Heavy metals in drinking water are a public health issue. These naturally occurring elements are toxic even at low concentrations and can accumulate in the body over time, a process known as bioaccumulation. Their presence in water supplies stems from both natural sources and human activities like industry and agriculture, raising global health concerns.
Common Contaminants and Their Origins
Lead
Lead is a neurotoxin that enters water supplies through the corrosion of plumbing materials. Older homes, particularly those built before 1986, often have pipes, fixtures, and solder containing lead. As these materials degrade, lead particles leach into the water. The water’s chemical properties, such as acidity and temperature, influence the corrosion rate.
Arsenic
Arsenic is a metalloid found in certain rocks and soil, from which it can dissolve into groundwater. Industrial activities like mining and smelting can release arsenic into the environment. Agricultural practices, including the use of certain pesticides and fertilizers, also contribute to its presence in water sources.
Mercury
The main sources of mercury in water are industrial waste and atmospheric deposition from burning fossil fuels like coal. This airborne mercury settles onto land and into water, eventually contaminating groundwater. Improper disposal of products containing mercury, such as batteries and fluorescent light bulbs, also contributes to this pollution.
Cadmium
Cadmium enters water systems through industrial discharge from mining and metal refining. Another source is the corrosion of galvanized pipes, as cadmium can be an impurity in the pipe’s zinc coating and leach into the water. Runoff from agricultural soils treated with certain phosphate fertilizers can also carry cadmium into water supplies.
Chromium
Chromium exists in different forms, including the beneficial nutrient Chromium-3 and the toxic Chromium-6. The main source of Chromium-6 in drinking water is industrial pollution from processes like chrome plating, wood preserving, and manufacturing dyes. It can also enter water sources through the erosion of natural chromium deposits.
Health Implications of Exposure
Exposure to heavy metals in drinking water can lead to a range of health issues, with the severity depending on the specific metal and concentration level. The effects can be acute, appearing shortly after exposure to high levels, or chronic, developing over years of exposure to lower levels. Vulnerable populations, including children, pregnant women, and individuals with pre-existing health conditions, are more susceptible to the toxic effects of these contaminants.
Lead exposure is particularly damaging to the nervous system, and its effects on the developing brains of children can be irreversible. It can lead to learning disabilities, behavioral problems, and a lower IQ. In adults, lead can cause kidney damage, reproductive issues, and high blood pressure. Arsenic is a known carcinogen, linked to an increased risk of developing skin, bladder, and lung cancers after long-term exposure.
Mercury primarily affects the nervous system and the kidneys, and chronic exposure can result in neurological damage, memory loss, and motor skill impairment. Cadmium is toxic to the kidneys and can cause them to malfunction with long-term exposure. It has also been linked to bone damage and an increased risk of certain cancers. The toxic form, Chromium-6, is also classified as a carcinogen and is associated with an increased risk of cancer when ingested.
Identifying Contamination in Your Water Supply
Since heavy metals are odorless, tasteless, and colorless, you cannot detect them through sensory examination. A primary step to understanding your water quality is to review your local water utility’s annual Consumer Confidence Report (CCR). Public water suppliers are required to produce these reports, which detail detected contaminant levels and compare them to federal safety standards. These reports are often mailed to customers or made available online.
While CCRs provide a good overview of the general water supply, they do not reflect the specific water quality at your tap, which could be affected by your home’s plumbing. For a more direct assessment, at-home test kits are available from hardware stores. These kits can provide a quick indication of certain metals but are generally less precise than professional analysis.
For the most accurate results, sending a water sample to a state-certified laboratory is the recommended method. This is particularly advisable for households with private wells, older plumbing, or specific health concerns. A certified lab can perform a detailed analysis to detect a wide range of contaminants, providing a precise picture of your water’s safety.
Water Treatment and Filtration Solutions
Several water treatment technologies are available to remove heavy metals from drinking water at home. These systems are typically installed at the point-of-entry, treating all water entering the house, or at the point-of-use, treating water at a specific tap. The choice of system depends on the specific contaminants present and their concentrations.
Reverse osmosis (RO) systems are effective at removing a wide array of contaminants, including heavy metals like lead, arsenic, and mercury. These systems work by forcing water through a semi-permeable membrane that blocks the passage of contaminant molecules. RO units are typically installed under the sink and provide purified water through a dedicated faucet.
Distillation is another method for water purification. A distillation system boils water to create steam, which is then cooled and condensed back into a liquid in a separate container, leaving heavy metals behind. While effective, distillation can be a slower process and requires more energy than other filtration methods.
Carbon filters certified by the National Sanitation Foundation (NSF) can also be a solution. It is important to look for filters specifically certified under NSF/ANSI 53, which confirms their ability to reduce health-related contaminants, including lead and mercury. These certified filters are available in various forms, such as pitchers, faucet-mounted units, and under-sink systems.