There is that milky stuff that your tap emits when you turn it on for water. It’s a water purifier called chlorine. Also used to disinfect other water sources such as the swimming pool, chlorine, in its true definition, is a poison.

It was used as a poison mustard gas in World War I and as a chemical weapon in the Iraq War. Chlorine is also the primary ingredient in bleach and in disinfectants. It is also used to make plastics, insecticides, and solvents for dry cleaning and metal degreasing.

So, what if that clear, clean-looking liquid you use every day – to quench your thirst, to bathe and shower in, and to wash your dishes and laundry in contributed to dozens of everyday ailments, including heart attacks in the long run, eye defects, sinus and throat irritation, low sperm count, childhood asthma...

Now relax. The concentration of chlorine in your tap water is too ‘dilute’ to be poisonous. However, if consumed in large quantities, such harms are possible. Worse still, one risks damaging hair cuticles and skin rashes.

But like Dr Frederick Fundi Gatare says, many drugs can also be a poison and kill yet we still use them as medicine. 

The medical director of Rutongo Hospital in Rulindo District says any drug taken in over dose can be harmful, but when taken in the right amount, there shouldn’t be a worry.

Yvette Carine Kasine, the head of water and quality control in the Energy Water and Sanitation Authority, says there is no relationship between residual chlorine concentration and water colour.

The dangers lurking in swimming pools 

Although there are restrictions on the levels of disinfectants permitted in tap water, there seems to be little or no regulation on the amount permitted in pool water. 

This poses a real threat to swimmers because, again, you absorb more through your skin and through inhalation than you do through your digestive tract. 

One particular study showed that the dose of chloroform, a specific trihalo-methanes, was 141 times higher than what you’d get from a 10-minute shower and 93 per cent higher than what you’d get from a glass of chlorinated tap water.

But, like Olivier Niyonkuru, a swimming pool attendant at Sanitas Hotel in Kigali, says, treatment of a pool is critical. 

"Chlorine is the best treatment used and when you use a lot, it’s not healthy, when you use little, it’s still not good since germs aren’t killed,” Niyonkuru says.

"The amount of chlorine used will show because of different effects like the amount of sunshine. When there is a lot of sun and hot temperatures, the chlorine quickly dissipates. The colour of the pool has nothing to do with the amount of chlorine that was put,” Niyonkuru says. 

However, the fact that several studies have shown that people who swim in or work around indoor pools have a much higher incidence of asthma is a cause for concern. Researchers in Belgium found that nitrogen trichloride (produced by chlorine) is a cause of occupational asthma in indoor swimming pool workers like lifeguards and swim instructors.

Trichloride is one of the byproducts that forms when chlorine mixes with an organic substance. In a swimming pool, that would most likely result from sweat, dander, urine, or other bodily substances. 

Niyonkuru also warns that when putting the chlorine the attendant is supposed to be careful as not to spill the chlorine on the poolside, as it can be harmful to users. 

"Chlorine is used in water treatment because the raw water from lakes, rivers and underground is usually contaminated by different microorganisms which can be harmful to humans. To avoid such, chlorine is used for water disinfection before its consumption or other uses like swimming,” Kasine said.

According to the Rwanda Bureau of Standards, drinking water quality chlorine must be in a range of 0.2 – 0.6 mg/L. Below 0.2mg/L, the water can be easily contaminated. Above 0.6 mg/L, both the odor and taste of the water could be harmful to human health.

Dr Rachna Pande, a specialist in internal medicine at Ruhengeri Hospital, while responding to a reader’s concern in the Healthy Times, said as per health regulations, chlorine used for disinfecting water is in amounts which would kill the germs but would be safe for human consumption. 

"The greatest risk comes from reaction of chlorine with other organic byproducts present in water. However, the World Health Organisation says the risk posed by these byproducts are too low to cause infections,” Dr Pande said.

Chlorinated water & science

According to the Mind and Health web site, chlorine, in high concentration or when consumed over a long period of time, has been proven to harden arteries, destroy proteins in the body, irrita has been proven to harden arteries, destroy proteins in the body, irritate the skin and sinuses, and aggravate asthma, allergies, and respiratory problems. 

But chlorine also has a number of byproducts, each of which carries its own list of side effects. Chloroform speeds the aging process and causes cholesterol to oxidize, and DCA (dichloro acidic acid) has been shown to cause liver cancer in lab animals.

A US Council of Environmental Quality study, the web site claims, states that cancer risk among people drinking chlorinated water is 93 per cent higher than among those whose water does not contain chlorine.

One of the main reasons why chlorine is so useful for so many different applications is because it so readily combines with other substances. 

The problem is, once it combines with other compounds—even if the compounds themselves are completely safe—the end results can form deadly toxins such as dioxin and PCBs, and carcinogens such as THMs (trihalo-methanes).

So, if you’re drinking tap water, you can be sure you’re gulping down these and other carcinogens by the glassful. But relying on bottled water or buying a filter for your faucet is not feasible in the long run. 

You do not only ingest it through the mouth. Harmful as chlorine can be when you absorb it through your digestive tract, it’s nothing compared to the toxic levels you absorb through inhalation. For instance, your shower is considered one of the most toxic place you can be in. The steam that is created when you take a hot shower is filled with chlorine that enters directly into your lungs.

Mind and Health web site argues that the mucous membranes of your bronchi, the breathing tubes that connect your larynx to your lungs, are highly absorbent of basic chemicals such as chlorine. 

Breathing it in provides a more direct portal for the substance to enter your bloodstream—which then spreads it thoughout the body.