The peak pollen times in this geographical area are spring (trees – a time period not included in our study), June (grasses) and September (weeds).
The high domestic price is paired with an enormous potential market: an estimated 35 million Americans suffer seasonal allergies, and many of us will be feeling that first tickle of dread later this month, when spring tree pollen begins to barge into our air passages like molecular roustabouts.
People living near the lower Yellow River know it by the name chunshu, meaning "spring tree".
Maple showed the longest average duration (25 days), while the mid-spring tree pollens showed shorter durations.
We found that the mid-spring tree pollens were most consistently and strongly associated with both OTC allergy medication sales and asthma syndrome ED visits.
Also, the mid-spring tree pollens may appear to have the largest impacts on these outcomes possibly because their concentrations are simultaneously high during the relatively narrow time window.
We see coherence in the associations between tree pollens and OTC allergy medication sales and asthma syndrome ED visits in that they were both most strongly associated with mid-spring tree pollens and not associated with the early-spring pollens (elm and poplar).
The magnitude of associations is substantial, especially mid-spring tree pollen types (maple, birch, beech, ash, oak, and sycamore/London planetree) with cumulative rate ratios up to 2.0 for OTC allergy medication sales (e.g., 1.9 [95 % CI: 1.7, 2.1] for ash pollen) and up to 1.7 for asthma syndrome ED visits (e.g., 1.7 [95 % CI: 1.5, 1.9] for ash pollen).
But the last few springs, those trees were virtually silent.
Another seasonal threat to the fruit crop, Mr. Fisher said, is that in rainy springs, when trees bloom in sustained wet conditions, "pollination is impacted, because bees and many other common pollinators don't like the rain".
