Springtime brings the familiar woes of seasonal allergies for millions of people. Climate change seems to be exacerbating allergy season, as researchers have discovered that common allergen-producing plants, such as ryegrass and ragweed, emit smaller particles known as “subpollen particles” (SPPs) in greater quantities than previously thought. Interestingly, intact pollen grains from these plants, which can enhance cloud formation, are likely to have the most significant impact on the climate.
Pollen serves as a natural means for plants to reproduce and exchange genetic material. When exposed to moisture, pollen grains can burst into tiny SPPs, measuring less than a micron in length. These smaller particles can reach the lower respiratory system, causing prolonged inflammation compared to larger pollen grains.
Both SPPs and intact pollen grains act as ice nucleation sites, initiating the formation of clouds. However, SPPs and pollen form smaller, denser clouds that retain more precipitation. This phenomenon contributes to climate change by trapping radiant heat. Consequently, elevated temperatures prolong the release of pollen, intensifying the allergy problem.
Brianna Matthews, Alyssa Alsante, and Sarah Brooks previously studied the emission of SPPs by oak trees under different humidity levels. In their latest research, they sought to investigate how ryegrass and ragweed release SPPs in humid conditions and how these particles impact ice cloud formation.
The team collected samples of ryegrass and ragweed and subjected them to varying humidity levels and bursts of wind in a specialized “pollen chamber” to simulate real-world conditions. They evaluated the number of SPPs per pollen grain and the ice nucleation abilities of both types. Surprisingly, the researchers found that previous experiments underestimated the quantity of SPPs by a factor of 10 to 100 for these plants. The discrepancy likely arose due to less realistic methods of spreading the pollen and generating SPPs in the previous studies.
While ragweed and ryegrass SPPs exhibited minimal ice-nucleating capabilities, whole pollen grains facilitated cloud growth. The researchers suggest that these updated parameters and emission numbers of pollen grains and particles could improve the accuracy of climate models.
In summary, climate change influences allergy season by increasing the emission of smaller subpollen particles from allergen-producing plants. These particles can cause more inflammation and have a greater impact on respiratory health. Additionally, pollen grains and subpollen particles affect cloud formation, contributing to climate change through the retention of radiant heat. By studying the emission and properties of pollen particles, researchers can refine climate models for more accurate predictions.
Source: American Chemical Society