On the Influence of Pre- and In-seasonal Meteorological Conditions on Grass Pollen Interannual Variations in the UK

Up to 30% of the UK population are sensitized to grass pollen. Therefore, grass
pollen is considered the most allergenic pollen type in the UK. Estimating the grass
pollen season severity and interannual variation is a key task in aerobiological
studies. The season severity is quantified using the Seasonal Pollen Integral
(SPIn) - the integral over time of daily pollen concentration. This severity is tightly
connected to personal exposure and the symptoms among hay fever sufferers.
Recent studies suggest that the SPIn interannual variation is related to variation
in pre- and in-seasonal meteorological conditions at the specific region. Here, we
investigate whether the SPIn interannual variation can be explained by variation in
pre-seasonal precipitation and in-seasonal air temperatures in the UK. Seven UK
pollen observation sites have been chosen in the study: Worcester, Plymouth, Isle
of Wight, Belfast, York, Islington (London) and Ipswich. The pollen observations
cover the 1996-2018 grass pollen seasons, where we include those years without
substantial gaps in the daily time series, thereby providing 116 pollen seasons to
be included in the study. Maximum daily air temperature and precipitation data have
been taken from the global summary of the day meteorological dataset. The SPIn,
temperature and precipitation data have been transformed to interannual variations
relatively mean value at each pollen observation site. The transformed time series
have been analysed by looking for correlation between variations in pre-seasonal
precipitation, in-seasonal air temperature and SPIn. The results show positive
and significant correlation between pre-seasonal precipitation and SPIn variations
(R = 0.35, p-value < 0.001) at the selected sites. Station-wise, the correlation is
positive and significant at Worcester (R = 0.54, p-value < 0.01) and Ipswich (R =
0.81, p-value < 0.05). Correlation between in-seasonal air temperature and SPIn
variations is also positive and significant (R = 0.33, p-value < 0.001) at the sites.
Station-wise, the correlation coefficient is positive and significant at Worcester,
Plymouth and Islington (R = 0.51, 0.50, 0.59, respectively p-value < 0.05). The
study indicates that the SPIn variation is not a regional scale phenomenon in
the UK. Instead, it appears to be related to local environmental effects. It is also
shown that the pre- and in-seasonal meteorological conditions are statistically
correlated with the SPIn, which may be explained by the fact that governing
processes affecting the SPIn are related to both pollen production (pre-season) and
atmospheric conditions (in-season).