IS CITY LIVING GIVING MORE OF US ALLERGIES?
The world is undergoing the largest wave of urban growth in history.1 And the incidence of allergies is significantly higher in urban areas.2,3,4,5 What factors could be playing a role?
LESS EARLY EXPOSURE
Studies show that farm and rural exposure early in life may provide protection from allergies.6
MORE TIME INDOORS
Less time spent in contact with the natural environment could be contributing to the increase in allergies.7,8
Increasing CO2 levels leads to larger plants & more potent pollen.9,10
LONGER ALLERGY SEASON11
Spring pollen season is beginning six days earlier than it did in the 1960s.10
1. Urban population growth. World Health Organization website. http://www.who.int/gho/urban_health/situation_trends/urban_population_growth_text/en/ Published 2014. Accessed March 2014.
2. Pawankar et al. WAO White Book On Allergy http://www.worldallergy.org/UserFiles/file/WAO-White-Book-on-Allergy_web.pdf
3. Ring J, Krämer U, Schäfer T, Behrendt H. Why are allergies increasing? Curr Opin Immunol. 2001 Dec; 13(6):701-8.
4. Stevanović S, Nikić, D. Exposure to air pollution and development of allergic rhinitis and asthma. Medicine and Biology. 2006 Jan; 1371:114-118.
5. Braun-Fahrländer C, Gassner M, Grize L, et al. Prevalence of hay fever and allergic sensitization in farmer's children and their peers living in the same rural community. SCARPOL team. Swiss Study on Childhood Allergy and Respiratory Symptoms with Respect to Air Pollution. Clin Exp Allergy. 1999; 29(1):28-34.
6. Hölscher, Bernd, Christian Frye, H. Wichmann, and Joachim Heinrich. Exposure to pets and allergies in children. Pediatric allergy and immunology 2002; 13(5): 334-341
7. Hanski I, et al. Environmental biodiversity, human microbiota, and allergy are interrelated. PNAS. 2012; Vol 109, No 21, Pages 8334–8339.
8. Norback D. Michel I. Widstrom J. Indoor air quality and personal factors related to the sick building symdrome. Scand J Work Environ Health 1990:16:121-128.
9. National Wildlife Federation: Extreme allergies and global warming. http://www.nwf.org/pdf/reports/NWF_AllergiesFinal.pdf. Accessed April 25, 2014.
10. Root TL, Price JT, Hall KR, Schneider SH, Rosenzweig C, Pounds JA Fingerprints of global warming on wild animals and plants. Nauture. 2003; 421(6918):57-60.
11. Ziska, Lewis, Kim Knowlton, Christine Rogers, Dan Dalan, Nicole Tierney, Mary Ann Elder, Warren Filley et al. Recent warming by latitude associated with increased length of ragweed pollen season in central North America. Proceedings of the National Academy of Sciences. 2011; 108, (10): 4248-4251.