Angry Toxicologist

Tap Water’s Low Blow?

Most cities and towns use chlorine or bromine to disinfect water. When the water is polluted, chlorine or bromine reacts with the pollution (agricultural runoff is probably a bigger problem here than traditional industrial pollution) to create what are called disinfection by-products (DBPs). DBPs are associated in humans with adverse pregnancy outcomes (usually miscarriage)*. Since DBPs damage DNA and are considered carcinogens at some level, researchers thought that it was likely that DBPs would affect sperm as well. Rodent studies show that some DBPs do harm sperm quality; however, there hasn’t been a human study on sperm quality in response to DBP exposure.
A study published recently in Environmental Health Perspectives looked at 228 men who were in a study of couples to look at DBP-induced spontaneous abortion. They were grouped into three levels of exposure: 1) low DBPs, 2) low brominated but moderate chlorinated DBPs, and 3) low chlorinated but moderate brominated DBPs. Moderate meant that the DBP levels were close to the EPA limits.

What the study found is quite surprising. No adverse effect was found for the different DBPs; in fact, there were higher sperm counts at the high exposures with no change in quality. There was a decrease in sperm count associated with the total DBP levels but there was no change in sperm quality which would be expected if there were a toxic effect on the sperm.

Caveats: The study was on people that haven’t been shown to have reproductive problems. A small decrease in sperm count would be more serious to someone with low counts already. Also, it’s not clear what might happen over the limits.

AT’s conclusion: Hey, toxicologists aren’t always the bearers of bad news! Women, drink purified water while pregnant or trying to get pregnant**; men who are trying, drink any water you want, unless it’s after the heavy fertilizing in the spring when many DBPs go over EPA limits (many water testers know when this is coming so they test around it. You can’t totally rely on the water report you get).

*Don’t blame your water provider for DBPs. They have to disinfect the water so you don’t get violently ill and are saddled with polluted water they can’t really control (Rock<->Water Provider<->Hard Place). It’s the upstream pollution that needs to be fixed. This is why NYC has such great water; for over a centruy NYC has protected it’s source water, and this saves it large money too. Clean water with lower costs? I wish all cities had that vision.

** When I say purified water I don’t mean bottled spring water or distilled water or purified by Britta filters or any of that stuff. I mean the 1 or 2.5 gallon jugs labeled “drinking water”. It’s usually purified by reverse osmosis (which is the best way to do it), and it’s the cheapest water you can buy at the store (usually can be found as a generic brand). Britta will get out a lot of DBPs but there’s a lot of junk it doesn’t get out. Most bottled water (Aquafina, Poland Spring,…ETC) is just some other place’s tap water.


  1. #1 speedwell
    August 14, 2007

    The Whole Foods Market near us has a bottle-refilling machine that does produce reverse-osmosis water. So long as you keep your bottles scrupulously clean, this might be an option for you.

  2. #2 John
    August 14, 2007

    Aquafina’s website says that it is filtered through reverse osmosis. I thought almost all of the non-spring waters were filtered that way.

  3. #3 Wilfred
    August 14, 2007

    Okay, this is probably a weird question, but why don’t you use ozone or filters to clean the water?

  4. #4 angrytoxicologist
    August 14, 2007

    John, thanks for letting me know about Aquafina. Any RO treated water is great. I’d stay away from the fill ’em yourself stations. Glacier water stations have been found to have gotten over EPA limits for various things from time to time (about 33% of the time back in 2002 or so). Their website says their water is RO filtered; I’m not sure if this is a change from before or not. I’d stick to the cheap generic jugs, but that’s just me.

    Some places do. Why doesn’t everyone: $$. It’s actually MUCH more cost effective to put in place upstream pollution prevention measures than trying to filter the junk out (we’re talking millions of dollars for a mid-size water system). Why don’t we do it? Pollution prevention is very unpopular with legislators (the ag lobby is very powerful and doesn’t want the state telling them they need buffer zones around waterways, or how to use their fertilizer). See: PA/MD/VA problems with cleaning up the Chesapeake. Everyone knows what to do, but know one wants to do it, really.

  5. #5 wildcardjack
    August 15, 2007

    My local water supply (Tyler, Tx) tastes really good. One of the lakes they draw from develops an algae problem in the summer so they don’t draw from it under normal circumstances in the summer. This is a flavor issue. And possibly a run off issue from the onion and tomato farms the area is noted for.

    I don’t like buying bottled water for the wasteful use of plastic, but recently I have bought a case. I figured it was the easiest way to get 24 half liter bottles that I could keep refilling until I take a bottle with me one day and pitch it somewhere.

  6. #6 Sandra Porter
    August 15, 2007

    Oh Wildcardjack,

    I bet you’re drinking geosmin!

  7. #7 davidp
    August 16, 2007


    Ozone and U.V. systems disinfect the water at the treatment plant but microorganisms growing in the pipes can re-infect the water as it flows through the pipes. Adding Chlorine keeps the water disinfected all the way to the consumer’s tap. That’s the explanation given to my wife’s mother when they debated what treatment to put into her rural Australian town’s water supply.

    Generally the water is filtered pretty intensively before chlorination to reduce the production of organic disinfection by-products and reduce the level of chlorination required. I don’t think normal filtering can exclude all pathogens or dissolved contaminants, such as dissolved fertilizer.

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