A study of oak-pollen production and phenology in northern California: prediction of annual variation in pollen counts based on geographic and meterologic factors.

To assess the characteristics of oak-pollen production and dispersal, 9 years of weekly volumetric air sampling, with modified swing-shield rotoslide pollen samplers, were obtained in San Francisco and San Jose, Calif. The Mediterranean climate of coastal California supports 9 million acres of oaks of nine different species. The major pollen contributors in the two sampling areas are coast live oak (Quercus agrifolia Neé) and valley oak (Quercus lobata neé). Sampling data indicate that grains may be wind transported at least 16 km (10 miles). A strong correlation exists between pollen capture and total rainfall a full year before pollen release. The correlation is statistically significant, based on a Spearman rank test. A positive regression line slope demonstrates that the greater the precipitation, the stronger the stimulus for pollen production. The median count can be predicted within a factor of two with high probability a full year before release. During most seasons, the peak pollen collection from coast live oak and valley oak occurs in early April. A second peak production period, in mid-May, represents the conglomerate of other oak-pollen types. However, there are major yearly differences in the relative amounts of pollen released during these two periods. Consequently, individual oak pollinosis may depend as much on variable production by the major species as on the total quantity of airborne oak pollen. These data will help clinicians predict and prepare for the intensity of the oak-pollen season and explain seasonal variations in clinical symptoms from year to year. The question of cross-reacting and specific allergens among oak species can be answered by RAST-inhibition studies.(ABSTRACT TRUNCATED AT 250 WORDS)