An attempt was made to compare pollen counts determined by the volumetric method (Burkard sampler) with the gravitational method (Durham’s sampler) during the flowering seasons of evergreen coniferous trees such as (1) Japanese cedar, Cryptomeria japonica (abbreviation in this article: JC) and (2) Cupressaceae family, mainly hinoki cypress, Chamaecyparis obtusa (abbreviation: Cup). Observations were carried out in the cities of Fukuoka, Sagamihara and Funabashi over five consecutive years. The pollen counts obtained by Durham’s method correlated very well to the counts obtained by the Burkard technique. Intensity of airborne pollen dispersion varied regionally and from year to year. Very low pollen counts were observed in Fukuoka in 2004 and excessively high pollen counts in Sagamihara in 2005. Comparison of the results derived from Durham’s sampling method with those derived from Burkard’s sampling method revealed that these two methods are equally suitable for monitoring exposure to airborne JC and Cup pollen. To determine the starting days of JC and Cup pollen dispersion, Durham’s technique is not inferior to Burkard’s technique, but rather defines the start of pollen dispersion more distinctly. A long-term record of pollen counts obtained by Durham’s technique from 1986 to 2008 in Fukuoka, revealed that the predictive values showed very low pollen counts in the case of particularly low July temperatures in the year before. As a conclusion, continuation of airborne pollen monitoring by the volumetric method (Burkard’s sampling technique) in comparison with the gravitational method (Durham’s sampling technique) will be required to evaluate the validity of the two methods for the climatic conditions of Japan. On the other hand, potential advantages of pollen data obtained by Durham’s sampler deserve international re-evaluation.
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