Despite what people may think, Chlorine is actually a very important component in [drinking water disinfection](https://www.icis.com/resources/news/2010/06/28/9370375/chlorine-s-importance-in-water-treatment-set-to-grow/). Although it does not completely sterilize water, it does prevent dangerous bacteria from growing—think [legionella](https://www.cdc.gov/legionella/about/causes-transmission.html)—which can lead to illness and death. But surprisingly, when you smell or taste what seems like swimming pool water or bleach, it is often trihalomethanes (also known as THMs) and other [chlorine disinfection byproducts](https://www.cdc.gov/safewater/chlorination-byproducts.html).<br><br> 

<center>![Imgur](http://i.imgur.com/QQslDjx.jpg)</center><center><sup>Image by [gcardinal from Norway (Water drop, single)](http://creativecommons.org/licenses/by/2.0)</sup></center>

<h2>What are disinfection byproducts?</h2>
Disinfection byproducts form when the chlorine reacts with [total organic carbon (TOC)](https://cfpub.epa.gov/si/si_public_record_report.cfm?direntryid=63371) found in water sources. The best way to describe TOC is dirt, but specifically it is the carbon stored in soil's organic matter. It is comprised of decomposing plants and animals, root discharge, microorganisms, etc. [THMs](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1257669/) are the result of a reaction between the chlorine used for disinfecting water and the natural organic matter in the water. Exposure to elevated levels of THMs have been linked to cancer and gestation problems, but the danger stems from [inhaling or absorbing THMs through your skin,](http://gochemless.com/learning-center/microbiology/trihalomethanes/) not drinking water with THMs.<br><br> 
<center>![Imgur](http://i.imgur.com/aLYBX7h.png)</center><br><br>
Unfortunately, **ALL** drinking water regulations are based on consumption (drinking)--they do not take dermal or inhalation exposure into account. Yet we use our drinking water in so many ways: bathing, dishwashing, clothes washing, cooking, and cleaning, and so on. These chemicals volatize into the air from the water in our shower steam or appliances, essentially causing indoor air pollution. And just like they enter our bodies when swallowed, these chemicals can be absorbed by our skin and inhaled into our lungs. 
<h2>So what can you do?</h2>
Demand more from your water provider—it is their responsibility to clean the water properly like the regulations intend. As with any water related concern, you should always review your area's Consumer Confidence Report. Each year, your water supplier is required distribute the report to residents. You can access it [here](https://ofmpub.epa.gov/apex/safewater/f?p=ccr_wyl:102). If the TTHM levels are elevated, you should contact your drinking water utility and question whether their TOC reduction practices are adequate.