of 1.0 mg/dl was used to measure lead levels. Analysis of each sample was performed in duplicate, and the mean of both measurements used as the final value. To prevent contamination, all glassware was routinely washed and soaked in two successive dilute nitric acid baths (0.8 mg/L) and then thoroughly rinsed in ultra-pure double-distilled deionized water. Additionally, all reagents, glassware and sample collection devices were checked for contamination by lead. No contamination was found when randomly selected tubes used to collect and store blood for lead assay were tested. Briefly, the tubes were washed with 10% nitric acid (HNO3) and the effluent measured by atomic absorption spectrophotometer, as described by Jacobson et al.18 for low lead concentration. Certified lead reference solutions (obtained from Sigma-Aldrich Co. LLC, USA) for atomic spectrometry were used as a control. Based on the current United States’ CDC’s action limit, blood lead levels .10 mg/dl were regarded as elevated.12
Discussion This study shows that one-third of children in the Enugu area have blood lead levels .10 mg/dl and onethird had levels in the range of 5–10 mg/dl. A report by CDC in the United States found that 6% of American children aged 1–2 years and 11% of black (nonHispanic) children aged 1–5 years had levels .10 mg/ dl.1 A study of lead exposure in two geographical wards in Jos, Nigeria, found that up to 34% of children had levels .10 mg/dl.3 This was an improvement on the 70%5 recorded earlier in the same geographical location. Another survey of three communities in Nigeria showed that 45% of children had blood lead levels .10 mg/dl.4 It has been established that childhood lead poisoning is directly associated with handto-mouth-related activities.5,19,20 A study in Enugu reported mean (SD) lead levels in paint flakes from residential buildings to be in the range of 39.4 (1.1) to 69.8 (4.9) mg/dl with the highest levels being found in housing mainly for the under-privileged.21 Higher than recommended lead levels have been reported for paints manufactured in Nigeria.22 In such an environment, Table 1 Blood lead levels in 100 children in relation to age range Blood lead level, mg/dl Age range, y
Minimum
Maximum
Mean (SD)
#5 (n563) 6–10 (n524) .10 (n513)
0.3 3.8 4.3
17.3 17.7 16.2
7.5 (5.1)* 11.3 (5.7){ 9.4 (4.6){
*{ Values with different symbols are significantly different (P,0.05)
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engage in more activities that could expose them to lead contamination. Older children are also more exposed to environmental lead contamination through consumption of food sold at the roadside. High lead levels have been reported in some foods sold in outdoor markets in Nigeria.36–38 High blood lead levels in younger children is ascribed to flaking house paint, living near a gasoline seller, male gender, increasing maternal and paternal education, use of a lead ore eye cosmetic, being of Muslim faith and living near a battery smelter.3 Thus, while high blood lead levels in younger children may be caused by increased hand-to mouth activity in the home, higher levels in older children might result from cumulative exposure during early childhood and increased exposure from the outdoor environment.36–38 The lack of a significant difference between mean levels in children aged 6–10 years and those aged .10 years agrees with a study which reported a lack of difference in levels between the ages of 3–6 and 7– 15 years.39 The higher blood lead levels in males is similar to other studies in children5 and adults.40 Higher blood lead levels in adult males is attributed to the effects of environmental and occupational exposure and to lifestyle factors. In the case of children, boys may be more reckless than girls and indulge in more activities that can expose them to lead. Children in Enugu are exposed to unacceptable levels of lead, as in other parts of Nigeria. There is a need for public health education on the dangers of lead poisoning. Further studies are required to identify the sources of lead exposure in Nigeria. Paediatricians should be aware of the possibility of lead poisoning in their patients.
Figure 1 Scatterplot of blood lead levels against age
children are exposed to lead through contact with leadcontaminated, dust, soil, paint and water during indoor/outdoor play. In addition to the home environment, children can also be exposed to lead in domestic water supplies: a dangerously high lead content (well above the WHO tolerable limit) has been reported in well water in Enugu.8 The persistent shortage of potable water in Enugu and its environs means that residents are obliged to make frequent and extensive use of well water for domestic purposes. This might have contributed in part to the high prevalence of elevated blood lead levels observed in this study and supports other studies which demonstrate that Nigerian children are exposed to unacceptable levels of environmental lead.23 Studies have reported symptoms of lead poisoning even at blood levels well below 10 mg/dl.24–26 Although lead exposure is harmful to adults as well as children, children are more susceptible to the neurobehavioural toxicity of lead exposure because of their developing nervous systems and higher lead absorption rates, and also because they are more likely to engage in hand-to-mouth practices which are likely to expose them to lead contamination.10,27–29 Lead is a cumulative metabolic poison with no known physiological relevance which may cause widespread toxicity in exposed individuals.1,30 Lead generates reactive species in the body which damage cell structures by combining with S-containing amino acids and interfering with oxygen transport and energy generation,31 DNA transcription,32 synthesis of vitamin D and cell membrane integrity.33 Additionally, lead causes massive enzyme inhibition in the body by displacing their natural co-factors which are also metal ions such as zinc, calcium and iron,12 and causes anaemia by inhibiting d-amiolevulinic acid dehydratase and ferrochelatase.17 In children, these biochemical effects may impair proper growth and development, which may have an impact later in adulthood.10,15,16 The significantly higher blood lead levels in the older children in this study is in agreement with other reports.34,35 Children under 5 years of age receive more supervision than older children who are freer to
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References 1 Centers for Disease Control and Prevention. General Lead Information: Questions and Answers, 2007. Available at: www.cdc.gov/exposurereport/metals/pdf/lead.pdf 2 Adekunle IM, Ogundele JA, Oguntoye O, Akinloye OA. Assessment of blood and urine Pb levels of some pregnant women residing in Lagos, Nigeria. Environ Monit Assess. 2010;170:467–74. 3 Wright NJ, Thacher TD, Pfitzner, MA, Fischer PR, Pettifor JM. Causes of lead toxicity in a Nigerian city. Arch Dis Child. 2005;90:262–626. 4 Keating EM, Fischer PR, Pettifor JM, Pfitzner M, Isichei CO, Thacher TD. The effect of calcium supplementation on blood lead levels in Nigerian children. J Pediatr. 2011;159:845–50. 5 Pfitzner MA, Thacher TD, Pettifor JM, Zoakah AI, Lawson JO, Fischer PR. Prevalence of elevated blood lead levels in Nigerian children. Ambul Child Health. 2000;6:115–23. 6 Yahaya S. Lead poisoning from mining kills 163 in Nigeria. Thomson Reuters, 2010. http://www.reuters.com/article/2010/ 06/04/us-nigeria-poisoning-idUSTRE6534JE20100604 7 Me´decins Sans Frontie`res. Lead Poisoning Crisis in Zamfara State, Northern Nigeria: MSF Briefing Paper, 2012. Available at: www.msf.org 8 Ogbu ISI, Onyekwere TO. Lead content of well water in Enugu South – East Nigeria. J Coll Med. 2004;9:119–20. 9 Harvey B, ed. Managing elevated blood lead levels among young children: Recommendations from the Advisory Committee on Childhood Lead Poisoning Prevention.
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12
13 14
15 16 17
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19 20 21 22
23 24
Atlanta, GA: Centers for Disease Control and Prevention, 2002. Needleman H. Lead poisoning. Ann Rev Med. 2004;55:209–22. Rubin R, Strayer DS, eds. Environmental and nutritional pathology. Rubin’s Pathology: Clinicopathologic Foundations of Medicine, 5th edn. Philadelphia, PA: Lippincott Williams and Wilkins, 2008; pp 266–71. Xu J, Yan HC, Yang B, Tong LS, Zou YX, Tian Y. Effects of lead exposure on hippocampal metabotropic glutamate receptor subtype 3 and 7 in developmental rats. J Neg Results Biomed. 2009;8:5–8. Dart RC, Hurlbut KM, Boyer-Hassen LV. Lead. In: Dart RC, ed. Medical Toxicology, 3rd edn. Philadelphia, PA: Lippincott Williams & Wilkins, 2004; pp 1426–36. Cleveland LM, Minter ML, Cobb KA, Scott AA, German VF. Lead hazards for pregnant women and children: part 1: immigrants and the poor shoulder most of the burden of lead exposure in this country. Part 1 of a two-part article details how exposure happens, whom it affects, and the harm it can do. Am J Nurs. 2008;108:40–9. Nevin R. How lead exposure relates to temporal changes in IQ, violent crime, and unwed pregnancy. Environ Res. 2000;83:1– 22. Nevin R. Understanding international crime trends: the legacy of preschool lead exposure. Environ Res. 2007;104:315–36. Barbosa F Jr, Tanus-Santos JE, Gerlach RF, Parsons PJ. A critical review of biomarkers used for monitoring human exposure to lead: advantages, limitations, and future needs. Environ Health Perspect. 2005;113:1669–74. Jacobson BE, Lokltch O, Qulgley GC. Improve sample preparation for accurate determination of low concentration of Pb in whole blood by graphite furnace analysis. Clin Chem. 1991;37:515–19. Chisolm JJ, Hanson HE. The exposure of children to lead. Pediatrics. 1956;18:943–58. Griggs RC, Sunshine I, Newill VA, Newton BW, Buchanan S, Rasch CA. Environmental factors in childhood lead poisoning. JAMA. 1964;187:703–7. Nduka JKC, Orisakwe OE. Maduawguna CA. Lead Levels in paint flakes from buildings in Nigeria: a preliminary study. Toxicol Indust Health. 2008;24:539. Adebamowo EO, Clark CS, Roda S, Agbede OA, Mynepalli KCS, Adebamowo CA. Lead content of dried films of domestic paints currently sold in Nigeria. Sci Total Environ. 2007;388:116–20. Vaziri ND. Mehanisms of lead-induced hypertension and cardiovascular disease. Am J Physiol Heart Circulatory Physiol. 2008;295:454–65. Schwartz J, Otto D. Lead and minor hearing impairment. Arch Environ Health. 1991;46:300–5.
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25 Schwartz J. Low level exposure in children’s IQ: a metal analysis and search for a threshold. Environ Res. 1994;65: 42– 55. 26 Fulton M, Raab G, Thomson G, Laxen D, Hunter R, Hepburn W. Influence of blood lead on the ability and attainment of children in Edinburgh. Lancet. 1987;1:1221–6. 27 Baghurst P, McMichael A, Wigg N, Vimpani G, Robertson E, Roberts R, et al. Environmental exposure to lead and children’s intelligence at the age of seven years. The Port Pirie Cohort Study. N Engl J Med. 1992;327:1279–84. 28 Bellinger DC. Lead. Pediatrics. 2004;113:1016–22. 29 Lidsky TI, Schneider JS. Lead neurotoxicity in children: basic mechanisms and clinical correlates. Brain. 2003;126:5–19. 30 World Health Organization. Guidelines for Drinking Water Quality, volume 2. Health Criteria and other Supporting Information. Geneva: WHO, 1984; pp 111–19. 31 White LD, Cory-Slechta DA, Gilbert ME, Tiffany-Castiglioni E, Zawia NH, Virgolini M, et al. New and evolving concepts in the neurotoxicology of lead. Toxicol Appl Pharmacol. 2007;225:1–27. 32 Drill S, Lowe B, Meyer D. The environmental lead problem in multimedia perspective in Canada. J Appl Physiol. 1979;98:2201–6. 33 Flora SJ, Mittal M, Mehta A. Heavy metal induced oxidative stress and its possible reversal by chelation therapy. Indian J Med Res. 2008;128:501–23. 34 Hense HW, Filipiak B, Novak L, Stoeppher M. Nonoccupational determinants of blood lead concentrations in a general population. J Epidemiol. 1992;21:753–62. 35 Watanabe T, Nakatsuko H, Shimbo S. Reduced cadmium and lead burden in the past 10 years in Japan. Intern Arch Occup Environ Health. 1996;68:305–14. 36 Adekunle IM, Olorundare O, Nwange. Assessments of Pb levels and daily intakes from green leafy vegetables of southwest Nigeria. Nutr Food Sci. 2009;39:413–22. 37 Nnorom IC, Igwe JC, Oji-Nnorom CG. Trace metal contents of facial (make-up) cosmetics commonly used in Nigeria. Afr J Biotech. 2005;4:1133–8. 38 Maduabuchi JMU, Nzegwu CN, Adigba EO, Aloke RU, Ezomike CN, Okocha CE, et al. Pb and cadmium exposures from canned and non-canned beverages in Nigeria: a public health concern. Sci Total Environ. 2006;366:621–6. 39 Onag A, Oksel F, Taneli B, Hakerlerler H. Environmental exposure to cadmium and lead in the pediatric age group. Water Air Soil Pollut. 1997;105:661–5. 40 Sirivarasai J, Kaojaren S, Wananukul W, Srisomerang P. Nonoccupational determinants of cadmium and lead in blood and urine among a general population in Thailand. Southeast Asian J Trop Med Public Health. 2000;3:180–7.
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Blood lead levels in children attending a tertiary teaching hospital in Enugu, southeastern Nigeria Emmanuel I. Ugwuja1, Innocent S. I. Ogbu2, Elizabeth A. Umeaku2, Festus C. Otuu2 1
Department of Chemical Pathology, Faculty of Clinical Medicine, Ebonyi State University, Abakaliki, Nigeria, Department of Medical Laboratory Science, College of Medicine, University of Nigeria, Enugu, Nigeria
2
Background: Reports have demonstrated widespread lead contamination of the Enugu environment and the possibility of childhood lead poisoning. Objective: To determine the blood lead levels of children attending University of Nigeria Teaching Hospital, Ituku Ozalla, Enugu, Enugu State. Method: Blood samples from 100 children were analysed for blood lead concentration using an atomic absorption spectrometer. Results: The mean (SD) age was 6.2 (2.13) years (range 1–15) and the mean (SD) blood lead level was 8.7 (5.4) mg/dl (range 0.3–17.7). Thirty-three per cent of the children had blood lead levels .10 mg/dl, which is the United States Center for Disease Prevention and Control action limit, and 36% of the children had blood lead levels of 5–10 mg/dl. Mean (SD) blood lead level in the 6–10-years age group was 11.3 (5.7) mg/dl and 9.4 (4.6) mg/dl in the .10-years age group, which is significantly higher than in the 1–5-years age group [7.5 (5.1) mg/dl, P50.03]. Males had significantly higher mean (SD) blood lead levels than females [9.6 (5.8) vs 6.8 (3.8), P50.03]. Conclusion: One-third of children had blood lead levels .10 mg/dl, particularly older and male children. Blood lead screening should be considered for sick children, and further screening of blood lead levels in children should be undertaken in Enugu and other parts of Nigeria, and efforts made to identify the sources of exposure. Keywords: Blood lead level, Lead poisoning, Screening, Enugu
Introduction Lead poisoning in children is a major health problem worldwide.1 Although Nigeria switched to unleaded gasoline in 2003, other identified sources of lead exposure include flaking house paint, use of traditional medicine, lead-contaminated food and water, and use of unregulated cosmetics.2 The extensive industrial use of lead has also contributed to environmental contamination. The prevalence of children’s elevated blood lead levels (.10 mg/dl) ranged from 34% to 70% in different geographical locations in Nigeria.3–5 In 2010, massive lead poisoning was reported in some villages in the north-central state of Zamfara which claimed the lives of about 355 children,6 particularly in the town of Bagega where an estimated 1500 children were exposed to lead poisoning.7 Well water in Enugu was Correspondence to: E I Ugwuja, Department of Chemical Pathology, Faculty of Clinical Medicine, Ebonyi State University, PMB 053, Abakaliki, Nigeria. Email: [email protected]
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found to be contaminated with lead.8 Lead poisoning in children is defined as blood lead levels (BLL) of .10 mg/dl.9 Lead is toxic to the heart,10 kidneys11,12 and the reproductive and nervous systems.11–14 At blood lead levels .10 mg/dl, there is a high probability of permanent neurological damage1 which manifests as low intelligent quotient (IQ), reduced short-term memory, decreased attention, reading and arithmetic ability, poorer fine motor skills, and impaired emotional regulation and social engagement.14 Exposure to lead during childhood has also been associated with anti-social behaviour later in life.10,15,16 Children absorb ingested lead10 more readily than adults and this may partly explain why the effects of lead are more serious in children than in adults.17 Symptoms of lead poisoning are non-specific and the condition may not be suspected when an exposed child presents to the clinic. The aim of this study was to determine blood lead levels in children attending the Paediatric Out-Patient Department.
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Subjects and Methods Study location The study was conducted in the Paediatric OutPatient Department of the University of Nigeria Teaching Hospital, Ituku Ozalla, Enugu in southeastern Nigeria. Enugu has a population of 722,664. It is located in the Cross River basin and the Benue trough at an elevation of 1000 m. The highlands surrounding Enugu are mostly sandstone and the lowlands are on shale. The average annual rainfall is around 2000 mm.
Blood lead levels in children
Children were allocated to the following age groups: #5 years, 6–10 years and §10 years. The Ethics and Research Committee of the University of Nigeria Teaching Hospital, Ituku Ozalla approved the study protocol.
Statistical analysis The data were analysed for mean and standard deviations, and comparison of means was undertaken using the paired t-test with statistical significance set at P(0.05.
Subjects
Results
Children aged 1–15 years were recruited from the Paediatric Out-Patient Clinic between June and August 2011. The children were attending the hospital for various health problems. During this period, a total of 133 children were seen at the clinic. The aims of the study were explained to the parents, after which their consent was sought. Patients included in the study were those whose parents reside in the Enugu metropolis, who freely gave their consent to participate in the study, those whose health problems were minor, such as malaria, and those attending for a general check-up. Children with major conditions such as seizures, neurological disorders and other symptoms that could be associated with lead toxicity were excluded from the study. A total of 100 children were recruited.
Blood lead levels ranged from 0.3 to 17.7 mg/dl with a mean (SD) of 8.7 (5.4). 33% (33/100) of the children had blood lead levels .10 mg/dl, 36% had levels ranging from 5 to 10 mg/dl and 31% had levels ,5 mg/ dl. Children in the age groups #5, 6–10 and .10 years had mean (SD) blood lead of 7.5 (5.1) mg/dl, 11.3 (5.7) mg/dl and 9.4 (4.6) mg/dl, respectively (Table 1). Blood lead levels were significantly higher in older children (Fig. 1). Males had significantly higher mean (SD) blood lead levels than females [9.6 (5.8) vs 6.8 (3.8) mg/dl, P50.03].
Laboratory methods Venous blood samples were collected into lead-free navy-blue top vacutainer tubes (Becton-Dickinson, Rutherford, NJ, USA) containing sodium heparin and stored at 4uC prior to lead analysis. An atomic absorption spectrophotometer (Bulk Scientific, AVG model 201) equipped with a graphite furnace with a detection limit of 1.0 mg/dl was used to measure lead levels. Analysis of each sample was performed in duplicate, and the mean of both measurements used as the final value. To prevent contamination, all glassware was routinely washed and soaked in two successive dilute nitric acid baths (0.8 mg/L) and then thoroughly rinsed in ultra-pure double-distilled deionized water. Additionally, all reagents, glassware and sample collection devices were checked for contamination by lead. No contamination was found when randomly selected tubes used to collect and store blood for lead assay were tested. Briefly, the tubes were washed with 10% nitric acid (HNO3) and the effluent measured by atomic absorption spectrophotometer, as described by Jacobson et al.18 for low lead concentration. Certified lead reference solutions (obtained from Sigma-Aldrich Co. LLC, USA) for atomic spectrometry were used as a control. Based on the current United States’ CDC’s action limit, blood lead levels .10 mg/dl were regarded as elevated.12
Discussion This study shows that one-third of children in the Enugu area have blood lead levels .10 mg/dl and onethird had levels in the range of 5–10 mg/dl. A report by CDC in the United States found that 6% of American children aged 1–2 years and 11% of black (nonHispanic) children aged 1–5 years had levels .10 mg/ dl.1 A study of lead exposure in two geographical wards in Jos, Nigeria, found that up to 34% of children had levels .10 mg/dl.3 This was an improvement on the 70%5 recorded earlier in the same geographical location. Another survey of three communities in Nigeria showed that 45% of children had blood lead levels .10 mg/dl.4 It has been established that childhood lead poisoning is directly associated with handto-mouth-related activities.5,19,20 A study in Enugu reported mean (SD) lead levels in paint flakes from residential buildings to be in the range of 39.4 (1.1) to 69.8 (4.9) mg/dl with the highest levels being found in housing mainly for the under-privileged.21 Higher than recommended lead levels have been reported for paints manufactured in Nigeria.22 In such an environment, Table 1 Blood lead levels in 100 children in relation to age range Blood lead level, mg/dl Age range, y
Minimum
Maximum
Mean (SD)
#5 (n563) 6–10 (n524) .10 (n513)
0.3 3.8 4.3
17.3 17.7 16.2
7.5 (5.1)* 11.3 (5.7){ 9.4 (4.6){
*{ Values with different symbols are significantly different (P,0.05)
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engage in more activities that could expose them to lead contamination. Older children are also more exposed to environmental lead contamination through consumption of food sold at the roadside. High lead levels have been reported in some foods sold in outdoor markets in Nigeria.36–38 High blood lead levels in younger children is ascribed to flaking house paint, living near a gasoline seller, male gender, increasing maternal and paternal education, use of a lead ore eye cosmetic, being of Muslim faith and living near a battery smelter.3 Thus, while high blood lead levels in younger children may be caused by increased hand-to mouth activity in the home, higher levels in older children might result from cumulative exposure during early childhood and increased exposure from the outdoor environment.36–38 The lack of a significant difference between mean levels in children aged 6–10 years and those aged .10 years agrees with a study which reported a lack of difference in levels between the ages of 3–6 and 7– 15 years.39 The higher blood lead levels in males is similar to other studies in children5 and adults.40 Higher blood lead levels in adult males is attributed to the effects of environmental and occupational exposure and to lifestyle factors. In the case of children, boys may be more reckless than girls and indulge in more activities that can expose them to lead. Children in Enugu are exposed to unacceptable levels of lead, as in other parts of Nigeria. There is a need for public health education on the dangers of lead poisoning. Further studies are required to identify the sources of lead exposure in Nigeria. Paediatricians should be aware of the possibility of lead poisoning in their patients.
Figure 1 Scatterplot of blood lead levels against age
children are exposed to lead through contact with leadcontaminated, dust, soil, paint and water during indoor/outdoor play. In addition to the home environment, children can also be exposed to lead in domestic water supplies: a dangerously high lead content (well above the WHO tolerable limit) has been reported in well water in Enugu.8 The persistent shortage of potable water in Enugu and its environs means that residents are obliged to make frequent and extensive use of well water for domestic purposes. This might have contributed in part to the high prevalence of elevated blood lead levels observed in this study and supports other studies which demonstrate that Nigerian children are exposed to unacceptable levels of environmental lead.23 Studies have reported symptoms of lead poisoning even at blood levels well below 10 mg/dl.24–26 Although lead exposure is harmful to adults as well as children, children are more susceptible to the neurobehavioural toxicity of lead exposure because of their developing nervous systems and higher lead absorption rates, and also because they are more likely to engage in hand-to-mouth practices which are likely to expose them to lead contamination.10,27–29 Lead is a cumulative metabolic poison with no known physiological relevance which may cause widespread toxicity in exposed individuals.1,30 Lead generates reactive species in the body which damage cell structures by combining with S-containing amino acids and interfering with oxygen transport and energy generation,31 DNA transcription,32 synthesis of vitamin D and cell membrane integrity.33 Additionally, lead causes massive enzyme inhibition in the body by displacing their natural co-factors which are also metal ions such as zinc, calcium and iron,12 and causes anaemia by inhibiting d-amiolevulinic acid dehydratase and ferrochelatase.17 In children, these biochemical effects may impair proper growth and development, which may have an impact later in adulthood.10,15,16 The significantly higher blood lead levels in the older children in this study is in agreement with other reports.34,35 Children under 5 years of age receive more supervision than older children who are freer to
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