Pollen Allergy Becoming a Mainstay

Pius Chi-Shing Lee

Pollen allergy is more commonly known as hay fever. Medically speaking, it is called seasonal allergic rhinitis —- a provocation of the immune system to overreact to pollen from trees, grasses, and weeds. Hay fever occurs mainly in the spring and fall when pollen from trees, grasses, and weeds are in the air. Pollen allergy affects not only the respiratory systems, sometimes it also affects hearing and seeing due to inflammation of the eyes and ears due to reactions to guard against pollen dwelling in a person’s external organ sensitivities. Symptoms of hay fever include: itchy, watery eyes; sneeze; cough; runny nose; nasal congestion; sinus pressure, which may cause facial pain; sore throat; headache; swollen, bluish skin beneath the eyes; decreased sense of taste or smell; and increased asthmatic reactions.

Recently, hay fever has been exponentially more widespread across the board in geographical and seasonal extents. In Central and Southern Europe it reached a startling 40% of the population. In the United States the afflicted population was a close second runner-up at 30%. Asia has a large range of affliction rates depending on the types of vegetation and shrubs around population centers. In this respect, Japan has much cedar forest and plays a leading role in afflicting about 30% of her population. There were many emergency room admissions across the world due to severe cases of hay fever.

Becoming Personal

I did not have hay fever, at least not to my awareness, until Thuyen-Anh and I after our marriage moved permanently to the United States and made our home in Greater Washington D.C.  Washington D.C. enjoys temperate weather with distinctive winters and summers. Spring and fall in D.C. are not necessarily noticeable or prolonged. This adds to the complication of difficulty to predict pollen/spore out-burst for trees in the spring and grass in the summer. D.C. is an envy of many national capitals that it has a rich flora diversity of temperate forests surrounding the urban centers all across DC, Maryland, and Virginia (DMV) districts, dubbed the Greater Washington. It may be one of the most greenish-and-vegetated capitals of the world. This impacts the 6.3 million residents in the DMV area. Therefore the combination of large concentrations of human populace and lush vegetation adjacent with one another is a recipe for a large affliction rate of hay fever.

I am a firm believer of “you are what you eat”. It is invariant with respect to the spiritual, emotional and physical being of mine.  The Bible is unequivocal in advocating this natural law: “Do not be deceived: God cannot be mocked. A man reaps what he sows. Whoever sows to please their flesh, from the flesh will reap destruction; whoever sows to please the Spirit, from the Spirit will reap eternal life. Let us not become weary in doing good, for at the proper time we will reap a harvest if we do not give up” (Galatians 6:7-9). In other words: Goodness begets goodness; and badness begets badness. When I first gained entry into the U.S. via California (CA) as an immigrant, it was during the spring season. My close relative who hosted us had rather severe hay fever symptoms. I could not sympathize with him, and thought that he was among the few unfortunates. He stunned me saying that he did not have any trouble nor knew anything about hay fever until he settled down in the U.S. The abrupt turning point came to him after he lived in CA for about seven years. He sneezed and coughed terribly in the spring. His condition did not improve with administration of cold medicines. The timing of the symptoms coincided with pollen outbursts. He predicted that I would be more sympathetic and be afflicted by hay fever myself in seven years. The irony was that I became sympathetic and bitter as his prediction materialized. It was also quite abrupt that I began to suffer miserably in my seventh year mark since migration to the U.S.

Incubation and permeation happen every day in me during all these in-between seven years, as suggested by the aforementioned scripture (Galatians 6:7-9). The correct medical term for the gradual heightening of the immune system toward pollen is called sensitization. An individualistic threshold decides when the chemically inert pollen starts to be recognized by the sensitized immune system to be destroyed and expelled.  For me, in my seventh year since migration, my hay fever symptom-outbreak overwhelmed me.

Pollen Forecasting Mitigates Exposures

In the USA the weather forecasting business is an area of civic service completely open for competition and entrepreneur partnerships. Pollen forecasting is a category of weather forecast. Pollen forecast becomes an essential information service for people to plan their outdoor activities. As a trained meteorological forecaster, I began to study pollen forecasting. It became a soothing and relief-binding hobby. It perhaps concludes in recommended treatments. There exists an array of hay fever treatments both short term and long term. There are seasonal immunotherapy shots where the patient receives a series of allergens in gradually increased dosages to train the immune system to brush off the allergens as non-foreign objects. Pollen forecasting must be specific to the pollen species. Its usefulness is measured by its specificity and forecast lead-time — how much time the event was foretold ahead of the event.

In terms of the technicalities involved, pollen forecasting is rather akin to those of pollution forecasting. By definition pollen is definitively not a pollutant. Pollutants are polluting substances resulting from natural or man-made activities. However, one analyzes the input and outcome processes of the forecasting methodologies between pollutant forecast and pollen forecast, they are almost exactly the same. The only major difference is that a pollen grain is non-reactive chemically and is transported as an inert particle.

Air Pollution Exacerbate Pollen Allergenicity

An air-pollution forecaster looks attentively at the chimneys of factories and exhaust pipes of combustion engine vehicles to quantify and identify the amount and chemical characteristics of a pollutant such as nitrogen oxides (NOx), a pollen forecaster looks at the phenology of a vegetation to derive quantity and speciation of the emitted pollens. The latter is a much simpler calculation both physically and chemically speaking. In air pollution the emission quantification process is rather messy and heuristic. It includes multiple phase emissions: gaseous emissions with various thermal buoyancy and particulate phases of large range of sizes: ultra-fine to micrometer diameter particles. It involves tedious book-keeping and verification processes of emission types and source strengths. In comparison, pollen emission quantification is rather simple as the uniformity question is generally less problematic than man-made emission sources. Ragweed plants are the weeds most likely to cause allergies. One plant can produce nearly 1 billion grains of pollen. They are all particles usually in the 100 micrometer diameter ranges and are only emitted at ambient temperature with zero buoyancy. In terms of chemistries of the emission for the two phenomena, air pollutants are usually highly reactive when they are newly emitted at high temperatures such as Nitrogen Oxide (NO) from tail pipes of petroleum car engines. On the other hand, pollen particles freshly emitted are rather inert with uncontaminated surfaces. The transport of air pollutants for air quality forecasting purposes is a combination of local, regional and global extent depending on the species of the pollutants, meteorological conditions and the chemical regimes of the transport paths to be encountered. This is not quite the case for pollen transport as the pollen particles are largely super-sized particulates (hundreds of times larger than Particulate Matter of 2.5 micrometer or smaller diameters —– (PM2.5) aerosols). Pollen is strongly subjected to gravitational settling and is usually deposited within 1000 km of the emission source. Therefore pollen transport is local and regional.

pollen particle
Colorized pollen particle under electron microscope (Wiki)

Table illustrates the differences between man-made air pollutants and pollen forecasting.

O U T C O M E Pollutant forecastPollen forecastremark
SafeguardHuman healthHuman healthrespiratory
AdvisoryMitigation and pollution abatementMitigation and medicationLead time is critical
T A R G E TTarget speciesLargely chemically activeLargely chemically non-activeAggravated allergenicity
Particulate sizeSub-micrometer (gas and PM2.5 )100 micrometer in diameterPollens gravitationally settled
RangeLocal, regional and globalLocal and regional 
E M I S S I O NModelingMessy and heuristicMinimal heterogeneity 
Instance of releaseInitial buoyancy and momentumZero buoyancy and momentumHot internal combustion
QuantificationInventory and satellite observationsPlant phenology 
modificationsPlume heights,.., etc.Hydrology & tree canopy 

Freshly emitted pollen particles are chemically inert. They are transported through polluted air and can accrue and accumulate pollutants on their surfaces. This is bad news for the population who is allergic to pollen. The contaminated pollen is many times more potent to aggravate allergic reactions.  For instance, when a pollen particle accrues pollutants that produce ozone, it will set off a chain of chemical reactions that changes the pollen’s protein structure. The altered allergen is then more likely to bond with nitrogen dioxide, which exacerbates immune response. Even when the ozone-altered allergens don’t react with nitrogen dioxide, two of them can bond with one another, forming a larger molecule that is extra-irritating to the immune system. Pollutants are to make pollen-associated-allergies particularly powerful, especially in humid, hot and smoggy environments.

Aggravation of pollen allergenicity by air pollutants is an extremely worrisome bad news when compounded with the two following realities: (1) the pollen season is longer and stronger as the world temperature increases, and (2) Urbanization concentrates the populace making both air pollutants and pollen-associated-allergen close to home.

Hang on tight, the pollen phenomena is just beginning.

Author: Pastor. (Dr.) Pius Lee is the Director of the Development Division of NYSTM. In 2021, he retired from the National Oceanic and Atmospheric Administration (NOAA) of the United States, and was selected the winner of NOAA’s Administrator’s Award for the Air Pollution Forecasting Research Group in 2020. Pastor Lee and Mrs. Ancy Thuyen-Anh, Lee have three sons and one daughter. The couple relocated from the capital, Washington, to New York to take up the post.

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