Because some TTHMs are mutagenic, it is plausible that these compounds alter the DNA of gametes or otherwise initiate time-sensitive, lethal effects that manifest themselves as first trimester, spontaneous abortions or congenital defects. Animal toxicology studies and possibly in vitro experiments on embryonic animal cells in culture will be required to elucidate the specific ways in which TTHMs produce deadly effects. For now, it seems that the mechanism of TTHM havoc may be a chronic one in that daily exposure over a period of weeks rather than an acute incident is required for the association with miscarriage. The fact that most of the spontaneous abortions occurred by the eighth week of gestation, when the foundations of all major organ systems are present, suggests a critical period in organogenesis when one or more TTHMs are embryolethal. Obviously, chlorination disinfection of water will not be discontinued any time soon as a result of the studies linking tap water to first trimester miscarriage.
Chlorination is imperative to keep public water supplies free of most deadly pathogens.
Developing alternative methods of disinfection or techniques that reduce the production of chlorine byproducts continues to be the focus of long-range plans to improve water treatment processes. The February 1998 report by Waller et al., associating tap water and spontaneous abortion, has caused widespread public anxiety. In the absence of definitive facts about the reproductive risks of tap water, it seems prudent that pregnant women and others concerned about water quality should err on the side of caution by implementing preventative strategies to keep their water safe. First, patients should obtain information about TTHM content of tap water from the water board or similar agency in their area by asking for a complete water quality report. Pregnant women and those contemplating pregnancy should discuss local TTHM concentrations with their physicians and be counseled to make an educated choice about prophylactic strategies.