A new study says that people who drink too much water may be putting themselves at risk of developing waterborne illness.
But the risk is much lower than previously thought, researchers say.
New Scientist’s Nick Wilcox investigates.
The study, which was published in the journal Environmental Health Perspectives, looked at the risk of waterborne illnesses associated with drinking too much chlorinated water.
The researchers found that people with no history of severe illness were almost four times as likely to develop a waterborne infectious disease as those with a history of a severe illness.
Drinking too much chlorine may be the biggest factor in causing waterborne diseases, the study found.
People who drink more than six glasses of chlorinated drinking water a day have an average of 10 times the risk that people drinking less than three glasses a day, according to the study.
That compares with an average risk of about 5,000 infections per 100,000 people per year in the UK, the authors say.
People with anemia are particularly at risk, as they tend to have lower levels of red blood cells.
“People with reduced hemoglobin and anemia have a lower risk of disease-related illnesses, but if you have reduced hemolysis or anemia, your risk of getting a water-borne infectious infection is higher,” the study’s lead author, Dr Matthew Loehlin, told New Scientist.
“A low hemoglobin level is also associated with more frequent use of disinfectants and chlorination systems, which can lead to water-transmitted diseases.”
Dr Loeharlin said the study also looked at a number of factors that could be associated with the higher risk of illness.
“If you have low hemolytic anemia or low red blood cell count, for example, you may be more likely to get water-related infections, such as chlorhexidine-associated diarrhea,” he said.
The findings were based on data from around the world and included studies in the US, Australia, France, Canada and the Netherlands.
In the US and Australia, people who had low levels of iron were found to have a significantly higher risk than those with normal iron levels, according the study authors.
In Canada, people with low iron levels were found, among other things, to be more prone to developing water-associated diarrhoea and more likely than those who had high levels to develop diarrhoeas.
In both the US (and Australia) and Canada, high rates of chronic kidney disease were linked to low iron.
Dr Loxharlin says that if a person’s blood levels of both iron and hemoglobin are low, then it’s unlikely that they will be able to survive the effects of a water contaminated with the pathogens that cause waterborne infections.
But if a water with a high level of both the pathogens and the water disinfectant is used, then the risk can be substantially increased.
Dr Matthew Loxhatil, lead author of the study, told the New Scientist that there is currently no evidence that chlorhexidase-producing bacteria can produce chlorine dioxide, the main ingredient of chlorine disinfectants, which is the key ingredient in chlorine dioxide.
And in the EU, chlorine dioxide is not currently banned.
In fact, the European Commission has decided to allow it to be used in some circumstances, such a when treating disinfectants or when there are limited supplies of disinfectant.
But in the United States, chlorhexids were banned by the Environmental Protection Agency in 1997 and were banned in the rest of the world in 2001.
Dr Wilcox said that while chlorhexide-producing organisms are not present in the drinking water, they may be present in some water supplies.
There are no proven studies to show that chlorine dioxide has any harmful effects on people, he added.
“There’s not enough information to say definitively whether or not chlorhexides cause harm,” he told New Sider.
It’s important to remember that these are only estimates, and that these things are subject to change, he said, adding that the study could be adjusted in future if it proved that there was no health benefit to chlorhexida use.
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