Government is nothing but the balance of the natural elements of a country.
José Martí, Our America, 1891
Predicting Heat Worldwide
An international team of climate experts, health officials, and meteorology agencies sponsored by the United Nations Environment Programme (UNEP) are joining forces to install heat health watch and warning systems worldwide. The systems, based on a University of Delaware (UD) computer program, are already operating in Philadelphia, Pennsylvania, and Washington, DC. Over the next several years, similar systems will be installed overseas in Rome and Shanghai to provide health officials with up to 60 hours' advance warning of dangerously hot weather, says Laurence S. Kalkstein, director of UD's Synoptic Climatology Center.
Plans for the Italian warning system were discussed over 1-2 February1999, when Kalkstein met in Rome with representatives from Italy's Lazio Health Authority, the World Meteorological Organization, the World Health Organization, and the Italian Meteorological Service. The meeting followed a 28 January 1999 announcement by the American Geophysical Union concerning climate change and greenhouse gases. While climate researchers are still struggling to address "significant scientific uncertainties regarding climate change" the union said in an official position statement, it recommends "the development and evaluation of strategies such as emissions reduction, carbon sequestration, and adaptation to the impacts of climate change."
In the meantime, Kalkstein and other participants at the February meeting contend that heat warning systems are crucial for a number of reasons. Heat claims some 1,500-2,000 lives every summer in the United States alone. Around the world, Kalkstein says, the heat-related death toll may be much higher, particularly in developing nations where air-conditioning is scarce. And, he says, stifling heat may indirectly trigger many more deaths resulting from heart attacks, strokes, and other medical conditions.
Moreover, the U.S. Environmental Protection Agency (EPA) has reported that global temperatures are rising as the burning of fossil fuels and other human activities add greenhouse gases to the atmosphere. Specifically, EPA data suggest that the average land-surface temperature on Earth has increased by 0.4-0.6°C (0.8-1.0°F) over the last century. If temperatures rise by several degrees in the 21st century, as some scientists have predicted, heat could cause additional deaths, "especially among children, senior citizens, anyone in poor health, and those in high-risk neighborhoods, where heat-trapping homes make people more vulnerable to very hot weather conditions," Kalkstein says.
Regardless of global warming, ongoing weather events such as El Niño routinely produce unhealthy heat levels, says Tanja Cegnar, head of climatology at the Hydrometeorological Institute of Slovenia in Ljubljana. "The current variability of climate and the intensity of heat in large, urbanized areas point to the need for this heat-warning technology," she says. Hot weather also can contribute to health risks associated with harmful ozone levels, such as asthma and cardiovascular illnesses, and it can promote the spread of diseases such as malaria and dengue fever, says UNEP representative Hiremagalur Gopalan.
Initially sponsored by the EPA, the Philadelphia system analyzes National Weather Service forecasting data, cross-referencing it with the city's historic mortality rates as well as with meteorological variables including temperature, humidity, and cloud cover. In other words, explains Jonathan Samet, a professor in and chairman of the Department of Epidemiology at the Johns Hopkins University School of Hygiene and Public Health in Baltimore, Maryland, the software "builds from a statistical model describing the relationship between weather and mortality."
Robert A. Muller, director emeritus of the Southern Regional Climate Center at Louisiana State University in Baton Rouge, supports the new technology as an improvement on traditional methods of assessing hazardous heat. Historically, weather warnings have been based on a heat index. The problem with this approach, Muller says, is that you could have, for example, a high heat index every day, all summer long, in Louisiana, but only rarely in Philadelphia or Baltimore--and those fewer hot days may be more hazardous to the latter populations. Shorter runs of high temperatures in northern regions, he explains, will have a greater health impact than a long run of very warm, humid temperatures in southern climates because warm-weather residents and structures are adjusted to the heat.
In a January 1997 EHP article, Kalkstein reported that acclimatization by people and structural variations from city to city may explain why heat claims more lives in New York City than in Phoenix. For example, says Kalkstein, people in hotter areas are accustomed to the heat and adjust their behavior (e.g., by staying indoors, wearing lighter clothing), whereas in colder climes, when extreme heat occurs people may not modify their behavior to accommodate it. Also, homes in the Northeast, particularly in poorer areas that may lack air-conditioning, are red brick row houses with windows on only two sides and tar roofs, all of which trap heat. In contrast, in the South poorer people often live in frame houses with light colored roofs and windows on four sides, which helps mitigate the heat. The total number of "excess" deaths (above what would normally occur) in a given summer in Philadelphia was calculated by Kalkstein to be 129, versus 0 for Miami [EHP 105(1):84-93]. Kalkstein says that each city has a particular heat threshold above which the number of deaths begin to rise. A key benefit of the UD system is that it is customized to reflect a given city's response to heat waves.
Jeff Moran, a spokesperson for the Philadelphia Department of Public Health, says the heat warning system seems to be working for his city. Its success, he says, relies on Philadelphia's framework for responding to hazardous weather conditions. Whenever the system predicts a heat wave, he explains, Philadelphia officials distribute media advisories, activate telephone hotlines, alert neighborhood volunteers, open air-conditioned shelters, expand outreach to the homeless, and coordinate efforts with local utilities or take other actions, depending on the level of risk predicted. "The information [generated by the computer program] is no good unless you have channels of communication in place so that you can act on a warning once you have it," he says.
Lawrence Robinson, deputy health commissioner for public health promotion at the Philadelphia Department of Public Health, says, "Putting into place an emergency response program involving a large number of agencies and individuals requires a rapid shift of personnel and resources. The UD system allows us to launch these special services exactly when they are needed to save lives."
Says Samet, "Implementation of the [UD] warning system in several areas can serve two purposes: we gain a prospective test of the system, and refinements can be made based on the findings." The systems, therefore, are "a first step in predicting days that may kill, and taking steps to prevent this from happening," he adds. Kalkstein estimates the cost of developing and installing the Italian heat warning system to be between $50,000 and $75,000.
Climate-controlled Disease?
According to a report issued by the American Academy of Microbiology, feeling "under the weather" may be a more literal circumstance than it seems. The report, entitled Climate, Infectious Disease and Health: An Interdisciplinary Perspective, is based on the findings of an academy colloquium held 20-22 June 1997 in Montego Bay, Jamaica. The colloquium was attended by researchers, professors, and representatives from diverse public health and government agencies who reviewed the current state of the knowledge of the effects of climate and weather change on human health, and developed recommendations for a future plan of action.
According to the World Health Organization's World Health Report 1998, infectious diseases killed more than 17 million people in 1997. Climate can influence the occurrence of infectious diseases in a number of ways, through temperature, precipitation, wind and ocean currents, and El Niño-Southern Oscillation (ENSO) sequelae. Colloquium co-chair Jonathan A. Patz, director of the Program on Health Effects of Global Environmental Change in the Department of Environmental Health Sciences at the Johns Hopkins School of Public Health, notes, however, that the interaction of climatic variables can be complex and unpredictable. "Predicted change in disease risk or transmission is not simple," he says. "Multiple factors must be considered."
Climate and weather conditions affect vectorborne diseases by influencing the reproductive success of the vectors that spread the diseases, and by altering the incubation period of certain mosquito-borne viruses. For example, warmer temperatures shorten the time needed for the virus responsible for dengue fever to become activated within its mosquito host. On the other hand, hot temperatures can also reduce the survival of mosquitoes and ticks. Warmer conditions also correlate with increased populations of some microorganisms that cause waterborne diseases, such as the Vibrio cholerae bacterium, which causes cholera. In addition, rainfall and flooding (which result in the watery habitats optimal for certain disease vectors and microorganisms) and runoff (which can transport pathogens from the feces of infected pasture animals) may also cause increased transmission of diseases among humans. Higher ambient temperatures foster the growth of pathogens that thrive in or on food, such as Salmonella. Some airborne diseases are believed to be affected by climate and weather conditions, as evidenced by their seasonal nature. For example, meningococcal meningitis (spinal meningitis) occurs in sub-Saharan Africa most frequently during the dry season from December through June, and subsides markedly during the rainy season.
While much may be known about individual diseases, colloquium participants agreed that there are serious knowledge gaps in understanding the complex relationship between weather, climate, and infectious disease. The report suggests three improvements to remedy these gaps.
First, data collection methods must be improved. Morbidity and mortality data-gathering methods around the world are far from standardized and may vary widely in reliability from region to region. The report suggests measuring genetic markers of particular microorganisms as a way to trace a pathogen through the ecosystem, and studying the influence of microenvironments (such as occur in underground storm drains and houses) on vector survival rates.
The report points to the ENSO Experiment as an example of effective cross-disciplinary collaboration. The ENSO Experiment is a research endeavor that examines the relationship between ENSO and other climate-related phenomena and human health, and explores the potential for using climate forecast information to provide early warning of conditions posing a public health threat. The project is coordinated by the National Oceanic and Atmospheric Administration and was initiated in 1997 as a result of the colloquium. The ENSO Experiment studied the 1997-1998 ENSO then underway; today, studies sponsored by several different agencies continue to track the human health aftermath of that phenomenon.
Second, modeling studies must be undertaken to elucidate links between climate and infectious disease. According to the report, one of the primary goals of model building for research on weather-disease links is to be able to predict outbreaks of disease in response to particular climatic variables. The report says models are needed not only to organize and assess the new data that are being collected, but also to reassess data that are already available. Several new models are being developed, such as a model by Mercedes Pascual of the Center of Marine Biotechnology at the University of Maryland Biotechnology Institute in Baltimore, which will examine the predictability of cholera in endemic regions and its relationship to climate variability.
Third, the report stresses the need for collaboration and communication among scientists, and between scientists and the public. The report calls for an international collaborative research effort and the establishment of new research centers specifically to study the relationship between climate, weather, and disease. The report also cites the need for increased and longer-term funding. Traditional research funding cycles run 2-3 years, which is in sharp contrast to the 25 years recommended by the report for a comprehensive study documenting the weather-disease relationship. The report particularly stresses the need to develop new weather-disease databases, linked nationally and internationally, that are interdisciplinary in content and accessible to all interested researchers, and to link existing databases maintained by independent groups of scientists. The report points out that, while there are electronic data sets to be found all over the world, few of the existing databases are either coordinated or designed to be used in conjunction with others.
Finally, the report calls for the drafting of a shared terminology to unite scientists separated by language and discipline, and for scientific journals to publish weather-disease articles that straddle traditional disciplinary boundaries. The report also urges graduate and medical schools to implement courses in weather-disease studies, and encourages scientists to gain popular support for such research by educating the public through demonstration of the value of this research to society.
The When, Where, and How of Environmental Hazards
When the TV news forecasts sun but clouds loom instead, life goes on. People shrug, curse, and grab an umbrella. But when scientists try to predict global warming, earthquakes, or nuclear waste leaks, their uncertainty is much harder to shake off. Then there's the question of what to do in the face of such uncertainty. At the annual meeting of the American Association for the Advancement of Science, held in Anaheim, California, in January 1999, scientists debated the use and abuse of scientific predictions in environmental policy, as well as the traditional policy of erring on the side of caution when in doubt as to the nature and extent of environmental hazards.
Through a glass darkly. Predicting and quantifying risk from environmental hazards is still a somewhat murky science, but new paradigms may improve the accuracy of these exercises.
In one session, scientists took turns revealing gaping holes in scientific prediction. For instance, Orrin Pilkey, a geologist at Duke University in Durham, North Carolina, and Daniel Metlay of the U.S. Nuclear Waste Technical Review Board lamented the decade-old dispute over storing radioactive waste under Nevada's Yucca Mountain. Under pressure to pick a spot for dumping the waste, Department of Energy policy makers put blind faith in mathematical models of pollution flux at the site, said Pilkey. Relying on these models for years, scientists didn't bother to draw water samples from under the mountain, he said, and when they did, they found it hard to predict whether the waste might in fact seep into groundwater. Following the discovery, political debates, scientific wrangling, and media headlines ensued. By then, Metlay added, the department's policy makers had become "hostages of time," struggling to meet federal waste disposal deadlines and relying on mathematical models to help do it.
There's a smarter route to environmental prediction, Pilkey and Metlay said--a tighter partnership between policy makers and scientists, complete with plenty of independent geology research for any proposed nuclear waste site, and less reliance on models. This call for better communication between scientists and policy makers resounded at the session, as the panel outlined uncertainties in global climate change, California earthquakes, and eroding North Carolina beaches. Better communication, said Daniel Sarewitz, a geologist at Columbia University in New York, "allows the policy makers to understand the limits of science, and it allows scientists to understand what policy makers need to know."
Such communication is not the current paradigm, said Sarewitz, who has worked as a consultant to the House of Representatives Committee on Science, Space, and Technology. He said that climate change is one example of the United States' flawed approach toward weaving scientific prediction into policy. "The idea is that a scientific answer--[for instance,] a global warming prediction--can be found, and then policy makers can apply rules to deal with it." A better tactic, Sarewitz said, is to recognize up front that scientists may never know enough to predict global warming accurately. They might do more good teaming up with policy makers and everyday citizens to find alternatives to prediction such as flexible strategies that may help a given community confront the range of global warming possibilities. "The instinct is to predict," Sarewitz said. "But the promise of prediction just isn't always met."
In such cases, age-old adages such as "better safe than sorry," "first, do no harm," and "look before you leap" may come into play. The transformation of such adages, however, into an emerging environmental philosophy caused great debate at the meeting. Scientists explained the theory behind and possible uses of the so-called "precautionary principle," which holds that industry and governments should prevent pollution, technology, or other activities that have even the potential to harm human or environmental health.
The controversy lies in the fact that some scientists suggest society should go as far as stopping a new technology or polluting activity in its tracks when it appears that it might harm others--even if scientists can't actually prove that it does. While this idea has crept into a few pollution laws in Germany and the United Kingdom, it's a far cry from environmental policy in the United States, which relies on techniques such as risk assessment and cost-benefit analysis to weigh the pros and cons of a polluting activity. Toxicologists at the meeting pressed the scientific panel to explain how they could base sound environmental policy on a philosophy that doesn't require scientific certainty about a substance's toxicity. Steve Breyman, a political scientist at Rensselaer Polytechnic Institute in Troy, New York, countered that he and others want to "err on the side of human health," and that there are many examples, such as lead poisoning and smoking, of how people's health suffered while scientists debated risk.
Ken Geiser, director of the Toxics Use Reduction Institute at the University of Massachusetts in Lowell, described several relatively easy ways to put the precautionary principle into play, such as replacing potentially toxic chemicals with more neutral substitutes, recycling materials, and tinkering with production processes to produce less pollution. For the past decade, the institute has been advising Massachusetts companies how to do these things without hurting profits or productivity. Geiser and his colleagues advocate "clean production," a style of manufacturing that cuts pollution to minimal levels. This kind of approach, Geiser argued, is a feasible way to a more sustainable society.
The primary push for the precautionary principle comes from the Science and Environmental Health Network, a national nonprofit organization of scientists and environmentalists. It remains to be seen whether the U.S. Environmental Protection Agency or other federal government agencies will ever formally adopt the principle, Breyman said. He suggested, however, that increasing disease and ecosystem damage may bring precaution foremost in the public's mind.
Tracking Risk
When the cluster of children's leukemia cases featured in the recent movie A Civil Action surfaced in Woburn, Massachusetts, in the mid-1980s, state epidemiologists weren't even tracking cancer cases. Scientific scrutiny of the interplay between genes and the environment has come a long way since then. But panelists at the annual meeting of the American Association for the Advancement of Science, held in Anaheim, California, in January 1999, posed the question that now presents itself to researchers crossing traditional disciplinary boundaries: how to decipher ever-larger amounts of complex data.
"We've gone about as far as we can go independently with the two sciences that feed public health, toxicology and epidemiology," said panelist Christopher Schonwalder, the NIEHS director of international programs. "Now is the time to bring them together if our understanding is to advance," he said.
Combining cancer registries and right-to-know laws, for example, boosts the study of environmental hazards, said Sandra Steingraber, an ecologist with the Women's Community Cancer Project and author of Living Downstream. "Thanks to activism, a pipeline is being built between the two giant databases," she said.
Investigators have recognized the futility of tracking the risk from specific etiologic agents, pointed out Devra Lee Davis of the World Resources Institute, "because disease patterns will always reflect mixed environmental hazards." Similarly, exposure patterns are used more to provide warnings about potential hazards than to forecast disease outcomes. "Exposure occurs to a finite number of materials," Davis said. "Health is a function of many variables."
Studying genes or the environment independently, panelists said, is giving way to studying the interactions that cause human disease. Yet, according to Columbia University researcher Ruth Ottman, "There has been surprisingly little work to date on what that interaction is, how to detect it, and what kinds of study designs should be used to look at these questions."
Modelers face challenges on both fronts. Efforts to develop models to describe the risk of exposure from single agents have been frustrated, reported Oak Ridge National Laboratory researcher Troyce Jones. The carcinogenic mechanisms are simply too complex, and the immune system too variable. "In spite of all the knowledge at this meeting and all the knowledge in the published literature, we can barely, barely get past 'go' going either direction--backwards from disease to exposure, or from exposure to disease," Jones said. As researchers continue to shift from answering the question of what a dose is to what a dose does, he said, better risk assessment and policy can be formulated. Specifically, he said, analysis of databases derived from considerations of reactive oxygen can generate direct indices of how the immune system is modulated by different environmental variables.
Joellen Lewtas, a toxicological chemist with the U.S. Environmental Protection Agency, reported success with using biomarkers in her work in the Czech Republic to look at the progression from exposure to what ultimately could be increased cancer risk. DNA adduct measurements from the study, in particular, offer some opportunity to combine epidemiological data with toxicological data, Lewtas explained. Such measurements reflect not only exposure, absorption, and transport but also metabolism, DNA repair, and cell turnover. "Biomarkers can provide very specific evidence of exposure and confounding exposures," Lewtas explained. "They can be used to evaluate molecular dose and damage related either to health outcomes or . . . to the exposure biomarkers, which in turn provide the basis for studying susceptible subpopulations."
Researchers attempting to interpret data on disease susceptibility genes face equally complex problems. "For the most part, we have a hard time explaining the effect of one gene polymorphism in relationship to an exposure," said NIEHS researcher Douglas Bell.
Although researchers working with the Environmental Genome Project and similar projects have identified roughly 60,000 variants among disease susceptibility genes and hundreds of variants in specific genes involved in environmental exposures, deciphering the data is where things get tricky. "As we layer on hundreds and thousands of variations, I suspect it will be a very difficult task for the epidemiologists, statisticians, geneticists, and biochemists who try to explain exactly what's going on at a biological level," Bell said. "In reality, there may be many alternative pathways at each step in the exposure-disease path and we really don't know how to model or even think about these systems at this point."
Understanding the interaction between genes and environment enables scientists to have greater accuracy and precision in the measurement and detection of both genetic and environmental effects, said Ottman. She offered a series of epidemiological models of interaction at the meeting and remains confident that as more genes that affect disease risk continue to be identified, testing of interaction models will become more feasible; the next step is disease prevention.
Despite exciting emerging perspectives on exposure, interactions, and risk, for now, said Schonwalder, "we don't know a lot, but one thing we can say for sure is that we're not getting it right. We're spending billions of dollars to control chemicals and we don't know which ones are really hazardous and which are not. We're either overcontrolling, which means we're spending a lot of money in the economy that doesn't need to be spent, or we're undercontrolling, in which case we're causing a lot of human suffering and disease and we're spending an awful lot on health care." Finally, Schonwalder said, "The returns on investment in research toward understanding disease cause and effect can be huge."
A New Window on a Molecular Doorway
Research published in the January 1999 issue of Nature Medicine may help scientists make a good thing--gene therapy--even better. Investigators at the University of North Carolina at Chapel Hill (UNC) have found that the presence of *Vß5 integrins (a certain type of receptor protein) on cell surfaces makes it easier for those cells to be infected with adeno-associated virus (AAV), a commonly used gene therapy vector, or delivery mechanism. By better understanding how AAV enters cells, scientists will have more information for deciding how and when to use the virus for effective human gene therapy.
Gene therapy works by using a genetically altered vector to convey replacement genes to diseased cells. AAV is commonly used for this purpose because it can infect several different kinds of cells (unlike, for example, the AIDS virus, which attacks only a specific type of white blood cell). It is also nonpathogenic, so practitioners don't have to worry about the vector causing adverse health effects in their patients. AAV is currently used in gene therapies for cystic fibrosis, Parkinson's disease, and hemophilia, among other conditions.
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The key to infection? Identification of the Vß5 integrin as a secondary receptor for adeno-associated virus (AAV) offers evidence of how viruses infect cells, and may provide grist for new gene therapies.
Photo credit: C. Summerford, R. J. Samulski |
Integrins occur in various combinations of 1 of 16 different alpha subunits and 1 of 8 different beta subunits. Understanding the role that the *Vß5 integrin plays in AAV uptake will allow researchers flexibility in exploiting its properties, depending on the needs of the disease being treated. For instance, they could upregulate the receptor (or increase its numbers on the cell surface) to enhance uptake.
The UNC research team built upon earlier studies that showed that adenovirus interacts with *V integrins to facilitate internalization of the virus. Adenovirus uses two different receptors to mediate viral infection. The first receptor attaches wandering viruses to the cell surface, and the second receptor, the *Vß5 integrin, actually "pulls" the virus inside the cell. Because AAV coevolved with adenovirus, the UNC team thought that the two viruses might share one of the same receptors. In fact, they found that they share the secondary receptor but not the first.
The team compared hamster cell lines that either lacked *Vß5 or specifically expressed *Vß5. The cells were exposed to recombinant forms of adenovirus and AAV. They found that infection rates of the *Vß5-positive cells were 260% higher for AAV (and 320% higher for adenovirus) than in the cells that lacked the *Vß5 integrin. To determine whether, and to what extent, *Vß5 speeds AAV entry into a cell, the scientists applied a strain of the virus tagged with fluorescent dye to the two cell lines. The *Vß5-positive line was found to internalize the virus at a much faster rate (within 10 minutes) than the *Vß5-deficient line (which took up to 60 minutes). Candace M. Summerford, a graduate student at the Gene Therapy Center at UNC who led the study, says, "We're looking at a phenomenon that facilitates viral entry but isn't absolutely necessary." However, she continues, "How fast the virus can get into the cell may define the odds of infection." Summerford's team is currently investigating the use of AAV as a vector for anticancer strategies.
According to R. Jude Samulski, director of the Gene Therapy Center, AAV is a defective parvovirus, meaning it is unable to complete its life cycle on its own. It needs the assistance of a "helper" cell such as adenovirus or, as was more recently discovered, herpesvirus. Because AAV can coexist with at least two different helper viruses, it may have multiple avenues of entry into a cell; that is, it may have access to the sum of the different cells targeted by its helper cells. Identification of the viral receptors for AAV has helped researchers understand the broad access to cells of this virus. It is this "tropism" of AAV that makes the virus a good choice for a gene therapy vector, because it can be used to transport replacement proteins into several different environments, making it a sort of all-terrain vehicle of gene therapy.
A better understanding of how AAV enters cells may also help scientists understand the more pathogenic strains of parvovirus, such as the B19 strain, which causes erythema infectiosum ("fifth disease") in humans. This disease is symptomized by a rash, low-grade fever, fatigue, joint pain, and swelling. B19 infection can be dangerous for patients with blood disorders such as sickle cell anemia and hemophilia. In pregnant mothers, infection with the B19 strain can result in spontaneous abortion.
Since the turn of the century, the average daily temperature in the United States has increased by 0.4oC. Most of that increase has happened during the last 30 years, and there is mounting evidence that atmospheric pollution will cause this warming trend to continue into the next century. With the warmer weather have come other climatic changes: the rate of evaporation seems to be decreasing in the United States on average, while cloud cover and precipitation seem to be increasing. There is evidence, too, that the nation can look forward to a future with more violent storms.
In the wake of these observations, the question of how climate change will effect both the environment and human health takes on vital importance and terrific complexity. Will the temperature increases cause hundreds more heat-related deaths in states such as Texas and Florida? Will diseases that are native to hot climates such as dengue and cholera find a warmer north more hospitable, and if so, will science be able to prevent their spread? Are water treatment systems prepared for flood events that could sweep more contaminants into drinking water?
Analyzing all the health-related outcomes of climate change and predicting human response to those outcomes may sound like an impossible task, but the U.S. Environmental Protection Agency has enlisted dozens of researchers from 11 universities and public institutions to do just that. The fruit of their research can be found on the Climate Change and Human Health Web site, located at http://www.jhu.edu/~climate/.
The Climate Change and Human Health Web site stems from a $3 million Environmental Protection Agency grant to Johns Hopkins University, and fulfills one of the agency's main objectives. "One of the key purposes of the grant was to make this information public," explains Rebecca Freeman, a doctoral student in the Department of Geography and Environmental Engineering at Johns Hopkins and the creator of the Web site. "One way to do this, obviously, is to disseminate our research via the Internet. We're trying to encourage communication among scientists and to collect feedback from informed readers." The site will also put the group's findings where they can be utilized by the policy makers who may be in the best position to mitigate the health consequences associated with global warming.
The site offers visitors insight into the complexity of the problems of climate change and the progress being made in addressing them. For example, among the abstracts and progress reports located on the site are descriptions of a study being undertaken by a group focusing on the potential spread of Cryptosporidium in Lancaster County, Pennsylvania. Despite the comparatively small scope of the project, it has involved years of complicated research spanning many disciplines. First, the group mapped Lancaster watersheds and runoff patterns to find the areas that are prone to flood. Then, water treatment systems and well fields were superimposed on the map, and a countywide survey was taken to find where in the area Cryptosporidium was dwelling. Knowing this helped researchers predict what drinking water supplies might become infected during a violent storm event. But the project has also raised other questions, such as whether the operators of water treatment systems would be able to respond quickly enough to prevent tainted water from reaching people's taps, whether people would heed advisories to boil drinking water, how much of an effect a diarrheal disease such as cryptosporidiosis would have in a place like Lancaster County, and what the overall cost to society of such an incident would be.
Many of the computer-based tools that are helping researchers answer such questions are linked to the Climate Change and Human Health Web site and can be accessed by following the Analysis Tool Box link on the home page. There are links on the Analysis Tools page to available software packages that assist scientists in conducting epidemiological studies, mapping projects, and performing statistical demographic, and population analyses. Besides cryptosporidiosis, other health end points that are currently being analyzed include cholera, hantavirus, Lyme disease, dengue, and dengue hemorrhagic fever.
On the home page are links to the seven major divisions of the project: climate analysis, remote sensing, spatial analysis, hydrologic modeling, geographic information systems, public health effects, and risk communication and characterization. As the project progresses, these links will provide visitors with detailed descriptions of the research in each area, the group's preliminary conclusions, and plans for future research.
A list of the principal researchers in the Climate Change and Human Health project is available by following the Expert Database on the home page. Each researcher's name is linked to a description of his or her current research and a list of literature citations. More climate change-related literature citations can be found through the Publications Database link on the home page.
The very latest project publications can be found by following the News and Events link on the home page. Also under this link is a listing of upcoming meetings and conferences relating to climate change, such as the Second International Conference on Ecosystems and Sustainable Development, scheduled for May 31-June 2 in Southampton, United Kingdom, and the 4th International Congress on Energy, Environment, and Technological Innovation, to be held 20-24 October 1999 in Rome. Links are provided to assist visitors with getting more information about these events.
Besides Johns Hopkins, other institutions participating in the project are the University of Maryland, Pennsylvania State University, the University of Delaware, the Georgia Institute of Technology, Science Communication Studies, the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, the University of South Florida, the U.S. Department of Agriculture, the University of Texas in Houston, and the New Orleans Mosquito Control Board.
Last Updated: April 15, 1999