Air Date: Week of February 13, 1998
Researchers suggest that Californians should boil or filter tap water, or use reliable bottled water. Based on a study of 5,000 pregnant women there just published in the journal Epidemiology, pregnant women who drink a lot of tap water could be at increased risk for miscarriage if the water contained high levels of chlorine by-products called tri-halo-methanes. Dr. Shanna (Shawn-ah) Swan co-authored the study. From her office at the California Department of Health Services in Emeryville, California she spoke with Steve Curwood. Swan says women who consume more than 5 -eight ounce glasses of tap water a day had the highest risk of miscarriage.
CURWOOD: This is Living on Earth. I'm Steve Curwood. Know your local water supply. That seems to be the message from some new research in California. A study of 5,000 pregnant women there, just published in the journal Epidemiology, found that pregnant women who drink a lot of tap water could be at increased risk for miscarriage. Dr. Shanna Swan coauthored the study. We spoke to her in her office at the California Department of Health Services in Emeryville, California. She says women who consume more than 5 8-ounce glasses of tap water a day had the highest risk of miscarriage if the water contained high levels of chlorine byproducts called trihalomethanes.
SWAN: It was increased from 9 and a half percent to about 16%. That's an 80% increase.
CURWOOD: That's getting on the scale of almost twice as many.
SWAN: That's close to twice as many. Right.
CURWOOD: Why do you suspect the trihalomethanes?
SWAN: Well, there have been a number of studies suggesting that trihalomethanes affect reproductive risk. These studies were conducted both in humans and in animals. There have been studies on increased risks of miscarriage; a small study of birth defects, particularly neural tube defects; low birth weight; and prematurity. So, it was a natural question to ask.
CURWOOD: Now, the reason people put chlorine in municipal drinking water supplies is to try to get rid of contaminants, particularly bacterial contaminants. And if water utilities were to cut their use of chlorine, wouldn't there be an increased risk of contamination making it into people's drinking water?
SWAN: Yes, that is an important concern. And I think the overriding message that people should remember is that chlorine is in there for a very good reason. And it has prevented a great deal of disease and death, possibly. However, we're not sure that the amount that's allowed in there now is absolutely necessary for health. And that's the kind of deliberation that EPA is undergoing now, with their consideration of down-regulating trihalomethanes.
CURWOOD: What levels do you consider to be too high of trihalomethanes?
SWAN: In our study, the cutoff for a high was 75 micrograms per liter. That is lower than either the current standard or the proposed standard.
CURWOOD: Which is the regulation? One hundred micrograms per liter.
SWAN: Right, current regulation.
CURWOOD: And what is the proposed level of notification?
SWAN: The proposed level is 80, but it's also based on an annual average as well as a system-wide average.
CURWOOD: And where would you put the level at right now, based on the research that you've seen?
SWAN: I don't think that based on one study alone, you know, we can recommend changing the levels.
CURWOOD: How can one find out if one has high exposure to these chemicals?
SWAN: You can ask your utility. They will tell you, and for many utilities it will be on your bill or on your annual statement.
CURWOOD: And if you do have high exposure to these, is there anything that someone at home can do?
SWAN: Well, there are 4 options which they might consider. The first thing to remember, though, is that it's important for pregnant women to drink lots of water. So whatever you do, don't stop drinking water. The 4 options are to let the water stand in the refrigerator, although this is somewhat controversial; to boil the water before drinking it for one minute, but that's kind of cumbersome; to use an activated carbon filter, being sure to use an approved filter and service it regularly; or you could drink bottled water, remembering that bottled water is not guaranteed to be safer than tap water, and will vary from area to area.
CURWOOD: Shanna Swan is chief of the Reproductive Epidemiology Section of the California Department of Health Services. Thanks so much for speaking with us.
SWAN: Thank you, Steve.
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