Investigating Sources of Elevated Lead in Drinking Water

Abstract

Lead exposure poses as a risk factor for various adverse health effects including intellectual delays, reduced IQ, and behavioural problems in children, as well as cognitive decline in adults. Lead enters drinking water through corrosion of leaded materials such as lead pipes, solder, and brass devices.

Three rounds of residential and non-residential lead monitoring were conducted to evaluate the corrosion control implemented by Halifax Water, and to identify sites with elevated lead concentrations. Follow-up testing was conducted at several sites to determine the sources of lead, and the factors that contributed to high lead release. Finally, a bench scale experiment was conducted to determine the impacts of plumbing flux on metal release.

The lead action level for residential testing was exceeded only in the round that was conducted during the winter. Lead concentrations were also higher in the winter rounds than the fall round of non-residential sampling. The seasonal lead variation was likely caused by fluctuations in aluminum residuals in the water leaving the plant. Frequency of use, age, and outlet manufacturer were factors that were associated with elevated lead levels.

Follow-up studies were conducted at several fountains to determine the source of elevated lead levels. These fountains typically contained several leaded components and received infrequent use. Fountains with leaded components that received high, regular usage had often provided samples with low lead levels.

Drinking fountains that were banned and recalled in the US for potentially containing lead lined cooling tanks were found at eight locations throughout the study area. It was found that three of the eight likely contained the lined cooling tanks. High lead levels were present in samples collected from these fountains, even at sites with frequent usage. Low-use sites with the lead lined tank produced the highest lead levels in this study. Fountains suspected of containing lead lined tanks were removed and replaced, and the lead levels were significantly reduced at these sites.

The impact of plumbing flux on metal concentrations was relatively short in duration, lasting only a week for most metals, with the exception of tin. Lead levels were found to stabilize under all flux conditions following roughly 40 L of flushing. Flux type was the main factor contributing to the elevated metals. The traditional petroleum flux was much more resistant to flushing than the water soluble flux, as it caused elevated tin levels for several weeks and a tacky flux deposition in the copper pipe remained even three months after the start of the experiment. The high amount of chloride from the flux was aggressive towards the copper corrosion, but it is unclear if this would have led to copper pitting corrosion.