Water Pollution's Cancerous Impact: Understanding The Toxic Link

Water pollution is a pressing issue that poses significant risks to human health, including an increased likelihood of cancer. A range of contaminants, from arsenic to radioactive materials and disinfection byproducts, have been linked to various forms of cancer. The presence of these carcinogens in drinking water has been associated with thousands of cancer cases, with the number potentially exceeding 100,000 in the US alone. This issue is not limited to a specific region, as both surface water and groundwater sources are affected, and the legal limits for contaminants have not kept pace with the latest scientific findings. As a result, even water that meets legal specifications may still pose health risks.

Arsenic in drinking water

Arsenic is a naturally occurring element that can be found in the earth's crust, air, water, and land. It is highly toxic in its inorganic form and can pose a significant threat to public health when present in drinking water. Ingesting high levels of arsenic is a known cause of bladder cancer, and long-term exposure to inorganic arsenic in drinking water can lead to chronic arsenic poisoning, with skin lesions and skin cancer being the most characteristic effects.

The International Agency for Research on Cancer (IARC) has classified arsenic and arsenic compounds as carcinogenic to humans, and arsenic in drinking water is specifically listed as carcinogenic. In addition to skin cancer, long-term exposure to arsenic may also cause cancers of the bladder, liver, lungs, and kidneys. The first symptoms of long-term exposure are usually observed in the skin and include pigmentation changes, skin lesions, and hard patches on the palms and soles of the feet. These changes may occur after a minimum of five years of exposure and can be a precursor to skin cancer.

According to a study by the Environmental Working Group, contaminated tap water causes 100,000 cancer cases in the US over a lifetime, with most of the risk coming from naturally occurring arsenic. Systems that rely on groundwater sources, such as aquifers, have higher concentrations of arsenic and contribute to a higher risk of cancer. It is estimated that more than 350,000 people in the United States may be supplied with water containing arsenic levels above the acceptable limit.

The current recommended limit of arsenic in drinking water is 10 μg/L, set by the World Health Organization (WHO). However, millions of people worldwide are exposed to arsenic at concentrations much higher than this guideline value. In regions where arsenic contamination of drinking water is significant, it is crucial to provide safe water supplies and implement measures to reduce arsenic levels.

Recent research from Texas A&M University indicates that even low levels of arsenic exposure pose significant health risks, including an increased risk of kidney cancer. This study analyzed cancer data and water testing data across 240 Texas counties and found that exposure to arsenic levels above 1 part per billion raised kidney cancer risk by 6%, and exposure above 5 parts per billion increased the risk by 22%.

Radioactive materials in water

Radioactive materials, also called radionuclides, are both naturally occurring and human-made. They are a natural part of our environment, and small amounts of radiation are common in the air, water, and soil around us. However, coming into contact with too much radiation can cause health problems, including cancer.

Sources of Radioactive Materials in Water

Radioactive materials can get into groundwater and surface waters from both natural and human-made sources. Naturally occurring radionuclides, such as radium, polonium, radon, and uranium, are present in the earth's crust and atmosphere and can be found in small amounts in groundwater and surface water. Human-made radionuclides can also contaminate water sources through activities such as nuclear weapons testing, nuclear power plant operations, and the use and disposal of radiopharmaceuticals.

Health Effects of Radioactive Materials in Water

Ingesting water containing radioactive materials can lead to an increased risk of cancer, especially if consumed daily over many years. This is because radioactive materials emit radiation, which can damage cells in the body and increase the risk of cancerous cell growth. The health effects of radioactive materials in water depend on the type of radionuclide, the level of exposure, and the duration of exposure.

Protecting Yourself from Radioactive Materials in Water

The U.S. Environmental Protection Agency (EPA) has set standards for the maximum allowable levels of radionuclides in drinking water to protect public health. These standards include limits for alpha particles, radium, uranium, and beta/photon emitters. If you have a private well, you can have it tested for radionuclides through an accredited laboratory. Home water treatment systems, such as water softeners and reverse osmosis systems, can also help reduce the levels of radionuclides in your water.

While small amounts of radioactive materials in water are common, exposure to high levels or prolonged exposure to low levels of these contaminants can have adverse health effects. It is important to monitor the levels of radionuclides in drinking water and take appropriate measures to protect public health.

Chlorine byproducts in water treatment

Chlorine is added to drinking water to kill bacteria, viruses, and other microorganisms that cause disease and immediate illness. When chlorine is added to water, it can combine with naturally occurring organic matter in the water to form compounds called disinfection byproducts (DBPs). DBPs can cause negative health effects after regular, long-term exposure.

The US Environmental Protection Agency (EPA) has set limits for several types of DBPs. All public water systems that disinfect must regularly test their treated water to measure levels of regulated DBPs. If they are above the limits set by the EPA, the water system must take action to reduce the DBPs.

The most common DBPs are trihalomethanes (THMs), which are formed when chlorine interacts with organic materials in the water. THMs are a major component of DBPs in treated water. Studies indicate that dermal and inhalation exposures to THMs can be significant.

With collaborators in Spain, DCEG investigators evaluated DBP in relation to bladder cancer risk in the Interdisciplinary Case-Control Study of Bladder Cancer in Spain, considering exposure via ingestion, showering/bathing, and swimming in pools. THM exposure estimates revealed an excess of bladder cancer among individuals with estimated household levels above 49 mg/L. A similar elevation of risk was seen in the New England Bladder Cancer Study at the same levels of THM exposure, and confirmed the risk observed associated with showering/bathing, but not swimming pool use. In this study, there was also indication that brominated species of THMs were potentially more important for risk than chlorinated THM species.

With collaborators at the University of Minnesota and the University of Iowa, DCEG investigators evaluated intake of DBP from public drinking water in relation to cancer risk in the Iowa Women’s Health Study. They found that women with higher average THM in public water supplies had increased risks of rectal cancer, but evidence of associations with colon cancer was inconsistent. There were no associations for cancers of the kidney and ovary.

Nitrate in groundwater

Ingesting nitrate can lead to the endogenous formation of N-nitroso compounds (NOCs). NOCs are potent animal carcinogens. Population-based case-control studies in Iowa and Nebraska found increased risks of colon, kidney, and stomach cancer among those with higher ingestion of water nitrate and higher meat intake. This is due to the increased formation of NOCs.

A nationwide population-based cohort study in Denmark found that nitrate in drinking water may increase the risk of colorectal cancer. The study followed 1.7 million individuals between 1978 and 2011 and identified 5,944 incident CRC cases. The risk of CRC was 16% higher for those exposed to the highest levels of drinking water nitrate compared to those exposed to the lowest levels. The increased risk was observed at nitrate levels above 3.87 mg/L, which is well below the current drinking water standard of 50 mg/L.

The U.S. Environmental Protection Agency's (EPA) nitrate limit has been called into question by recent studies. The current limit is 10 parts per million, but studies suggest that even at levels half the legal limit, there is a higher risk of bladder, ovarian, and colorectal cancer. The EPA has initiated a health assessment of nitrate, and the results will inform any updates to the drinking water standard.

The nitrate problem has built up over decades, mainly due to the use of crop fertilizers and manure in farm regions. Septic tanks, lawn fertilizer, and wastewater treatment facilities also contribute to nitrate pollution. The concentration of nitrate in the nation's waterways and aquifers is a man-made phenomenon. Researchers call it a global problem that will take decades to resolve.

Lead pipes

The use of lead in pipes, paint, and other industrial applications has led to its presence in water supplies, posing risks to human health. Lead pipes, in particular, can leach lead into drinking water, leading to potential lead exposure and ingestion. This is a concern as lead is a carcinogenic element, classified by the IARC as a "possible human carcinogen" based on sufficient animal data and limited human data.

The toxic effects of lead exposure are well-documented, and it is known to cause a range of adverse health issues in both the short and long term. Short-term exposure to high levels of lead can result in abdominal discomfort, headaches, irritability, and numbness or tingling in the hands and feet. Long-term exposure, especially at high levels, can lead to more severe and persistent problems, including behavioural and cognitive issues, harm to the brain and nervous system, increased risk of miscarriage, cardiovascular and respiratory complications, and reproductive problems.

Of particular concern are the cancer-causing properties of lead. Studies have shown a potential link between lead exposure and an increased risk of certain types of cancer, including lung, throat, stomach, and intestinal cancers. Lead acetate, when administered to rodents, has been found to cause kidney cancer, brain cancer (gliomas), and lung cancer. While the evidence in humans is weaker, some studies have suggested an increased risk of lung and stomach cancer in highly exposed workers, such as those in lead smelter or battery industries.

The mechanism by which lead contributes to cancer development is believed to be related to its ability to inhibit DNA repair and act synergistically with other carcinogens. Lead exposure can cause damage to healthy cells, leading to uncontrolled cell growth and the formation of tumours. Therefore, the presence of lead pipes in water distribution systems can be a potential risk factor for water pollution-related cancers.

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