Water pollution occurs when water becomes contaminated, usually by chemicals or microorganisms. Pollution can cause water to become toxic to humans, which can lead to infections and health problems.

Water is an essential resource for all life on Earth. If a water source becomes contaminated due to pollution, it can lead to health issues in humans, such as cancer or cardiovascular conditions.

This article explores the causes of water pollution, how it can affect human health, and what people can do to help prevent it.

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Image credit: JEAN AURELIO PRUDENCE/L’Express Maurice/AFP via Getty Images

Water is a natural resource that all living creatures require. Clean water is also used in manufacturing and for social and economic development.

However, according to the United Nations (UN), 2.2 billion people lack access to safe drinking water services.

The UN and the World Health Organization (WHO) list the following statistics on water pollution:

  • Over half the global population do not have safely managed sanitation services.
  • Around 2 billion people live in countries with high levels of water stress, meaning the amount of water available is less than the amount required.
  • Experts estimate that by 2025, half the world’s population will live in a water-stressed environment.
  • Around 785 million people do not have basic drinking-water services.
  • Since the 1990s, water pollution has worsened in almost all rivers in Asia, Latin America, and Africa.

Water is sometimes referred to as the universal solvent, as it dissolves more substances than any other liquid. However, this ability means that water is easily prone to pollution.

Below are just some of the many ways that water pollution can occur.

Sewage and wastewater

After being used, water becomes wastewater. Wastewater can be domestic, such as water from toilets, sinks, or showers, or from commercial, agricultural, or industrial use. Wastewater also refers to rainwater that washes oil, grease, road salt, debris, or chemicals from the ground into waterways.

The UN estimates that 80% of wastewater returns to the ecosystem without being treated or reused.

In 2017, the UN found that 2 billion people worldwide did not have access to facilities such as toilets or latrines. The organization also discovered that 673 million people openly defecate outside.


The agriculture industry is one of the biggest consumers of fresh water. In the U.S., it is responsible for around 80% of the nation’s water consumption. Agriculture is also the main source of pollution in rivers and streams in the U.S.

One way that agriculture causes water pollution is through rainwater. When it rains, pollutants, such as fertilizers, animal waste, and pesticides get washed from farms into waterways, contaminating the water.

Contaminates from agriculture usually contain high amounts of phosphorous and nitrogen, which encourage the growth of algal blooms. These blooms produce toxins that kill fish, seabirds, and marine mammals, as well as harming humans.

Additionally, when these algal blooms die, bacteria produced as the algae decompose use up oxygen in the water. This lack of oxygen causes “dead zones” in the water where fish cannot live.

The United Nations Educational, Scientific and Cultural Organization (UNESCO) estimate that there are roughly 245,000 square kilometers of dead zones globally.

Plastics and garbage

Approximately we produce 1.4 billion tons of waste each year. Of this annual waste, 10% comprise plastics. Due to the widespread use of plastics, experts estimate that 4.8–12.7 million tons of waste enter the ocean each year.

Plastic and garbage can enter the water in many ways:

  • debris falling off ships
  • trash blowing into the ocean from landfills
  • garbage swept into the sea via rivers from people discarding used items such as food packages
  • people throwing their trash on to the beach

Once in the water, plastic and garbage can harm marine life and human health. Fish may eat trash, mistaking it for food, and end up dying.

As plastic slowly breaks apart, microplastics form. These are small fragments of plastic that are less than 5 millimeters in size. Fish may consume these microplastics, which may then be eaten by humans.

The UN state that plastic debris in the ocean causes the deaths of over a million seabirds each year. Plastic debris is also responsible for the deaths of more than 100,000 marine mammals annually.


Oil pollution can occur when oil tankers spill their cargo. However, oil can also enter the sea via factories, farms, and cities, as well as via the shipping industry.

Radioactive waste

Radioactive waste can endure in the environment for thousands of years, making safe disposal difficult. If improperly disposed of, it can enter the water, making it hazardous to humans, marine life, and the environment.


Fracking is the process of extracting oil or natural gas from rock. The technique uses large amounts of water and chemicals at high pressure to crack the rock. The fluid created by fracking contains contaminants that can pollute underground water supplies.

The following are some negatives ways that water pollution can directly affect human health.

Ingesting microplastics

A person may ingest microplastics via drinking water or through eating contaminated seafood. At Tokyo Bay in 2016, scientists examined 64 anchovies for microplastic consumption — 77% had microplastics in their digestive systems.

People have also discovered them within salt, beer, and other food items.

Studies show microplastics may cause oxidative stress, inflammatory reactions, and metabolic disorders in humans. However, further research is needed to confirm these effects.

Consuming water contaminated by sewage

The WHO note that, globally, around 2 billion people use a drinking water source with fecal contaminants. Contaminated water can harbor bacteria, such as those responsible for diarrhea, cholera, dysentery, typhoid, hepatitis A, and polio.

According to the UN, every year, approximately 297,000 children under five die from diseases linked to poor sanitation, poor hygiene, or unsafe drinking water.

Drinking water containing chemical waste

Chemical pollutants, such as pesticides, fertilizers, and heavy metals can cause serious health problems if ingested.

In 2014, residents in Flint, Michigan, experienced water contamination due to inadequate testing and treatment of their water supply. The contaminated water caused rashes, hair loss, and itchy skin. Lead levels in the bloodstream of children who drank the water doubled.

A person who ingests chemical toxins in their water can be at risk of:

  • cancer
  • hormone disruption
  • altered brain function
  • damage to immune and reproductive systems
  • cardiovascular and kidney problems

Swimming in contaminated water can also trigger:

  • rashes
  • pink eye
  • respiratory infections
  • hepatitis

A person who wishes to reduce water pollution can help by:

  • reducing plastic usage and recycling plastics when possible
  • disposing of household chemicals properly
  • keeping up with the maintenance of their vehicle to ensure it is not leaking harmful substances
  • avoiding using pesticides
  • making sure to clean up dog waste
  • making sustainable choices regarding food and drinks
  • considering going vegan or vegetarian

Water pollution is a serious environmental issue that can be caused by many contaminants. Human health can be affected by consuming, entering, or washing in polluted water.

There are various ways to help to limit water pollution. If a person experiences any effects of water pollution, they should speak to their doctor.