ustxtxb_obs_2010_06_25_50_00016-00000_000.pdf

THE TEXAS WATER DEVELOPMENT BOARD’S GOAL IS TO REDUCE WATER CONSUMPTION TO 140 GALLONS PER PERSON, PER DAY. ARE CURRENTLY WITHIN THESE LIMITS CITIES THAT USE THE MOST WATER: CORPUS CHRISTI, DALLAS, HUNTSVILLE. IN 2008, THE TOP TEN WATER USERS IN THE CITY OF DALLAS COLLECTIVELY USED 60 MILLION GALLONS OF WATER fi READ the Elm Fork report c at txlo.com!elmfork VIEW a presentation on San Marcos water contaminants at tx1o.comlsanmarcos consists of effluent from Denton’s wastewater treatment plant. The stream then flows into Lake Lewisville, a drinking water supply for millions in Dallas-Fort Worth. The toilet-to-tap phenomenon is becoming more common as cities look to recycled wastewater to offset diminishing freshwater supplies. Dallas, like dozens of other cities in Texas and around the nation, has detected trace amounts of emerging contaminants in its water supplies. “You name the compound; somebody has probably found it in somebody’s water source or the effluent coming out of the [treatment plant],” says Charles Stringer, an assistant director of Dallas Water Utilities. The same holds for tap water. Unwittingly, Americans are drinking a cornucopia of chemicals albeit in tiny amountsthat in many cases we know little about. In the most comprehensive, peer-reviewed study to date, the Southern Nevada Water Authority tested the tap water of 15 utilities that collectively serve 28 million Americans. Thirteen had measurable levels of contaminants, including the anti-convulsant phenytoin, the pesticide atrazine and the insecticide DEET. Such reports have roused public concern and convinced the federal government to take a tentative step. In October, the EPA announced it’s considering pharmaceuticals for regulation under the Safe Drinking Water Act. In Texas, water utilities and elected officials are only beginning to grapple with the problem. A task force created by the Texas Legislature in 2009 is looking into ways to keep pharmaceuticals out of landfills and wastewater systems. On the local level, cities are not required by federal law to test wastewater or drinking water plants for emerging contaminants. Many choose not to, partly out of fear that the results will be misinterpreted. “If you say you’ve got aspirin in your water at one picogram per liter, somebody says, oh my god there’s aspirin in the water,” Stringer says. “The cities that are trying to be proactive and look at it are getting the hell beat out of them.” Dallas is proactive, Stringer says. In November, the U.S. Geological Survey published the results of extensive sampling in the Elm Fork of the Trinity River, a drinking water source for Dallas that is downstream from other cities’ discharges. The scientists also tested the water after it had been treated for people’s taps. The federal agency found that 38 of the 42 most frequently detected compounds in the river water including the pesticide atrazine, the gasoline addiinsecticide Diazinon, whose sale is illegal for nonagricultural purposesmade it into the tap water. While the concentrations didn’t exceed federal or state standards, the study notes that only half of the detected compounds have human-health benchmarks in those standards. The city of San Marcos commissioned Texas State University toxicologist Glenn Longley and one of his students to test surface water there for 23 emerging contaminantspharmaceuticals, fire retardants, fragrances, pesticides and others. While Longley found 18 chemicals in the water, only onebisphenol A, or BPA, the controversial plasticizer found in Nalgene bottlesmade it into the city’s tap water. Toxicologists have only just begun the difficult task of figuring out what effects these contaminants may have on human health. Most of these contaminants are not new Some have been “emerging” in the environment for decades. But the development of ultrasensitive instruments has now enabled scientists to detect the compounds at concentrations down to parts per trillion. It’s as if a powerful new telescope suddenly picked up a galaxy in a previously dark part of the skythe difference being that these chemicals hit uncomfortably close to home. Toxicologists have just begun the difficult task of figuring out what effects these contaminants might have on human health. A single contaminant might do nothing. But in combination with others, the effect could be enhanced, particularly for vulnerable groups like children or pregnant women. What sort of health effects arise from complex mixtures of chemicals in drinking water? No one knows. One challenge, among many, is that it’s difficult to perform toxicity tests for humans. “It’s not like on the aquatic side,” says Dana Kolpin, head of the U.S. Geological Survey’s Emerging Contaminants in the Environment Project. “We’re doing experiments with biologists where we’re exposing minnows or other organisms to, say, effluent or spike levels. You just can’t do that with humans.” Shane Snyder, a professor of environmental engineering at the University of Arizona and co-director of the Arizona Laboratory for Emerging Contaminants, says he’s been asked to brief a Congressional committee on this issue. It’s “very difficult” to do a risk assessment for mixtures, he says, especially when chemicals can simultaneously act on different pathways in the body. For example, one substance might damage the liver, while another present at the same time disrupts the endocrine system. “You could get a more profound effect [collectively] than from each one separately,” says Snyder. Snyder says there’s far more to learnand perhaps fearfrom what happens when emerging contaminants go through the treatment process. Some seem to disappear, but they could be subtly transformed into something more toxic by widely used disinfectants like chlorine. “In my mind there is no question that humans are exposed to more disinfection byproducts than any other contaminants through their drinking water,” Snyder says. “It concerns me as a scientist and a toxicologist that those classes of compounds are understudied.” About 20 percent of disinfection byproducts are regulated, Snyder says. Sixty percent haven’t even been identified. WHILE THE EFFECTS on humans remain mysterious, the ecological effects of water-borne chemicalseven at extremely low levelsis becoming well established. THE TEXAS OBSERVER WWW.TEXASOBSERVER.ORG