Health and Climate Change: 7 Ways You Are Being Harmed

From the increase in frequency of heatwaves to the spread of infectious diseases, changing weather patterns are already affecting us all


The consequences of climate change sometimes appear far off. But warming and changing weather patterns are already driving changes in public health. The following are seven ways in which climate change affects you and your well-being.

The Green Report


Heatwaves are increasing in frequency, intensity, and duration throughout the world. The nature of heatwaves is also affected by climate change. Nighttime temperatures have been climbing twice as fast as average temperatures since 1970, meaning less relief at night. (When the temperatures at night don't fall in farm country, the cows go down. The same holds true for us.) In addition, the warmer atmosphere holds more water vapor -- seven percent more for each one-degree Celsius warming -- raising humidity levels, thus heat indices, which determine how we feel during a heatwave. The combination of factors make heatwaves today all the more lethal, and the consequences include cardiorespiratory illness, and dehydration and diarrhea in children. Thousands have lost their lives in recent heatwaves in Europe, Russia, and India, for example.

Asthma and Allergies

The total number of asthma sufferers in the U.S. has more than doubled since 1980 and several exacerbating factors stem from burning fossil fuels.

Mosquito-borne diseases are appearing higher in the mountains of Africa, Asia, and Latin America, where glaciers are retreating.

Increased carbon dioxide (CO2) and warming both boost pollen production from fast-growing trees in the spring and ragweed in the fall. The allergenic proteins in the pollen become stronger with higher levels of CO2.

You may have observed that poison ivy is proliferating. Increased CO2 also stimulates poison ivy growth and boosts the chemical within it (uruschiol) that causes the contact dermatitis.

Small particulates from burning fossil fuels (e.g., diesel, coal), in addition to clogging our airways, attach to pollen and mold spores and help deliver them deep inside our lung sacs. Furthermore, ground-level ozone -- photochemical smog, chiefly from other tail pipe emissions -- injures the lung linings and primes the allergic response. The reaction that forms ozone also increases during heatwaves.

Meanwhile, climate change has extended the allergy and asthma season two to four weeks in the Northern Hemisphere (depending on latitude) since 1970. In addition to the anxious suffering induced by asthma, the loss of school days and lost productivity attributable to asthma in the U.S. cost us $56 billion in 2007 -- and that number continues to climb.

Spread of Infectious Diseases

Climate change encourages the spread of infectious diseases in two ways: Warming expands the geographic conditions conducive to transmission of vector-borne diseases (VBDs) while extreme events often leave clusters of mosquito-, water - and rodent-borne diseases (and spread toxins).

First, mosquito-borne diseases are appearing higher in the mountains of Africa, Asia, and Latin America, precisely where glaciers are retreating and plant communities are migrating upward. (Mountains are superb laboratories for studying climate change, because of their verticality. One can go from desert to tropical to polar conditions in just five miles.) Today, Malaria is circulating in the Nairobi, a mile high city; malaria has occurred high in the mountains of Bolivia; and dengue fever is spreading throughout the highlands of Vietnam.

In the U.S., tick-borne Lyme disease (LD) is the most important VBD. Its range is increasing as winters warm. LD case reports rose eight-fold in New Hampshire in the past decade and 10-fold in Maine (and today include all of its 16 counties). Babesiosis, or animal malaria, also carried by ticks, is growing in the northeast and threatens the blood supply.

Warmer winters and disproportionate warming toward the poles mean that the changes in range are occurring faster than models (based on average temperatures) projected. Biological responses of vectors and plants to warming are, in general, underestimated and may be seen as leading indicators of warming due to the disproportionate winter and high-latitude warming.

Note: While temperatures have risen in the U.S. some one-degree Fahrenheit in the past century, those in Maine have gone up 1.4 degrees and winters have warmed three degrees. On the other side of the continent the changes are even more dramatic. Alaska's temperature has risen 3.4 degrees while its winters have risen 6.4 degrees, bringing in stinging insects (wasps), mosquitoes, and pine bark beetles, all while melting tundra and coastal inundations are forcing communities to relocate, causing untold emotional and mental stress.

Then, to extreme events. Extreme weather events are increasing in frequency and their very nature is intensified by global warming. With the warmed atmosphere holding more water vapor and the warming ocean the repository for the last century's global warming, rain is coming down with increasing intensity across the continual U.S. The yearly amount has increased seven percent overall since 1970, while two-inch/day rains, four-inch/day rains, and six-inch/day rains have increased 14 percent, 20 percent, and 27 percent, respectively. Rains in the U.S. over two-inches/day are associated with E. coli and cryptosporidium infections. Heavy rains and flooding can also spread toxic chemicals and leave new breeding sites for mosquitoes.

Pests and Diseases Affecting Forests, Crops, Marine Life

Pests and diseases affecting forests, crops, and marine life are also encouraged in a warmer world. Bark beetles are over wintering (absent sustained killing frosts) and moving to higher latitudes and altitudes, and getting in more generations each year from Arizona to Alaska. Drought in the west also affects tree resistance, drying the resin in the bark that normally drowns the beetles as they try to drive through.

Presented by

Paul Epstein

Paul R. Epstein, M.D., M.P.H., is associate director of the Center for Health and the Global Environment at Harvard Medical School and is a medical doctor trained in tropical public health. He co-authored the book Changing Planet, Changing Health.

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