NSF/ANSI 53 lead-certified point-of-use filters (POUs) have been distributed to consumers in many cities facing lead-in-water crises including Washington, D.C., Flint, MI, Newark, NJ, and University Park, IL. After questions repeatedly arose about POU effectiveness in treating samples with relatively high levels of lead, we examined 10 POU pitcher and faucet filter brands under extreme conditions (e.g., ≤200% of rated capacity, influent lead levels of ≈1000 μg/L). Our tests sought to validate the successful performance documented in some field testing and replicate the underperformance observed in others. While verifying very good performance (i.e., <10 μg/L effluent lead) across most brands and situations, we encountered a few failures, including leaking units, premature clogging, and a filter with a large hole in the medium. We also synthesized waters with colloidal lead that proved to be especially difficult to treat, as evidenced by 50% of influent lead passing through some replicate POUs that would have passed NSF/ANSI 53 lead certification testing. While the POUs almost always dramatically reduced consumer lead exposure level, even when operated beyond their rated capacity, this study highlights instances in which treated water exceeded thresholds of 5, 10, and even 15 μg/L lead.

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