Immediate and one-year post-intervention effectiveness of Maryland's lead law treatments

A 1994 Maryland law prescribes a lead-based paint risk reduction standard for pre-1950, privately owned rental housing. This standard, applied at each tenancy change, can be met by sampling to verify that dust lead loadings are within acceptable limits or by performing specific lead hazard reduction treatments, followed by an independent visual inspection without dust sampling. We evaluated the ability of visual inspection to predict treatment completion and dust lead loadings. Fifty-two Baltimore housing units were enrolled and received the law-specified treatments. Before treatment, study risk assessors conducted visual assessments and dust lead wipe sampling in each unit. After treatment, Maryland-certified visual inspectors conducted the law's required visual inspection, followed by the study risk assessors, who performed a separate visual assessment and collected dust wipe samples. One year later, study risk assessors performed another visual assessment and dust wipe sampling (n=34). Dust lead loadings declined significantly immediately after prescribed lead treatments were implemented. Fifty-three percent, 20%, and 47% of units had at least one sample that exceeded 1995 EPA/HUD floor, window sill and window trough clearance guidance of 100, 500 and 800 microg/ft2, respectively. Overall, 73% of units had one or more immediate post-intervention single surface sample results exceeding the 1995 clearance values that were in effect at the time of the study. One-year post-intervention loadings remained significantly below pre-intervention levels for floors but not window sills or troughs. Visual assessments alone, without dust lead testing, did not ensure that prescribed treatments were completed or that dust lead loadings were below clearance values.