Campus & Community

SPH analyzes area tap water

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Disinfection by-products in Mass. tap water ‘concerning,’ says epidemiologist

Environmental epidemiologists from the Harvard School of Public Health (SPH) analyzing tap water samples from 36 surface water systems throughout Massachusetts have found high levels of disinfection by-products (DBPs), which form during water treatment and transport, and a wide range of by-product activity in the water supplies they tested. The study appears in the February issue of Environmental Health Perspectives (

The DBPs analyzed in this study were MX (3-chloro-4 (dichloromethyl)-5-hydroxy-2(5H)-furanone) and total trihalomethanes (TTHM). MX concentrations in Massachusetts tap water were as high as levels previously reported in Finland, where similar research on MX and DBP levels is being conducted. Some one-third of the samples in the study exceeded the previous reported high in the United States of 33 nanograms per liter. And three water samples exceeded the levels that Finland had reported of 67 nanograms per liter. One sample in the study showed an MX concentration of 80 nanograms per liter.

Disinfection by-products are formed when organic and inorganic matter combine with disinfectants, such as chlorine, used to cleanse water supplies. Certain DBPs have been shown to be carcinogenic in animal studies. And toxicologic studies have shown the liver and kidneys to be targets. In laboratory rats MX has an estimated cancer potency 170 times greater than chloroform.

Using 88 tap water samples from 36 Massachusetts communities taken between spring 1997 and fall 1998, the researchers studied how the formation of DBPs are influenced by water treatment.

Within the communities in the study, 24 used chlorine to disinfect the water supply with 10 of those towns chlorinating their water twice prior to distribution. One town used ozone and another used chlorine dioxide for disinfection. The remaining 12 used chloramine to disinfect their water supply. The researchers found that chlora’Tmination and filtration resulted in greatly reduced MX levels and that water supplies that had been chlorinated multiple times prior to distribution were associated with higher MX and TTHM levels. Also noted in the findings is that MX and TTHM levels are generally higher in the spring compared with the fall season.

“This study and similar ones carried out by researchers in Finland point out what could be an important public health problem that has been largely ignored, measuring concentrations of carcinogenic by-products that are produced when drinking water supplies are disinfected,” said Joel Schwartz, associate professor of environmental epidemiology at SPH. “The results are concerning but not alarming; more research needs to be done, and we need to consider ways to disinfect the water supplies that will also reduce by-product formation and activity.”

The research was supported by the Kresge Center for Environmental Health.