Lead in Drinking Water

As issues with lead in drinking water increase across the US, we take a look here at the background to lead in water; the causes, the consequences, and how it can be managed.

Most water treatment works have effective processes for removing lead from source water to below safe levels. In the recent contamination examples of both Flint (U.S) and Hong Kong, the lead was not present in the water leaving the treatment works but entered the stream as it travelled to users’ homes – through lead distribution pipes in Flint and high lead content soldering in Hong Kong.

Whilst the source of lead may be different, the root causes are the same: cutting corners to cut costs. In Hong Kong, the use of cheap, poorly regulated construction contractors resulted in pipes being soldered with material that contained up to 500 times the safe limit of lead. In Flint, a change of water source and lack of proper treatment caused the phosphate lining of the lead distribution pipes to erode, exposing the water to a lead source. These issues were compounded with a lack of proper testing that made it impossible to take the right action early on. Inevitably, the lead from both sources leached into the drinking water, taking it past safe drinking limits by orders of magnitude.

Background to lead in water

Lead is a pervasive environmental contaminant. The adverse health effects of lead exposure in children and adults are well documented, and no safe blood lead threshold in children has been identified. Lead can be ingested from various sources, including lead paint and house dust contaminated by lead paint, as well as soil, drinking water, and food. In 2004, 143,000 deaths and a loss of almost 9 million disease-adjusted life years were attributed to lead exposure worldwide, primarily from lead-associated adult cardiovascular disease and mild intellectual disability in children. As children absorb lead more readily than adults and represent approximately 80% of the disease impact attributed to lead, policies and actions within the United States have focused on the younger population.

Figure 1 – Timeline of lead poisoning prevention policies and blood lead levels in children aged 1 to 5 years old, categorised by year. Source: National Health and Nutrition Examination Survey, United States, 1971-2008.

Beginning in the 1970s, lead concentrations in air, drinking water, food, dust and soil began to be substantially reduced, resulting in significantly reduced blood lead levels (BLLs) in children throughout the United States.

As a result of the overall reduction of lead in the environment, there was an estimated decrease in BLLs of around 15 μg/dL (150 μg/litre) and a related estimated economic benefit of $110–$300 million in earnings for children born after 1976 who were not exposed to high levels of lead. A recent cost-benefit analysis suggested that for every dollar spent to reduce lead hazards, $17–$220 is saved. This cost-benefit ratio compares favourably to that of other public health interventions such as vaccines.

Current situation

Many homes however, still contain drinking water service lines made from lead as well as fittings containing lead. Adequate corrosion control reduces the leaching of lead plumbing components into drinking water and the majority of public water utilities are in compliance with the Safe Drinking Water Act Lead and Copper Rule (LCR) of 1991, which has set an action level for lead of 15 μg/litre.

Since 1991, tap water lead levels in the United States have substantially decreased. However, conditions still exist that could allow children to be exposed to water lead levels greater than 15 μg/litre. Drinking water from systems with lead service lines that do not have optimised corrosion control may not be in compliance with LCR and even systems with lead service lines that are in compliance can still expose children to lead levels greater than 15 μg/litre because the LCR permits up to 10% of sampled homes to exceed the action level of 15 μg/litre.

Water from systems that serve less than 25 persons and water from private drinking water wells is not regulated under the Safe Drinking Water Act, so are not routinely tested for lead. As a consequence, it is estimated that around 40–45 million people in the United States drink water that is not subject to the LCR regulations.

Changes in water treatment and disinfection practices can also substantially undermine lead corrosion control. In the mid-1990s, the District of Columbia (DC) water utility used free chlorine to decrease coliform bacteria in water. When free chlorine was replaced with monochloramine because of carcinogen concerns, the drinking water became more corrosive and susceptible to lead leaching, producing elevated levels of lead in tap water. Only when measures to reduce corrosivity, using orthophosphates, were employed did lead levels reduce.

The continuing occurrence of elevated lead levels, from various sources, has highlighted the need for comprehensive monitoring of drinking water from the perspective of the end user, along with effective strategies when the action level has been exceeded.

Although the Environmental Protection Agency (EPA) has the primary responsibility for ensuring the safety of drinking water, state and local childhood lead poisoning prevention programs are important partners in ensuring that the public is protected from lead exposure.

SA1100 Scanning Analyzer

The SA1100 Scanning Analyzer is an accurate portable scanning voltammetry instrument certified by the EPA as an acceptable method to use in lead field analysis, with a lower limit of detection of 2 μg/L.

Independent comparative analysis demonstrated excellent correlation of test results between the SA1100 and laboratory based instrumentation. Each test using the SA1100 Scanning Analyzer takes approximately 3 minutes and costs considerably less that a test conducted by AAS.

The simplicity of the Palintest instrument made for easy integration into the testing program and the reduced cost per test allowed three times the number of sample analyses on drinking water fountains in the school facilities for the same cost. If any fountain exceeded the lead warning concentration of 10 μg/L, samples would be taken to the certified laboratory for confirmation of elevated lead levels on the AAS. In the meantime, the fountain would be immediately removed from service, thereby removing the risk and allow for swift corrective actions and location of the source of the issue in a more effective manner.

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