The Good and Bad of Chlorinated Water

My buddy, Catherine, asked me to check that if you just leave your tap water out will the chlorine off-gas from the water overnight thus be chlorine free by the time you drink it.  We were discussing the merits of filtering your drinking water along with chlorine and thyroid health.  So, I delved into what turned out to be a rather complex topic.

Here's a quote from an article from High Times:

'​It’s no longer enough to leave your tap water out for day to let the chlorine evaporate, because water is being treated with chloramine, which takes so long to evaporate that other methods of removal or neutralization are needed.
For a lot of reasons, chloramine sanitizes water more effectively than simple chlorine gas. In fact, chloramine’s slow evaporation rate is one of the reasons it’s used instead of chlorine. Taking this into account, gardeners and clean water lovers alike need other methods of removing this noxious compound.'

Okay, Here's a quote from ThoughtCo. about the merits of chlorine and it's dangers for human consumption:

Chlorine is a highly efficient disinfectant, and it is added to public water supplies to kill disease-causing bacteria that the water or its transport pipes might contain....But Harrison says that all this disinfecting has not come without a price: Chlorine introduced into the water supply reacts with other naturally-occurring elements to form toxins called trihalomethanes (THMs), which eventually make their way into our bodies. THMs have been linked to a wide range of human health maladies ranging from asthma and eczema to bladder cancer and heart disease. In addition, Dr. Peter Montague of the Environmental Research Foundation cites several studies linking moderate to heavy consumption of chlorinated tap water by pregnant women with higher miscarriage and birth defect rates.

Need more proof? Here's what the Canadian Cancer Society has to say about tap water and cancer.

For decades, researchers have studied the long-term effects of using chlorinated tap water. Most studies have shown that when people are exposed to chlorinated water over long periods of time, it slightly increases their risk of bladder cancer. Some studies have also found links to colorectal cancer, but we need more research to be sure of this link.
Several chlorination by-products are possible causes of cancer. Studies have shown that trihalomethanes (THMs) and haloacetic acids (HAAs), which are the most common chlorination by-products, can cause cancer in laboratory animals.

The Canadian Cancer Society recommends the following:

You may be able to reduce your exposure to chlorination by-products by: 

• using activated carbon filter systems in your water pitcher
• attaching a filter to your tap
• using devices that filter all the water in your house

However, levels of chlorination by-products may not be reduced by all types of products mentioned here. And you can still be exposed to by-products when you shower or swim in a pool treated with chlorine.
If you choose to use these types of products, make sure they are certified to National Sanitation Foundation (NSF) standards. Also change the filters according to the manufacturer’s instructions to avoid contamination from bacteria and other microbes.

Okay, so this has been my justification to using a water filter.  Right now I am using a Brita filter but see the importance of having a complete filtration system and avoiding chlorinated pools.  Hope this helps, Catherine.

References:
Sirius J., ​Grow Hack: How to Remove Chlorine From Tap Water, ​www.hightimes.com, February 12, 2015
​Larry West, Why is Chlorine Added to Tap Water,​ www.thoughtco.com, March 22, 2016
Here's the Link to the Cancer Article: ​http://www.cancer.ca/en/prevention-and-screening/be-aware/harmful-substances-and-environmental-risks/chlorinated-water/?region=on