Presence and concentration of lead in keys and keyring items

Environmental lead is a persistent hazard that disproportionately affects children. Keys are known sources of lead exposure in children, but little is known about the specific lead content or frequency of lead in keys. We identified differences in lead concentration and frequency across items with different physical characteristics.

This study tested a convenience sample of keys and keychain objects using an X-ray Fluorescence (XRF) analyzer.

The mean lead concentration across 362 objects tested was 1722 ppm (SD 3657 ppm; range 95.5-44 400 ppm). Lead was present in the majority (64%) of objects tested. Door keys had the highest concentration of lead (mean 2646 ppm; SD 3701 ppm). Door keys had significantly more lead than both vehicle keys (p<0.0001) and electronic fobs (p=0.0004). Gold-coloured keys contained significantly more lead than silver-coloured keys (p<0.0001). Copied keys were significantly more likely to contain detectable levels of lead compared with original keys (p<0.0001); however, this relationship was not significant when controlling for key type. There was a positive association between key age and lead concentration (p=0.009).

Keys were less likely to contain lead if they were silver-coloured; car keys or electronic fobs; and newer. However, several categories of keys with less lead contained high lead levels, and the majority of items tested (64%) contained more lead than limits on lead in keys that were implemented in Minnesota after data collection (90 ppm). The levels of lead identified highlight the need for public education and potential additional regulatory guidelines for keys.