Christine A. Rogers

Human health effects of a changing global nitrogen cycle

Changes to the global nitrogen cycle affect human health well beyond the associated benefits of increased food production. Many intensively fertilized crops become animal feed, helping to create disparities in world food distribution and leading to unbalanced diets, even in wealthy nations. Excessive air- and water-borne nitrogen are linked to respiratory ailments, cardiac disease, and several cancers. Ecological feedbacks to excess nitrogen can inhibit crop growth, increase allergenic pollen production, and potentially affect the dynamics of several vector-borne diseases, including West Nile virus, malaria, and cholera. These and other examples suggest that our increasing production and use of fixed nitrogen poses a growing public health risk.

Interaction of the Onset of Spring and Elevated Atmospheric CO2 on Ragweed (Ambrosia artemisiifolia L.) Pollen Production

Increasing atmospheric carbon dioxide is responsible for climate changes that are having widespread effects on biological systems. One of the clearest changes is earlier onset of spring and lengthening of the growing season. We designed the present study to examine the interactive effects of timing of dormancy release of seeds with low and high atmospheric CO2 on biomass, reproduction, and phenology in ragweed plants (Ambrosia artemisiifolia L.), which produce highly allergenic pollen. We released ragweed seeds from dormancy at three 15-day intervals and grew plants in climate-controlled glasshouses at either ambient or 700-ppm CO2 concentrations, placing open-top bags over inflorescences to capture pollen. Measurements of plant height and weight; inflorescence number, weight, and length; and days to anthesis and anthesis date were made on each plant, and whole-plant pollen productivity was estimated from an allometric-based model. Timing and CO2 interacted to influence pollen production. At ambient CO2 levels, the earlier cohort acquired a greater biomass, a higher average weight per inflorescence, and a larger number of inflorescences; flowered earlier; and had 54.8% greater pollen production than did the latest cohort. At high CO2 levels, plants showed greater biomass and reproductive effort compared with those in ambient CO2 but only for later cohorts. In the early cohort, pollen production was similar under ambient and high CO2, but in the middle and late cohorts, high CO2 increased pollen production by 32% and 55%, respectively, compared with ambient CO2 levels. Overall, ragweed pollen production can be expected to increase significantly under predicted future climate conditions.

Dustborne and airborne fungal propagules represent a different spectrum of fungi with differing relations to home characteristics

Background: Exposure to fungi is often assessed by culturing floor dust or air samples. Our objective was to evaluate the relationships between dustborne and airborne fungi and to identify factors that modify these relationships.

Elevated atmospheric carbon dioxide concentrations amplify Alternaria alternata sporulation and total antigen production.

Background Although the effect of elevated carbon dioxide (CO2) concentration on pollen production has been established in some plant species, impacts on fungal sporulation and antigen production have not been elucidated. Objective Our purpose was to examine the effects of rising atmospheric CO2 concentrations on the quantity and quality of fungal spores produced on timothy (Phleum pratense) leaves. Methods Timothy plants were grown at four CO2 concentrations (300, 400, 500, and 600 μmol/mol). Leaves were used as growth substrate for Alternaria alternata and Cladosporium phlei. The spore abundance produced by both fungi, as well as the size (microscopy) and antigenic protein content (ELISA) of A. alternata, were quantified. Results Leaf carbon-to-nitrogen ratio was greater at 500 and 600 μmol/mol, and leaf biomass was greater at 600 μmol/mol than at the lower CO2 concentrations. Leaf carbon-to-nitrogen ratio was positively correlated with A. alternata spore production per gram of leaf but negatively correlated with antigenic protein content per spore. At 500 and 600 μmol/mol CO2 concentrations, A. alternata produced nearly three times the number of spores and more than twice the total antigenic protein per plant than at lower concentrations. C. phlei spore production was positively correlated with leaf carbon-to-nitrogen ratio, but overall spore production was much lower than in A. alternata, and total per-plant production did not vary among CO2 concentrations. Conclusions Elevated CO2 concentrations often increase plant leaf biomass and carbon-to-nitrogen ratio. Here we demonstrate for the first time that these leaf changes are associated with increased spore production by A. alternata, a ubiquitous allergenic fungus. This response may contribute to the increasing prevalence of allergies and asthma.

Air Quality Measurements for the Aerosol Research and Inhalation Epidemiology Study

Abstract Measurements of pollutant gases, airborne particulate matter mass and composition, and meteorology have been made at a core site near downtown Atlanta, GA, since August 1998 in support of the Aerosol Research and Inhalation Epidemiology Study (ARIES). This site is one of eight in the Southeastern Aerosol Research and Characterization network. The measurement objective is to provide a long-term, multivariate dataset suitable for investigating statistical associations of respiratory and cardiovascular disease with airborne particulate matter composition, meteorology, and copollutant gases through epidemiologic modeling. Measurements are expected to continue through 2010. Ancillary multiyear measurements at additional sites in the Atlanta metropolitan area and in short-term exposure assessments have been used to estimate the exposure/measurement error associated with using data from a central site to approximate human exposures for the entire area. To date, 13-, 25-, and 53-month air quality datasets have been used in epidemiologic analyses.

An evaluation of two methods used for microscopic analysis of airborne fungal spore concentrations from the Burkard Spore Trap

The Burkard Volumetric Spore Trap is a common and efficient instrument used to collect outdoor air samples. In North America, two slide counting methods have been widely used by aerobiologists: the single longitudinal traverse method and the twelve transverse traverse method. The purpose of this study was to compare the two counting methods by assessing fungal spore concentrations of ascospores, basidiospores, smut teliospores, Cladosporium, Alternaria, Epicoccum, Curvularia, Drechslera, Pithomyces, other spores, and total spores at two metropolitan Tulsa, Oklahoma sites (Tulsa and Hectorville) during September 1996. Results showed that both methods were sensing parallel fluctuations in average daily spore concentration, although the twelve transverse traverse method usually resulted in higher concentrations. At the Tulsa site, the twelve transverse traverse method gave statistically higher concentrations than the single longitudinal traverse method except for Epicoccum, Pithomyces, smut teliospores, and other spores. At the Hectorville site, however, only Cladosporium and basidiospores showed that the twelve transverse traverse method was statistically higher than the single longitudinal traverse method. Comparison with concentrations obtained by counting the total slide surface of two slides indicated that neither method was equivalent to the total slide spore count, although the twelve transverse traverse method gave a lower absolute percent difference from the total slide surface concentration. While the twelve transverse traverse method gave slightly better approximations of the spore concentration, the increase in accuracy may not justify the extra effort required to analyze with this method.

Effectiveness of Germicidal UV Radiation for Reducing Fungal Contamination within Air-Handling Units

ABSTRACT Levels of fungi growing on insulation within air-handling units (AHUs) in an office building and levels of airborne fungi within AHUs were measured before the use of germicidal UV light and again after 4 months of operation. The fungal levels following UV operation were significantly lower than the levels in control AHUs.

Comparison of pollen sampling with a Burkard Spore Trap and a Tauber Trap in a warm temperate climate

Aerobiological data have been widely used by many scientists, including those that study modern flora as well as those wishing to reconstruct past vegetational associations. Burkard (Hirst-type) volumetric spore traps are widely used instruments for studying airborne pollen, while Tauber traps are typically used to analyze pollen deposition. The present study compared the pollen collected by these two methods in Tulsa, Oklahoma a warm temperate area with year-round pollen. There was a strong correlation between the pollen influx from the Tauber traps and cumulative sum of average daily airborne pollen concentrations recorded with the Burkard spore trap over the course of 12 months from 1 Feb 1997 through 1 Feb 1998. The correlation coefficient between all taxa over the 12 months was 0.914; while the correlation coefficient for the monthly totals was 0.972. The data showed that both methods reflected local anemophilous vegetation although variations occurred in the prevalence recorded by both samplers.

Indoor fungal exposure

Fungi affect humans in complex ways and are capable of eliciting a number of disease responses, such as infectious, allergic, and irritant and toxic effects. Fungal exposure is unequivocally associated with exacerbations of asthma, although the role of fungi in causing the disease is yet to be determined. The association between home dampness and respiratory health effects is strong, and fungal exposure is suspected to be associated with this linkage. Fear of toxin exposures has generated debate over the possible toxic health effects of airborne fungi; however, several recent reviews discount the health impacts of mycotoxin through indoor exposures. Nevertheless, fungal contamination of indoor environments is undesirable. Knowledge of sources and characteristics of fungal spore release and dispersal are important for understanding the processes of exposure. Environmental monitoring for fungi and their disease agents are important aspects of exposure assessment, but few guidelines exist for interpreting their health impacts. Much work is needed in isolating, characterizing and standardizing fungal disease agents to properly assess the prevalence of fungal health effects.

Application of aeropalynological principles in palaeoecology

Abstract Accurate palaeoecological interpretations of pollen data require a thorough knowledge of the processes involved in the production and dissemination of pollen. This paper examines the timing of pollination and pollen production of anemophilous taxa at various scales. Aspects of timing that are discussed are the environmental triggers for pollination, the sequence of pollination, implications of the position in the sequence, geographic variation in flowering, and diurnal rhythms. Aspects of pollen production that are discussed are, daily variation of airborne pollen, effect of climate within a season and over several decades, interannual variability, and other potential causes of fluctuations in production such as gender switching. Understanding the changes in pollen abundance over these temporal and spatial scales may help to refine the pollen-vegetation relationship.