Trihalomethanes: You Don’t Have Cholera (But You Might Still Have a Problem)

When was the last time you missed work because you had cholera?  Never, because for the last hundred years or so, U.S. water distribution systems have been disinfecting drinking water by adding chlorine.

Chlorine itself is a cheap and effective killer of bacteria and viruses which would otherwise find their way into our drinking water, which makes it one of the biggest public health breakthroughs of the 20th century.  It does, however, have a drawback- as chlorine disinfects, it breaks down as it comes into contact with other compounds in the water.

Things you can’t pronounce may still be bad for you:

The results of this breakdown are carcinogenic trihalomethanes (or “THMs”) and haloacetic acids (“HAA5”).  People exposed to high concentrations over long periods of time have an increased risk of cancer and liver, kidney, and nerve damage.  This danger has led the EPA to use its authority under the Safe Drinking Water Act to set “maximum contaminant levels” (commonly referred to as “MCLs”) for these compounds.

Rural water systems are more likely to have these issues with the Ohio EPA:

In Ohio, many rural water systems exceed their MCLs for these compounds and end up getting hit with EPA findings and orders to lower their levels.  Why rural systems?  Because the water has fewer end users and travels longer distances, the chlorine stays in the pipe longer and has more time to break down.

In response, rural systems tend to do at least one of four things- they 1. flush (dump water out at an end point to increase the volume of water moving through the system in order to get fresher water faster), 2. they aerate (which removes the THMs), 3. they treat with activated carbon (which removes both THMs and HAA5s), 4. they change their input system (e.g. the amount of chlorine used or location of its addition or the treatment method itself).

If you are a customer or operator of a rural water system, then at some point you are going to hear about chlorine disinfection byproducts.  It may not be as exciting or newsworthy as lead in Flint, Michigan’s water supply (by the way Flint also exceeded safe THM levels) but it’s certainly an ongoing challenge for water distribution systems in rural Ohio.

But hey- good news- at least you don’t have cholera.  So there’s that.

For some good summary guidance on the subject, the EPA’s fact sheet is below:

http://www.epa.state.oh.us/Portals/28/documents/pws/Byproductsfactsheet.pdf

-Posted by CCI