A progressive global increase in the burden of allergic diseases has affected the industrialized world over the last half century and has been reported in the literature. The clinical evidence reveals a general increase in both incidence and prevalence of respiratory diseases, such as allergic rhinitis (common hay fever) and asthma. Such phenomena may be related not only to air pollution and changes in lifestyle, but also to an actual increase in airborne quantities of allergenic pollen. Experimental enhancements of carbon dioxide (CO) have demonstrated changes in pollen amount and allergenicity, but this has rarely been shown in the wider environment. The present analysis of a continental-scale pollen data set reveals an increasing trend in the yearly amount of airborne pollen for many taxa in Europe, which is more pronounced in urban than semi-rural/rural areas. Climate change may contribute to these changes, however increased temperatures do not appear to be a major influencing factor. Instead, we suggest the anthropogenic rise of atmospheric CO levels may be influential.

Pollen released by urban flora-a major contributor to airborne allergen content during the pollen season-has a considerable adverse impact on human health. Using aerobiological techniques to sample and characterize airborne biological particulate matter (BPM), we can identify the main species contributing to the pollen spectrum and chart variations in counts and overall pollen dynamics throughout the year. However, given the exponential increase in the number of pollen allergy sufferers in built-up areas, new strategies are required to improve the biological quality of urban air. This paper reports on a novel characterization of the potential allergenicity of the tree species most commonly used as ornamentals in Mediterranean cities. Values were assigned to each species based on a number of intrinsic features including pollination strategy, pollen season duration, and allergenic capacity as reported in the specialist literature. Findings were used to generate a database in which groups of conifers, broadleaves, and palm trees were assigned a value of between 0 and 36, enabling their allergenicity to be rated as nil, low, moderate, high, or very high. The case study presented here focuses on the city of Granada in southern Spain. The major airborne-pollen-producing species were identified and the allergenicity of species growing in urban green zones was estimated. Corrective measures are proposed to prevent high allergen levels and thus improve biological air quality.

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Bacterial precipitation of barite (BaSO 4 ) under laboratory conditions is reported for the first time. The bacterium Myxococcus xanthus was cultivated in a solid medium with a diluted solution of barium chloride. Crystallization occurred as a result of the presence of live bacteria and the bacterial metabolic activity. A phosphorous-rich amorphous phase preceded the more crystalline barite formation. These experiments may indicate the involvement of bacteria in the barium biogeochemical cycle, which is closely related to the carbon cycle.The mechanism by which barite precipitates in undersaturated seawater is one aspect of the Ba biogeochemical cycle that still remains unknown. Considerable research has focused on this element over the last 2 decades, since it is known to be a reliable indicator for variations in marine biological productivity (for examples, see references 3, 6, 9, 11, 16, and 17). Chow and Goldberg (5) first proposed that barite formation is biologically mediated; Bishop (3) and Dehairs et al. (6) provided evidence that such precipitation occurs in the upper water column in microenvironments of decaying organic matter and other biogenic remains. Morphologies and sizes of marine barite crystals in the water column and in marine sediments (for examples, see references 6 and 16) also indicate a possible biogenic origin. Barite precipitation by living organisms (protozoa) has been demonstrated in lacustrine freshwater environments (4,10,19). In marine environments, intracellular barite crystals have also been found in vacuoles of unicellular Exanthemachrysis gayraliae (12) and in Xenophyophorea (14). However, these organisms do not appear to account for the abundance of barite crystals in the water column, and the living organisms which directly precipitate barite have not yet been identified in seawater (1). Thus, a reasonable proposal would seem to be that bacteria play a role in this process. As an initial approach to the investigation of bacterial barite production, an experiment was performed using Myxococcus xanthus, an abundant and ubiquitous heterotrophic soil bacterium (8). This microorganism has been demonstrated to induce precipitation of sulfates, phosphates, and carbonates (reference 13 and references therein; 20). Although myxobacteria are recognized mainly as soil bacteria (8), they are also found in marine environments (15). Barite production under laboratory conditions. Living and dead M. xanthus cells (strain 422 provided by the Spanish TypeCulture Collection, Burjasot, Valencia, Spain) were inoculated on a solid culture medium with Ba (CM-Ba) (0.4% yeast extract, 2 mM BaCl 2 ⅐ 2H 2 O, 2% purified Difco agar-agar in distilled water [pH 7]). The inoculum was prepared by cultivating M. xanthus in liquid CT medium (7) for 72 h at 28°C with shaking (200 rpm) in order to obtain a density of ϳ2 ϫ 10 9 cells/ml. In living-cell experiments, 20-l aliquots of the M. xanthus inoculum were deposited on the solid medium. Dead cells were obtained by using heat (by autoclaving at 120°C for 20 ...

This research demonstrates that both the allergenic activity as well as the pollen particles follow in a similar curve, except in periods before or succeeding the main Olea pollen season. The study of the distribution of the allergenic particles according to their sizes reveals that the highest concentrations are between 3.3 and <0.7 micro m, thus indicating that allergenic activity primarily involves paucimicronic particles.