Chesapeake has a long history of water issues. When it became an independent city in 1963, it remained dependent on the surrounding cities for its water supply. In the mid-1970s, Chesapeake turned to the Northwest River as an alternative. Bordered by swampland and trees, the river water contains large amounts of organic materials such as leaves, twigs, and algae.
Like nearly every city in the country, Chesapeake adds chlorine to its water supply. Chlorine kills dangerous microbes that cause dysentery and cholera, but when chlorine mixes with organic materials, it also causes the formation of trihalomethanes (THMs), a toxic by-product that has been proven harmful at high levels. In 1979, the Environmental Protection Agency (EPA) attempted to balance the benefit with the risk by setting the amount of THMs allowed in public drinking-water supplies at 100 parts per billion (ppb). The Northwest River's high concentration of organic materials -- the levels fluctuate with the seasons and are especially high in the hotter months -- greatly increased the risk that the THMs in Chesapeake's water supply could spike above the EPA limit at different times throughout the year.
Problems started coming to light in 1998, when Chesapeake tore down two towers at its water-processing plant to make way for a new reverse-osmosis system. A construction proj-ect of this sort would more than likely cause a spike in THM levels, possibly beyond EPA limits, so the utility director asked the state's local health department to request a temporary waiver of EPA water-quality standards.
That was the first time Nancy Welch, M.D., the director of Chesapeake's health department, had ever heard of THMs. The utility director also gave Dr. Welch a copy of a study that had been published that year in the medical journal Epidemiology; it suggested a link between drinking tap water with a high level of THMs and an increased rate of miscarriage. The authors, California Department of Health Services researchers Shanna Swan, Ph.D., and Kirsten Waller, M.D., examined the records of 5,144 pregnant women and found that those in their first trimester who drank five or more glasses of tap water a day containing 75 ppb or more of THMs were 65 percent more likely to miscarry than women with low exposure. The EPA had been doing its own investigation into THM levels, and a year after the Swan-Waller study was released, it lowered the allowable amount from 100 ppb to 80 ppb.
After examining the records closely and speaking with colleagues, Dr. Welch was deeply concerned that the THM levels in Chesapeake's water were often above this limit, and she decided to go public. She sent an advisory -- to family practitioners, ob-gyns, internists, and the media -- suggesting that pregnant women should boil their tap water, install a tap filter, or drink bottled water. "It was a personal call, and I was focused on sharing information with the public," Dr. Welch says. "The idea of a lawsuit wasn't on my mind."