Dear EarthTalk: I know that global warming causes extreme weather and melts glaciers and causes sea level rises. But how does it increase the spread of disease?
—Curran Clark, Seattle, WA
Climate change accelerates the spread of disease primarily because warmer global temperatures enlarge the geographic range in which disease-carrying animals, insects and microorganisms—as well as the germs and viruses they carry—can survive. Analysts believe that, as a result of global temperature rises, diseases that were previously limited only to tropical areas may show up increasingly in other, previously cooler areas.
For example, mosquitoes carrying dengue fever used to dwell at elevations no higher than 3,300 feet, but because of warmer temperatures they have recently been detected at 7,200 feet in Colombia’s Andes Mountains. And biologists have found malaria-carrying mosquitoes at higher-than-usual elevations in Indonesia in just the last few years. These changes happen not because of the kinds of extreme heat we’ve experienced in recent months, but occur even with minuscule increases in average temperature.
But extreme heat can also be a factor, and the nexus of global warming and disease really hit home for North Americans in the summer of 1999, when 62 cases of West Nile virus were reported in and around New York City. Dr. Dickson Despommier, a Columbia University public health professor, reports that West Nile Virus is spread by one species of mosquito that prefers to prey on birds, but which will resort to biting humans when its normal avian targets have fled urban areas during heat waves.
"By reproductive imperative, the mosquitoes are forced to feed on humans, and that’s what triggered the 1999 epidemic," Despommier says. "Higher temperatures also trigger increased mosquito biting frequency. The first big rains after the drought created new breeding sites." He adds that a similar pattern has been recognized in other recent West Nile outbreaks in Israel, South Africa and Romania.
Bird flu is another example of a disease that is likely to spread more quickly as the Earth warms up, but for a different reason: A United Nations study found that global warming—in concert with excessive development—is contributing to an increased loss of wetlands around the world. This trend is already forcing disease-carrying migrating birds, who ordinarily seek out wetlands as stopping points, to instead land on animal farms where they mingle with domestic poultry, risking the spread of the disease via animal-to-human and human-to-human contact.
A Congressionally-mandated assessment of climate change and health conducted in 2001 predicted that global warming will cause or increased incidences of malaria, dengue fever, yellow fever, encephalitis and respiratory diseases throughout the world in coming decades. The assessment also concluded that insect- and rodent-borne diseases would become more prevalent throughout the U.S. and Europe.
The news isn’t good for less developed parts of the world either. Researchers have found that more than two-thirds of waterborne disease outbreaks (such as cholera) follow major precipitation events, which are already increasing due to global warming.
CONTACTS: Natural Resources Defense Council Consequences of Global Warming, www.nrdc.org/globalWarming/fcons.asp.
Dear EarthTalk: I’m going to be remodeling and was wondering: Are there floorings or wall coverings available that won’t aggravate my child’s respiratory problems?
—Mary, Lake Zurich, IL
For those with chemical sensitivities, the home is sometimes anything but a refuge. Volatile organic compounds (VOCs) such as formaldehyde can "off-gas" from carpets, wallpaper and paints, irritating lungs and promoting headaches and itchy eyes. Luckily, there are increasingly more options to traditional building materials and furnishings that are both kinder to Mother Earth and safer for our health.
For flooring, the Seattle-based Environmental Home Center recommends cork, linoleum, bamboo and selected hardwoods as the best choices from an indoor air quality standpoint. If you choose any of these options, make sure installers use non-toxic adhesives as the devil—leaking VOCs—is often in such details.
For those seeking something plusher underfoot, Earth Weave and Natural Home, among others, use natural fibers such as wool, jute, hemp and rubber to create attractive, chemical-free carpeting for both wall-to-wall and area rug applications. Both companies avoid toxic dyes and mothproofing as well as stain-repellents, relying instead upon the natural resiliency of the materials they incorporate.
And don’t stop at the carpet. All-natural wool padding, which is usually needled together to avoid the VOCs often found in adhesives, will keep the top layer soft without introducing toxins to the underfoot mix. Traditional carpets and pads can off-gas a smorgasbord of noxious chemicals, including VOCs.
A raft of new wall-coverings has also come to the rescue in recent years. Most wallpaper is not made from paper at all, but from a malleable plastic called polyvinyl chloride (PVC), which generates several known carcinogens, including dioxin, during its production. One green alternative is Sherwin-Williams" non-vinyl Easychange brand. Made from paper, it requires no special solvents or adhesives to install, and is stocked in a variety of designs and styles. Another good choice is Pallas Textiles" DialTones line, made from discarded phonebooks. Also, Environmental Home Center makes its own Innovations brand, which is made from nontoxic polyester and wood pulp, using water-based inks completely free of heavy metals.
In the paints category, there are now many non-toxic or low-VOC offerings, including AFM Safecoat, Livos, BioShield, Yolo and Olivetti. GreenHome.com stocks many of these, and mainstream paint dealers may carry eco-friendly paints from more familiar names, like Benjamin Moore or Sherwin-Williams.
Remodelers beware, though: Changing out your flooring and wall coverings won’t banish chemical irritants entirely. Many homes built or remodeled during the 1970s were insulated with formaldehyde foam, which can remain a health nuisance long after installation. Luckily, there are now plenty of greener insulation choices, such as cellulose, cotton and radiant metal barriers. Open-cell spray insulations such as Icynene or Air Krete are also popular with green builders, as they are effective, inexpensive and easy to apply. Some of these products are available at Home Depot and Lowe"s, but small green building supply retailers can be researched at GreenerBuilding.org.