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Fossil fuels, allergies, and a host of other ills

2008; Elsevier BV; Volume: 122; Issue: 3 Linguagem: Inglês

10.1016/j.jaci.2008.07.015

1097-6825

Paul R. Epstein,

Indoor Air Quality and Microbial Exposure

Our defenses are under assault from a growing spectrum of challenges. For allergies and asthma, most research has focused on indoor pollutants, genetic predispositions, and socio/emotional factors. During the past decade, however, there has been an explosion of new work regarding outdoor sources of respiratory irritation and sensitization, and all these emerging issues are associated with the combustion of fossil fuels. In the past 3 decades, asthma rates have risen several fold throughout the developed and developing world. There are multiple drivers and some are additive; others are acting synergistically. Rising ragweed pollen is the leading edge. Repeated studies1Ziska L.H. Caulfield F.A. Rising carbon dioxide and pollen production of common ragweed, a known allergy-inducing species: implications for public health.Aust J Plant Physiol. 2000; 27: 893-898Google Scholar, 2Wayne P. Foster S. Connolly J. Bazzaz F.A. Epstein P.R. Production of allergenic pollen by ragweed (Ambrosia artemisiifolia L.) is increased in CO2-enriched atmospheres.Ann Allergy Asthma Immunol. 2002; 80: 669-679Google Scholar, 3Rogers C.A. Wayne P.M. Macklin E.A. Mullenberg M.L. Wagner C.J. Epstein P.R. et al.Interaction of the onset of spring and elevated atmospheric CO2 on ragweed (Ambrosia artemisiifolia L.) pollen production.Environ Health Perspect. 2006; 114: 865-869Crossref PubMed Scopus (198) Google Scholar confirm that elevated CO2 stimulates weeds to produce pollen disproportionately to the photosynthetically derived growth in their biomass. It seems weedy, opportunistic species that thrive better in disturbances profit most from CO2, putting the excess carbon into their male, reproductive, territorially seeking parts. Poison ivy (Toxicodendron taxa) does extraordinarily well, growing in vine abundance and toxicity, the chemical within it, urushiol, becoming stronger,4Mohan J.E. Ziska L.H. Schlesinger W.H. Thomas R.B. Sicher R.C. George K. et al.Biomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmospheric CO2.Proc Natl Acad Sci U S A. 2006; 103: 9086-9089Crossref PubMed Scopus (124) Google Scholar just as the pollen grains in ragweed become more allergenic (as demonstrated by electrophoresis).5Singer B.D. Ziska L.H. Frenz D.A. Gebhard D.E. Straka J.G. Increasing Amb a 1 content in common ragweed (Ambrosia artemisiifolia) pollen as a function of rising atmospheric CO2 concentration.Funct Plant Biol. 2005; 32: 667-670Crossref Scopus (138) Google Scholar Inside inner cities, a “CO2 dome” forms,6Ziska L.H. Gebhard D.E. Frenz D.A. Faulkner S. Singer B.D. Cities as harbingers of climate change: common ragweed, urbanization, and public health.J Allergy Clin Immunol. 2003; 111: 290-295Abstract Full Text Full Text PDF PubMed Scopus (309) Google Scholar trapping ambient CO2 levels in the 400s, 500s, and 600s of parts per million by volume. (The global average is now 387 ppm; preindustrially it was 280 ppm.) High levels of CO2 inside the dome-shaped urban heat island effect affect inner-city ragweed (and fast-growing trees in spring) and most likely contribute to the heat-trapping in the urban setting, whereby temperatures can range 10°F above those in the surrounding countryside. Ground-level ozone from nitrogen oxides, another by-product of burning fossil fuels, combined with volatile organic compounds, is another heat-trapping (and lung tissue–damaging) agent. Increased ground-level ozone or photochemical smog exacerbates asthma and most likely initiates new cases,7McConnell R. Berhane K. Gilliland F. London S. Islam T. Gauderman W. et al.Asthma in exercising children exposed to ozone: a cohort study.Lancet. 2003; 359 (386-3)Google Scholar and ozone formation is increased during heat waves (which are increasing with climate change from burning fossil fuels). Trees are also feeling the effect of rising CO2.8Klironomos J.N. Rillig M.C. Allen M.F. Zak D. Kubiske M. Pregitzer K. et al.Increased levels of airborne fungal spores in response to Populus tremuloides grown under elevated atmospheric CO2.Can J Bot. 1997; 75: 1670-1673Crossref Scopus (42) Google Scholar The Duke University Free-Air CO2 Enrichment (FACE) experiments in North Carolina found that loblolly pines grown under elevated CO2 grow a bit more but produce 3 times the number of cones and seeds.9LaDeau S.L. Clark J.S. Pollen production by Pinus taeda growing in elevated atmospheric CO2.Funct Ecol. 2006; 10: 1365-1371Google Scholar Fast-growing pioneering trees—the opportunist trees—that like forest edges and pop up after disturbances (like fires, cuttings, blights, and blow-downs) appear to do especially well. Since the 1970s, the date of spring flowering has advanced 30 days,10Emberlin J. Detandt M. Gehrig R. Jager S. Nolard N. Rantio-Lehtimaki A. Responses in the start of Betula (birch) pollen seasons to recent changes in spring temperatures across Europe.Int J Biometeor. 2002; 46: 159-170Crossref PubMed Scopus (205) Google Scholar the seasons changing with a changing climate from burning fossil fuels. Extraordinary spring pollen counts have been recorded in recent years (long-term records, save for in the paleo [ice] record, are sparse), and the early arrival of spring is extending the spring allergy and asthma seasons. (Allergies are also being reported anecdotally in the not-so-dead of winter; flowers sprout during especially warm Januaries.) In seasons with increased warmth and moisture, as during the 2008 spring, the addition of CO2 and nitrogen provide a plethora of stimuli, making for hyperproductive tree pollen production. (Coastal marine systems are also feeling the effects of overfertilization, with nitrogen from multiple sources—sewage, agriculture, and aerosolized nitrogen from coal-fired plants.) Some arbuscular mycorrhiza, fungi that hug the roots of trees, nourishing and supporting their growth (which pop up as mushrooms, their fruiting bodies), are also getting a boost from more CO2 and are making a lot more spores.11Treseder K.K. Egerton-Warburton L.M. Allen M.F. Cheng Y. Oechel W.C. Alteration of soil carbon pools and communities of mycorrhizal fungi in chaparral exposed to elevated carbon dioxide.Ecosystems. 2003; 6: 786-796Crossref Scopus (50) Google Scholar And now to a “nasty synergy.”12Lovejoy T.E. Climate change and epidemiology.in: Morse S.A. Emerging viruses. Oxford University Press, New York (NY)1993: 261-268Google Scholar Diesel particles, known respiratory irritants, turn out to be excellent delivery systems for aeroallergens (pollen and spores). Pollen grains and spores attach to diesel particles, as shown by scattering electron microscopy,13Knox R.B. Suphioglu C. Taylor P. et al.Major grass pollen allergen Lol p1 binds to diesel exhaust particles: implications of asthma and air pollution.Clin Exp Allergy. 1997; 27: 246-251Crossref PubMed Scopus (269) Google Scholar and are carried deep inside the lungs to the twigs and leaves of the pulmonary tract. The diesel particles (from burning fossil fuels) also contain nitrates that irritate mast cells, boosting the allergenic assault. Before leaving the particulates (from burning fossil fuels and forests), black soot has just been found to play a stronger role in global warming than previously appreciated.14Ramanathan V. Carmichael G. Global and regional climate changes due to black carbon.Nat Geosci. 2008; 1: 221-227Crossref Scopus (2399) Google Scholar Black soot traps outgoing long-wave radiation—as do CO2, CH4, ozone, chlorofluorocarbons, and H2O—and, as it settles in ice and snow, decreases the reflectivity (albedo) of otherwise reflecting surfaces (ie, holding heat). Its influence is now calculated to be 0.9 W/m2, whereas that of CO2 is 1.66 W/m2. The good news is that the black carbon can wash out in weeks, whereas CO2 lasts for a hundred years. Cleaning the composition of fuels we use means removing sulfates (which cool by reflecting sunlight and seeding clouds) and the black soot that enhances warming. CO2 itself has other consequences. Oceanic absorption is leading to ocean acidification, threatening coral reefs and other calcareous marine life by altering the saturation states of calcite and aragonite (CaCO3). Agricultural weeds are also getting a boost. Today, weeds, pests, and pathogens destroy an estimated 42% of growing and stored crops (equaling ∼$300 billion losses) annually.15Pimentel D. Patzek T.W. Ethanol production using corn, switchgrass and wood; biodiesel production using soybean and sunflower.Nat Resources Res. 2005; 14: 65-76Crossref Scopus (1016) Google Scholar While rising CO2 favors growth of weeds (requiring more herbicides), the higher C:N ratio in the leaves means that insect pests must eat more leaf mass to gain the nitrogen they need to grow16Lindroth R.L. Consequences of elevated atmospheric CO2 for forest insects.in: Korner C. Bazzaz F.A. Carbon dioxide, populations, and communities. Academic Press, London1996Google Scholar (increasing pesticide use). Herbicides, fungicides and pesticides—all derived from petrochemicals—are persistent organic compounds that further challenge the immune (and reproductive) systems. There is yet another problem stemming from a solution to the climate crisis. Burning ethanol from crops produces CO2 equal to that it takes up (this is no surprise) but also emits acetaldehyde and formaldehyde, volatile organic compounds that help form smog. Burning ethanol/gasoline mixtures also produces aromatics (eg, polycyclic aromatic hydrocarbons), and burning biodiesel produces more NOxs and particulates than burning gasoline. Indeed, we can only reduce all these hazards by minimizing the liquid fuel we use. Thus the panoply of healthy solutions includes walking and biking, smart (mixed-use) urban growth, vastly expanded public transport, and hybrid electric vehicles (cars, buses, trains, and ships) plugged into a smart, cleanly powered grid.17Epstein P.R. Moomaw W. Walker C. Healthy solutions for the low carbon economy: guidelines for investors, insurers and policy makers. Center for Health and the Global Environment, Harvard Medical School, Boston (MA)2008Google Scholar Aside from the health consequences of climate change and the potential for catastrophic impacts on Earth's life-support systems,18Epstein P.R. Mills E. Climate change futures: health, ecological and economic dimensions. Center for Health and the Global Environment, Harvard Medical School, Boston (MA)2005Google Scholar, 19IPCC Climate change 2007: impacts, adaptation and vulnerability. IPCC Secretariat, Geneva, Switzerland2007Google Scholar, 20Hansen J. Sato M. Ruedy R. Kharecha P. Lacis A. Miller R. et al.Dangerous human-made interference with climate: a GISS modelE study.Atmos Chem Phys. 2009; 7: 2287-2312Crossref Scopus (186) Google Scholar the rise in atmospheric levels of carbon dioxide from burning fossil fuels and felling forests is affecting plants in ways few projected just a decade ago. The cumulative impacts of the increased aeroallergens, particulates, ground-level ozone, and the early arrival of spring and persistence of fall are altering air quality and respiratory health. The most aggressive scenarios portend much higher CO2 levels that exist today, while some leading scientists struck by climate instability and the impacts of CO2 on ocean pH are calling for a return to 350 ppm. For social, ecologic, and health reasons, we must wean ourselves from fossil fuels. Beyond combustion lies their exploration and extraction, mining, and refining—all hazardous to our health and the environment. The quest for oil spoils coasts and drives nations into wars, while the mountain top removal silts streams and valleys, spawning cancer clusters. Combustion causes air pollution, acid rain, and climate change. There are major choices to be made along the path away from fossil fuels. The public health, healing, and health research professions have a key role to play. By examining the life cycle costs of the fuels we use and of proposed technologies and practices, we can help policymakers and industrial leaders make well informed decisions. With the right set of financial incentives and policy instruments, we may just be able to help steer society onto a path leading to a healthy and sustainable energy future.