Materials and Public Health
by Geotimes Staff
Earth resources are the foundation of modern civilization, crucial to almost every facet of our lives. And yet we know that some geologic materials pose significant health risks that jeopardize individuals, communities and even whole populations. In some instances, people are exposed when they move into areas with high concentrations of these materials, such as when houses are built above uranium-rich rock units that produce radon gas. More often, exposure is the unintended consequence of mining and other human activities that release geologic materials into the surface environment.
In this feature, our writers take a look at the current status of five well-known Earth materials that regulatory agencies, such as the U.S. Environmental Protection Agency, have identified as significant health risks: arsenic, asbestos, mercury, silica and radon. Most of these materials have been the subject of public health scares in the past, and several have been in recent headlines. News reports warned of possible risks to rescue workers at the World Trade Center site due to high asbestos levels in the dust. Arsenic was front-page news when President Bush considered changes to drinking-water standards adopted in the final days of the Clinton administration. In the case of crystalline silica, some readers may be surprised to learn that efforts are underway to develop stricter regulation of the second most abundant element in the crust!
Many geoscientists are actively engaged in mitigating the health impacts of these and other geologic materials by identifying exposure pathways, mapping geographic distribution, monitoring water and soil concentrations and identifying natural background levels in areas where remediation is being undertaken. Despite these efforts, collaborations with the public health community have been limited. But that may be changing. The recently announced partnership between the U.S. Geological Survey and the National Institute of Environmental Health Sciences may open the door to greater collaboration between geoscientists, epidemiologists and other scientists working to protect public health.
Asbestos in Libby, Montana
Yell "Fire!" in a movie theater and you'll clear out the room in seconds. Yell "Asbestos!" and the theater will clear out almost as fast. Asbestos is a well-known and highly publicized threat to human health and is perhaps the most devastating occupational hazard in U.S. history. But policy-makers, geologists and public health organizations don't agree on the risks asbestos poses to the general public.
Asbestos is controversial because of its many tiny fibers. If these fibers shed out from asbestos-containing materials they create an airborne dust, which when inhaled can penetrate lung tissue and cause asbestosis, mesothelioma and lung cancer. The U.S. Occupational Safety and Health Administration (OSHA) and Environmental Protection Agency (EPA) make no distinction between the two kinds of asbestos - chrysotile and amphibole - though geologists and some public health experts who say that chrysotile's cylindrical fibers are less damaging to the lungs than the splintery fibers of amphibole minerals.
The term asbestos describes a variety of fibrous, nonflammable minerals with flexibility and high tensile strength. Their unique properties were used mostly between the 1940s and 1970s in fireproof insulation, vinyl flooring, pipe insulation, ceiling tiles, brake linings and roof coatings. Chrysotile, a serpentine mineral, is also known as "white asbestos" and makes up about 95 percent of asbestos found in buildings in the United States. The other asbestos minerals - crocidolite, amosite, anthophyllite, tremolite and actinolite - are amphiboles that aren't commonly used in commercial products.
OSHA began regulating workplace asbestos in 1970, around the time when miners and construction workers, who worked with the fibrous material, began reporting serious lung disease. At that time, the United States used about 800,000 metric tons of asbestos per year. OSHA published the Asbestos Standard for the Construction Industry, which outlined four categories of asbestos contamination, and specified precautions and disposal techniques for each class. For instance, if asbestos insulation is removed (Class 1), contractors and supervisors trained in asbestos removal must be onsite wearing respirators and protective clothing.
In the late 1970s and early 1980s, EPA followed suit by banning any new uses for asbestos, designating it a class A human carcinogen (on par with secondhand cigarette smoke) and drafting the Asbestos Hazard Emergency Response Act (AHERA). In 1986, President Reagan signed the Act, which also put into effect the Toxic Substances Control Act, requiring all public and private schools to survey their structures for asbestos and implement an "appropriate response action."
Ironically, ridding a building
of asbestos can make the air inside more hazardous than before. When asbestos
materials are torn out from walls, ceilings and between pipes, asbestos
dust contaminates the air. Had the asbestos materials not been touched
in the first place, the fibers would remain harmlessly contained in the
ceiling tiles of the insulation.
Responding to EPA and OSHA regulations, worried schools districts and homeowners spent billions ripping asbestos products out of their buildings. In 1999, removing asbestos materials in the United States cost about $3 billion. Throughout the 1990s, New York City schools alone spent more than $100 million on asbestos removal.
"Asbestos abatement is pretty much a fiasco," Tim Flood, an epidemiologist at the Arizona Health Department, told USA Today in 1999. "It's hard to think of a worse investment. Many more lives would be saved if the money were spent on drug prevention, guardrails, sunscreen, medical research, almost anything really."
Asbestos legislation continues to evolve as does research on the suite of asbestos minerals. EPA's response to asbestos has changed markedly over the years. In 1983 the agency's asbestos handbook stated that removing the material is always appropriate, while their 1990 handbook acknowledged that asbestos removal may cause more contamination than leaving it in place. Now, according to its Web site, "EPA's advice on asbestos is neither to rip it all out in a panic nor to ignore the problem under a false presumption that asbestos is risk free … asbestos material in buildings should be located [and] it should be appropriately managed."
At this year's EPA Asbestos Health Effects Conference in Oakland, Calif., scientists discussed asbestos fiber testing techniques, carcinogenic effects and mineral classification. But in terms of dealing with instances of asbestos contamination such as in Libby, Mont., "the conference was disappointing," says Aubrey Miller, a doctor working with patients sick with amphibole asbestos-caused disease. "A situation like this demands the best, most progressive thinking to understand the health problems we're seeing - the old rules don't apply here."
in Libby, Montana
In Libby, Mont., residents have been dealing with a different kind of asbestos fiasco. Their families and community have been profoundly affected by amphibole asbestos from a vermiculite mine in the town. From 1963 to 1990, W.R. Grace and Co. mined vermiculite in Libby to make a home insulation material called Zonolite. The asbestos-laced vermiculite was transported to a plant in northeast Minneapolis to be processed. Now, communities in both Montana and Minnesota report that hundreds of their residents are stricken with asbestos-related diseases.
EPA testing of indoor air, dust, insulation, and yard and garden soil from 35 homes in Libby found evidence of tremolite (also classified as richterite) asbestos. When medically screened, 18 percent of individuals who lived, worked or played in Libby for at least six months prior to 1990 had lung abnormalities indicative of asbestosis. Of W.R. Grace employees, the figure was 49 percent. "We know tremolite causes illness," says Aubrey Miller, a doctor working jointly with Libby and the EPA. "And in Libby we're seeing illness in people who never worked at the mine, which is something new." Libby is currently under consideration for Superfund status by the EPA. In northeast Minneapolis, the Zonolite plant that processed Libby's vermiculite provided piles of free "stoner rock" (waste vermiculite rich in asbestos) for the public. Nearby residents used the "rock" as fill in gardens, sandboxes, lawns and driveways until this March, when EPA tests found that the rocks contained dangerous levels of tremolite. So far, 24 employees of the processing plant, formerly owned by Western Mineral Products Co., have died from asbestos-related diseases. One man, who never worked in Libby or at the Minneapolis processing plant, but remembered playing in piles of "stoner rock" as a child, died from asbestosis at the age of 42.
Minnesota's Department of Health is currently conducting an extensive survey of about 1,700 Minneapolis residents to determine rates of asbestos illness, exposure and home contamination. The department is also publicizing the causes of asbestos illnesses at public meetings. "We want to identify who's been exposed and give them information on clinics, diagnosis and health insurance," says Rita Messing of the Minnesota Department of Health.
Public outcry over the dangers of radon in the home began in 1984 after a young family man and engineer set off the national alarm. It was an accident. While leaving work at the Limerick, Pa., nuclear power plant, Stanley Watras walked through a newly installed radiation detector and shocked the checkpoint officials. Watras was the only person contaminated. He even set off alarms coming in to work. When his home was checked for radiation, the safety officials found radon measuring 650 times the average level.
In New York and in Sweden, energy-efficient homes had been cropping up with excessive radon, because, it was thought, insulation to make homes less "leaky" was trapping the natural gas. Radon was a known health hazard produced by the decay of uranium in the bedrock, but it was considered more of an issue for miners and homes with little ventilation. With Watras' home a prime example, suddenly radon became a problem anyone might already have without knowing it, leaky house or not.
In 1879, 21 years before Friedrich Dorn discovered radon, miners in the Erz Mountains of Czechoslovakia were dying from respiratory diseases attributed to dust exposure. As radioactivity became better understood, studies focused on uranium miners. Uranium and thorium have half-lives of billions of years and as they decay they create radium, which decays to form radon gas. The half-life of radon is only 3.8 days. But during radon's short decay to a stable lead isotope, the gas produces four alpha particles. A sheet of paper can stop an alpha particle with only molecular damage to the paper. When inhaled, those alpha particles hitchhike on dust and smoke and deliver their minor attacks as they stick to the cell walls of the lungs. The high rate of lung cancer among miners was linked to a one-two combination of accumulative radon exposure and cigarette smoking.
While most homes don't have radon levels nearly as high as mines, the Environmental Protection Agency estimated that almost one-third of the lung cancer deaths in 1995 among people in the United States who never smoked may have been linked to long-term exposure to high levels of indoor radon. All rocks and soils have uranium - some more than others. The amount of radon transmitted through the foundation into low-pressure regions of a house or office depends on how much radon is produced in the rocks, how much of the gas escapes into pore spaces, and how permeable the soil is around the building. The U.S Geological Survey has mapped potential areas of high radon across regions of the United States, Puerto Rico and Guam.
The EPA and the Office of the Surgeon General recommend that all houses be tested for radon. If radon levels of more than 4 picocuries per liter of air are found, action should be taken to confirm the tests. The building may need to have vents installed that will redirect the radon back outside.
Now, 16 years after the Watras case, homeowners are more savvy. Many are testing their homes before selling them to prevent lawsuits from the new owners. Short-term radon kits can cost as little as $10. But radon tests are not ubiquitous. In This summer, after an employee in Lyme, N.H., was diagnosed with lung cancer in May, tests showed that the town offices had high levels of radon gas. Despite our current understanding of the health hazard, radon is still a problem.
More recently, scientists have shifted the question of radon to how much of the natural gas poses a risk in groundwater supplies and drinking water. Agitating the water through the use of laundry or showers can allow a small amount of radon gas to escape into the air. The risk from water supplies, however, is small compared to the primary health threat of radon entering households through soil. For more information on indoor radon, visit www.epa.gov/iaq/radon/. The 1999 Risk Assessment of Radon in Drinking Water can be found at www.nap.edu/catalog/6287.html?onpi_newsdoc091598.
The ancients called it quicksilver for its color and the way it flowed like a liquid. It was later named after the Roman messenger god who flew through the sky. Both names were apt, for mercury is the only metal that exists as a liquid at room temperature and the only one that effortlessly volatilizes into the atmosphere.
Mercury is poisonous, however, and its mobility, coupled with its persistence, makes it one of the most challenging toxic substances to control.
Mercury is found in minerals
such as cinnabar - deposits of which, as at Almadén, Spain, have
been mined for thousands of years. Volcanic activity, eolian processes,
volatilization from land and ocean surfaces and the combustion of fossil
fuels all loft mercury vapor into the atmosphere, where it can remain for
years. Once in the atmosphere, mercury spreads widely.
Humans find mercury quite useful. Alchemists used mercury in an effort to transmute base metals into gold. Their efforts were not so far-fetched, however, as mercury readily forms an amalgam with gold and is effective in helping remove the precious metal from surrounding rock.
Mercury's density changes little in the liquid state. That property, plus the fact that mercury does not adhere to glass, makes it almost perfect for use in instruments such as thermometers and barometers. And its ability to conduct electricity lends it to use in switches and relays. Mercury also serves as a seal and coolant in nuclear reactors. Its vapors are used in lamps, and the metal is a common component of pharmaceuticals, fungicides and dental fillings.
As a result of the widespread use of mercury, the concentration of this versatile element in the environment has increased dramatically since the industrial revolution - and human and ecosystem health have suffered the consequences. All natural forms of mercury - elemental (vapors), inorganic and organic - may adversely affect health.
Inhaled mercury vapors damage the lungs, but their most damaging effects are to the central nervous system. With violent tremors and bizarre behavior, the "mad hatter" syndrome is the most serious health effect. Contaminated groundwater is a widespread source of mercury vapors that can diffuse into buildings where humans live and work. People may ingest inorganic mercury salts, such as mercuric chloride, from contaminated soils or sediments, damaging the gastrointestinal tract and even more damage to the kidneys.
Elemental and inorganic mercury, however, is not readily absorbed into the digestive tract, unlike the organic forms. Methyl mercury is the chief organic form of mercury. Synthesized by anaerobic bacteria common in anoxic environments such as wetlands, it is the most toxic of all forms - elemental, inorganic or organic.
Methyl mercury easily disperses through water and air, and concentrates up the food chain. For instance, humans who regularly eat fish containing mercury can accumulate it in their bodies to toxic levels over a period of time. Methyl mercury can kill brain cells and other types of neurons. Earlier this year, the Food and Drug Administration (FDA) advised that pregnant women, women of childbearing age, nursing mothers and young children avoid eating certain kinds of fish that may contain high levels of methyl mercury, such as shark, swordfish, king mackerel, and tilefish.
Great strides have been made to reduce mercury contamination in the environment. Mercury thermometers are rarely used; some industries have eliminated or greatly reduced their use of the metal. But a great deal of work remains to be done.
Geotimes contributing writer
Naturally occurring arsenic in drinking water is a hot topic of debate these days. At a recent public hearing, the House Subcommittee of Environment, Technology and Standards listened to testimony on the most up-to-date research on the science, benefits and costs of regulating arsenic in drinking water. "What we are examining here is the danger from arsenic in extremely minute amounts, equivalent to one teaspoon of arsenic in about 1.3 million gallons of water," said Chairman Vernon Ehlers.
At the hearing, Robert Goyer from the National Academy of Science's National Research Council (NRC) presented a study published this past September that links bladder and lung cancer to arsenic exposure from drinking water. This study comes at the request of the Environmental Protection Agency (EPA), which, in January, proposed lowering arsenic's maximum allowable level in drinking water to 10 parts per billion.
The NRC study is one tool to aid the EPA in its cost-benefit analysis of enforcing the proposed lower standard. Although the technology exists to remove arsenic from water down to a level of 3 parts per billion, no full-scale arsenic removal plants have been built and tested. The actual cost on a national level is still uncertain, although one EPA estimate puts the number at $181 million a year under the proposed 10 parts per billion standard, and the American Waterworks Association Research Foundation has estimated costs as high as about $590 million a year. Legislation could subsidize the construction cost of new treatment facilities for small communities, but individuals may also pay the price with increased water bills. Testifying at the hearing, Scott Rubin, an attorney for the National Rural Water Association, said individual home water bills could quadruple - a price residents of some small rural communities cannot afford.
At the same time, however, the EPA estimates that reducing the maximum allowable arsenic standard to 10 parts per billion could prevent between seven and 33 deaths from bladder and lung cancer annually. The NRC report found that when men and women daily consume water containing 3 parts per billion of arsenic, their chance of developing lung or bladder cancer in their lifetime is 1 in 1,000. At 10 parts per billion, the risk jumps to more than 3 in 1,000. And National Resources Defense Council senior attorney Erik Olson pointed out that even at that lowest standard, the cancer risk is "ten times higher than what the EPA says is acceptable." The EPA normally assumes an acceptable risk as 1 in 10,000.
In 1975, the EPA set a maximum allowable level of 50 parts per billion of arsenic in drinking water. The 1996 Amendments of the Safe Drinking Water Act required the EPA to set a new standard by Jan. 1, 2001. After evaluating more than 6,500 pages of statements from 1,100 commentators, the EPA used its discretionary authority under the 1996 legislation to lower the standard to a level that "maximizes health reduction benefits at a cost that is justified by the benefits." So, in January 2001, under the Clinton administration, the EPA set a new standard of 10 parts per billion. Subsequently, the Bush administration suspended enforcing that standard to the 54,000 community water systems in the United States until the NRC could review it.
The NRC addressed the hazards of consuming water contaminated with arsenic based on risk data from southwestern Taiwan and northern Chile. The NRC's new health risk estimates exceed those on which the EPA based its pending January ruling.
The symptoms and signs of arsenic poisoning differ among individuals, population groups and geographic areas, making it difficult to assess arsenic's health burden. Also, no method exists yet to distinguish cases of internal cancer caused by arsenic from those induced by other factors.
Information on where arsenic occurs naturally in groundwater largely comes from U.S. Geological Survey (USGS) maps. A USGS map from May 2000 shows that arsenic is most prevalent in groundwater in the Southwest (see page 34 this issue). The USGS sampled from wells that draw water from aquifers used for drinking water.
Arsenic is widely distributed throughout Earth's crust. According to the USGS, arsenic in groundwater is most commonly the result of the dissolution of minerals and ores from weathered rocks and soils. Volcanism and forest fires can release arsenic into the atmosphere. And arsenic is used in industrial products, such as paints, dyes, metals, drugs, soaps and semiconductors. Wood preservatives use about 90 percent of industrial arsenic in the United States. Agricultural applications, mining and smelting add to the arsenic inventory.
Inorganic arsenic can occur in the environment in several forms, but in groundwater, it is most commonly found as trivalent arsenite or pentavalent arsenate. Chlorinating water converts the trivalent arsenic species to the pentavalent form, according to Sheryl Luptowski at the National Sanitation Federation (NSF), a nonprofit organization that tests products that affect public health. She says some commercially available home water filters can remove arsenic from water. Filters that use reverse osmosis technology can remove the pentavalent arsenate found in chlorinated water. Another kind of filter, called a distiller, can remove both species of arsenic. Visit the NSF Web site for more information: www.nsf.org.
Lisa M. Pinsker
Go to your local hardware store and find a bag of potting soil. Observe the fine print on the bag. You might find a warning that the potting soil is a carcinogen.
It probably contains quartz, a form of crystalline silica. In fact, just about anything made of quartz, granite, sandstone, sand or clay contains a form of silica: bricks, ceramics, roads, concrete, sandpaper, foundry molds, filters for municipal water supplies, dessicants, toothpaste, paper and materials for industry - just to name a few.
We have long known that breathing in small pieces of crystalline silica can scar lung tissue and cause silicosis. In 1930, as it began to recognize crystalline silica as the source of "miner's asthma," the U.S. Department of Labor held its first conference on silicosis. Since then, the Occupational Safety and Health Administration (OSHA) has regulated how much respirable crystalline silica workers are exposed to, and the American Conference on Governmental Industrial Hygienists and the National Institute for Occupational Safety and Health both recommend limits on how much crystalline silica dust workers should breathe.
According to the International Agency for Research on Cancer (IARC), a World Health Organization group based in Sweden, crystalline silica, when inhaled, is a carcinogen in some cases. IARC reviewed the scientific literature to make its ruling, and thus concluded that people working in some ore mines or quarries or ceramics factories faced an excess risk of lung cancer. Research on whether silicosis leads to cancer is ongoing.
Shortly after IARC's ruling,
OSHA in the United States sought to follow suit and consider cancer risk
as part of its comprehensive ruling on crystalline silica. That project
went on hold last year, but it is still on OSHA's radar screen.
The question, says mineralogist William Moll, is, "How do we take the second most common mineral on Earth and call it a carcinogen?"
Moll works with the Sorptive Minerals Institute, which represents industries that make products from clay - such as cat litter. The IARC ruling could affect such industries, which use silica-based materials in their products. For example, under California's Proposition 65, or the Safe Drinking Water and Toxic Enforcement Act of 1986, the state recognizes crystalline silica as a carcinogen. As a result, bags of cat litter sold in the state would have to be labeled as carcinogens, says Lee Coogan, executive director the Sorptive Minerals Institute.
Working to prevent economic troubles for the cat litter industry, the Sorptive Minerals Institute tapped the knowledge of mineralogists, including Moll, and collected enough data to win a Safe Use Determination from California's Office of Environmental Health Hazards Assessment in June 1999. The state judged that, in pouring, scooping, and generally being around cat litter, a person would not be exposed to enough quartz to be in danger.
More importantly, Moll says the institute's research suggests that crystalline silica can be harmful in some forms but not in others. IARC's determination included a clause that cancer risks varied by industry and process, suggesting that hazard could vary with the crystalline silica's form and phase. Not every study of every ore mine, for example, showed that workers faced an excess cancer risk.
Taking this idea further, the Sorptive Minerals Institute study suggested that crystalline silica might only be harmful after it was newly crushed and its crystal structure was disturbed, but perfectly fine if the crystal face was in the same shape it was in 15 million years ago, Moll says. This fact could pose health risks to a sandblaster or quarry worker, but not to someone pouring cat litter or visiting the beach.
"Silica is a complex substance,
and to try and do a one-size-fits-all regulation isn't fair," Coogan says.
In the process, the institute's research introduced a new line of thinking that more researchers, particularly mineralogists, need to pursue in studying the health hazards of crystalline silica. Such is the opinion of Virginia Colten-Bradley, who worked as a consultant for OSHA as it examined how to address IARC's decision. The National Toxicology Program concludes that sufficient evidence exists to show that respirable silica can cause cancer in experimental animals, but that the evidence for its carcinogenity to humans is limited. The problem with animal experimentation, Colten Bradley says, is that researchers usually crush the quartz before putting it into test subjects's lungs, usually rats. The crushed quartz could react differently in the rats' bodies than unaltered quartz. These studies don't account for the way changing the mineral's surface or its crystal structure can change the experiment's outcome, she says.
Right now the OSHA ruling is on hold. But, Coogan adds, "This is going to be something that's going to go on for a long time."
For more on the cost/benefit analysis of arsenic's maximum allowable standard, visit the EPA Office of Ground Water and Drinking Water Web site.
The National Sanitary Foundation provides information on water filtration methods and products.
The Occupational Safety and Health Administration Web site on asbestos.
American Lung Association Web site about health effects of asbestos.
Facts on crystalline silica from Occupational Safety and Health Administration with links to other relevant Web sites.
The International Agency for Research on Cancer Web site.
Food and Drug Administration warning about mercury in fish.