|August 01, 2013|
Something in the air: how global warming is spreading toxic dust
|When Rose Eitmiller found a new house on Sweet Pea Lane in Dewey-Humboldt, Ariz., population 3,613, she felt at home. She was still mourning the death of a daughter whom she always called "Sweetpea," and the place seemed right to her.|
But that move in 2004 only brought more heartache for Eitmiller. Four years later, U.S. EPA dug up her front lawn in a successful search for arsenic, and Dewey-Humboldt soon became a Superfund site.
Now the town is one of several locations in the western United States that scientists say could become a major source of airborne arsenic poisoning due to global warming and breakneck human expansion.
"If arsenic's in the air, if all that stuff is in the air, there's really nothing you can do," Eitmiller said. "That's the sad thing, you really can do nothing once you're here, and I've been here going on nine years."
Arsenic ore is present throughout nature, and rainfall gradually washes arsenic particles through the soil into the groundwater, often in small enough amounts that are safe for humans to consume. Sometimes this natural concentration is augmented by man-made arsenic, usually from factories, smelters or mines.
Dewey-Humboldt, nestled in the heart of the Prescott Valley between Phoenix and Flagstaff, has both natural arsenic and deposits of the toxic chemical from a retired mine and a retired smelter. Scientists from the University of Arizona are testing to see how much is getting into the air.
As global warming means rain becomes less frequent in some areas, and soil and rocks dry up, scientists think much of the arsenic that should be leaching into the groundwater will instead be blown into the air.
"Here in Dewey-Humboldt," Eitmiller said, "we're not getting the rain that we used to get."
The expanding dangers of dust
The West is getting dustier. A recent study from the University of Colorado found that dust depositions have dramatically increased in the past 20 years, due to increased aridity, wind transport and human activities.
Clark Lantz, a University of Arizona professor researching arsenic in dust in Dewey-Humboldt, is looking specifically for how dangerous the arsenic in the town's dust might become. By studying the composition of the dust, he's hoping to determine how likely it would be for the arsenic fractions to break away from the dirt particles that they're riding on and create greater exposure and damage to the human body.
"As climate change occurs, I think there'll be areas where it becomes more arid, and if arsenic is part of the geologic landscape it could potentially become a problem," Lantz said.
Based on his preliminary research, Lantz thinks the highest exposure levels in Dewey-Humboldt are still from water. Airborne arsenic would be an "additional burden," he said. One of the most significant complications he noted was how airborne dust could affect human lungs via inhalation, since arsenic ingested in water only reaches the stomach.
If inhaled particles were small enough, they'd be able to slip through the lining of the lungs and enter the bloodstream.
The health effects from inhaling arsenic are still largely unknown. EPA has classified inorganic, or man-made, arsenic as a human carcinogen. Exposure to arsenic has been strongly linked to problems such as heart disease, hypertension, and bladder and lung cancer.
A recently study by scientists at Texas Tech University also found that safe levels of arsenic and estrogen, when combined, can double the risk of prostate cancer, raising the possibility that even "safe" levels of arsenic could become harmful when combined with other toxins in the environment.
Stirring things up
While the Southwest is getting dustier, it's also attracting more new residents than any other region in the country. Nevada, Arizona and Utah were the three fastest-growing states in the country according to the 2010 census. Scientists think this rapidly swelling human presence is also contributing to the rising dust problem.
The Nellis Dunes Recreation Area (NDRA) is one example of this expansion. The rocky, burnt-out orange landscape, 20 minutes from the Las Vegas strip, has been attracting increasing numbers of outdoor enthusiasts riding dirt bikes, dune buggies and all-terrain vehicles since it opened about 40 years ago. Last year the site saw around 300,000 visitors.
Researchers from the University of Nevada, Las Vegas, recently learned the NDRA also carries the highest levels of naturally occurring arsenic ever recorded on Earth. Brenda Buck, a soil geology professor at UNLV, she said she was "shocked" to see such high concentrations.
"There's no reason to think that area would be high in arsenic. There's no mining," she said.
"We're expanding into regions that weren't disturbed previously," she added. "And anytime you disturb them, that increases dust, especially in arid regions."
In her study, Buck compared arsenic levels from Owens Valley, a region in Southern California with notoriously poor air quality, to the NDRA. A study reported average arsenic concentrations of 40 parts per million in dust fractions smaller than 50 micrometers. In Nellis Dunes, arsenic concentrations hit 290 ppm for 10-micrometer dust fractions.
"My guess is if we started to measure dust in more areas, this area would not retain this record for long," Buck said.
Riders on the dunes could be exposed to coarse and finer particles, she said. Las Vegas residents would probably only have to worry about finer particles, in which Buck found the highest concentrations of arsenic, reaching them. "Which is bad," she said, "because it's the finer stuff that gets deeper in your lungs."
The health assessment was launched after a preliminary study found it took very low doses to produce signs of health effects. Buck will be testing the effects of arsenic on mice as well as on humans, asking volunteers to drive around the NDRA and then find out how much arsenic they ingest. She doesn't expect to have results for 12 to 18 months.
Gone with the wind
The emergence of dust and airborne contaminants poses a tougher containment challenge. As opposed to contaminants like arsenic in groundwater, which is easy to find, detect and contain, airborne particulates can travel thousands of miles, across state and international borders.
Experts say the only way to ensure containment and possible remediation of airborne contaminants is stopping them at the source.
J.C. Neff, a geologist at the University of Colorado who has studied the increase in dust emissions, said agriculture and mining are two of the easier sources to head off. But it's not always that easy. "On a larger scale, you can't pin it on one activity or another," he said, "which makes it difficult to say how we're going to address it."
The contaminants may be even harder to contain if no one is looking for them.
EPA regulates only industrial arsenic emissions, which would exclude the organic arsenic found at Nellis Dunes, which would qualify under geological emissions.
Furthermore, the Clean Air Act regulates only particulates smaller than 10 micrometers, more popularly known as PM 10.
"Those large particles overwhelm the concentration of smaller particles," Neff said, adding that larger particles lodge in the upper respiratory tract and could cause entirely different health problems.
Eitmiller, speaking on the phone, sighed as she sat on her back porch, gazing out at the mountains rising out of the windswept scrublands. "It truly is a beautiful place," she said. "I had no idea it was contaminated."
For now, the scientists are just happy the issue is beginning to get attention.
"I grew up on a cattle ranch," Buck said. "You see dust all the time, you don't think it's dangerous. People are just starting to get the message out that just because it's dirt doesn't mean it's safer."