Lead has been regarded as a toxic substance since the time of the Romans. It is ubiquitous in our environment, and its toxic properties have been written about for centuries. Exposure to lead is known to produce a spectrum of injury, particularly in children, yet society continues to struggle with its negative impacts on human health.
In this article, Environmental Expert, Michael Klein, P.E. provides an overview of why lead has become ubiquitous in modern society. Within the context of municipal water systems, he discusses the steps that are being taken to safeguard human health from toxic lead exposures.
Lead: The (Once) Logical Choice
The positive attributes of lead have made it a popular choice with artists, craftsmen, and engineers for more than 8,000 years. Available in abundance, lead is commonly found in nature combined with other elements, but can be extracted and refined with relatively simple processes. In addition to its abundance and ease of refinement, the physical properties of lead contribute to its popularity; lead offers a low melting point, is resistant to corrosion, and is highly malleable.
Lead continues to be prominently used in industrial processes and non-consumer products worldwide. Examples of modern applications for lead are numerous and include batteries, industrial paint products, radiation shields, and other uses. If not for the toxicity of this element, lead would play an even more prominent role in consumer products and infrastructure.
How Does Lead Get Into Water?
There are a number of scenarios that can potentially introduce lead into drinking water, but this article will focus exclusively on water distribution networks. While lead exposure can result from contamination of the source water or lead content in ceramics or other drinkware, those scenarios represent widely differing pathways of exposure and different regulatory frameworks.
Contamination in Distribution Networks
The installation of lead pipes in the United States on a major scale began in the late 1800s, particularly in larger cities. By 1900, more than 70% of cities with populations greater than 30,000 used lead constructed water conveyance lines. Although lead was more expensive than iron (the material of choice until that time), lead pipes had 2 significant advantages over iron ones: they lasted much longer than iron (about 35 years compared with 16) and, because they are more malleable, they could be more easily bent around existing structures.
Lead in drinking water is likely from the lead in household plumbing or service lines. Older homes, built prior to the mid-1950s, are more likely to have lead pipes and service lines. Homes built between the mid-1950s and 1989 are not likely to have lead pipes or service lines. However, there may be lead in some fixtures or solder used to connect the pipes. Homes built after 1989 are unlikely to have lead in pipes, service lines, solder or joints. Submersible pumps, especially the leaded-brass variety are also a source of lead contamination and have been found to release lead into the water supply under certain environmental conditions and, therefore, may be a concern for those that rely on a well to supply potable water.
The amount of lead from the plumbing system that may be dissolved depends upon several factors. This includes acidity or pH, water temperature, the age of the plumbing, water quality and standing time of the water in the plumbing system.
- Under the U.S. Environmental Protection Agency’s (EPA) 1991 Lead and Copper Rule (LCR), municipal water utilities must sample a population number of homes at high risk for elevated lead levels, such as those known to have leaded plumbing components. The size of the municipal water system determines how many samples must be collected in each sampling period (the maximum required is 100), and the sampling interval can vary from 6 months to 3 years, depending on past compliance. Under the LCR, utilities are required to notify customers and take remedial action if more than 10% of the households sampled have tap water with lead levels exceeding 15 part per billion (ppb). The remedial action to reduce the lead levels in the water might include changing chemical treatment methods to make the water less corrosive or, if treatment fails, to replace lead pipes that lie beneath publicly owned spaces such as streets and sidewalks.
Health Effects of Lead Consumption
Lead is a cumulative toxicant that affects multiple body systems and is particularly harmful to young children. Young children are particularly vulnerable to the toxic effects of lead and can suffer profound and permanent adverse health effects, particularly affecting the development of the brain and nervous system. Lead also causes long-term harm in adults, including increased risk of high blood pressure and kidney damage. Exposure of pregnant women to high levels of lead can cause miscarriage, stillbirth, premature birth and low birth weight, as well as minor malformations.
Removing Lead from Drinking Water
Lead can only be prevented from entering the water by reducing the corrosiveness of the water to acceptable levels and by replacing water mains, service connections and household plumbing containing lead. At the point of use, a water filter that is attached to the tap can be used to lower lead to acceptable levels. The filter should conform to the National Sanitation Foundation (NSF) International standard for reducing lead (NSF/ANSI 53). An up to date listing of filters that meet the NSF 53 standard for lead can be found at http://www.nsf.org/certified/dwtu.
Boiling water will not remove lead and, in fact, may concentrate lead levels as some of the water evaporates during boiling. Houses with lead service lines or where lead is a concern and the drinking water has been sitting in the lines for 6 hours or more should flush the water system by running the cold water faucet for at least 5 minutes or until the water gets very cold prior to use. This helps to rid the lead that may have leached out of pipes while the water was standing in the piping. In addition, homes where lead is an issue should not consume water from the hot water tap as heated water may contain higher lead levels.
Where lead has been demonstrated to be an issue, water suppliers should consider the adoption of appropriate corrosion control measures including addition of corrosion inhibitors and monitoring pH and alkalinity levels in the piping system as this will reduce lead levels in finished water.
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Civil Engineer & Environmental Expert
Michael has operated water, waste water, and industrial treatment systems and has conducted and directed environmental investigations and hazardous waste remediation per the Environmental Protection Agency (EPA) Superfund requirements. This experience in the management of hazardous materials was performed under the regulatory framework as administered by the Department of Energy (DOE), EPA, Occupational Safety and Health Administration (OSHA) and Department of Transportation (DOT).
Michael is a Professional Engineer (P.E.) registered by the National Council of Examiners for Engineering & Surveying (NCEES), licensed in more than fifteen states and the District of Columbia.