A Plan for Schools to Reduce Pollen-Allergies and Related Allergic-Asthma
Pollen-Allergy Prevention and Control Program:
The problem: Allergies and asthma levels continue to rise around the world. School-aged children are the most susceptible. Modern landscaping (with its extensive use of newer clonal horticultural male selections of “litter-free” shrubs or trees) is often highly allergenic. Pollen levels in city schools are often very high and getting worse. Compounding this problem, due to global warming and pollen’s interaction with urban air pollution, pollen production today is greater, and individual (urban) pollen grains are far more allergenic than ever before. Many of the most allergenic landscapes are found at elementary and secondary schools. The current situation is no longer sustainable.
Asthma: Having a pollen-allergy is frequently a precursor to the development of asthma. More than 80% of those with asthma also have pollen-allergies. Allergies are also the most common trigger that initiates sudden episodes of asthma.
The solution: These recommendations below will not “cure” pollen-allergies or asthma, but they will greatly reduce many of the triggers. Symptoms may be reduced, and unlike many drug therapies, there are no negative physical reactions to these proactive programs.
Any one of these recommendations (Actions) will help reduce exposure to school pollen; the more recommendations a school decides to apply, the better, and the quicker, their results will be.
Action # 1. Ask your city leaders to follow the innovative lead of cities such as Albuquerque, New Mexico, and enact a tough local Pollen Control Ordinance, one with some teeth in it. Ban the sale and planting in city limits of the most allergenic plants. Fruitless (male) mulberry trees, male box elder clones, male junipers and male yews should be on every list… however, in each area, given its geography and climate, there will be other highly allergenic shrubs and trees that should also be included. (Example, in Los Angeles, olive trees, cypress and male Podocarpus should be included in the ban.)
Action # 2. A plan should be approved and set in motion at once so that each year a certain percentage of the worst, the most highly allergenic shrubs and trees be removed from the school landscape. Replacements to be scheduled with allergy-friendly choices. The more ambitious this plan is, the more effective it will be.
Action # 3. Because of the horticultural practices of the last 40 years, almost every modern school now has far more male plants than females. Male plants shed large amounts of allergenic pollen; female plants trap pollen and shed no pollen. The current sexual imbalance is not healthy or sustainable. Because of systemic reluctance toward removing already growing trees, it’s not expected that enough male trees will be removed, therefore: a serious program should be initiated, where every year a large number of known female trees (and shrubs) are planted with the aim of eventually achieving some form of natural balance of the sexes. With large allergenic trees such as oaks, sycamores and numerous other deciduous species, if not outright removed, these trees can be pollarded each winter, and this will stop their pollen production. This will need to be re-done each dormant season to continue to be effective.
As with Action # 2, the more aggressively done, the sooner positive results will be seen.
Action # 4. Species biodiversity is a worthy goal, but with certain allergenic species, diversity of that particular species is, from a human health perspective, a flawed goal. For example, birch trees (Betula species) are well known to cause pollen allergies and birch pollen cross-reacts with many other species, causing an extended negative effect. Each species of birch tree has a short bloom period when it sheds pollen. However, if numerous different birch species are planted in a landscape, as each species will bloom in its own time, this effectively greatly extends the time of exposure to this pollen. With birch and similarly allergenic tree species, it’s recommended that no more be planted at all, and if necessary that only one species be used, at the most.
Action # 5. Because insects make up so much of the diet of virtually all song birds, allergy-friendly trees that provide food for them should be planted in much larger numbers. The importance of wild birds in allergy/asthma reduction should not be underestimated. Insect pests often infest landscape shrubs and trees. If unchecked their numbers soon explode, and the plants become covered in insect dander and sticky secretions (“honeydew”). Airborne mould spores land on these secretions and quickly proliferate. The result is a shrub or tree that is now highly allergenic.
Song birds are our best defence against these pests (usually some species of aphids, whitefly, scale or mealybug) and keep their numbers in check. Each year schools should plant a number of plants specifically to attract and feed wild native song birds. Many fruiting native species, in particular, are useful for attracting wild birds. (It should be noted that male shrubs and trees produce no food for birds.)
Action # 6. In many schoolyards, there is at least one common weed that triggers more than its share of pollen allergy. Each school should consider a long-range plan for eradication of these. Many decades ago, the city of Montreal, Canada, undertook just such a program. They enlisted the help of school children, scouting groups, church and other civic groups. The city posted and passed out fliers with tips on identification at all stages, and in less than seven years, 100% of the ragweed in Montreal had been eradicated. For many years after this Montreal was widely advertised as the place to go in the fall to escape ragweed allergy. (Alas, in subsequent generations Montreal became lax about this, and now has a great deal of ragweed.)
In each area, there may be a different noxious weed species to focus on. In San Diego and Santa Barbara, California, for example, there is little ragweed, but castor bean (Ricinus communis) has become a noxious invasive weed, and its pollen is a prime asthma trigger. If ragweed grows in the area the school children should be taught to identify it in all growth stages. Under supervision, the children can be encouraged through various methods to pull up all young ragweed plants they see anywhere close to their own homes or schools.
Action # 7. Lawns are popular at almost all schools, but some species of lawn grasses cause more allergy than others. Except the mild-winter area grass, Common Bermuda grass, almost all other types of grasses will not flower and release pollen if they are kept mowed on a regular basis (hybrid Bermuda grasses will not flower if regularly mowed).
All school lawns should be kept mowed on a weekly basis, and areas with common Bermuda grass should be switched over to a less allergenic lawn sod as soon as possible.
Also whenever possible, use of female clones of grasses such as buffalograss should be encouraged. These cultivars use very little water, require less fertilization, and they produce no pollen. There are now selections of female buffalograss (Buchloe dactyloides) suitable for almost all areas.
Hybrid Bermuda grass lawns normally do not produce any pollen, and a tall fescue lawn will also produce very little grass pollen if it is mowed weekly.
It should also be understood that a thick, healthy, regularly mowed lawn makes an excellent trap for pollen that comes from nearby shrubs or trees. When this pollen lands on the lawn, it eventually gravitates down below the surface of the grass and effectively is taken out of circulation.
Action # 8. School children should be taught to identify and know the shrubs and trees that grow at their schoolyards. If these are dioecious (separate-sexed) species, then the children should be taught to tell the difference between a male and female plant. All holly or juniper bushes are, for example, dioecious, and only the female plants will ever produce any berries. If children understand the connection between male plants and pollen, then they will take this information home with them and help educate their parents. The result will be that their yards will also, in many cases, start to become more allergy-friendly.
*Note: To identify the most allergenic shrubs or trees (and also the least allergenic) the Ogren Plant Allergy Scale (OPALS) is a very useful tool. OPALS has been available to the public since 1998 and is used by many allergists and numerous organizations including the USDA Urban Foresters and numerous state and local offices of the American Lung Association. Its use is endorsed by the Public Health Department in the most current Strategic Plan for Asthma in California.
“All plants, just like all people, are not created equal. The very best treatment for allergy is to avoid the offending substance.” Allergist David A Stadtner, MD, Stockton, California
- Aerobiology, Plane tree pollen levels could be locally very high, reflecting the proximity of the source. MA Gonzalo-Garijo, Differences in spatial distributions of airborne pollen concentrations at different urban locations within a city, Children’s’ Hospital, Badajoz, Spain 2006
- Airborne & Allergenic Pollen of North America, Dr. Walter H. Lewis, John Hopkins University Press 1979
- Amendment to the Pollen Ordinance, Air Quality Tree Flyer handout, Albuquerque City Government, Albuquerque, NM 2009
- American Lung Association recommends plants which have pollen rating of 6.0 or less, using the OPALS ranking, University of California at Davis, Florasource, UC Verde, 2009
- Analysis of changes in flowering phases and airborne pollen, Journal of Environmental Engineering and Landscape Management, The Lithuanian Academy of Sciences and The International Academy of Ecological and Life Protection Sciences, Lithuania, 2010
- Differences in the spatial distribution of airborne pollen concentrations at different urban locations within a city. Gonzalo-Garjo MA, Tormo-Molina R, Muñoz-Rodríguez AF, Silva-Palacios I., Journal of Investigative Clinical Allergy, Allergy Section of Children’s University Hospital of Christ, Badajoz, Spain, 2006
- Japanese study shows that the prevalence of cedar pollinosis varied not only with the proximity to cedar trees, but also with the volume of road traffic. David W. Kennedy, William E. Bolger, S. James Zinreich – 2001, Diseases of the Sinuses, BC Decker, Inc. Ontario, Canada L8N 3K7
- Outdoor air pollution, climatic changes and allergic bronchial asthma exposure to air pollution increases airway responsiveness to aeroallergens, G. D’Amato, Division of Pneumology and Allergology, Hospital A.Cardarelli, Via Rione Sirignano 10, 80121, Napoli, Italy, 2002
- Strategic Plan for Asthma in California, California Department of Public Health, Mark B. Horton, MD, MSPH, Director: Identify the asthma triggers associated with landscaping (for example, pollen as major organic/biologic trigger) and promote low allergen landscaping around public and private properties. Asthmagenic Landscaping (www.allergyfree-gardening.com ), section 5.1.9, 2008-2012, Link: http://www.cdph.ca.gov/programs/caphi/Documents/AsthmaStrategicPlan.5-5-08.pdf
- Subjects living in urban areas are more likely to experience allergic respiratory symptoms, particularly those induced by pollen allergens, than subjects living in rural areas. North American pollinosis due to insect-pollinated plants, Lewis WH, Vinay P., John Hopkins University Press, 1979
- The increasing trend of seasonal respiratory allergy in urban areas, G.D’Amato MD, G. Liccardi, Division of Pneumology and Allergology, Naples, Italy, Allergy 2002
- Travels of airborne pollen, Eugene Cecil Ogden, Gilbert S. Raynor, Janet V. Hayes, published Washington DC, by U.S. Environmental Protection Agency, 1975
- UFORE, Urban Forest Effects Model, USDA, 2001, Dr. David J. Nowak, project leader, Northeastern Research Station, USDA Forest Service, USDA, Newtown Square, PA.
- Urban Green Zones and Related Pollen Allergy: A review. Some guidelines for designing spaces with low allergy impact, Paloma Carinanos, Manuel Casares-Porcel, Department of Botany, Faculty of Pharmacy, Campus de Cartuja, University of Granada, 18071 Granada, Spain, Journal of Landscape and Urban Planning, December 2010