Air pollution below WHO levels decreases by 40 % the links of terrestrial microbial networks

Air pollution has a deleterious impact on public health and the environment. There is few knowledge on the effect of air pollution on terrestrial microbial communities, despite the major role of microbes in ecosystems. Here, we designed an in situ trial ecosystem to assess the impact of moderate atmospheric pollution, below World Health Organization (WHO) thresholds, on an indigenous microbial communities, including bacteria, fungi, ciliates, algae, cyanobacteria, testate amoebae, rotifers and nematodes, extracted from terrestrial bryophytes. These micro-ecosystems were placed at a rural, an urban and an industrial site in France and were thus exposed to various levels of nitrogen dioxide (NO₂), from 6.6–67.9 μg·m^?3, and particulate matter, from 0.7–7.9 μg·m^?3. Microbial analysis was performed by microscopy. We determined atmospheric temperature, relative humidity and particulate matter with diameter lower than 10 µm (PM₁₀), Cu, Cr, Fe, Ni, Pb, Zn in PM₁₀, and (NO₂). Results show a significant impact of chronic moderate exposure to NO₂ and copper Cu-associated particulate matter on the global microbial network complexity. This is evidenced by a loss of about 40 % of microbial co-occurrence links during incubation. Most lost microbial links are ecologically positive links. Moreover, most changes in community co-occurrence networks are related to testate amoebae, a major top predator of microbes. Overall, our findings demonstrate that air pollution can have strong deleterious effects on microbial interactions, even at levels below WHO thresholds.     

Intrauterine brain teratoma: a case report of imaging (US,MRI) with neuropathologic correlations

Fetal brain tumors are rare and teratoma is considered as the most common. Fetal MR Imaging is currently used to evaluate cases of ventricular dilatation. We report a case of cerebral immature teratoma detected by ultrasonography because of ventricular dilatation at 24 gestational weeks. MRI was the more accurate imaging method in depicting the tumor and its consequences on brain development as well as in taking a decision with regard to the management of pregnancy. Copyright © 2003 John Wiley & Sons, Ltd.     

INUNDATION TOLERANCES OF RIPARIAN WILLOWS AND COTTONWOODS1

ABSTRACT: Throughout western North America, willows and cottonwoods are dominant woody plants in riparian zones, streamside areas that are periodically flooded. This study compared tolerances of willows‐Salix discolor, S. exigua, and S. lutea‐and cottonwoods‐Populus angustifolia, P balsamifera, and P deltoides‐to water inundation, one component of stream flooding. Rooted cuttings were grown for 152 days in 10 cm tall pots in water depths from 2.5 to 10 cm (inundated). Shoot and root elongation growth of the inundated cottonwoods were reduced 23 and 45 percent, while S. lutea was relatively unaffected and the inundated sandbar willow, S. exigua, displayed 72 and 43 percent increases in shoot and root elongation. The inundation reduced transpiration in P deltoides and for mature P balsamifera trees that were flooded by a small reservoir on Willow Creek, Alberta. Those flooded trees died in their second year of inundation. The greater inundation tolerance of willows versus cottonwoods is consistent with observations along Midvale Creek, Montana, where beaver dams created a pond in which P trichocarpa died while willows thrived after five years. These patterns of inundation tolerance are consistent with elevational zones of occurrence as willows‐and particularly the sandbar willow—occur at low elevations close to the stream. The understanding of inundation tolerances should assist in the provision of hydrologic patterns that will conserve and restore these shrubs and trees along streams and could permit their establishment along artificial reservoirs.     

The non-target organism Caenorhabditis elegans withstands the impact of sulfamethoxazole

The widespread usage of antibiotics in agriculture leads to releases into the environment, but there is insufficient knowledge of the side-effects on non-target organisms. Therefore, we investigated the effects of the sulfonamide-antibiotic sulfamethoxazole (SMX) on Caenorhabditis elegans at phenotypic, biochemical and molecular biological levels. Multiple endpoints, including life history traits, thermal stress resistance and lipid peroxidation, as well as gene expression profiles, were determined after exposure of the nematodes to SMX. In contrast to expectations, SMX prolonged the lifespan and increased both the body size and pharynx pumping rate. On the other hand, SMX delayed reproductive timing and caused lipid peroxidation. The total number of offspring and thermal stress resistance were unaffected. The up-regulation of hsp-16.1 indicated stress in general and the increased lipid peroxidation oxidative stress in particular. This oxidative stress indicated that mitohormesis was the likely cause of the longevity and that enhanced pumping frequency was probably the reason for the increased growth. The sole adverse effect was delayed initial reproduction. This delay, however, can be crucial for r-strategists, such as the bacterivorous model animal used, in sustaining their populations in the environment in the presence of predators. Bacterivorous animals, in turn, are essential to maintaining nutrient recycling via the microbial loop.     

Response of hydrothermal vent vestimentiferan <Emphasis Type="Italic">Riftia pachyptila</Emphasis> to differences in habitat chemistry

Vestimentiferan tubeworms, which rely on intracellular sulfide-oxidizing autotrophic bacteria for organic carbon, flourish at deep-sea hydrothermal vents despite the erratic nature of their habitat. To assess the degree to which differences in habitat chemistry (sulfide, pH/CO₂) might impact host and symbiont metabolic activity, Riftia pachyptila tubeworms were collected from habitats with low (H₂S < 0.0001 mM) and high (up to 0.7 mM) sulfide concentrations. The elemental sulfur content of the symbiont-containing trophosome organ was lower in specimens collected from the low-sulfide site. Symbiont abundance, RubisCO activity, and trophosome carbon fixation rates were not significantly different for individuals collected from low- versus high-sulfide habitats. Carbonic anhydrase activities were higher in the anterior gas exchange organs of R. pachyptila from the low-sulfide habitat. Despite large differences in habitat chemistry, symbiont abundance and autotrophic potential were consistent, while the host appears to tailor carbonic anhydrase activity to environmental CO₂ availability.     

Characterising sources and sinks of rural VOC in eastern France

Fifty non-methane hydrocarbons (NMHC) and seventeen carbonyl compounds were measured at a French rural site from 1997 to 2001, as part of the EMEP programme. Data handling was based on an original source-receptor approach. First, the examination of the levels and trends was completed by the comparison of the seasonal distribution of rural and urban VOC/acetylene ambient ratios. This analysis has shown that most of the compounds derived from mixing and photochemical transformation of mid-range transported urban pollutants from the downwind urban area. Then, identified sources and sinks were temporally apportioned. Urban air masses mixing explains, at least, 80% of the wintertime levels of anthropogenic NMHC and isoprene. In summer, photochemistry dominates the day-to-day distribution of anthropogenic NMHC whilst summertime isoprene is also controlled by in-situ biogenic emissions. Then, the results of C(1)-C(3) carbonyls were discussed with respect to their direct biogenic and anthropogenic emissions and photochemical production through the [carbonyl/auto-exhaust tracers] emission ratio. Diluted vehicle exhaust emissions mainly contribute to the total content of lower aldehydes in winter while other processes control lower ketones. Secondary production is predominant in summer with at least a 50% high intensity. Its dependence upon temperature and radiation is also demonstrated. Finally, the importance of the primary and secondary biogenic production of acetone and formaldehyde is assessed. In particular, biogenic contribution would explain 37 +/- 25% of acetone levels in summer.     

Quantitative cancer risk assessment and local mortality burden for ambient air pollution in an eastern Mediterranean City

Health risks posed by ambient air pollutants to the urban Lebanese population have not been well characterized. The aim of this study is to assess cancer risk and mortality burden of non-methane hydrocarbons (NMHCs) and particulates (PM) based on two field-sampling campaigns conducted during summer and winter seasons in Beirut. Seventy NMHCs were analyzed by TD-GC-FID. PM_2.5 elemental carbon (EC) components were examined using a Lab OC-EC aerosol Analyzer, and polycyclic aromatic hydrocarbons were analyzed by GC-MS. The US EPA fraction-based approach was used to assess non-cancer hazard and cancer risk for the hydrocarbon mixture, and the UK Committee on Medical Effects of Air Pollutants (COMEAP) guidelines were followed to determine the PM_2.5 attributable mortality burden. The average cumulative cancer risk exceeded the US EPA acceptable level (10⁻⁶) by 40-fold in the summer and 30-fold in the winter. Benzene was found to be the highest contributor to cancer risk (39–43%), followed by 1,3-butadiene (25–29%), both originating from traffic gasoline evaporation and combustion. The EC attributable average mortality fraction was 7.8–10%, while the average attributable number of deaths (AD) and years of life lost (YLL) were found to be 257–327 and 3086–3923, respectively. Our findings provide a baseline for future air monitoring programs, and for interventions aiming at reducing cancer risk in this population.