​Hidden contaminants

Some unwanted nasties in water are obvious from its colour, smell and general appearance. Water with a yellowish tinge, metallic smell and with scum floating on the top is obviously unclean.

Microbial contaminants are often undetectable by humans and it is possible for them to exist in a water supply for years before problems emerge and harmful organic items can seep into the local supply from fertilizers and pesticides used in agricultural areas.

Waterborne contaminants can also leach into the supply from industrial plants. Depending on the nature of the organic material, there can be a number of risks that result from water contamination.

The effects of waterborne contaminants

Depending on the matter which has entered the water supply, risks to human and animal health including elevated risks of cancer, reproductive issues and impairment to the eyes, kidneys, liver and other vital organs. There are also short-term risks of immediate sickness and diarrhoea and more serious diseases such as typhoid.

What are common waterborne contaminants?

​These include:


Leaves and twigs
Mould spores
Faecal matter
Bacteria (Legionella, Salmonella)
Parasites (Cryptosporidium)


Metal ions (Iron, Aluminium, Arsenic)
Heavy metals (Copper, Zinc, Lead)
Dirt, Sediment, Particulate
Disinfectants (Chlorine, Chloramine)
Pesticides (Nitrate, Phosphates)
Salts (Potassium, Sodium, Chlorides)
Scale causing minerals (Calcium & Magnesium)

Bacteria and viruses: which can also exist in polluted water, for example, microbial bacteria which can be transmitted from faecal matter in the water supply and lead to diarrhoea disease. (In the nineteenth century, typhoid and cholera wiped out large numbers of the population and were transmitted through the drinking of unclean water contaminated with faecal matter.)

Organisms: such as Cryptosporidium Parvum which is a gastrointestinal parasite that causes diarrhoea and has no cure.

Agricultural chemicals: particularly nitrates, which can be harmful for young babies who are bottle-fed.

​Emerging water contaminants

There is also concern that chemicals that exist in daily personal care products such as soap, and pharmaceutical drugs, such as the contraceptive pill, are contaminating the water leading to endocrine disruption.

The impact of elements such as EDCs, PCPs, pharmaceuticals and perchlorate are all being investigated further by global water authorities and research bodies to assess the possible risks and impact.

Are these all of concern?

Not necessarily. All water will naturally have contaminants from the earth such as minerals and these can be beneficial at the right levels. For example, fluoride is sometimes added to the water intentionally to support oral health.

However, unwanted and dangerous water contaminants – such as lead and arsenic – can cause serious issues, as can bacterial contaminants. Waterborne disease is still one of the main causes of disease and death in developing countries, particularly amongst children.

A lack of safe water also prevents subsistence economies from developing, so the broader effects of poor-quality water extend beyond immediate health.

What contaminants are in my water ?