Asthma, Rhinitis, Other Respiratory Diseases
Cities as harbingers of climate change: Common ragweed, urbanization, and public health,☆☆

https://doi.org/10.1067/mai.2003.53Get rights and content

Abstract

Background: Although controlled laboratory experiments have been conducted to demonstrate the sensitivity of allergenic pollen production to future climatic change (ie, increased CO2 and temperature), no in situ data are available. Objective: The purpose of this investigation was to assess, under realistic conditions, the impact of climatic change on pollen production of common ragweed, a ubiquitous weed occurring in disturbed sites and the principal source of pollen associated with seasonal allergenic rhinitis. Methods: We used an existing temperature/CO2 gradient between urban and rural areas to examine the quantitative and qualitative aspects of ragweed growth and pollen production. Results: For 2000 and 2001, average daily (24-hour) values of CO2 concentration and air temperature within an urban environment were 30% to 31% and 1.8° to 2.0°C (3.4° to 3.6°F) higher than those at a rural site. This result is consistent with most global change scenarios. Ragweed grew faster, flowered earlier, and produced significantly greater above-ground biomass and ragweed pollen at urban locations than at rural locations. Conclusions: Here we show that 2 aspects of future global environmental change, air temperature and atmospheric CO2, are already significantly higher in urban relative to rural areas. In general, we show that regional urbanization-induced temperature/CO2 increases similar to those associated with projected global climatic change might already have public health consequences; we suggest that urbanization, per se, might provide a low-cost alternative to current experimental methods evaluating plant responses to climate change. (J Allergy Clin Immunol 2003;111:290-5.)

Section snippets

Ragweed establishment

Beginning in April 2000, a transect involving rural (Buckeystown), semirural (Carrie Murray Nature Center), suburban (Towson University), and urban (Baltimore Science Center) locations was established within Maryland. Seed (A artemisiifolia ) was obtained from Valley Seed Company (Fresno, Calif) from a common seed lot of ragweed. All seeds were mixed and distributed randomly into a common soil type at monitoring sites along the transect. The common soil is classified as a Cordurus silt-loam

Urbanization-induced environmental change

Both [CO2] and ambient air temperature were related to the level of urbanization. Urbanization increased the average daily (24-hour) [CO2] by 30% and 31% in 2000 and 2001, respectively, in comparison with the farm site, the absolute CO2 values being consistent between years for each site (Table I).

. Locations and descriptions of data collection sites along the rural/urban transect

SiteDescription[CO2]CDD (°C)Difference+Avg (°C)
2000
Organic farmRural site—control386 ± 19.0b3428.40
Nature center

Discussion

There has been considerable speculation about the medical implications of climate change.3 Previous laboratory-based investigations suggesting greater potential for seasonal allergic rhinitis resulting from CO2 included stimulations of ragweed pollen production.8, 9 However, the applicability of these results to in situ conditions remained speculative. To reduce speculation, the current experiment sought to use urban environments as a surrogate for future climatic change to provide a realistic,

Acknowledgements

We thank the following people for invaluable services: Corrine Parks and Sue Patz, of the Baltimore Parks and Recreation Department's Carrie Murray Nature Center; Bruce Baldwin, of the Baltimore Science Center; Drs Larry Wimmers and Ralph Scott, of Towson University; Nick Maravel, of Nick's Organic Farms; Susan Gebhard, for editing; Dr Richard Sicher, of the USDA Alternate Crops and Systems Laboratory, for nitrate and nitrite analysis of rainwater; Dr Jonathan Patz, of the Johns Hopkins School

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    Funding sources: Dr Ziska is funded through the Agricultural Research Service (ARS, CRIS #1270-21000-020-00D); a cooperative research agreement was established between ARS and Surveillance Date Incorporated (SDI) for determination of pollen counts and immunochemical analysis. No direct payments, stock options, patent licensing agreements or other commercial ownerships occurred between SDI and ARS.

    ☆☆

    Reprint requests: Lewis H. Ziska, PhD, Alternate Crop and Systems Laboratory, United States Department of Agriculture, Agricultural Research Service, 10300 Baltimore Avenue, Beltsville, MD 20705.

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