Tap water disinfectants linked to birth defects.

Jul 02, 2012

Righi, E, P Bechtold, D Tortorici, P Lauriola, E Calzolari, G Astolfi, MJ Nieuwenhuijsen, G Fantuzzi and G Aggazzotti. 2012. Trihalomethanes, chlorite, chlorate in drinking water and risk of congenital anomalies: A population-based case-control study in Northern Italy. Environmental Research http://dx.doi.org/10.1016/j.envres.2012.04.014.

Synopsis by Beth Feingold

Babies whose mothers drank tap water that contained two disinfection byproducts were more likely to be born with cleft palate and spina bifida. The results are the first to show a link between exposures to the byproducts in early pregnancy and birth defects in infants.

The drinking water in northern Italy is potentially putting babies at risk for certain birth defects, reports a study published in the journal Environmental Research.

It's not the water per se, but exposure to the chemical byproducts that form from the disinfectants added to kill disease-causing microbes. The babies of mothers who drank the water during the first three months of pregnancy had increased risks for a host of anomalies, including renal defects, cleft palate and spina bifida.

This is the first study in which people investigated and found a relationship between exposure to the byproducts chlorite and chlorate in drinking water and increases in the risk of birth defects. The study is part of a larger project that is investigating long-term exposure to disinfection byproducts in drinking water.

Chemical disinfectants can create byproducts when they are added to drinking water. They form when the disinfectants interact with organic matter in the water. For example, trihalomethanes (THMs) are a byproduct of chlorine – the world's classic water disinfectant. THMs are linked to cancer and birth defects. The total amount of THMs in tap water is regulated in the United States, Europe and other countries with treated water systems.

The Emilia Romagna region of northern Italy treats drinking water with two other disinfectants, either alone or in tandem: chlorine dioxide and sodium hypochlorite. The chemical byproducts (DBPs) produced from these disinfectants can include chlorite, chlorate and chloride ions.

The effects DBPs have on public health are largely unknown because assessing their health effects is difficult. People are largely exposed to DBPs through drinking tap water, breathing them during a bath or shower and engaging in other water activities like swimming in treated pools.

Chlorite is regulated and has been linked to blood problems in animal toxicology studies. Animal studies suggest chloride ions and chlorate have potential health effects, including impaired neurological development and thyroid function and delays in female sexual development.

In this study, researchers examined the link between eight classes of birth defects and the mother's exposure during the first trimester of pregnancy to THMs, chlorite and chlorate in drinking water. They compared 6,134 babies born with congenital anomalies (gathered from the Regional Malformation Registry) to babies born without abnormalities (gathered from the country’s Regional Birth Register) in the region of Emilia Romagna, Italy. They determined the water authority that had delivered the water to the mother's residence during her first months of pregnancy, then estimated her exposure to DBPs using data from 222 local water authorities that measure chlorate voluntarily and THMs and chlorine as required to meet regulatory standards.

Italy's limit for chlorite is 700 micrograms per liter (μg/L) of water. In this study, 3.4 percent of women were expected to have been exposed to levels exceeding that level during their first trimester. Statistically, these women appear to have more than 3 times the odds of giving birth to newborns with renal defects, and nearly 7 times the odds of having a baby with abdominal wall defects.

Since Italy does not regulate chlorate, local authorities set the high exposure level as anything greater than 200 μg/L. Expectant mothers in the higher chlorate exposure group had 9.6 times the risk of having a baby with cleft palate as compared to mothers in the low exposure group. Their babies also had nearly 5 times the risk of spina bifida and nearly 3 times the risk of obstructive urinary defects.

These associations with chlorite and chlorate took into account several factors, including the mother’s age, previous abortions, single or multiple birth, whether the parents were related, and the city's socioeconomic condition.

Due to the small numbers of cases in each of the eight categories, larger studies will be needed to confirm the associations reported in this study. Additionally, since it was a retrospective study and the DBP values were not measured directly, there may be instances in which women were placed in incorrect exposure groups.

As alternative disinfection methods to chlorine – like chlorine dioxide – gain more use in Europe and North America, cities will need to consider and protect the public from the potentially detrimental effects of under-regulated byproducts like chlorate and chlorite. The results from this human study will guide future studies.

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