Monday, April 21, 2008 | 2 a.m.
The fish in Las Vegas Bay look healthy on the outside, but it’s what’s inside that matters.
For more than a decade scientists have found that some fish in the bay and in the Las Vegas Wash, where treated wastewater is released back into Lake Mead, have mutated reproductive systems and different hormone levels than fish in other parts of the lake.
Now scientists are trying to determine whether those differences are the result of long-term exposure to releases of hundreds of millions of gallons each week of wastewater that contains trace amounts of hormones such as estrogen, as well as other chemicals and pharmaceuticals. Local water and wastewater managers are teaming up with federal agencies on a $1 million, two-year experiment that will test the effects of different kinds of wastewater on the reproductive systems of fathead minnows.
Starting this summer, scientists will raise generations of the minnows, stand-ins for the endangered razorback sucker and other native fish, in tanks at Clark County’s wastewater treatment plant on Flamingo Road. They’ll expose the little bait fish to the effluent that runs down the Las Vegas Wash into Lake Mead every day.
The goal is to see whether the wastewater — as opposed to ground water contaminated by local industry, chemicals in runoff, temperature differences or other factors — causes changes in the fish.
“When we look at the health of fish in the lake, you never know exactly what caused them (the changes) because they occurred over so many years,” said Lynn Orphan, regional water quality manager for the Clean Water Coalition, one of the participating agencies. She added that it is important to “invest time and money into making sure our water is as clean as we can make it.”
Scientists also hope to test whether new wastewater treatment techniques, including the use of ozone and special filters, lessen or eliminate the effects on fish.
In addition to the potential to improve the bay, wash and lake for fish, the study could also benefit humans. If the study helps scientists find new ways to improve water quality in Lake Mead, it would improve Las Vegas’ drinking water supply and recreation and fishing opportunities, as well as conditions for other wildlife, said representatives of several of the agencies involved.
There are no health warnings about consuming fish from Lake Mead, nor restrictions on fishing near the wash, according to the state and the National Park Service. There are, however, signs warning that the water in the wash is treated effluent.
A spokesman for the water authority, J.C. Davis, said a study of the effects on human health of the presence of tiny concentrations of chemicals from wastewater in Las Vegas’ drinking water is being peer reviewed.
“There is no indication based on existing science that these pose any threat to human health,” Davis said, adding that the authority will continue to study the issue.
Participating in the study are the Southern Nevada Water Authority, which represents water providers throughout the county; the Clark County Water Reclamation District, which operates wastewater treatment plants; the Clean Water Coalition, whose members include Clark County and three other valley water reclamation districts; the U.S. Fish and Wildlife Service; and the U.S. Geological Survey.
“Everyone has one common goal: the protection of Lake Mead and the best use of public dollars,” said Shane Snyder, research and development project manager for the water authority.
Orphan said her organization will contribute more than $300,000 toward the cost of the $1 million study. Erik Orsak, an environmental contaminants specialist with U.S. Fish and Wildlife, said his agency will contribute another $350,000. The rest of the cost will be covered with money from the Southern Nevada Public Lands Management Act, which allowed for the sale of public lands around Las Vegas. The water authority and the reclamation district will provide staff and the facilities for the testing.
Results from the study aren’t expected for at least two years. Xin Deng, who will receive his doctorate from the University of California this spring and did similar work at UC Riverside and UC Davis, was hired by the U.S. Geological Survey. He is scheduled to arrive in Las Vegas in early May, when construction will begin on tanks and other testing facilities at the wastewater treatment plant. The lab is expected to be complete by June or July, when testing will begin. Deng will conduct much of the analysis at Texas Tech University in Lubbock.
During the experiment, minnows will be exposed to a variety of wastewater and drinking water mixtures to see whether changes in their reproductive systems are more common when concentrations of wastewater are higher. Concentrations of wastewater are higher in the wash and bay than in the rest of the lake.
The fish will be exposed to regular tap water, tap water with estrogen or other chemicals added, the wastewater that runs into the wash and wastewater that has been treated with cutting-edge technology. Then scientists will compare which fish are healthier and whether one type of water causes more mutations in the fish’s reproductive systems. And because the fathead minnow reproduces very quickly, they will be able to observe several generations of the fish and whether those mutations increase over time.
The study will gauge the effects of the new, super-treated wastewater on the fish’s reproductive system. The plant, as part of a separate pilot project, will install the expensive equipment needed to perform the extra treatment this summer. Water officials have tested the technology on a small scale, but this pilot will test the technology with the full flows of the facility, more than 80 million gallons a day. Wastewater managers hope the extra treatments will reduce the amounts of contaminants, such as pharmaceuticals, that remain in the water after it has been treated.
The minnow tests will run for about a year so scientists can see whether the effects of exposure to wastewater are different in winter than in summer. During the summer, bacteria designed to consume contaminants in the water are more effective, which might effect the results, according to Doug Drury, deputy general manager of operations for Clark County Water Reclamation District.
Although Orsak, of U.S. Fish and Wildlife, didn’t want to make assumptions about what the study will find, he said it’s no secret that emerging pollutants, including estrogen from pharmaceuticals such as birth control pills, which are increasingly being studied worldwide, cause reproductive changes in fish.
The Southern Nevada Water Authority’s research and development project manager, on the other hand, said he’s not so sure the tests will show that contaminants in wastewater are responsible for changes in fish. Maybe the culprit is temperature or other sources of pollution, Snyder said.
Orsak said scientists have found male fish in the wild with elevated levels of a vitellogenin, a hormone typically found in large amounts only in female fish and necessary to produce egg protein. The wild fish also had higher-than-normal levels of estrogen in their blood.
In lab tests, scientists will check that fish are developing normal secondary sex characteristics, the fish equivalents of teenage boys’ facial and underarm hair — fatty tissue on their heads, which indicate a change to adulthood. They will also look for the vitellogenin.
The idea for the study surfaced when the Clean Water Coalition was undergoing an environmental review for a planned pipeline that would disperse some of the valley’s treated wastewater into the lake without sending it through the wash. The pipeline is designed to allow wastewater to better mix with the rest of the water in Lake Mead. The environmental review was approved in 2007.
But this isn’t the first study that’s been done on the fish in Lake Mead. In the mid-1990s, a USGS study found that fish in Lake Mead near the wash had greater incidence of hormonal and reproductive abnormalities than fish in other parts of the lake. The studies were replicated in 1999 and 2000, when scientists sampled fish in different seasons to see changes in hormone levels changed during spawning times.
USGS and U.S. Fish and Wildlife also collected fish in 2006 and 2007 to do additional studies. But the 2008 study will be the first to use fish raised in a controlled lab setting, rather than the complicated ecosystem in Lake Mead.
When studying fish in the wild, “we can only make inferences about what the causes (of reproductive changes) might be,” said Dr. Reynaldo Patiño, a professor at the USGS Texas Cooperative Fish and Wildlife Research Unit of Texas Tech. “It is far easier to determine cause-effect relationships in controlled laboratory studies than it is in field studies.”
But Snyder said it will be important to continue to monitor fish the in lake, including the razorback sucker, because the study is interpreting data gleaned from work with a different species, fathead minnows.
Still, it’s important to use the minnow rather than the threatened species.
“Being endangered, you don’t want to kill any of them,” Drury said. “The process is to see (whether there are) negative impacts, and if there are there will be dead fish.”