3 research outputs found
An Assesment of the Potential for Co-exposure to Allergenic Pollen and Air Pollution in Copenhagen, Denmark
Background.Co-exposure to air pollutants and allergenic pollen can elicit or exacerbate a number of conditions in susceptible individuals, including allergic airway diseases. Both concentrations and diurnal patterns are relevant when assessing potential health effects.
Methods.To assess which pollutants may be of particular relevance when investigating co-exposure with pollen, we examined yearly variation and diurnal patterns of pollutants on days with high pollen levels, and also for the remaining part of the pollen season. This analysis included measurements of grass and birch pollen, sulphur dioxide (SO2), ozone (O3), nitrogen dioxide (NO2) and particulate matter (PM) in the period 1997-2012.
Results.O3 concentrations were found to be higher on peak pollen days and high O3 concentrations coincide both seasonally and diurnally with high pollen counts, potentially leading to clinically relevant simultaneous co-exposure. NO2 and SO2 did not appear to coincide in concentration peaks with pollen counts, and concentrations were well below potential thresholds for adjuvant effects to the allergic reaction. Neither diurnal nor seasonal concentration peaks in PM were found to coincide with peaks in pollen concentrations, however daily average PM concentrations were higher on peak pollen days than on non-peak days.
Conclusion. This study indicates that when considering co-exposure effects from pollen and pollutants, O3 appears to be the most relevant pollutant to further examine for clinical effects of simultaneous co-exposures
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Belowground changes to community structure alter methane-cycling dynamics in Amazonia
Amazonian rainforest is undergoing increasing rates of deforestation, driven primarily by cattle pasture expansion. Forest-to-pasture conversion has been associated with increases in soil methane (CH4) emission. To better understand the drivers of this change, we measured soil CH4 flux, environmental conditions, and belowground microbial community structure across primary forests, cattle pastures, and secondary forests in two Amazonian regions. We show that pasture soils emit high levels of CH4 (mean: 3454.6 ± 9482.3 μg CH4 m−2 d−1), consistent with previous reports, while forest soils on average emit CH4 at modest rates (mean: 9.8 ± 120.5 μg CH4 m−2 d−1), but often act as CH4 sinks. We report that secondary forest soils tend to consume CH4 (mean: −10.2 ± 35.7 μg CH4 m−2 d−1), demonstrating that pasture CH4 emissions can be reversed. We apply a novel computational approach to identify microbial community attributes associated with flux independent of soil chemistry. While this revealed taxa known to produce or consume CH4 directly (i.e. methanogens and methanotrophs, respectively), the vast majority of identified taxa are not known to cycle CH4. Each land use type had a unique subset of taxa associated with CH4 flux, suggesting that land use change alters CH4 cycling through shifts in microbial community composition. Taken together, we show that microbial composition is crucial for understanding the observed CH4 dynamics and that microorganisms provide explanatory power that cannot be captured by environmental variables