Tap water link to Philadelphia ailments posed Increased cloudiness suggested as indicator of microbial contamination


PHILADELPHIA -- A study of tap water in Philadelphia from 1989 to 1993 has linked small increases in cloudiness, or turbidity, to gastrointestinal infections that cause nausea, vomiting and diarrhea in children.

Heightened turbidity can indicate microbial contamination, and even though turbidity levels in Philadelphia never exceeded federal limits during the study, the researchers said their findings suggested that tap water might be the source of millions of cases of unexplained illness all over the nation that people now attribute to food poisoning or unknown causes.

Other scientists cautious

But other scientists said they took a cautious view of the study because it was one of the first to connect illness with small increases in turbidity and because the findings were based on a complex statistical analysis that is hard to interpret.

Dr. Bill MacKenzie, of the Division of Parasitic Diseases at the Centers for Disease Control and Prevention in Atlanta, said: "It's intriguing and concerning, but you have to recognize it's one study at one hospital in one city with several different water supplies. Whether the findings in other places would be similar is unclear, and I'd certainly want to see studies done elsewhere before any regulations were made based on this study."

MacKenzie also noted that increased turbidity did not always mean there were more germs in the water: Harmless particles such as silt can also make water cloudy. In addition, microbial contamination can sometimes develop without an increase in turbidity.

Nonetheless, the new study, which was conducted by researchers from the Harvard School of Public Health and the federal Environmental Protection Agency and published in a recent issue of the journal Epidemiology, comes at a time of increasing concern about the health risks that may be associated with turbidity.

In an action unrelated to the study, the EPA has published plans to tighten the standards for turbidity in many large public water ,, systems. By November 1998, the maximum allowable turbidity will be only 20 percent of what is permitted today, and there will be new requirements to monitor filtration plants and to remove a specific parasite, Cryptosporidium, from drinking water.

In the future, turbidity standards will be tightened even further, said Robert W. Perciasepe, the assistant administrator for water at the EPA. He said the agency, along with the CDC, would also conduct studies to determine how much waterborne illness occurred in the United States.

Milwaukee outbreak

The changes in turbidity standards were prompted by a Cryptosporidium outbreak caused by tap water in Milwaukee in 1993. The outbreak infected 403,000 people and killed 50 to 100, even though the water system was in compliance with federal guidelines at the time.

The water was filtered and disinfected with chlorine, but chlorine does not kill Cryptosporidium. And even though filtration is supposed to remove the parasite, it can invade drinking water if lTC the filtration system is not working properly.

"Milwaukee was a wake-up call," said Jeffrey Hass, chief of the drinking water branch of EPA Region 3 in Philadelphia.

Water supplies in the United States are not routinely tested for individual parasites, viruses or bacteria. Instead of testing, most water departments filter or chlorinate, or both, with the expectation that treatment will get rid of microbes.

The Philadelphia study was directed by Dr. Joel Schwartz, an associate professor of environmental epidemiology at the Harvard School of Public Health.

He and his colleagues collected daily turbidity measurements made by the Philadelphia Water Department for five years, 1989 through 1993, and compared those measurements with the number of emergency room visits and hospital admissions during that period for gastrointestinal illnesses at Children's Hospital of Philadelphia. They studied children because they are especially vulnerable to gastrointestinal infections.

The team found that when turbidity rose, so did hospital visits. Among children 3 years old and older, emergency room visits increased by 10 percent four days after turbidity, which was still extremely low, rose by 25 percent. (The turbidity was not visible to the eye.)

Among younger children, the number of such visits increased by 6 percent 10 days after turbidity rose. Admissions also increased in both age groups. The time lags may reflect the incubation periods of particular infections.

Ronnie Levin, an author of the study and a senior scientist with the EPA in Boston, said that the increases in hospital visits did not represent outbreaks of waterborne disease. Rather, she said, they indicated an increase in endemic level of illness in normal children, some of whom may have been more sensitive than others to what she described as "garden-variety bugs in the water."

Levin also said the results in Philadelphia were not cause for alarm or a mad rush to buy bottled water or expensive home filtration systems.

"Philadelphia has a good treatment system, and they run it well," she said. The water is safe for most people to drink, she said.

Schwartz said those who were worried about germs could boil their drinking water for one minute.

Leanne Nurse, a spokeswoman for the EPA in Philadelphia, said that even though the EPA helped finance the study and one of its authors is an EPA employee, the agency would not comment on it until other EPA scientists had reviewed the data.

Dr. Barbara Herwalt of the Division of Parasitic Diseases at the CDC said that the true extent of waterborne disease nationwide was unknown because the source of most gastrointestinal infections was never identified.

Pub Date: 12/21/97

Baltimore Sun Articles
Please note the green-lined linked article text has been applied commercially without any involvement from our newsroom editors, reporters or any other editorial staff.