Aside from having the wind to aid them in traveling north, east, south and west, pollens have the ability to boost themselves into the skies. Pollens have been located as high as two to three miles in altitude. In reaching these altitudes they imitate balloons and glider planes. The pollens ride the warm currents of air up into the sky. Anyone who has taken a First Aid course (and who hasn’t?) has been taught to keep his nose to the ground in a room that’s on fire because hot air rises and cool air drops. In this manner the pollens rise during the day with the hot air currents.
THE NIGHT AIR
This simple principle of physics has been used to ac-count for the fact that hay fever sufferers experience aggravation of their symptoms after sunset or with the occurrence of cold winds. The explanation offered is that with the setting of the sun there is a descent of the pollens due to descending air currents. A similar effect is produced in the presence of cold winds.
The early investigators of hay fever recognized that night brought increased unpleasantness, but did not know why. For protection against increased symptoms in the evening they advised shutting out the “night air.” In this they were inadvertently advocating the best procedure for such relief. An example of the advice given is contained in Dr. Morrill Wyman’s account of his own behavior. In his book on hay fever he wrote the following:
“I avoid all irritants, dust and smoke during the day, and the evening air. The windows of my sleeping-room are closed early in the forenoon, and kept closed through the night.”
This advice is still good today, with some modern improvements that shall be discussed later.
HAY FEVER AT HIGH ALTITUDES
The hay fever ceiling seems to have had a variable career. With the early location of hay fever resorts in the White Mountain regions, 1500 feet was set as the hay fever-free altitude. Grass pollens sufferers were quick to refute this idea. Their symptoms prevailed at any altitude at which grass would grow. And grass grew above 1500 feet. As for tree pollen sufferers, they learned that it is necessary to get above the timber line in some areas in order to be free of the pollens responsible for their hay fever. Ragweed sufferers who went to hay fever resorts chosen solely for their high altitude were frequently disappointed.
The 1500-foot concept was soon raised to 4000 feet. Later 6000 feet was mentioned as a safe altitude. A survey of hay fever conditions in Denver, Colorado, disclosed hay fever plants at unusually high altitudes. At Allenspark, Colorado, situated 8400 feet above sea level, mountain sage was abundant enough to cause appreciable hay fever symptoms. Higher up, Silver Plume, at an altitude of 9189 feet, contained large quantities of horseweed, careless weed, and mountain sage. All three of these plants are well known western fall hay fever culprits.
Does this evidence mean that hay fever resorts at high altitudes are of no avail? Is the entire concept of hay fever relief at high altitudes merely a superstition? The answer to both questions is, no. Altitude is important but primarily in so far as it is associated with latitude.
A LESSON IN GEOGRAPHY
Latitude, if you can remember back to your school days, is defined as the distance north or south of the equator. This distance is measured in degrees as we measure circular distance in geometry. Degrees are used because the earth is represented as a sphere.
The latitude at the equator is zero. The heat or temperature at the equator is at a maximum because at this level the angle of the sun is such that its rays strike the earth nearly from above and have to go through less atmosphere to reach the earth. As you get further away from the equator, toward the north and south poles, the latitude in-creases and the temperatures become lower. In this way there has come to be recognized the three zones of the earth characterized by frigid, mild and torrid temperatures.
Applying our knowledge of geography to the hay fever problem we find that a high altitude plus a high latitude makes for a cold climate. And a cold climate impedes growth of the late summer hay fever plants. A low altitude plus a low latitude represents a torrid climate. Hay fever plants are equally discouraged by torrid climates.
THE MAP AND HAY FEVER
If you now look at the map (Fig. 12) it will help you to understand why certain areas have little fall hay fever while others have extended seasons. In the United States the upper regions of Maine are recognized as being relatively free of ragweed plants. The latitude in this region is about 46°. Moving across the map, to the left at about the same latitude, you find Sault Ste. Marie in Michigan, Prince Albert in Saskatchewan and Seattle in Washington. All of these localities show relatively little ragweed.
Representative of the Torrid Zones, at latitudes of 5° to 20° we find a similar scarcity of ragweed plants. Reports indicate an absence of ragweed in Hawaii, Honolulu, lower Mexico, Panama, Venezuela, Northern Brazil and British and Dutch Guiana. The tropical plants in these areas generally produce large and sticky pollens which rarely cause hay fever. Pollens from a few grasses do cause some symptoms among grass sensitive persons in several of these tropical regions.
In contrast with these ragweed-free areas existing at high and low altitudes, you will find consistent ragweed-hay fever territory clear across the United States at a latitude of about 40°. Starting at Maryland and traversing the United States at this latitude you pass through Ohio, Indiana, Illinois, Missouri, Kansas, Colorado, Utah and Nevada.
From the Departments of Health of each of these States we received the following replies to our inquiry for in-formation concerning any localities in that State which may be considered free of fall hay fever:
MarylandAs far as we can determine hay fever is well distributed over the State of Maryland. There is no locality free from this disease.
OhioI am very sorry to advise you the ragweed grows abundantly throughout the entire State of Ohio and has heavy pollination through August and September due to the late frosts that occur in Ohio.
IndianaI regret to tell you that there is no area in Indiana to which you could come to expect relief from hay fever.
IllinoisNo information of this kind available. In Scheppegrell’s book we find for Illinois: “The State Board of Health reports no location free from hay fever.”
MissouriTo the best of my knowledge and information there are no such areas to be found throughout the State.
KansasRagweed and other pollen bearing weeds are very prevalent over the State of Kansas and there is no section of the State considered to be free of hay fever.
ColoradoWe are sorry to inform you we have a great deal of ragweed in most of the lower altitudes of Colorado. In the higher mountain regions and resort towns there is comparative freedom from this type of vegetation. Some of the localities in which people usually receive freedom from ragweed hay fever are Estes Park, Leadville, Central City, Gold Hill, Cripple Creek and other localities around 8,000 feet or over in altitude.
UtahThe only sections of the State of Utah which are free from ragweed pollen in the autumn are the canyons and mountains. Ragweed and related weeds have a very wide distribution in Utah.
NevadaAs far as I have been able to determine, there is no place in the State of Nevada considered free of hay fever.
Now to complete the hay fever picture, locate South America on the map. In the portion which is south of the equator, at a latitude of 4o° comparable to that of Mary-land, you will find Argentina. You may recall our previous quotation that 2 percent of the population of Argentina suffered from hay fever.
In order that you are not misled by the foregoing examples it may be well to remind you that latitude alone is not the determining influence on hay fever plants. Often, in regions within the torrid zones hay fever is encountered in the mountains or towns at high altitudes. For example, in the higher slopes of India, cases of hay fever are known to occur. Conversely, in regions of greater latitudes, hay fever is found in the low lands. As an illustration of this we may point to the fact that hay fever effects are prevalent in Montreal and Toronto, Canada; while they are absent in parallel areas of Maine and New Hampshire.
In the last analysis hay fever conditions in any area will be determined by all the physiographical influences that prevail. That is, in conjunction with latitude and altitude there is the consideration of the elements of rainfall, humidity, sunshine, prevailing winds, soil conditions and civilizing influences.