Assessment of early-life lead exposure in rural Bangladesh

Lead is a well-known neurotoxic metal and one of the most toxic chemicals in a child's environment. The aim of this study was to assess early-life lead exposure in a pristine rural area of Bangladesh. The exposure was expected to be very low because of the absence of vehicle traffic and polluting industries. Lead was measured in erythrocytes, urine, and breast milk of 500 randomly selected pregnant women, participating in a randomized food and micronutrient supplementation trial in Matlab (MINIMat). Lead was also measured in urine of their children at 1.5 and 5 years of age, and in rice, well water, cooking pots, and materials used for walls and roof. All measurements were performed using ICPMS. We found that the women had relatively high median erythrocyte lead levels, which increased considerably from early pregnancy to late lactation (81-136microg/kg), probably due to release from bone. Urinary lead concentrations were unchanged during pregnancy (median approximately 3.5microg/L) and non-linearly associated with maternal blood lead levels. Children, at 1.5 and 5 years of age, had a median urinary lead concentration of 4microg/L, i.e., similar to that in their mothers. Rice, the staple food in Matlab, collected from 63 homes of the study sample, contained 1-89microg/kg (median 13microg/kg) dry weight and seems to be an important source of lead exposure. Other sources of exposure may be cooking pots and metal sheet roof material, which were found to release up to 380 and 4200microg/L, respectively, into acidic solutions. Based on breast milk lead concentrations (median 1.3microg/L) a median daily intake of 1.2microg was estimated for 3 months old infants. However, alternatives to breast-feeding are likely to contain more lead, especially rice-based formula. To conclude, lead exposure in women and their children in a remote unpolluted area was found to be surprisingly high, which may be due to their living conditions.