compared with children whose main water source was a private well in their compound. Four water samples, including two from com- munity wells, had lead concentrations that greatly exceeded the U.S. EPA action level for drinking water of 15 ppb. Most of the compounds that engaged in ore-processing activities (67%) began them in the 12 months preceding this investigation, when child mortality also increased. Although not captured in our survey, anecdotal evidence Table 4. Potential risk factors for child mortality. Acute childhood lead poisoning in Nigeria indicates that the increase in child mortal- ity was related to the increased use of flour- grinding machines located within the villages to grind ore. Before November 2009, at least one grinder was reported by villagers to be in each of the surveyed villages, but after November 2009, villagers reported that there were up to 10 grinding machines in each vil- lage. The increase in the number of grinding machines would likely amplify the amount of ground ore around the village and in Outcome Deceased Alive Crude OR (95% CI) p-Value (UNHCR 2007). The daily U5MR of this outbreak was more than six times the UNHCR benchmark and well above the over- all U5MR in the region (217 per 1,000) and in the nation (157 per 1,000). Children ≤ 24 months of age had 2.6 times the odds of death compared with older children, consistent with previous research that indicates that younger children are at greater risk for lead poisoning. This investigation was subject to at least four limitations. First, postmortem evalua- tions and blood lead samples were not avail- able for deceased children. Thus, not all of these deaths can be reliably attributed to lead poisoning, and BLLs in children who died cannot be compared with those who lived. Second, we were unable to determine whether other unmeasured cultural or nutritional fac- tors exist that may explain some of the high mortality rates. Third, the survey and envi- ronmental sampling were conducted by local staff with limited training, and no field blanks were obtained to validate sampling methods. Variation could have occurred in the way sur- vey questions were asked or how environ- mental samples were collected. Finally, we were able to determine only an approximate U5MR for the villages before the outbreak based on regional data. Despite these limitations, it is reasonable and prudent to conclude that most of the recent childhood deaths in these villages were caused by acute lead poisoning and to take steps to stop the exposure. This conclusion is based on high environmental lead concentra- tions, the percentage of children with elevated BLLs (97% > 45 µg/dL), the high incidence of convulsions before death (82%), and the sig- nificant reduction in mortality once treatment for lead poisoning was initiated and children were removed from the source of contamina- tion. Although mortality was reduced, it will take some time to fully characterize the extent of neurological damage that has occurred in these children. In this investigation, 85% of surveyed compounds had soil lead levels > 400 ppm, and some had levels 250 times the U.S. EPA threshold. Most compounds in this rural, impoverished setting were con- structed of dirt walls and floors. Children came in direct contact with large amounts of soil through daily activities, and this provides a constant and direct route of exposure for chil- dren. We also demonstrated a relationship of increasing exposure related to increasing odds of dying, because children whose compounds contained ≤ 1,200 ppm lead were less likely to die than children whose compounds contained > 1,200 ppm lead. Moreover, environmental contamination may not be limited to soil, and contamination of water sources is also possible. In our multivariate model, the odds of death were 3.7 times greater for children who had a community well as their main source of water Environmental Health Perspectives • volume 120 | number 4 | April 2012 Potential risk factor Maternal activities Breaks ore Yes No Grinds ore Yes No Washes ore Yes No Dries ore Yes No Separates ore Yes No Other environmental risk factors Mother performs ≥ 1 ore-processing activity Mother performs 0 ore-processing activities Soil lead level in compound (ppm) < 400 400–1,200 > 1,200 Dried ore in compound Yes No Main water source Community well Private well History of animal death in compound Animal death No animal death Demographic risk factors Age Birth–24 months 25–49 months Village of residence Village A Village B Risk factors Maternal activities Breaks ore Washes ore Other environmental risk factors Lead level in compound (ppm) < 400 400–1,200 > 1,200 Main water source Demographic risk factors Age (birth–24 months vs. 25–49 months) Table 5. Significant risk factors retained in final model. 56 62 20 98 22 96 38 80 23 95 74 44 8 20 90 46 72 35 83 89 29 88 30 78 40 132 213 25 320 28 317 48 297 42 303 163 182 53 111 178 82 263 38 307 195 150 181 161 181 164 1.5 (0.96, 2.2) 2.6 (1.4, 5.0) 2.6 (1.4, 4.7) 1.7 (1.0, 3.1) 1.9 (1.2, 2.9) Reference 1.2 (0.5, 2.9) 3.4 (1.5, 7.4) 2.0 (1.3, 3.2) 2.9 (1.8, 4.8) < 0.0001 0.08 0.002 0.002 0.05 0.0037 Reference 0.7 0.0026 0.0041 3.4 (2.0, 5.7) < 0.0001 2.4 (1.5, 3.8) 0.0003 2.6 (1.6, 4.2) 1.8 (1.1, 2.7) < 0.0001 0.01 Crude OR (95% CI) 1.5 (0.96, 2.2) 2.6 (1.4, 4.7) Ref 1.2 (0.5, 2.9) 3.4 (1.5, 7.4) 3.4 (2.0, 5.7) 2.6 (1.6, 4.2) p-Value 0.08 0.002 Ref 0.7 0.0026 < 0.0001 < 0.0001 Adjusted OR (95% CI) 1.8 (1.1, 3.0) 3.4 (1.7, 6.7) Ref 1.5 (0.6, 3.8) 3.6 (1.5, 8.5) 3.7 (2.0, 6.8) 2.6 (1.6, 4.4) 605