Worst Contaminants in Drinking Water

When you turn on the tap at home, you have the expectation that the water pouring out of your faucet is of drinking water quality and contaminant-free. While water suppliers do carry out hundreds of tests to ensure that this is the case, as water travels to your home, some toxins may still find their way into your tap water.

Of all the contaminants that may end up in your drinking water, some can be worse than others. To understand which water contaminants may be dangerous to your health, here is a rundown of the worst contaminants found in tap water:

Lead & Other Toxic Heavy Metals

Lead along with mercury, arsenic, chromium, and cadmium are some of the most toxic of heavy metals, causing heavy metal poisoning if ingested. Some of these heavy metals are so toxic they can cause damage to health even at low doses.

The sources of lead and other heavy metals could be erosion of natural deposits, but also old household plumbing systems, and industrial waste.

If you’re unsure about heavy metal presence in your tap water, a water testing kit can be helpful in establishing whether your tap water contains any heavy metals. If your plumbing system is very old, you need to take measures to replace it.

Another way to minimise your exposure to lead and other heavy metals is to install a water filter for heavy metal removal. Water filters that contain Kinetic Degradation Fluxion media, Ion Exchange Resin filters, some ceramic gravity water filters, or complex reverse osmosis filters are all good options when it comes to removing heavy metals from tap water.

Also Read: Best Filters for Heavy Metal Removal

Disease-Causing Microorganisms

Despite widespread chlorination, some pathogenic bacteria will still end up in your tap water. These are usually chlorine-resistant pathogens like E-Coli, Pseudomonas, Cryptosporidium, Giardia or Legionella.

Ingesting them with drinking water is not the only way to contract whatever disease they cause, sometimes a simple contact with mucous membranes is enough to cause problems.

Some of these pathogens cause severe gastrointestinal problems, vomiting, diarrhoea, or acute respiratory problems (e.g. Legionella).

The best line of defence against pathogens, cysts and viruses are ultraviolet water filters or boiling water for at least 5 minutes. While boiling water will kill off bacteria, it won’t help to remove other contamination issues.

Also Read: Best UV Water Filters


Fluoride can occur naturally or can be added to tap water. The benefits of artificial fluoridation are a topic of controversy with many opposing the addition of this toxic chemical to water supplies.

Opponents of artificial fluoridation argue that any benefits that fluoride may have against tooth decay can be achieved through topical application, and there is no need to ingest this substance as it can cause thyroid issues, it can affect ligaments, bones, and the nervous system, causing a host of cognitive disorders in children.

Many countries have either never adopted or ceased any fluoridation attempts, while countries like the US or UK still rely on water fluoridation.

Fluoride can be removed from water with the help of reverse osmosis filtration, activated alumina filters, ceramic filters and distillation filters.

Also Read: Best Filters for Fluoride Reduction


VOCs or volatile organic compounds are compounds that contain carbon along with other elements such as chlorine, oxygen, fluorine, hydrogen, sulphur, nitrogen or bromine.

VOCs easily become vapours or gases from liquid form. They are emitted from diesel exhaust, oil and gas fields, burning gasoline (gasoline also contains Methyl Tertiary Butyl Ether, another harmful contaminant), wood or natural gas, or they can be released by solvents, glues or paints.

Besides being an air pollutant, these substances easily end up in groundwater and drinking water sources as well.

Some VOCs are carcinogenic (e.g. carbon tetrachloride), others can cause anaemia, liver and kidney damage.

Because VOCs easily become gases or vapours, aeration can be one way of removing them from water. Another way would be using carbon block filters or multi-stage reverse osmosis water filter systems.

Pesticides & Herbicides

Herbicides enter water supplies from rainfall and irrigation on farmlands, which wash off herbicides into rivers or lakes. Pesticides enter water supplies from drains within the home. Both herbicides and pesticides are considered harmful for human health, interfering with hormonal activity, affecting reproductive and other organs in the body.

Pesticides and herbicides can be removed from water through filtration, and carbon block filters, reverse osmosis filters and some ceramic filters can all be used to remove these dangerous substances.

Chemical Disinfectants – Chlorine, Chloramine & their By-Products

As opposed to lead, chemical disinfectants are purposefully added to municipal water to kill off disease-causing microorganisms. Chlorine is a powerful oxidant, which can be absorbed by your skin and inhaled while bathing. It can have irritating effects on mucous membranes and skin.

Chlorine is particularly dangerous to those already suffering from asthma (it can trigger asthma attacks if inhaled) or suffering from skin conditions like psoriasis or eczema (exposure to chlorine can cause flare-ups).

In some countries chloramine may be used instead of chlorine, or it can be used as a secondary disinfectant, and it’s formed by adding ammonia to water that contains free chlorine. Both chlorine and chloramine can form by-products (e.g. Trihalomethanes) when combined with other water ingredients.

To remove chlorine, chloramine and their by-products from tap water look for carbon block filters, ceramic filters or reverse osmosis water filters.


Found in prescription drugs or veterinary medication, pharmaceuticals can also make their way into drinking water through improper disposal (e.g. flushing them down the toilet), runoff from factory farms, and poorly-controlled manufacturing processes.

Although usually detected in a range of nanograms to micrograms per litre, pharmaceuticals can cause health problems if present in higher concentrations.

Water filtration technologies like reverse osmosis can achieve above 99% removal rates. Likewise, gravity water filters like the Big Berkey are also efficient in removing pharmaceuticals from your tap water.

Best Filter Systems for High-Purity Water

As you can see, tap water can contain various contaminants, and while installing a water filter will help remove or reduce the levels of some of these contaminants, not all water filters reduce all types of contaminants, but there are some advanced water filters that can do a good job at removing or reducing most if not all the contaminants discussed in our article.

The best water filter systems that can produce high purity water are undoubtedly those that either feature several stages of filtration, or even if they feature a single filter cartridge, they use a blend of filter media to target a wide range of toxins.

For example, the H2O US3 6 Stage Advanced Water Filter System contains a single filter cartridge with a blend of sediment filter bed, silver-impregnated carbon, granular activated carbon, KDF, riolite and two other sediment filter beds. Thus, despite having a single cartridge, the H2O will efficiently target heavy metals, chlorine, its by-products, VOCs, bacteria and many other chemicals and organic contaminants.

Reverse osmosis water filters are another great choice for dealing with various water impurities. 5 and 6-stage reverse osmosis filters are the most common, but 9-stage RO filters can also be found for residential use.

The Pure-Pro Quick Change Pumped 6-Stage Reverse Osmosis System with Alkaline Filter is a multi-stage reverse osmosis that combines reverse osmosis filtration with carbon-based filters (both carbon block and granular filters) to remove heavy metals, fluoride, chlorine, chlorine by-products, VOCs, and sediments. The system also features an alkaline filter that restores healthy minerals lost during filtration.

The Pure-Pro comes with a booster pump to elevate water pressure levels where requirements for water pressure are not being met.

The BMB-30 NOVA PRO Direct Flow 9-Stage Reverse Osmosis System is an example of a 9-stage RO system, which also combines ultrafiltration with carbon filtration. The system comes with two reverse osmosis membranes, and it’s a direct flow system, meaning that it doesn’t need a reverse osmosis tank.

Some reverse osmosis filters or multi-stage whole house filters can be combined with UV water filters to eradicate pathogens found in tap water or other water sources (e.g. private well).

If you’re looking for an advanced countertop water filter both the Big Berkey or ProPur gravity water filters will remove most of the types of contaminants presented in this article, and more. Gravity water filters combine ceramic filtration with carbon filtration.

Gravity water filters don’t rely on water pressure, nor electricity to perform, and they can be used in emergency situations and even to filter water sources from rivers, lakes, and streams. They are easy to operate and rank highest in portability, which means you can take them with you pretty much anywhere you go.


If your tap water contains some of the contaminants discussed in this article, the best way to significantly reduce their levels or to remove them entirely is to install a multi-stage water filter system or a filter system that contains a blend of several filter media. This ensures a thorough filtration by targeting multiple contaminants at the same time.


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