Validation of a screening kit to identify environmental lead hazards.

In many states, environmental lead hazards are evaluated only after a lead-poisoned child has been identified. This passive approach is problematic because only a small fraction of children are tested for lead and those with elevated blood lead levels may have irreversible developmental damage. In order to reverse this paradigm, a new lead screening kit was developed. In this study, we validated the accuracy of the kit compared to the conventional methods. Forty-five participants used the kit to collect 3 dust, 3 soil and 2 paint samples in their homes. A researcher performed an in-situ analysis of the lead content in the paint and soil using a portable X-ray fluorescence (XRF) spectrometer. The soil, paint, and dust samples collected by the participants were then analyzed by XRF ex-situ. A strong linear correlation was found between the in-situ and ex-situ measurements for soil and dust samples, and a reasonable correlation was obtained for lead content of paint samples. The kit had very high degrees of specificity (true negative rate) and sensitivity (true positive rate) for detecting hazardous levels of lead in soil and dust samples. The agreement was more moderate for paint samples because some of the paint chips provided gave different readings from the front or back surface, but in-situ XRF only reads from the front surface. Overall, the kit gave a sensitivity of 87%, a specificity of 98% and an accuracy of 96% for detection of environmental lead hazards in samples collected from the home by untrained citizens. This suggests that widespread and inexpensive lead screening could be used to successfully identify hazards and ultimately decrease environmental lead exposure in children.

Risky bismuth: Distinguishing between lead contamination sources in soils.

In a broad environmental study in St. Joseph County, Indiana, elemental data from ∼2000 soil samples and ∼800 paint samples were collected with X-ray Fluorescence (XRF) spectroscopy. The observed lead concentrations were compared to other elemental concentrations in these data. A strong correlation between lead and bismuth concentrations was observed in a subset of the soil samples and in nearly all of the paint samples, with lead levels approximately 150 times higher than bismuth. However, some soil samples contained lead with no bismuth present. Since most lead sources likely contain bismuth as an impurity from refining of native lead ore, but leaded gasoline does not contain any bismuth impurities due to the manufacturing process of tetraethyl lead, it may be possible to distinguish environmental lead sources by XRF. To test if leaded gasoline could be the source of lead in the subset of soil samples containing no bismuth, leaded paint samples were analyzed with Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP-OES), which confirmed the presence of bismuth in leaded paint. Aviation gasoline, which contains tetraethyl lead, was also analyzed by ICP-OES to confirm the absence of bismuth in leaded gasoline. This discovery suggests that XRF can be used to rapidly distinguish different legacy lead contamination sources from one another. For low lead concentrations, elemental measurements of bismuth by ICP-OES can be used in environmental forensics to distinguish leaded gasoline contamination from other sources of lead.