Médecins Sans Frontières, Amsterdam, Holland 2 Médecins Sans Frontières, London, United Kingdom 3 Department of Management, Bar Ilan University, Ramat Gan, Israel 4 London School of Hygiene & Tropical Medicine, London, United Kingdom 5 Healthy Homes/Lead Poisoning Prevention Program, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America 6 Division of Clinical Pharmacology and Toxicology, Department of Medicine, University of Colorado School of Medicine, Denver, Colorado, United States of America 7 Department of Public Health, Federal Ministry of Health, Abuja, Nigeria 8 Federal Ministry of Health, Abuja, Nigeria 9 Federal Ministry of Communication Technology, Abuja, Nigeria 10 Guy's and St. Thomas' NHS Foundation Trust, London, United Kingdom Lanphear 2014 2014 This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

Jane Greig and colleagues from the medical humanitarian organization Médecins Sans Frontières describe the use of the oral chelating agent dimercaptosuccinic acid (DMSA) in several thousand young children with severe lead poisoning as a result of an environmental disaster in Zamfara, northern Nigeria. Please see later in the article for the Editors' Summary Background In 2010, Médecins Sans Frontières (MSF) discovered extensive lead poisoning impacting several thousand children in rural northern Nigeria. An estimated 400 fatalities had occurred over 3 mo. The US Centers for Disease Control and Prevention (CDC) confirmed widespread contamination from lead-rich ore being processed for gold, and environmental management was begun. MSF commenced a medical management programme that included treatment with the oral chelating agent 2,3-dimercaptosuccinic acid (DMSA, succimer). Here we describe and evaluate the changes in venous blood lead level (VBLL) associated with DMSA treatment in the largest cohort of children ≤5 y of age with severe paediatric lead intoxication reported to date to our knowledge.

Methods and Findings In a retrospective analysis of programme data, we describe change in VBLL after DMSA treatment courses in a cohort of 1,156 children ≤5 y of age who underwent between one and 15 courses of chelation treatment. Courses of DMSA of 19 or 28 d duration administered to children with VBLL ≥ 45 µg/dl were included. Impact of DMSA was calculated as end-course VBLL as a percentage of pre-course VBLL (ECP). Mixed model regression with nested random effects was used to evaluate the relative associations of covariates with ECP. Of 3,180 treatment courses administered, 36% and 6% of courses commenced with VBLL ≥ 80 µg/dl and ≥ 120 µg/dl, respectively. Overall mean ECP was 74.5% (95% CI 69.7%–79.7%); among 159 inpatient courses, ECP was 47.7% (95% CI 39.7%–57.3%).

ECP after 19-d courses ( n = 2,262) was lower in older children, first-ever courses, courses with a longer interval since a previous course, courses with more directly observed doses, and courses with higher pre-course VBLLs. Low haemoglobin was associated with higher ECP. Twenty children aged ≤5 y who commenced chelation died during the period studied, with lead poisoning a primary factor in six deaths. Monitoring of alanine transaminase (ALT), creatinine, and full blood count revealed moderate ALT elevation in <2.5% of courses. No clinically severe adverse drug effects were observed, and no laboratory findings required discontinuation of treatment. Limitations include that this was a retrospective analysis of clinical data, and unmeasured variables related to environmental exposures could not be accounted for. Conclusions Oral DMSA was a pharmacodynamically effective chelating agent for the treatment of severe childhood lead poisoning in a resource-limited setting. Re-exposure to lead, despite efforts to remediate the environment, and non-adherence may have influenced the impact of outpatient treatment.

Please see later in the article for the Editors' Summary Editors' Summary Background Lead, a toxic metal that occurs naturally in the earth's crust, is now present throughout the environment because of human activities. For many years, lead was added to paint and gasoline and used in solder for water pipes. In addition, the mining, smelting, and refining of some metallic ores releases lead into the environment. Inhalation of contaminated air, consumption of contaminated food and water, and contact with dust that contains lead raises venous blood lead levels (VBLLs) and causes many health problems, particularly in children. Children who ingest large amounts of lead can develop anemia, muscle weakness, kidney damage, and life-threatening encephalopathy (brain swelling). Although fatal lead poisoning is now rare in resource-rich countries, it nevertheless remains a major global health problem. Over a three-month period in early 2010, for example, about 400 young children died in Zamfara State, Nigeria, from unexplained, intractable fits. By May 2010, it was clear that recently expanded gold mining had caused widespread environmental lead contamination in the region, and an environmental management program was begun to reduce lead levels in the surface soils.

Why Was This Study Done? In response to the lead poisoning outbreak, the not-for-profit organization Médecins Sans Frontières (MSF) began a medical management program to reduce VBLLs that included treatment with the oral chelation agent dimercaptosuccinic acid (DMSA). Chelation agents bind metal ions and facilitate their removal from the body, thereby reducing the likelihood of lead moving from the blood to the brain. Lead encephalopathy has been commonly treated by injecting another chelator called CaNa2EDTA, but the discovery of more than 1,000 cases of childhood lead poisoning in rural villages in Nigeria meant that MSF needed a chelation approach that could be applied rapidly in a remote resource-limited setting. Additionally, although CaNa2EDTA has been in common use for severe lead poisoning for longer than DMSA, and is commonly recommended in guidelines, the evidence base does not support one treatment as superior.

Here, in a retrospective analysis of MSF program data, the researchers evaluate the changes in VBLLs before and after courses of oral DMSA treatment in children aged five years and below living in Zamfara to gain new insights into this understudied treatment for severe childhood lead poisoning. What Did the Researchers Do and Find? The researchers measured VBLLs before and after treatment with DMSA in 1,156 children (inpatient and outpatient) with high amounts of lead in their blood who underwent one or more courses of chelation treatment lasting 19 or 28 days by calculating each child's end-course VBLL as a percentage of the child's pre-course VBLL (ECP). Considering all the treatment courses given between June 2010 and June 2011, the mean (average) ECP was 74.5%. That is, on average, VBLLs measured at the end of treatment courses were reduced by a quarter compared to VBLLs at the start of treatment courses. Among 159 inpatient courses of DMSA, the ECP was 47.7% (a halving of pre-course VBLLs).

The ECP after 19-day courses was lower in older children, after first-ever courses, after courses with a longer interval since a previous course, after courses that included more directly observed doses (DMSA given in the presence of a health-care worker), and in children with higher pre-course VBLLs. Nine of the children included in this analysis died during the study period; lead poisoning was probably involved in three of these deaths. Importantly, no clinically severe adverse effects related to DMSA were seen during the study period, and no laboratory findings were recorded that required treatment discontinuation. What Do These Findings Mean? Because many changes were made to the treatment given to the affected children in Zamfara during the study period and because no information is presented here on clinical outcomes, these findings cannot be used to reach any definitive conclusions about the effectiveness or safety of oral DMSA as a treatment for lead poisoning in young children.

However, these findings show that chelation was associated with a large reduction in the death rate among probable or suspected cases of childhood lead poisoning in Zamfara and provide new information about oral chelation that may help agencies such as MSF provide urgent treatment for lead poisoning in resource-limited settings where intravenous chelation is not feasible. Moreover, the finding of a lower ECP after inpatient treatment courses compared to after outpatient courses suggests that re-exposure to lead and non-adherence to treatment may have influenced the impact of outpatient treatments. Thus, it is essential that medical management of lead poisoning in resource-limited settings be accompanied by environmental remediation and that efforts are made to support adherence to treatment in the community by implementing directly observed treatment wherever possible. Additional Information MedlinePlus provides a list of links to further information about lead poisoning (in English and Spanish) This study was funded as part of MSF operations. Lundbeck donated some DMSA, but had no role in the treatment programme or in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

The findings and conclusions in this presentation have not been formally disseminated by the Centers for Disease Control and Prevention/the Agency for Toxic Substances and Disease Registry and should not be construed to represent any agency determination or policy. Data Availability The authors confirm that, for approved reasons, some access restrictions apply to the data underlying the findings. Research data are accessible via the MSF open data policy for researchers who meet the criteria for access to confidential data ( 10.1371/journal.pmed.1001739.g004 Figure 4 Geometric mean (95% CI) of absolute pre-course and end-course VBLL for all courses nested by village and patient, by treatment dose regimen. 10.1371/journal.pmed.1001739.g005 Figure 5 Unadjusted end-course VBLL as a percentage of pre-course VBLL (ECP) by pre-course VBLL (μg/dl) (<italic>n = </italic>3,180).

10.1371/journal.pmed.1001739.g006 Figure 6 Histogram of latest VBLL during the entire study period as a percentage of pre-chelation VBLL per child. As the role of repeated courses on combined overall change cannot be extracted, change includes effect of all courses (e.g., 5-d and CaNa2EDTA courses). This does not represent the end of treatment in most cases, but rather an interim measure at the end of the study period. 10.1371/journal.pmed.1001739.t004 Number of courses by dose regimen and administration regimen. Regimen US Centers for Disease Control and Prevention (2014) CDC's national surveillance data (1997–2012). Available: Accessed 10 October 2013. 34 Morrison M (2011) Lead poisoning. In: Kliegman RM, Stanton BMD, St. Geme J, Schor N, Behrman RE, editors. Nelson textbook of pediatrics, 19th edition. Philadelphia: Elsevier. pp.

2448–2453. 35 Kosnett MJ (2005) Lead. In: Brent J, Wallace K, Phillips S, Burkhart KK, Donovan, et al.., editors. Critical care toxicology: diagnosis and management of the critically poisoned patient. Philadelphia: Elsevier. 36 Médecins Sans Frontières Ethics Review Board (2013) Standard operating procedures. Geneva: Médecins Sans Frontières. Available: Accessed 19 July 2013. 37 Brown MJ (2011) Evaluation and recommendations for preventing lead poisoning among the internally displaced roma population in Kosovo from the Centers for Disease Control and Prevention. Available: Biol trace Pb 2016 "Pb poisoning in children on a scale unheard of for decades has been detected in rural northwestern Nigeria. A total of 161 deaths in two villages have been attributed to an incident from May 2009 to May 2010, with hundreds and potentially thousands more people becoming seriously ill [7, 8].

Significant progress in understanding the effects of the neurotoxic action of Pb in young organisms had led to the creation of a system of diagnosis and treatment of lead poisoning and a gradual reduction of Bsafe^ levels in the blood to 10 μg/dL [9, 10]. " Data · May 2016 · International Journal of Environmental Research and Public Health Vertical distribution of lead (Pb) in farmlands around contaminated goldmine in Zamfara state, Northern Nigeria "After the emergence of the outbreak the Village head asked the people to move the processing from their houses to a distance of about 500 m away from their houses. According to a survey carried out by MSF, Nigeria federal and state public health agencies, U.S.

Centers for Disease Control and Prevention (CDC), TerraGraphics Environmental Engineering (TG), and the World Health Organization (WHO) about 400 children less than five years of age were killed and thousands more people are said to be affected, including more than 2000 children left with permanent disabilities (Plumlee et al., 2013; Dooyema et al., 2012; Lo et al., 2012; von Lindern et al., 2011). There still remains the risk of Pb movement to the food chain through the re-location and continued artisanal mining activities (UNICEF, 2011). " [Show abstract] [Hide abstract] ABSTRACT: Anthropogenic activities such as artisanal gold mining have been shown to contaminate soils. When these soils are cultivated, lead (Pb)-related human health risks are expected consequent to consumption of crops produced from such soil. This study was conducted with the aim of determining the vertical distribution of Pb in Pb-contaminated farmlands around contaminated goldmine.

Eight soil profile pits were dug 1 m deep and 1 m wide in eight different farmlands, two farmlands per cardinal point (North, South, East and West). Two replicates of disturbed samples were taken from each of the profile pits at incremental depths of 20 cm from soil surface up to 100 cm. Also composite samples were randomly taken at each farm where the profile pits were sunk. The vertical distribution of Pb with the highest concentration was 2025 mg kg-1 in Farm II of Dareta North at the surface soil beside the gold ore processing site. Farms in Dareta South recorded lower values than Dareta North with values ranging from 1310 to 1586 mg kg-1. All Pb concentration obtained in this study exceeds the international threshold value for Pb in soils (300 mg kg-1) for both EU and USA. These results have great health implication on cropping activities which remains the main activities of households in the village. Management practices such as those that will render Pb to become unavailable or bio-accumulated is suggested while an active legal institution should be in place to check indiscriminate gold mining.

Full-text · Article · Dec 2015 Low Levels of Awareness of Lead Hazards among Pregnant Women in a High Risk—Johannesburg Neighbourhood "Evidence of lead exposure has also been found in children's playgrounds [16], mining towns [17], subsistence fishing villages [18], and in traditional medicines [19]. Recent incidents of large-scale, community-wide lead poisoning occurred in Zamfara, Nigeria, from informal gold mining [20] and in Dakar, Senegal, from dismantling batteries [21], emphasising the ongoing risk of lead poisoning in African communities. " [Show abstract] [Hide abstract] ABSTRACT: Background: The widespread use of lead and elevated risk of lead exposure in South African children justifies a need for high levels of awareness of the sources, exposure pathways, and measures to reduce this risk in children. This study aimed to determine the levels of knowledge of lead hazards among pregnant women in an area where children had already been established to be at a high risk of lead exposure and poisoning.

Methods: Following informed consent, a structured questionnaire was administered to 119 pregnant women attending antenatal clinic services at Rahima Moosa Mother and Child Hospital, west of central Johannesburg. Questions were asked about social, demographic and residential characteristics, as well as knowledge, perceptions, behaviours and practices in relation to child lead hazards. Conclusion: Overall awareness of the dangers of lead in pregnancy was low (11%). Amongst those who had heard of it, only 15% thought that lead could cause detrimental health effects. A consequence of this low level of awareness of lead hazards is a high potential for the participants and their children to unwittingly be exposed to environmental lead from various sources, thereby undermining preventative approaches. Full-text · Article · Nov 2015 . Distribution of VBLL by neurological status in children # 5... - Figure 2 of 8 Figure 2. Distribution of VBLL by neurological status in children # 5 years, with first-ever pre-chelation VBLL $ 45 m g/dL. VBLL tested from 1 June 2010 to 30 June 2011. VBLL = venous blood lead level.

doi:10.1371/journal.pone.0093716.g002 Context Lead poisoning is not a new phenomenon. Though debate continues as to whether it was described by Hippocrates [1], and the hypothesis that it contributed to the fall of the Roman Empire remains in dispute [2,3], humans have been exposed to lead as a toxicant since at least the start of industrialisation. It continues to be a significant cause of morbidity. In 2004, lead poisoning accounted for about 0.6% of the global burden of disease and 9 million disability-adjusted-life-years [4]. Lead affects mechanisms as diverse as energy metabolism, apoptosis, cell adhesion, intercellular and intracellular signalling, protein maturation, and genetic regulation [4]. As a result, lead poisoning causes a continuum of sub-clinical and clinical features including hyper- tension [5], nephropathy [6], infertility [7], anaemia, behavioural changes including violence [8], and decreased IQ (intelligence quotient) [9]; as well as severe manifestations such as acute encephalopathy and death [10,11,12].

In resource-rich nations, deaths from lead encephalopathy are a largely historical phenomenon. Hundreds of children died from lead poisoning in the USA in the first half of the 20 th Century when lead use was widespread [13]. Lead-related deaths in US cities in the 1950s and 1960s were primarily related to lead paint ingestion [11,12]. One Baltimore hospital reported 36 cases of severe lead encephalopathy between 1954 and 1956 [14], while 38 cases were reported in Chicago between 1959 and 1963 [15] examples of a broader problem that reported figures likely grossly underestimate. The last recorded death from lead encephalopathy in the USA was in 2006 [16], preceded by one in 2000 that was itself the first since 1990 [17]. Reports of lead-related deaths are uncommon in resource-poor settings, and mostly detected though outbreaks, such as the 18 deaths in Senegal linked to lead acid battery recycling in 2007 [18].

In March 2010, a M ́decins Sans Fronti `res (MSF) disease surveillance team in Zamfara State, northern Nigeria, was contacted by leaders and health staff of a local village with reports of high mortality in young children following an unknown illness. MSF was invited to assist in investigating these reports by the state Ministry of Health. MSF carried out an initial assessment and rapidly assembled a dedicated response team and 24-hour care in the village clinic. Children presented with sudden onset of abdominal pain and/or vomiting, intractable seizures with or without fever, then sometimes rapid progression to death. Symptoms were unresponsive to initial treatment by the MSF team for common endemic diseases such as malaria and meningitis, and anti-convulsants had little effect. Over 2 months until 17 May 2010, nearly 300 children aged # 5 years presented in four villages with these symptoms with a mortality of 48%. There were anecdotal reports of a recent increase in small-scale ore processing with dry-milling to extract gold. An outbreak of severe lead poisoning was confirmed [19,20,21].

Initially, seven rural villages were identified as extremely lead contaminated due to dust dispersed by artisanal mining activities within the villages, with an estimated 3000 children aged # 5 years at risk of lead poisoning. Identification activities included active case finding by MSF and investigations by State Ministry of Health with Nigeria Centre for Disease Control and US Centers for Disease Control and Prevention (CDC, USA), and environmental testing by TerraGraphics Environmental Engineering and CDC, USA [22]. The true scale of contamination in the region remains unclear [23]. Extensive environmental remediation has been undertaken [20]. Health promotion has focused on removing the lead exposure harming children by relocating ore processing activities and minimising further lead contamination of the villages. The focus of the MSF emergency medical response was clinical lead surveillance and chelation therapy. All children aged # 5 years from the seven villages where remediation was taking place were offered screening by MSF as their villages were remediated. Treatment in the absence of environmental remediation has limited impact, so screening in unremediated villages was considered futile.

Children with venous BLL (VBLL) $ 45 m g/ dL (the MSF protocol and CDC recommended chelation threshold) from remediated villages [24] were offered chelation therapy, the outcomes of which will be reported separately. Children from unremediated villages presenting to an MSF facility with signs of encephalopathy and therefore at immediate risk of death were tested and treated with chelation therapy if required, and discharged to an uncontaminated location when possible. Although there has been some characterisation of the clinical pattern of lead toxicity [4,10,25] and the VBLL threshold for encephalopathy is often stated to be in the range of 70–100 m g/dL [4,26], there are limited data on the VBLL threshold above which life-threatening effects including encephalopathy are likely to occur in children [10,25,27,28]. In this paper we describe nearly 1000 lead exposed children with VBLL $ 45 m g/dL, and the clinical and demographic characteristics associated with neurological features using basic clinical examination.

This is the largest reported retrospective analysis of data from children # 5 years with VBLL in this range. For the period June 2010 to the end of June 2011, we included all children aged # 5 years with a first-ever VBLL $ 45 m g/dL recorded before chelation therapy and whose neurological status was recorded within 7 days of this VBLL. Screening and treatment were provided by MSF. Children were identified via an MSF door-to-door census that detailed children aged # 5 years living in each residential compound. Screening for enrolment to the MSF chelation programme included a brief clinical history and examination, with particular attention to neurological status. Neurological assessment included history of seizures, change in behaviour, delay or loss of developmental milestones, peripheral neuropathies, gait, assessment of reflexes, and level of consciousness (alert/voice/pain/unresponsive [AVPU] assessment scale [29]). Detailed demographic and clinical data were recorded on standardised forms by medical staff.

Only key data were entered into an electronic database, including enrolment data: AVPU, neurological manifestations (summarised as none, present [not severe], severe), recent seizure history (yes/no). In addition, key inpatient data were entered: seizures during hospitalisation (yes/ no; if yes, change during admission) and other neurological symptoms during hospitalisation (none, present [not severe], severe; if present, change during admission). Neurological status for this analysis was described by a composite measure of neurological signs or symptoms and AVPU as severe neurological features (1), presumptive seizures (2), mild neurological features (3), or no neurological features identified (4) (Table 1), with categories 1–3 combined as ‘‘any neurological features’’. VBLL was measured using the Lead Care II point-of-care analyser (Magellan Biosciences, Chelmsford Massachusetts), using manufacturer-recommended protocols, with samples testing above the upper limit of 65 m g/dL retested using a dilution method developed with CDC and described elsewhere [30].

Regular quality control for VBLL was provided by CDC, USA, using inductively-coupled plasma mass spectrometry (ICPMS): point-of- care values of 120 clinical samples (13% diluted in project from . 65 m g/dL) were on average 4.0 m g/dL lower than ICPMS (limits of agreement [31] 2 19.7 m g/dL to + 11.7 m g/dL). VBLL results were categorised: 45–64, 65–79, 80–99, 100–119, 120–199, $ 200 m g/dL. Haemoglobin was measured on all venous samples by the HemoCue Hb 301 point-of-care testing system (HemoCue, Angelholm, Sweden) prior to 22 nd November 2010, and by the Sysmex Automated Hematology Analyzer, KX-21N (Sysmex, Hyogo, Japan) after this date.

Venous samples were also used to assess alanine transaminase (ALT) (HumaLyser 2000 [Human, Wiesbaden, Germany]). Where symptoms such as fever were suggestive of malaria, a malaria rapid diagnostic test (RDT) was performed (HRP-2 tests as the endemic cases and seasonal outbreaks are almost exclusively due to Plasmodium falciparum ). Prevalence levels in children between the ages of 6 months to 59 months in the area are 48.2% [32]. Children with positive test results were immediately treated with artemisinin-based combi- nation therapy (ACT) for uncomplicated malaria and artemether for severe malaria. Haematological and biochemical parameters were categorised [33]: haemoglobin (g/dL) low ( , 10 if , 2 years old, , 11 if 2–5 years), high ( . 13 if , 2 years, . 14 if 2–5 years), or normal; ALT (U/L) normal (0–42), mildly elevated ( . 42–100), moderately elevated ( .

100–1000), or severely elevated ( . 1000). MUAC (mid- upper arm circumference) for nutritional status was recorded as green ( $ 135 mm), yellow ( $ 125 to , 135 mm), orange ( $ 110 to , 125 mm; moderately malnourished) or red ( , 110 mm; severely malnourished) for children aged $ 6 months, or not applicable for infants , 6 months. Age at time of VBLL was grouped as 0– , 6 months, 6– , 12 months, 1– , 2 years, 2– , 3 years, 3–5 years, based on USA Environmental Protection Agency guidance regarding behavioural and physiological development stages for environmental assessment [34]. Selected clinical and laboratory data were routinely entered into an electronic database specifically designed (by JG) to support patient care and programme management. Data were analysed using STATA 10.1 (StataCorp, Texas, USA).

Baseline characteristics were described as counts and percentages of patients in each category and compared with chi-squared or Fisher’s exact tests unless a high proportion of data was missing. VBLL by neurological status category was calculated as geometric means with 95% confidence intervals (95% CI) due to non-normally distributed data, accommodating clustering by village of residence by using robust standard errors. Log VBLL values by neurological status categories were compared by Analysis of Variance with Scheffe test between groups. Odds ratios (OR) for any neurological features (compared to none) were estimated for the following variables based on review of descriptive data, completeness and plausibility, with random effects (for village of residence as a variable potentially incorporating various unmeasured factors such as level of environmental contamination): gender; age at time of VBLL; baseline VBLL category; nutritional status (MUAC); and haemoglobin. A multivariable multi-level logistic regression random effects model to estimate adjusted OR of the outcome of any neurological symptoms included factors significant at p , 0.10 in the unadjusted analysis or with plausible epidemiolog- ical or biological association.

Backward selection was used to choose prognostic variables for the final model, discarding those no longer associated (p . 0.10) with the outcome after adjustment for other variables. P-values were calculated for the strength of association of each variable with the outcome using Wald tests, and the VBLL categorical variable assessed as continuous to test for trend. Interaction was not plausible with the retained variables. The sensitivity of the model was assessed for severity of neurological features. The role of malaria was assessed in patients who had been tested for malaria due to symptoms (33%), adjusting for age and VBLL. This study met the standards set by the independent MSF Ethics Review Board for retrospective analyses of routinely collected programmatic data [35], here being data collected to facilitate life-saving clinical care. These standards include, but are not limited to, assurances of confidentiality, involvement of local partners and minimal harm to patients. Coded identification numbers were used and personal identifiers and all unnecessary data were removed from the dataset. Review of anonymous routinely collected programmatic data does not constitute research under the National Health Research Ethics Committee of Nigeria guidelines. CDC USA staff involvement did not require CDC Human Subject Review as CDC personnel were not involved in treating patients.

Between 1 June 2010 and 30 June 2011 approximately 95% of children in the seven remediated villages were screened; 972 children met the inclusion criteria (Figure 1). Among another 160 children meeting age, VBLL and date criteria, but with inadequate record of neurological status in their clinical file, geometric mean VBLL was lower than for those with recorded neurological status (65.3 m g/dL [95%CI 61.5–69.4] vs 79.4 [95%CI 62.6–100.7]; p = 0.010), however there was no difference in the proportion female (46.9% vs 49.2%; p = 0.59), or the age distribution (p = 0.87). Among the 972 children included, 340 (35%) had a VBLL $ 80 m g/dL. The maximum VBLL recorded was 708 m g/dL.

73 (8%) children had a VBLL 120–199 m g/dL and 27 (3%) had VBLL $ 200 m g/dL (Table 2). Proportionally more children aged 1– , 2years had VBLL $ 120 m g/dL than in the other age groups (25% [39/159] vs 7% for all other ages combined [61/813; all other age groups were each separately , 13%]; p , 0.001) (Table 2). 14 children had died by 30 June 2011; lead poisoning was likely a primary cause in five of these deaths as these children had recent high VBLL (104–460 m g/dL) and symptoms consistent with lead encephalopathy, with no other obvious cause of death.

Most (885 [91%]) children had no neurological features, 34 (4%) had seizures witnessed by medical staff and/or reduced level of consciousness, 47 (5%) had a guardian-reported history of recent seizures but no altered consciousness on presentation, and six (1%) displayed some other signs of neurological abnormality (Table 3). The geometric mean VBLL for all groups with neurological features was . 100 m g/dL (157.6 m g/dL for mild neurological features, 106.9 m g/dL for presumptive seizures and 170.1 m g/dL for severe neurological features) compared with 65.9 m g/dL for those without neurological features (Table 3; Figure 2). The range of VBLL in each group was wide, such that children with no neurological features at first presentation had VBLLs up to 345 m g/dL, and children with neurological features had VBLL as low as 47 m g/dL (Table 3); only children with concurrent malaria had severe neurological features below VBLL 105 m g/dL.

Within age groups, neurological features were most common in 1– , 2 year olds (25% vs 6% for other ages; p , 0.001). 233 (72%) of 325 children tested for malaria had a positive RDT result. A positive malaria test was more common in children with neurological features than in those without (82% [56/68] vs 69% [177/257], respectively; p = 0.034) (Table 3); 19 children with neurological features did not have a malaria test recorded.

A positive malaria test was more common in children with VBLL , 80 m g/dL (n = 194 tested for malaria) who had any neurological features (95% [21/22]) compared to those without features (72% [123/172]; p = 0.016), but not significantly different with VBLL $ 80 m g/dL (76% [35/46] with neurological features vs 64% [54/ 85] without; p = 0.14). Poor nutritional status (malnourished [MUAC red or orange] vs not) was more common in children with neurological features than in those without (14% [9/66] vs 4% [31/700], respectively; p = 0.005). Most (75%) children had low haemoglobin regardless of neurological features; a non- significantly higher proportion of children with no neurological features had normal haemoglobin levels (24% vs 18%; p = 0.23).

A high proportion (24%) of children had no ALT results recorded; a low proportion of children had elevated ALT levels (9%), none were severely elevated (Table 3).

In logistic regression (unadjusted OR, random effects for village of residence), presentation with any neurological features was not associated with gender (OR = 1.08, 95%CI 0.68–1.72; p = 0.73), or low haemoglobin (OR = 1.39, 95%CI 0.77–2.50; p = 0.27), but was associated with age (highest for 1– , 2 years [OR = 9.42, 95%CI 5.23–16.96; p , 0.001] compared with 3–5 years), increasing VBLL (test for trend p , 0.001, starting from 80.0–99.9 m g/dL with OR = 3.06, 95%CI 1.43–6.53), and moderate-severe malnu- trition (OR = 4.76, 95%CI 2.02–11.31; p , 0.001).

The final multivariate analysis retained only age and VBLL as strongly associated with any neurological features after adjustment for the other factors and random effects for village (both p , 0.001). Children aged 1– , 2 years had the highest odds of neurological features compared with children age 3–5 years (adjusted OR 4.77, 95%CI 2.50–9.11); age 2– , 3 years was also associated with neurological features (adjusted OR 2.69, 95%CI 1.15–6.26) compared with children age 3–5 years.

Increasing VBLL (compared with the reference category of 45–64.9 m g/dL) was strongly associated with increased odds of neurological features (test for trend p , 0.001): adjusted OR 2.75, 95%CI 1.27–5.98 (VBLL 80–99.9 m g/dL); 3.84, 95%CI 1.62–9.09 (100–119.9 m g/ dL); and 22.95, 95%CI 10.54–49.96 ( $ 120 m g/dL) (Table 4). A sensitivity analysis using only the outcome of severe neurological features compared with all other patients gave similar overall results.

The association with VBLL was stronger and the trend robust (test for trend p , 0.001), but significant only from 100–119.9 m g/dL (adjusted OR 7.35, 95%CI 2.02–26.79; for VBLL $ 120 m g/dL adjusted OR 23.96, 95%CI 7.33–78.31). The adjusted OR were also higher for all ages with the largest associations for children aged 1– , 3 years (OR . 6 for both 1– , 2 y and 1– , 3 y) compared with children aged 3–5 years. Severe neurological features in children with a positive malaria RDT result were seen at VBLL as low as 50 m g/dL, while in those with a negative RDT the lowest VBLL with severe neurological features was 105 m g/dL, and in the one child with severe neurological features and no malaria test result the VBLL was 293 m g/dL.

In the 325 children with a malaria RDT result, the unadjusted OR of a positive RDT with any neurological features was 2.04 (95% CI 0.96–4.35; p = 0.065). After adjustment for age and VBLL there was evidence of a strong association of malaria with neurological features (adjusted OR = 3.60, 95% CI 1.42– 9.09; p = 0.007); after adjustment for malaria, age and VBLL showed a similar pattern of association with neurological features as in the entire cohort, that is, highest adjusted OR in 1– , 2 year olds and increasing adjusted OR with increasing VBLL. The MSF programmatic data collected during the response to the Zamfara lead poisoning disaster presents a cohort size and severity that is unprecedented. While lead poisoning was endemic in resource-rich countries in the early to mid-20 Century, an acute outbreak of this magnitude has not been reported in the literature. Chisolm et al .

reported 197 children exposed to lead including 41 cases of severe encephalopathy in 1952–1954 [12] and Greengard et al . reported 38 severe cases in 1962 and 1963 with blood lead levels in 20 fatalities of 90–825 m g/dL [15]. More recently, the Treatment of Lead-exposed Children (TLC) trial group reported a cohort of 780 patients, although all had VBLL , 45 m g/dL [36] and thus are not comparable with the patients in Zamfara. Reports in recent decades with similar numbers of children screened for lead poisoning have been based on general population datasets, with much lower geometric mean VBLLs, generally , 10 m g/dL [37,38]. Media reports of lead poisoning of hundreds of children in China in 2009 [39,40] indicated comparatively low lead levels, with no detailed reports published of acutely severely intoxicated children. Other recent studies have concerned low-level endemic lead poisoning [41,42].

In the 972 children included in this analysis, the geometric mean VBLL was 79.4 m g/dL, 35% had VBLL $ 80 m g/dL, and 9% had some clinically identified neurological features consistent with lead poisoning. An additional 696 children (35% of those screened) had first-ever VBLLs of 10–44.9 m g/dL and thus did not require chelation (and are not reported in this analysis), such that the range of exposure of this cohort of children is consistent with the entire clinical and sub-clinical spectrum of lead pathophysiology. Children with severe neurological features of altered consciousness or seizures witnessed by clinical staff had significantly higher VBLL than those with only a guardian-reported recent history of seizures. Having any neurological feature was strongly associated with increasing initial VBLL, with evidence of an increased OR at a VBLL of 80–99.9 m g/dL, becoming stronger at 100–119.9 m g/ dL and larger still from 120 m g/dL.

This is consistent with previous ranges given for the threshold above which encephalopathy risk is increased [4,10,26], strengthened by the robust evidence from this large cohort of poisoned children. Clinicians managing patients with lead poisoning should take into consider- ation the presence of neurological features and, particularly, the potential risk of life-threatening encephalopathy at VBLL above 80 m g/dL, particularly (as discussed in more detail below) in those with concurrent malaria. Severe neurological features were not seen below VBLL 50 m g/ dL and in the absence of a positive malaria test, not below 105 m g/ dL. Most children with neurological features at a lower VBLL ( , 80 m g/dL) also had a positive malaria test. In 325 children with symptoms suggestive of malaria who were tested by RDT, a positive result was independently associated with neurological features in addition to the trend associating increasing VBLL with neurological features. It is challenging to distinguish between features of cerebral malaria and lead encephalopathy clinically, and the presence of both lead and malaria were strongly associated with neurological features.

We postulate that it is also possible that haemolysis associated with malaria increases the relative proportion of free plasma lead at a given (whole blood) VBLL, increasing the lead available to cause encephalopathy. The interaction between malaria infection and lead toxicity is still uncertain and is an area for future research. Of children with no neurological features at the time of initial examination, 31% had VBLL $ 80 m g/dL, comparable to the United States National Academy of Sciences cohort [10]. Clinical signs and symptoms varied among children with similar blood lead levels, confirming that clinical features alone are poor predictors of the severity of lead poisoning and the risk of long-term neurological damage [21]. This variation may be due to a number of factors including duration of exposure and other factors which may influence absorption, storage, and effects of lead in the body such as genetic polymorphisms [43], co-morbidities, and essential trace element deficiency. The limited sensitivity and specificity of the neurological assessments and categorisation may also have contributed to the recorded variation. A larger proportion of children with neurological features were aged 1–3 years compared with those without neurological features.

The greatest proportion of high VBLLs were seen in children aged 1– , 2 years, and the strongest association with neurological features was in this age group after adjusting for VBLL. During the initial outbreak investigation (before lead poisoning was confirmed and before chelation therapy began) proportionally more children aged 1– , 2 years died amongst children displaying probable or suspected neurological features. We hypothesise that this risk pattern for both high VBLL and stronger association with neurological features may reflect a number of factors: variation in bioavailability of ingested lead; variation in exposure due to behavioural (i.e., hand-mouth) and developmental factors; imma- turity of the blood/brain barrier compared with older children and possibly other age-related influences on activities and movement around the contaminated villages and ore processing areas. Conversely, there are several reasons why children younger than 1 year may have been less at risk of raised VBLL and neurological effects: shorter duration of potential exposure by virtue of younger age; poorer mobility and less marked hand- mouth behaviour; and physiological variation in absorption.

However, the neurological damage done by lead, beyond fatal lead encephalopathy, is long-term [4,26] and only continued monitoring will allow us to fully document and understand the long-term sequelae of lead toxicity in this cohort. Lead poisoning related to industrial activity is an ongoing problem, with a recent outbreak in Senegal secondary to used lead acid battery recycling linked to 18 child deaths and 81 additional cases of poisoning [18]. In the United Nations-Administered Province of Kosovo, camps for internally displaced people were contaminated by industrial lead production, and children born there between 1999 and 2007 had lead levels up to 74 m g/dL [44]; children near a recently closed auto-battery recycling plant in the Dominican Republic had venous blood lead levels up to 130 m g/ dL [45]; and concerns continue about widespread exposure of children to lead from industries in China [36,46]. Other heavy metals such as mercury and cadmium also continue to cause contamination [47] and poisoning associated with industrial development [48,49].

With increased industrialisation in resource-poor countries and dumping of toxic waste, we expect greater frequency of undetected lower level poisoning and an increased risk of severe environmental toxicological emergencies. Whilst the Zamfara outbreak was at the most severe end of the spectrum, the true extent of lower-level poisoning and the implications for those exposed are unclear. Limitations to our data arise from the circumstance in which they were collected, namely an emergency humanitarian response to mass mortality and morbidity from lead poisoning. While screening was offered to all children in the seven villages remediated in the first year, tragically, hundreds of children had died before the excess mortality was notified and cause identified in these villages; these children were not included in this analysis. In the first 2 months of the response, 42 children did not have VBLL recorded immediately prior to starting chelation therapy (with an earlier screening BLL $ 65 m g/dL) due to logistical challenges, including three who had had witnessed seizures and three with presumptive seizures; these children were not included due to the likely effect of chelation on any VBLL taken after therapy was started.

Blood for VBLLs from these children were taken 1–11 days after commencing chelation therapy; 70% were still $ 80 m g/dL (range 15–241 m g/dL). Thus potentially some of the most severely poisoned children were not included in this analysis. The neurological data collected may have missed subtle neurological abnormalities that would not have been identified with the simple tools used that focused on detecting life- threatening encephalopathy. The VBLLs in the first months may not be precise due to the unanticipated need to determine appropriate dilution methods for the portable testing equipment, and because the Lead Care II will not be as precise as ICPMS. However, quality control showed that Lead Care II values were on average only 4.0 m g/dL lower than those measured using ICPMS. In addition, the multivariable model was assessed for sensitivity to excluding VBLL tests in the first months and the pattern of associations were not substantially altered (data not shown). Children with inadequately recorded neurological status at time of VBLL had a lower geometric mean VBLL, which may indicate that these children were less likely to have exhibited neurological features.

A sensitivity analysis of the model including all these patients as having had no neurological features did not alter the patterns of association (data not shown). The date of birth is often inaccurate or unknown in this remote, rural region, therefore most ages in this analysis are approximations, and thus age was categorised. In addition there was a substantial amount of missing data for some important variables such as the malaria RDT result. The fact that only symptomatic children were tested suggests that clinical malaria was present; however, as the RDT may be positive for weeks after treatment, microscopy would be needed to confirm acute infection. There is the potential that the neurological features seen may be related to comorbidities other than malaria or to permanent damage from previous high VBLLs. As with any large dataset, despite standardised forms, continuous use of data for clinical purposes, and regular data cleaning, it is possible that there was some misclassification, but this is considered unlikely to be differential. The strength of this dataset is its unequalled size, severity of lead exposure, and scope of routinely collected clinical data.

In this large cohort of 972 children exposed to environmental lead contamination, 35% of children # 5 years with a VBLL requiring chelation therapy ( $ 45 m g/dL) had VBLLs $ 80 m g/dL. There was evidence that a VBLL $ 80 m g/dL was associated with neurological features and strengthened as VBLL increased, and neurological features were also more likely in children aged 1– , 3 years compared to those 3–5 years. Severe neurological features were seen at VBLL , 105 m g/dL only if there was a concurrent positive malaria test, and among children tested for malaria, a positive malaria RDT result was strongly associated with neurological features after adjustment for age and VBLL. These results will help clinicians managing children with lead poisoning to determine which individuals are likely to be at greatest risk of developing neurological features and therefore potentially life- threatening encephalopathy. This is particularly important when managing large outbreaks for determining urgency of therapy and to help guide chelation protocols. Embed figure Published in

Question: What was the cause of an epidemic of 355 cases (46% fatal) between March and June 2010 in Zamfara State, Nigeria?
Answer: Lead poisoning