There are few well-established risk factors for childhood leukemias. While the frequency of childhood leukemias might be partially attributable to some diseases (accounting for a small fraction of cases) or ionizing radiation, the role of heavy metals has not been assessed. The objective of our study was to assess the potential association between levels of cadmium (Cd) and lead (PB) in soil and childhood leukemias incidence. We conducted a population-based case–control study of childhood leukaemia in Spain, covering 2897 incident cases gathered from the Spanish Registry of Childhood Tumours and including 14 Spanish Regions with a total population of 5,307,433 children (period 1996–2015). Cd and Pb bioavailable levels at every children’s home address were estimated using data from the Geochemical Atlas of Spain. We used logistic regression to estimate odds ratios (ORs) and their 95% confidence intervals (95%CIs); we included as covariates: sex, rurality, employment rate and socioeconomic status. Metal levels were analysed according to two definitions: as continuous variable assuming linearity and as categorical variables to explore a potentially nonlinear association (quantiles). Increases in both Cd and Pb topsoil levels were associated with increased probability of childhood leukemias incidence. The results for the models with the continuous variables showed that a unit increase on the topsoil level was associated with an OR of 1.11 for Cd (95%CI 1.00–1.24) and an OR of 1.10 for Pb (95%CI 0.99–1.21). Our study may point towards a possible link between residential Cd and Pb topsoil levels and the probability of childhood leukemias incidence. Residing in a location with the highest concentrations of these heavy metals compared to those locations with the lowest could increase the risk around a 20%, for both Cd and Pb.

儿童白血病几乎没有公认的危险因素。虽然儿童白血病的频率可能部分归因于某些疾病（占病例的一小部分）或电离辐射，但尚未评估重金属的作用。我们研究的目的是评估土壤中镉 (Cd) 和铅 (PB) 水平与儿童白血病发病率之间的潜在关联。我们在西班牙进行了一项基于人群的儿童白血病病例对照研究，涵盖了从西班牙儿童肿瘤登记处收集的 2897 例事件病例，其中包括 14 个西班牙地区，总人口为 5,307,433 名儿童（1996-2015 年期间）。使用西班牙地球化学地图集的数据估计每个儿童家庭住址的 Cd 和 Pb 生物可利用水平。我们使用逻辑回归来估计优势比 (OR) 及其 95% 置信区间 (95% CI)；我们将性别、农村、就业率和社会经济地位作为协变量。根据两个定义分析金属水平：作为假设线性的连续变量和作为探索潜在非线性关联（分位数）的分类变量。Cd 和 Pb 表层土壤水平的增加与儿童白血病发病率的增加有关。具有连续变量的模型的结果表明，表土水平的单位增加与 Cd 的 OR 为 1.11 (95%CI 1.00–1.24) 和 Pb 的 OR 为 1.10 (95%CI 0.99–1.21) 相关. 我们的研究可能指出住宅表层土壤镉和铅水平与儿童白血病发病率之间可能存在联系。