Climate change in Southern Arizona could trigger an increase in asthma, bronchitis, West Nile virus, allergies, dengue fever, valley fever, heat-related deaths and malaria.
These and other diseases could increase or arrive here as the climate warms, dries and displays more extreme hot and cold spells and fiercer storms due to emissions of carbon dioxide and other greenhouse gases.
Those warnings came from two scientists -- one local and one national -- who spoke at a weekend conference at University Medical Center on climate change's health effects.
More than 80 physicians, scientists, community activists and others attended Saturday's conference.
Other highlights:
--Children are likely most vulnerable to climate-induced disease, said Eve Shapiro, a Tucson pediatrician. They get dehydrated more easily, have faster metabolisms and eat more food for their size compared with adults, she said. They're outdoors more, breathing more pollutants.
--Pima County's Health Department has made strides in monitoring some diseases but has a ways to go for others, said Dr. Michelle McDonald, the department's chief medical officer. It's better at tracking mosquitoes and has vastly improved mosquito control and reduced stagnant-water pools. It has fared less well in dealing with environmental health risks, lacks capacity to track chronic respiratory diseases and doesn't have the staff to track heat-related deaths, she said.
--A risk exists that if coastal California is hit by rising sea levels from warming temperatures, evacuees may flee to Arizona, straining this state's services, said a suburban fire chief.
--While many speakers talked of government's responsibilities, emergencies stemming from climate change such as more extreme storms that knock out power to thousands of people may not have a government solution, said Rural Metro Fire Chief Les Caid.
"There is a personal responsibility that everyone has to be prepared," Caid said.
The scientists who spoke on specific diseases, professor Andrew Comrie of the University of Arizona and Jeremy Hess, a consultant for the federal Centers for Disease Control and Prevention, are backed up by many scientists worldwide in linking warming to health problems. But they acknowledge a lack of hard research documenting or predicting climate-change-disease links.
"There's almost nothing worldwide," Comrie, a prominent climatologist and an associate UA vice president for research, said in an interview. "It's difficult and complex. These are relatively recent issues."
But other indicators exist. One is a recent rapid increase in Arizona valley fever cases that coincides with a prolonged drought, which increasing numbers of scientists have linked to global warming. A second is the northward movement of disease-bearing mosquitoes due to warmer weather.
"We are at a point where already most of us in public health feel that dengue fever is not a matter of if but when," Pima County's McDonald said. "We have these mosquitoes well-established in Pima County. There are all the ingredients to get that disease."
The question is when either people or mosquitoes will bring the infection itself northward from Mexico, where it now occurs, scientists have said.
A third indicator is the long-accepted relationship between higher temperatures and the air pollutant ozone that causes respiratory ailments. Another indicator, nationally, is that a comprehensive study of waterborne-disease outbreaks has shown the vast majority are strongly associated with heavy rainstorms, said Hess. Waterborne diseases include diarrhea, cholera and hepatitis A, and could come from extreme rains associated with climate change that are expected to occur even in the arid Southwest.
"There is a climate component in every one of these. Is it everything? No. Is it nothing? No," Comrie said in an interview. "The disease-climate relationship has all the complexities of ecology and all the complexities of society. That makes it an interesting, challenging problem. But it makes quick answers tougher to get."
Climate change will likely amplify existing health problems, and problems will be linked in a way that hasn't happened before, Hess said in an interview. While society has adequate means to deal with many of the diseases, a breakdown in public infrastructure systems from climate-related emergencies could cause severe problems, he added.
"If you have a heat wave in Phoenix and the power grid breaks down, that could have a severe effect," Hess said.
In his talk, Comrie pointed to several factors making relationships between climate change and health hard to predict. The Earth has a vast array of complicated ecosystems in which insects, animals and people depend on one another. Infectious diseases have a wide range of transmission methods: directly from person to person, indirectly from person to person through insects, from animals to other animals to humans and from interactions of insects, other animals and people, he said.
When the environment is added, that creates a triangle of disease, featuring a host such as a person, an agent such as bacteria and the environment such as climate change. Social factors, such as land use, transportation, migration, population demographics and economics, also shape how these diseases spread, he said.
"There's a rogue's gallery of diseases. You can see the interrelationships. It's not just about butterflies, lizards and bees. We're in the same food web. We become predators. We're prey," Comrie said. "The fact that bugs bite us is perfectly normal."
Most conference speakers agreed public and local officials need to be prodded about climate-change threats. Hess, an assistant emergency medicine professor, showed a slide of an ostrich sticking its head in the sand to make that point, although he said the public has grown more receptive to the subject in the past two years.
"Climate is complicated. It forces us to think through what our responsibility is to future generations. It is expensive to deal with. A lot of people don't want to talk about it," said Hess, of Emory University's School of Public Health in Atlanta. "But the sand is getting hotter, and pretty soon, people have to get their heads out."
Diseases linked to climate change
--Valley fever: Spiked from less than 1,000 cases in 1997 to 5,000 or more cases in Arizona in 2006 and 2007. Increase causes are under study, but they're possibly linked to drought caused or aggravated by warming. Also could be caused by better reporting, construction dust and more vulnerable elderly people moving here.
--Dengue fever: 100 million cases caused annually worldwide and generally agreed to be moving north into northern Mexico. The aedes aegypti mosquitoes that cause it already live in Tucson. Warmer weather could move the disease to Arizona. The presence of swimming pools, artificial ponds and stagnant water could also draw disease-bearing mosquitoes.
--Chronic respiratory disease: Could rise if hotter temperatures raise ozone air pollution levels.
--Allergies: Could rise if earlier growing seasons for plants generate more pollen.
--West Nile virus: Could also increase with the continued northward movement of mosquitoes due to warmer weather.
--Asthma and other respiratory diseases: Could rise due to fungus and mold growth caused by extreme variations in temperature and precipitation.
--Heat-related desert deaths of illegal immigrants: Could increase as temperatures rise.
--Heart disease, coughing and breathing problems, decreased lung function: Could be aggravated if global warming brings more drought and dust.
--Malaria: Some areas of Arizona not now suitable for malaria-carrying mosquitoes could become suitable by 2050 due to warmer, more humid weather.
Sources: University of Arizona climatologist Andrew Comrie, Emory University assistant emergency medicine professor Jeremy Hess, and Sam Keim, a UA emergency medicine associate professor.
--Contact reporter Tony Davis at 806-7746 or tdavis@azstarnet.com. To see more of The Arizona Daily Star, or to subscribe to the newspaper, go to http://www.azstarnet.com. Copyright (c) 2008, The Arizona Daily Star, Tucson Distributed by McClatchy-Tribune Information Services. For reprints, email tmsreprints@permissionsgroup.com, call 800-374-7985 or 847-635-6550, send a fax to 847-635-6968, or write to The Permissions Group Inc., 1247 Milwaukee Ave., Suite 303, Glenview, IL 60025, USA.
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