Pilot study for utilization of dried blood spots for screening of lead, mercury and cadmium in newborns.

The exposure of pregnant women and young children to environmental pollutants is an ongoing concern of state and local public health departments. Of primary concern is the exposure to lead in lead-based paints, methyl mercury in contaminated fish and cadmium present at mining sites. The feasibility, utility and methodology of using blood spot cards collected for new born health screening purposes was studied for use in conducting routine state-wide surveillance of blood lead, mercury and cadmium levels in infants. Homogeneity of different lots of blank filter paper was examined. Mass measurements (weights) of filter paper punches were taken across three different lots of filter paper. Statistical analysis of the data was performed using one-way ANOVA, which indicated no significant difference in the means of all three lots, but high variances were noted. The three metals were examined in three different lots of filter papers purchased from the manufacturer. The lots had measurable amounts of cadmium and lead, but not mercury. Lead spike values were observed for roughly about 7% of the blank samples, indicating heterogeneous distribution of this metal. Statistical analysis of the data was also performed using a two-way ANOVA calculation with Tukey's pairwise comparisons. The results found that total mean metal loadings across the three lots were different. The concentration of the metals can be different from each other and the concentration of any one metal can differ across lots. Stability at different concentrations of the heavy metals in blood spotted onto filter paper with time and storage conditions was examined. Results indicate acceptable performance for at least 8.5 months for lead (near CDC's concern level) and for mercury (near NRC's concern level). The filter paper and blood spots were analyzed for metals using an acid extraction, followed by analysis using an inductively coupled plasma mass spectrometer (ICP-MS). Blood spot cards were studied from four different states across the Rocky Mountain region. Internal blank punches adjacent to the blood spot and actual dried spot punches from the same card were analyzed simultaneously. The blank punch indicated the amount of contamination present in the blood spot sample. Statistical analysis of the data was performed using MANOVA followed by calculations for each metal separately. This method was found to be suitable for assessing maternal exposure to lead and mercury using residual newborn screening specimens. Additional research into the applicability for cadmium is needed. Because of the intrinsic problem of contamination from the skin surface of capillary blood samples or other internal or extraneous sources, automatic re-analysis of elevated results assures minimal false positives are reported.