If the yellow tinge to the air has you reaching for the Claritin, you’re not alone. The blooming flowers have brought skyrocketing pollen levels, blanketing the Washington area under a yellow haze.
Tree pollen counts this week were “very high,” according to the U.S. Army Centralized Allergen Extract Laboratory. Last week, it appeared to peak — topping 2,500 grains per cubic meter. It’s not as bad now — 1,622 grains per meter — but that’s still plenty enough to bring watery eyes and a barrage of sneezes.
But just how much pollen is there wafting over the District? We can do some quick back-of-the-envelope calculations to help picture these wild values.
An individual grain of pollen is puny, oftentimes composed of only one or two cells. Every species of plant has a different size and shape of its pollen, but most grains are less than 200 micrometers (0.0002 meters) in diameter. That’s just 0.00787 inches across. We’ll take a middle-ground value — 75 micrometers — which is pretty well in line with what a lot of trees shed.
There are few estimates of how much a grain of pollen weighs, but a researcher at the University of Albany once reported that 2,000 grains of maize pollen weigh about 1 milligram. Maize pollen is similar in size to our 75-micrometer selection, so we’ll go with that.
And now let’s imagine the pollen that’s been driving us nuts is present only near the ground. After all, that’s where the plants live. We’ll assume the air is well-mixed up to about 10 meters (33 feet) in height. And now we crunch the numbers.
The result? 2.87 trillion grains of pollen are swirling in the air near ground level in Washington. That must weigh a ton, right? Wrong. Pollen is a microscopic aerosol. It’s puny. So the nearly 3 trillion grains in the air stack up to about 57 kilograms, or 127 pounds — roughly the weight of a teenager.
That estimate includes only what has made it into the atmosphere. There’s still an obscene amount on and in plants, so it’s easy to see why the 127-pound number may appear a little low. But for atmospheric particulates, even a few pounds of something can be significant.
Divvying it up, each D.C. resident would get a little over 4 million grains. Congratulations! That’s a little less than the weight of a dime.
If we were to gather it all, it would occupy 22.4 cubic feet. That’s the same as 447 family-size 1.5-quart ice cream carts, or 1,270 16.9-ounce water bottles.
And if you’re hungry, bon appétit. Washington’s airborne pollen weighs the same as more than 5,000 Oreos — or 3,960 if you’re a fan of DoubleStuf.
All this pollen isn’t going to stick around forever, though. Rain over the next few days will “scavenge” much of it out of the air, the springtime bloom moderating as summer rolls around. The end is in sight, though. If you can see through the yellow veil, that is.