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How Safe Is Your Drinking Water?

[fa icon="calendar"] May 5, 2020 10:00:00 AM / by Calvin Leong



Portrait of a young woman drinking water in the kitchen at home

In July 2019, the Malaysian Ministry of Health suspended the license of a local bottled drinking water company after the discovery of a bacteria called pseudomonas aeruginosa, in its bottled drinking water.

What Should Drinking Water Contain?

Drinking water should contain only water molecules. Anything else in drinking water is called a contaminant. Contaminants affect the quality of your water. They include physical, chemical, biological, or radiological substances. Not all contaminants are harmful to your health. For example, chlorine, manganese, iron, and aluminium may be present in the water, but will not cause any health problems.

Some of these substances can cause problems in your digestive, nervous, and reproductive systems. The people most at risk for these problems include older people, babies, children, pregnant women, and people with weak immune system.

Male mountain biker drinking water in the forest

Where Does Drinking Water Come From?

There are two sources of drinking water:

  • Surface water. This water collects in lakes, rivers, and reservoirs.
  • Ground water. This water comes from below ground. Well water is an example of ground water.

Water for public consumption can be either ground water or surface water. Surface water is usually treated by a public or private water treatment system before it goes to your home. Ground water systems do not always need to be treated. All public water systems are tested for quality.

Take caution when drinking directly from surface water, such as during hiking or camping. Surface water can contain bacteria or parasites, in addition to chemicals or compounds. Even clear, spring water should be filtered through a specialised filter before drinking.

What Can Contaminate Drinking Water?

Causes of contamination include:

  • Natural chemicals and minerals.
  • Man-made chemicals.
  • Chemicals and minerals released by mining or manufacturing processes.
  • Pesticides and fertilisers from land use.
  • Toxic spills, leaking fuel tanks, sewer overflows.
  • Water treatment plants that have broken pipes or tanks.

Common contaminants are usually from:

  • Sediments from soil erosion in surface water. These may change the colour of your water, but usually do not affect your health.
  • Calcium carbonate from limestone. These can make your water hard. Hard water reduces soap lather and may form a build-up (scale) in water heaters or boilers.
  • Natural metals, such as iron, aluminium, and manganese.
  • Natural chemicals, such as arsenic, radium, and uranium.
  • Chemical or metal sources that come from mining or manufacturing processes. These include lead, cadmium, chromium, copper, cyanide, mercury, and silver.
  • Volatile organic compounds from manufacturing plastics and other products.
  • Pesticides and fertilisers.
  • Tiny living organisms, including bacteria, virus, and parasites.

Mt. Fuji, Japan viewed from behind factories.

How Can Contaminated Water Affect Me?

Most drinking water contains a small amount of contaminants. The effects on your health depend on the type of substance and the amount in your water. Microbial contaminants can cause illness within hours or days. Damage from contaminants like pesticides, arsenic, lead, radium, or mercury can develop over many years. Common contaminants such as lead can cause physical and mental problems in children, high blood pressure and cancer in adults. Arsenic can cause liver and kidney damage and cancer. Birth defects can be caused by radium. Copper can cause anaemia, stomach, liver, or kidney damage.

Pesticides in the water can cause headaches, dizziness, numbness and weakness and even damage to your thyroid, reproductive system, liver, and kidneys.

Bacteria, viruses, and parasites (microbials) in drinking water are common causes for cholera, typhoid fever severe diarrhoea (dysentery) and liver infection (hepatitis).


Biologists testing water of natural river

What Steps Can I Take To Make Sure My Water Is Safe?

  • Test well water every year. If you have community water, your public water department regularly tests your water for safety. You can get a copy of this safety report from your water supplier.
  • Boil your water for up to 3 minutes if your public water department issues a "boil water advisory." The advisory is issued when a problem is detected in your water safety.
  • If you notice a change in the colour, smell, or taste of your water, have it tested or contact your public water department.
  • Install a carbon filter on your tap. This will remove some contaminants and  the taste of any chemicals used to treat your water.
  • Install a reverse osmosis filter system. This will get rid of more contaminants.
  • Change your water filters as instructed by the manufacturer.
  • Use bottles with specialised filters when drinking directly from surface water sources.
  • If you have a septic system, have it checked and pumped on a regular basis.
  • Use natural pesticides and fertilisers.
  • If you use bottled water, only use it in its original container. Ensure the bottled water quality is tested by the Ministry of Health, Malaysia. Store bottled water in a cool place. Do not reuse the bottles.

close up of an empty used plastic bottle on white background with clipping path


  • Drinking water should contain only water molecules. Any physical, chemical, biological, or radiological substances found in your water are called contaminants.
  • Common causes of contamination include natural and man-made chemicals and minerals.
  • Test well water every year. If you have community water, your public water department regularly tests your water for safety.
  • If you notice a change in the colour, smell, or taste of your water, have it tested or contact your public water department.

This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.


Azrina, H.E. Khoo, M.A. Idris, I. Amin, M.R. Razman Major inorganic elements in tap water samples in Peninsular Malaysia, Malays J Nutr, 17 (2011), pp. 271-276

A.Z. Aris, R.C.Y. Kam, A.P. Lim, S.M. Praveena, Concentration of ions in selected bottled water samples sold in Malaysia, Appl Water Sci, 3 (1) (2013), pp. 67-75

Chalchisa D., Megersa M., and Beyene A.: Assessment of the quality of drinking water in storage tanks and its implication on the safety of urban water supply in developing countries. Environ Syst Res 2018; 6: pp. 12

Department of Irrigation and Drainage, DID (2000).  Urban stormwater management manual for Malaysia. Ministry of Agriculture, Malaysia.

DOE  (1974).    Environmental  quality  act  1974  (Act  127)  &  subsidiary  legislations.    Department  of Environment Malaysia.  International law book services, August 1997.

DOE (1994).  Classification of Malaysian rivers.  Final report on development of water quality criteria and standards for Malaysia (Phase IV – River Classification).  Department of Environment Malaysia, Ministry of science, technology and the environment.

DOE (2002).   http://www.jas.sains.my/jas/river/riverbasins.htm.  Department of  Environment Malaysia, Ministry of science, technology and the environment.

DOE  (2003a).   The study  of pollution  prevention and  water quality  improvement  of Sungai  Langat.  Department of Environment Malaysia, Ministry of science, technology and the environment.

Galaitsi S.E., Russell R., Bishara A., Durant J.L., Bogle J., and Huber-Lee A.: Intermittent domestic water supply: a critical review and analysis of causal-consequential pathways. Water 2016; 8: pp. 274

Kumpel E., and Nelson K.L.: Intermittent water supply: prevalence, practice, and microbial water quality. Environ Sci Technol 2016; 50: pp. 542-553

Liu G., Bakker G.L., Li S., Vreeburg J.H.G., Verberk J.Q.J.C., Medema G.J., Liu W.T., and Van Dijk J.C.: Pyrosequencing reveals bacterial communities in unchlorinated drinking water distribution system: an integral study of bulk water, suspended solids, loose deposits, and pipe wall biofilm. Environ Sci Technol 2014; 48: pp. 5467-5476

Malaysian Ministry of Health (MMOH). National drinking water quality standard, Engineering Services Division, Ministry of Health, Malaysia. <http://kmam.moh.gov.my/public-user/drinking-water-quality-standard.html>; 2009


Learn More About Water Quality From These Websites:

Ministry of Health Malaysia- Mineral Water & Packaged Drinking Water

Quality of Water Resources in Malaysia

World Health Organization- Drinking Water

World Health Organization – Guidelines for Drinking Water Quality


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Topics: Wellness

Calvin Leong

Written by Calvin Leong

Calvin Leong holds a Master in Medical Education from the University of Dundee, United Kingdom. He is certified in Clinical Wound Care by the ASEAN Wound Care Association. Calvin has 20 years of clinical and lecturing experience focusing on Mentoring in Healthcare, Traumatology and Medical Sciences. Calvin is HRDC certified trainer. He is also a Life Member of The Malaysian Association for the Study of Pain (MASP) and the Malaysian Society of Wound Care Professionals (MSWCP).

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