Lead in drinking water

factors affecting lead concentration, health effects, and is flushing effective

Abstract

Background: Lead is a systemic toxin that affects multiple organs and impairs physical and mental development. Although lead is ubiquitous in the environment, majority of exposures to lead is through drinking water. Lead-based plumbing components are the primary reason. Flushing is a lead reduction technique commonly used to reduce lead in drinking water, but the efficacy of the technique has been questioned. The purpose of this research project was to determine if there were significant levels of lead found in the drinking water of 12 buildings (sites) owned and operated by a Health Authority before and after 30-second flush and to determine if flushing is an effective measure to reduce lead concentrations.
Materials and Methods: Lead in drinking water data was provided by Dr. Tom Kosatsky in an Excel spreadsheet. The data contained 184 pre-flush (≥ 8-hour stagnation period) samples paired to 184 post-flush (30-second duration) samples collected at locations within the 12 different sites. The sites were labelled A to L due to confidentiality. This data was then exported to NCSS, and statistical analysis in the forms of a two tailed t-test, one tailed one sample t-test, and repeated measures ANOVA was performed to determine if a statistically significant relationship between flushing and reduced lead concentrations exists.
Results: Out of 368 samples, 28% of stagnation samples contained lead concentrations greater than the MAC (n = 103) whereas, 9% of post 30-second flush samples contained lead concentration greater than the MAC (n = 33). Lead concentrations in the drinking water samples after flushing were significantly reduced below the MAC (p = 0.00000). However, lead concentrations from samples collected at sites A, C, and G were equal to or greater than the MAC. Statistical analysis failed to reject the null hypothesis that post-flush lead concentrations for samples collected at sites A, C, and G is greater to or equal to the MAC (A: p = 0.22708, C: p = 0.06866, and G: p = 0.70589).
Conclusion: Flushing is an effective measure in reducing lead concentrations at the tap to safe levels. However, the effectiveness of flushing and flushing duration is dependent on numerous factors such as the stagnation period, amount of lead-based plumbing supplying the drinking water and building size. Longer stagnation periods, increased lead-based plumbing, and large buildings all require longer flushing times to reduce lead concentrations to below 0.005 mg/L. The results of this can study can aid governments in developing polices that will eliminate existing lead infrastructure in British Columbia and Canada. Flushing is not a long-term solution in reducing lead concentrations at the tap to below 0.005 mg/L.