Children can be exposed to lead from multiple sources. Because leaded gasoline was a common high dose source of exposure for children living in urban area of Kinshasa [the ambient air levels in Kinshasa, ranging from 570 to 5220 ng/m3 in urban area in 2008 before the total phasing out ], the focus of public health efforts should continue to be on phousing out exposure to leaded gasoline.
However, there are other less-common sources of lead in Kinshasa that also have high-lead content. Since 2003–2008, Tuakuila et al. [15, 16] have provided valuable information on urban population’s BLLs and risk factors for elevated BLLs in Kinshasa. Other possible sources of lead exposure (GM, 95% CI) in Kinshasa include house paint chips (25 μg/g [15 – 36]), house Portland cement (15 μg/g [12 – 20]), indoor dust (720 μg/m2 [555 – 934]), playing area outdoor soil (39 μg/g [22 – 67]), drinking water (0.24 μg/L [0.16 – 0.37]), fired clay use for the traditional treatment of gastritis by pregnant women (190 μg/g [142 – 255]), car batteries recycling activities in certain residences (lead in soil was 51 μg/g [15 – 181] vs 35 μg/g [18 – 64] in residences without these activities). Because these surveys are based on an urban representative sample, estimates can be generalized only to the Kinshasa urban population, the sample is not designed to provide estimates for specific groups of DRC population such as others cities, rural or industrial areas where the studies of BLLs and the risk of elevated BLLs are not known. Local surveillance data are needed to assess and manage local risks.
Regarding our study population, great care was taken to select a representative sample of the Kinshasa children. In the absence of reliable demographic data, it is not possible to assess the exact representativeness of our sample. However, there are no reasons to suspect a bias caused by self- selection based on either high or low exposure to lead.
Demographic characteristics (age and sex) of children in this study were compared to those found in the same population in 2004 and 2008 [15, 16]. No significant differences were observed between the subgroup studied (Table 1), indicating that our sampling strategy (unweighted clusters) did probably not introduce a strong bias in the representativeness of our population sample.
The samples from 2004 and 2008 were analyzed in a different way (GFAAS) as those in 2011(ICP-MS). The ICP-MS method allows analyses of lead with low detection limits as compared to GFAAS method. However, analytical results are not significantly different [18–20]. Both methods can be used as a routine analytical method for the determination of lead in human blood samples .
Between 2004 and 2011 significant reductions in the BLLs of children from urban area of Kinshasa were observed (Table 3; Figures 1 and 2), with a consequent reduction in the proportion of children at risk of the neurobehavioral and other health and social ill effects associated with elevated lead exposure. It is highly likely that this reduction, at least in part, is associated with the introduction of unleaded gasoline since 2005 and completed in 2009. There is little evidence to indicate that factors such as lead water adduction pipes, socio economic status or industrial activities might have made a major contribution to the reductions in BLLs observed. First, while the BLLs of children were 12.4 μg/dL and 11.2 μg/dL in 2004 and 2008 respectively, lead stands at concentrations of 4 μg/L in drinking water  which is less than the 10 μg/L threshold set by the WHO. Second, according to PRB 2010 world population, 80% of population in DRC live under 2 dollars per day. Third, there are no industry releasing significant amounts of lead nor landfills were located near the study places .
The reductions in BLLs observed among children in this study are broadly comparable with what observed in several African countries . Data suggest that following the phase-out of leaded gasoline, the evidence of reduced levels is positive (12.4 μg/dL to 8.7 μg/dL), but many children still have levels that may harm their health. This may affect their neurobehavioral performance [1, 4, 8, 23]. Lead poisoning remains also highly prevalent among children in others African cities. For example, the BLLs were 6.4 μg/dL in South Africa  and 7.15 μg/dL in Uganda  after at least 4 years of the phase out of leaded gasoline. In 2007–2008 an investigation into the deaths of eighteen children living on the periphery of the City of Dakar, Senegal, showed severe lead poisoning from recycling of lead batteries in many households as the cause .
The prevalence of elevated BLLs in current study (41%) decreased dramatically as it was in 2004 (63%) and 2008 (71%), probably because of the DRC has recently completed in 2009 the phase out of lead in gasoline: a 30% decrease 2 years after the phase out of lead in gasoline began compared with studies the same population before the phase out [15, 16]. Predictable reductions in BLLs have been described in several countries [12, 13]. However, the prevalence of elevated BBLs in Kinshasa remains higher as compared with other African nations: 10% in South Africa  and 20.2% in Uganda , and continue to constitute a major public health concern, especially because of three insights. First, about 35% of children in current study had BLLs between 10 to 14 μg/dL (Figure 2), as it is known, the severity of signs and symptoms of lead poisoning increases with exposure . Second is the special susceptibility of children, even relatively low levels of exposure: lead can cause serious and in some cases, irreversible neurologic damage, leading to permanent intellectual impairment . Third, BLLs < 10 μg/dL have been associated with cognitive impairment and recent evidence suggests that there may be no safe level [3–9, 23].