Water Pollution And Cancer: A Toxic Link?

Water pollution is a serious issue affecting billions of people worldwide, and it has been linked to various diseases, including cancer. While water treatment methods have improved over the years, certain contaminants still pose a significant risk to human health. These contaminants can enter our water supply through various sources, such as industrial waste, agricultural runoff, sewage, and chemical dumps. Even with treatment, water pollution is present in almost all water supplies and can have long-term health effects.

Ingesting toxins through contaminated water can overwhelm the immune system and lead to the development of cancer cells. Certain chemicals and heavy metals found in polluted water, such as arsenic, have been linked to an increased risk of bladder, liver, lung, and kidney cancers. Other contaminants, like disinfection byproducts and nitrate, have also been associated with rectal and bladder cancer.

With aging water treatment infrastructure struggling to keep up with growing populations and modern-day contaminants, water pollution is becoming an increasingly concerning factor in cancer and other serious illnesses.

Arsenic in drinking water

Arsenic is a natural component of the earth's crust and is widely distributed in the environment in the air, water, and land. It is highly toxic in its inorganic form, which is the type found in water supplies.

Ingesting arsenic from water supplies is known to cause skin cancer. It has also been linked to liver, lung, kidney, and bladder cancer. The International Agency for Research on Cancer (IARC) has classified arsenic and arsenic compounds as carcinogenic to humans and confirmed that arsenic in drinking water is carcinogenic.

The first symptoms of long-term exposure to high levels of inorganic arsenic are usually observed in the skin and include pigmentation changes, skin lesions, and hard patches on the palms and soles of the feet. These occur after a minimum exposure of approximately five years and may be a precursor to skin cancer.

In addition to skin cancer, long-term exposure to arsenic may also cause cancers of the bladder and lungs. Arsenic has also been associated with other adverse health effects, including developmental impacts, diabetes, pulmonary disease, and cardiovascular disease.

According to the World Health Organization (WHO), an estimated 140 million people in at least 70 countries have been drinking water containing arsenic at levels above the recommended limit of 10 μg/L. The greatest threat to public health from arsenic originates from contaminated groundwater, which is naturally present at high levels in several countries, including Argentina, Bangladesh, Cambodia, Chile, China, India, Mexico, Pakistan, the United States, and Vietnam.

Chlorine by-products

Chlorinated water is produced when chlorine, used to disinfect water, interacts with organic materials in the water. This process forms a mixture of disinfection by-products (DBP), which can be harmful to human health. One of the most prevalent DBPs is trihalomethanes (THM), which can be absorbed into the body through the skin or inhalation.

Several studies have investigated the link between THM exposure and bladder cancer. One study found that people living in households with high levels of THM in their water had double the risk of bladder cancer compared to those with lower levels. Another study, conducted in Iowa, found associations between long-term exposure to high levels of THM and rectal and bladder cancers.

However, a large-scale cohort study in Sweden found no association between THM exposure and bladder cancer risk. The researchers assessed the association between drinking water THM levels and bladder cancer risk in over 58,000 men and women, with a 16-year follow-up period.

While the evidence is mixed, there is a suggestion that chlorination by-products may increase the risk of certain cancers, particularly bladder cancer. More research is needed to confirm these findings and fully understand the health risks associated with DBPs in drinking water.

Pesticides and fertilisers

Pesticides

Pesticides are designed to kill or control pests, but they can also be harmful to non-target organisms, including humans. When pesticides enter water bodies, they can cause the death of fish and other organisms or lead to reproductive issues. Some pesticides can also bioaccumulate in organisms, building up in their bodies over time. This can lead to biomagnification, where the concentration of the pesticide increases as it moves up the food chain, potentially affecting larger predators and humans who consume contaminated seafood.

There is evidence to suggest that exposure to pesticides is associated with an increased risk of certain types of cancer. For example, a review of studies published between 1992 and 2003 found positive associations between pesticide exposure and non-Hodgkin lymphoma, leukaemia, and several types of solid tumours, including brain and prostate cancer. Another study in Brazil found extensive contamination of drinking water by 11 proven, probable, or potentially carcinogenic pesticides. The study estimated that the contaminated drinking water could be responsible for a total of 542 cancer cases in the region, with over 80% attributed to two specific pesticides.

Fertilisers

Fertilisers primarily impact water quality through eutrophication. When fertilisers containing nutrients such as nitrogen and phosphorus enter water bodies, they can promote the excessive growth of algae, leading to a process known as an algal bloom. As the algae die and decompose, they deplete oxygen levels in the water, causing the death of fish and other aquatic organisms. In severe cases, this can create 'dead zones' where no aquatic life can survive.

Nitrate, a common component of fertilisers, has been linked to health issues such as methemoglobinemia or 'blue baby syndrome' in infants if it contaminates drinking water. Additionally, ingested nitrate can lead to the endogenous formation of N-nitroso compounds (NOC), which are potent animal carcinogens. Studies have found increased risks of colon, kidney, and stomach cancer among individuals with higher ingestion of water nitrate and higher meat intake.

Pharmaceuticals in water

Sources of Pharmaceuticals in Water

Pharmaceuticals enter water systems through various sources, including manufacturing plants, livestock operations, and human and animal waste. In a 2004-2009 study by the U.S. Geological Survey (USGS), scientists found that effluents from wastewater treatment plants (WWTPs) that received discharge from pharmaceutical manufacturing facilities had 10 to 1,000 times higher concentrations of pharmaceuticals compared to WWTPs that did not. These chemicals were traced downstream as far as 30 kilometres from one plant's outfall. Antibiotics and drugs used in the livestock industry, such as acetaminophen, caffeine, cotinine, diphenhydramine, and carbamazepine, have also been found in USGS studies. Additionally, pharmaceuticals that are not fully metabolised by the human body end up in wastewater leaving homes and entering sewage treatment plants.

Health Risks and Ecological Impacts

The presence of pharmaceuticals in water has raised concerns about potential adverse ecological effects and risks to human health. While there is limited evidence of a direct link between pharmaceuticals in water and cancer, studies suggest that long-term exposure to certain chemicals may increase cancer risk. For example, disinfection byproducts (DBPs), which form when chlorine used to disinfect water interacts with organic material, have been associated with increased risks of rectal and bladder cancer. Additionally, certain pharmaceuticals have been linked to developmental toxicity, endocrine disruption, and behavioural changes in wildlife.

Addressing the Issue

To reduce the presence of pharmaceuticals in the environment, proper disposal of leftover drugs is essential. The U.S. federal government has sponsored activities regarding drug disposal, and organisations like the Pharmaceutical Research and Manufacturers of America have concluded that flushing unused medicine should be avoided in favour of household trash disposal and take-back programs. "Social marketing" approaches can also be applied to educate the public and change behaviours related to drug disposal. Furthermore, there is a need for better interagency cooperation and data sharing among regulatory agencies to address this complex issue effectively.

Radioactive waste

The nuclear industry has developed and implemented technologies for the final disposal of radioactive waste, including deep geological repositories. However, there are concerns about the long-term safety of these repositories and the potential impact on future generations. The transport of radioactive waste also poses risks, although there have been no reported instances of radioactive release causing harm during transport.

Plutonium, a radioactive element, has been described as "the most toxic substance on Earth," with inhalation posing an increased risk of cancer development. However, comparisons between toxic substances are complex, and other toxins such as ricin and snake venoms may be more toxic than plutonium on a gram-for-gram basis.

Overall, radioactive waste is a significant concern due to its potential impact on human health and the environment. While the nuclear industry has made advancements in waste management, further research and strict regulations are necessary to minimize risks and protect vulnerable populations.

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