A Complete Guide to Contaminants: What is in your drinking water? [2021]

Updated: Jul 1

Springwell Whole House Water Filter

We all know the importance of hydration in keeping all the organs and systems of our bodies in their optimal shape. However, it’s equally essential to consume safe and healthy water to make sure your drinking water isn’t leaving any adverse effects on your health. Have you ever wondered about what’s in your drinking water? Even though the municipal tap water we use in our homes is processed according to the drinking water standards, but it doesn’t guarantee that there are no impurities that can deteriorate the quality of your drinking water.

This article will help you understand what your drinking water contains, how those contaminants affect the water, and how you can eliminate them. So, keep on reading!

Types of Drinking Water Contaminants

Water contaminants to look out for in your drinking water are divided into four categories:

1. Physical

2. Chemical

3. Biological

4. Radiological

Let us elaborate on each type of drinking water contaminant to help you better understand them.

Physical Contaminants

As the name implies, physical contaminants can change the physical appearance of drinking water. These impurities can make the water appear cloudy or hazy, and you may even notice sediment accumulate on top of the water. Physical contaminants are usually larger in size as compared to other types of contaminants. Some common forms of physical contaminants include dust, sand, sediment, dirt, and other organic substances.

Chemical Contaminants

Chemical impurities in drinking water are either natural or man-made. These contaminants can have a deteriorating effect on the quality of water and may contribute to health hazards. Chlorine or chloramines are the most commonly found chemical contaminants in drinking water which are added to the water during the process of disinfection. Moreover, herbicides and pesticides can also contaminate the water during overland flow. These toxic materials may not be fully removed during water treatment.

Biological Contaminants

It’s a no-brainer that every microorganism present in drinking water is known as a biological water contaminant. This group of water contaminants comprises viruses, bacteria, protozoans, and parasites. These microorganisms can either survive through the water treatment or pollute the water as it flows through pipelines to your home. These biological pollutants are commonly found in private well water supplies and can lead to serious health issues.

Radiological Contaminants

Most of us might not take these contaminants seriously because they are the least expected to be found in water. However, their negligible amount is still present in water. It’s important to keep in mind that these are the most dangerous water contaminants that can have a profound effect on our health. Some common radiological water toxins include uranium, plutonium, and cesium. Prolonged contact with these pollutants is considered to be dangerous.

EPA Drinking Water Contaminant Classification

The EPA has classified water contaminants into two categories: primary and secondary. Here’s what each category contains:

Primary Contaminants

The course of action provided by the Environmental Protection Agency defines a set of standards for drinking water that all public water suppliers are legally bound to follow. These rules ensure that consumers of public water are not exposed to dangerously high levels of certain water contaminants, known as primary contaminants. The EPA has imposed a ‘maximum contaminant level or MCL’ for each water contaminant considered to be hazardous to health.

The MCL for any contaminant is its highest quantity that can be present in the water before it makes the water unsafe for drinking. The public water companies are required to keep a regular check on the quality of water to ensure that the amount of primary contaminants doesn’t exceed the MCL defined by the EPA.

These primary contaminants are divided into categories to make them easy to identify:

· Microorganisms (such as viruses and bacteria)

· Inorganic chemicals particulates

· Disinfectants ( like chlorite and trihalomethanes)

· Organic chemical pollutants (styrene and benzene, for example)

· Metals (including lead, arsenic, nitrate, and chromium)

· Radionuclides (such as uranium and radium)

Secondary Contaminants

Besides the set standards for primary contaminants, the EPA has also issued guidelines for public water suppliers to help them manage their drinking water supply. These standards are not compulsory or legal. On the contrary, these are just guidelines known as NSDWRs or National Secondary Drinking Water Regulations and contain 15 secondary contaminants.

The elements on the list of secondary contaminants are a lot less probable to cause serious health problems but may have undesirable effects when present in a high amount. They are mostly responsible for aesthetic, cosmetic, or technical alterations in water.

The secondary contaminants that have aesthetic effects in water include iron, chlorine, copper, aluminum, manganese, zinc, foaming elements, and total dissolved substances. The contaminants which affect the water cosmetically are silver and fluoride. These agents can lead to discoloration of the skin or teeth. The elements with corroding, staining, and scaling properties are zinc, pH, chloride, iron, copper, total dissolved solids, and aluminum.

Contaminants of Emerging Concern

Although most of the above-listed water impurities have been present in our drinking water for decades recently, the EPA has highlighted a list of emerging contaminants that are shown to be increasingly high-risk over the last few years. These water impurities, called ‘contaminants of emerging concern’, mainly encompass pharmaceuticals and products of personal care.

Common Primary Contaminants


Below are commonly seen microbiological contaminants in drinking water:

Coliform Bacteria

E. Coli and fecal coliform are two of the common types of coliform bacteria found in water that indicate the presence of other harmful bacteria in drinking water. Even though these bacteria are not dangerous themselves, their existence usually signals that the water is contaminated. This is the reason their MCL or maximum contaminant level specified by the EPA is zero.


This is another microorganism with a maximum contaminant level of zero by the EPA. Cryptosporidium is a parasitic protozoan that can cause a myriad of health issues, like cramps, diarrhea, and vomiting.


Also called Giardia Lamblia, this parasite also has an MCL of zero. This microscopic organism is known to lay the ground for stomach bugs, known as giardiasis. It’s found in fecal waste and may be present in drinking water.


Legionella is one of the most vicious bacteria that are naturally present in public water supplies. This deadly microorganism can be life-threatening and is associated with inflammatory lung disease, called Legionnaire’s disease. Heating systems provide a favorable environment for these bacteria to multiply. Its MCL is also zero.


A number of viruses are also found in public water supplies and can lead to various health concerns, especially gastrointestinal problems, including diarrhea and vomiting. This is the reason their MCL is zero in the standards set by the EPA.

Inorganic Chemicals

Some of the common inorganic elements found in public drinking water are:


This naturally occurring metalloid chemical element has the ability to dissolve in groundwater. Well water had high levels of arsenic in it while its quantity is smaller in treated public water supplies. Prolonged exposure to this chemical can cause cancer, hypertension, cardiovascular diseases, and neurological problems.


This chemical element is tasteless and odorless and is present in natural habitats, like rocks, soil, and animals. Some forms of chromium are harmful to health, even on short-term exposure. Public water with mercury can lead to organ damage.


This element is found in small quantities in various foods, such as seeds, leafy green vegetables, nuts, some meats, and dark chocolate. However, high levels of copper can be harmful to health. Corroded pipes can transmit copper into drinking water. It may cause kidney and liver problems, vomiting, and stomach aches.


Most of us know fluoride for its benefits for dental health as it prevents tooth decay. 0.7 mg per liter of fluoride is added to public drinking water during treatment. Some studies link it to skeletal fluorosis and cancer.


Just like copper, lead is also mainly a problem of the areas with old pipelines because it also enters water via corroded pipes. Lead faucets and fixtures in old homes can also be the reason behind the presence of lead in your drinking water. Its MCL is zero because it’s a toxic compound. It can contribute to kidney problems, hypertension, and other issues even in small quantities.


This potentially dangerous metal can pass into drinking water from the environment, such as industrial and mining disposal and contaminated rain and snow. The MCL for mercury is 0.002 mg per liter according to the EPA’s standards. Higher concentration can cause problems related to kidneys, stomach, immune system, and lungs.

Nitrates and Nitrites

These groundwater pollutants are usually found in rural areas and their levels get regulated during water treatment. Exposure to large quantities of nitrates can result in a blood disorder, called methemoglobinemia.


Common contaminants found in water disinfecting compounds are:


One of the most abundantly present and controversial disinfectants in drinking water is chlorine. It’s used to remove slime and algae from water to make safe for drinking purpose. However, it gives a distinct taste and odor to water that many people don’t like. The level of chlorine above 4 mg/l can have negative effects on health, like aggravate allergic reactions.


This disinfecting agent is a synergy of chlorine and ammonia. It’s used as an alternative to chlorine to keep the water free from microorganisms that can lead to waterborne diseases. Its safe level is 4 mg per liter. It also alters the smell and taste of water but doesn’t stay in water for long.

Organic Chemicals