FAQ on water quality

What does “water quality” refer to?

The aesthetic, biological, chemical, physical and radioactive properties of water.

What is measured to understand water quality?

Aesthetic characteristics (odours, colour, dissolved solids); biological characteristics (bacteria, algae quantity), Chemical characteristics (pH, dissolved oxygen, biological oxygen demand, nitrogen & phosphorus nutrients, and organic & inorganic toxicants); Physical (temperature, turbidity and clarity, color, salinity, suspended solids, dissolved solids); Radioactive (alpha, beta and gamma radiation emissions).

When do “contaminants” (substances present in water) become “pollutants” (substances present in concentrations harmful to humans)?

It’s often true that contaminants can be detected at levels that are not harmful to humans. These contaminants become harmful when their concentration increases. Please see Table A3.3 (p 472) in the WHO’s Guidelines for drinking-water quality (pdf) to see the threshold for pollutants.

How can the contamination be stopped/removed?

First, protect water sources from pollution. Second, purify water at a treatment plant. Third, make sure the water distribution network from the plant is free of cracks and leaks that may introduce sewage and other pollutants (the problems in Flint, Michigan, were caused by polluted water corroding their pipe network). Fourth, maintain the quality of pipes in your home.

How does water pollution harm your health?

Bacteria, viruses, and protozoa in water can result in diarrhea, vomiting, and dehydration associated with hepatitis A, cholera, dysentery, typhoid, and so on. Some of these infections can be prevented by immunizations, but nobody can protect themselves from all possible adverse impacts of consuming polluted water.

Over the longer term, exposure to pollutants can result in many other problems, e.g., metals and mercury (reproductive impairments, death-induced toxicity), arsenic (organ and skin illnesses, cancer), nitrates (stomach cancer, reduced fertility), non-metallic toxins such as dioxins, furans and PAHs (endocrine disruption, cancer, cardiovascular difficulties), and so on.