Using colorimetric wipes to characterize lead surface levels in lead-exposed construction workers' homes and vehicles

Lead home investigations following the confirmation of a lead-poisoned child in the home require a lead-certified technician using an X-ray-fluorescence (XRF) portable analyzer, but XRFs are not always available. Colorimetric surface wipes that immediately change color on a gradient from yellow-to-red with lead could address this gap, but they have not been tested or utilized extensively in non-occupational settings.

To understand the usability of colorimetric wipes in lead home investigations with different potential sources of lead.

We collected 104 colorimetric wipes to assess lead levels on surfaces from nine homes and seven vehicles from lead-exposed construction workers living with children. Colorimetric wipe results (n = 81) were compared with inductively coupled plasma optical emission spectroscopy laboratory analysis.

Lead was detected on 46(58%) of home surface wipes, with highest percentage of red wipes from surfaces in kitchen, followed by entrance, living room, bedroom, and laundry room samples. For vehicle surface wipes, 17 (71%) detected lead, with the highest percent of red wipes in the trunk, followed by back and front seat areas. Wipe color readings were significantly and positively correlated with laboratory analysis (Kendall's τ = 0.42). At the 18 μg/sample threshold (i.e., level at which the wipe is expected to turn pink/red), the method showed high specificity (87%), moderate accuracy (78%), high negative predictive value (87%), and low false positive rate (13%). Of the wipes above 10 µg/sample public-health lead guideline, 80% changed color, suggesting high sensitivity.

The dissemination of colorimetric wipes for lead home investigations can reduce costs and improve the immediate screening of lead dust-contaminated surfaces in residential settings. Colorimetric wipes proved invaluable in identifying sources from lead take-home and lead-in-paint in the homes and vehicles of lead-exposed construction workers.