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PubMed2002

Ambient level volatile organic compound (VOC) monitoring using solid adsorbents--recent US EPA studies.

Ambient air spiked with 1-10 ppbv concentrations of 41 toxic volatile organic compounds (VOCs) listed in US Environmental Protection Agency (EPA) Compendium Method TO-14A was monitored using solid sorbents for sample collection and a Varian Saturn 2000 ion trap mass spectrometer for analysis. The adsorbent was a combination of graphitic carbon and a Carboxen-type carbon molecular sieve. The method detection limits (MDLs) for 11 samples were typically 0.5 parts per billion by volume (ppbv) and lower except for bromomethane and chloromethane, both of which exhibited breakthrough. Thirty-day sample storage on the sorbents resulted in less than a 20% change for most compounds, and water management was required for humid samples to avoid major anomalous decreases in response during analyses. The adsorbent-based system, a system using canister-based monitoring, and a semi-continuous automated GC/MS (autoGC) monitoring system with a Tenax GR/Carbotrap B/Carbosieve S-III adsorbent preconcentrator were compared using spiked ozone concentrations as a variable. In this comparison, the target compounds included a number of n-aldehydes as well as those listed in TO-14A. The effects of ozone on the TO-14A compounds were relatively minor with the exception of negative artifacts noted for styrene and 1,1,2,2-tetrachloroethane. However, a small, systematic decrease in response was evident for a number of aromatic VOCs and 1,1,2,2-tetrachloroethane when ozone was increased from 50 to 300 ppbv. Method averages for multiple runs under the same conditions were typically within +0.25 ppbv of their mean for most compounds. For n-aldehydes, strong positive artifacts using the autoGC preconcentrator and strong negative artifacts for the canister-based and carbon sorbent approaches caused major disagreement among methods. These artifacts were mostly eliminated by using MnO2 ozone scrubbers, although loss of the n-aldehydes for all methods occurred after a single sample collection of 1 h duration, apparently due to the interaction of the n-aldehydes and products of the O3, MnO2 reaction on the scrubber.

Adsorption↗
PubMed1994

Mycotic disease in the common New Zealand gecko (Hoplodactylus maculatus).

Two adult female geckoes (Hoplodactylus maculatus) from the National Wildlife Centre, Mt Bruce, Masterton, died within the period of a month and were presented to the Department of Veterinary Pathology and Public Health at Massey University for necropsy. The first gecko had numerous 1-2 mm diameter punctate ulcers of the skin over the ventral and dorsal regions of the body. The second animal had slight discolouration of some of the scales. Skin swabs were taken from each case for culture. There were no other gross lesions apparent at necropsy. Histologically, the only lesions in the first gecko were areas of epidermal and dermal ulceration involving fungi and bacteria. In the second gecko, there was limited inflammation in the skin, but in the lungs there was necrosis of the pulmonary septae and constituent muscle bundles caused by fungi whose septate mycelia extended into adjacent large blood vessels and caused mycotic thrombi; hyphae were also found in the spleen and liver. Paecilomyces sp. septate fungus was recovered from both geckoes and Pseudomonas spp. and a mixed Gram-negative flora were recovered from the cutaneous lesions on culture. The death of the first gecko was considered to be due to widespread ulcerative dermatitis, while that of the second gecko was thought to be due to mycotic pneumonitis and mycotic septicaemia. It is believed that environmental factors, such as cold temperature and high humidity, contributed to a reduction in the immune response in the affected geckoes, with the consequent development of overwhelming fungal infections.

Journal Article↗
PubMed2003

Air pollution and daily mortality in two U.S. counties: season-specific analyses and exposure-response relationships.

I used generalized additive models to analyze the time series of daily total nonaccidental deaths and deaths due to vascular disease over the period 1987-1995 in two major metropolitan areas, Cook County, Illinois, and Los Angeles County, California, in the United States. In both counties I had monitoring information on PM(10), CO, SO(2), NO(2), and O(3). In Los Angeles, monitoring information on PM(2.5) was available as well. In addition to full-year analyses, I performed season-specific analyses. I present the results of both single- and multipollutant analyses. Although components of air pollution were associated with total nonaccidental and vascular disease mortality in both counties, the results indicate considerable heterogeneity of these associations in the two locations and also from season to season. In Los Angeles County, the gases, particularly CO and SO(2) but not ozone, were more strongly associated with mortality than was particulate matter, which exhibited only weak and inconsistent associations with both mortality endpoints. Both PM(10) and the gases were associated with total and vascular disease mortality in Cook County. The association of the gases with both mortality endpoints appeared to be stronger and more robust than that of PM(10). Exposure-response analyses using flexible smoothers showed significant departures from linearity, particularly for PM effects.

Air Pollutants↗
PubMed1978

Estimation of whole-plant resistance to gaseous exchange independent of leaf temperature measurement.

For studies into the uptake of mercury vapor by wheat (Triticum aestivum), a simple theory and plant chamber were employed to estimate total leaf resistance of whole plants to water vapor exchange. The estimates were independent of leaf temperature, for which mean values were indirectly determined. The approach involved the measurement, at steady-state conditions, of the net change in water vapor flux per unit of leaf surface (Deltaq(v)) in response to a small induced change in absolute humidity (DeltaC(a)). Assuming that total leaf resistance (r(l)) was constant and that change in leaf temperature (T(l)) was negligible, total leaf resistance was calculated from the equation, [Formula: see text]While the assumptions concerning r(l) and T(l) may or may not be correct, evidence is presented which indicates that such assumptions did not significantly alter estimates of r(l) from their true values for changes in ambient relative humidity ranging from 0.011 to 0.074. Total leaf resistance of groups of whole plants estimated in this manner did not differ for ambient temperatures of 17, 25, and 33 C. Mean values of r(l) ranged from 83 sec cm(-1) in darkness to 2.4 sec cm(-1) at an illumination of 12.8 klux.

Journal Article↗
PubMed1991

Influence of ardacin supplementation on feedlot performance and digestive function of cattle.

A feedlot growth-performance trial and a metabolism trial were conducted to evaluate a dose response to ardacin (a glycopeptide antibiotic). Treatments consisted of an 88% concentrate finishing diet supplemented to contain (DM basis) 0, 8.25, 16.5., or 33 mg ardacin/kg. The growth-performance trial (129 d) involved 120 heifers and 120 steers in a randomized complete block design. There were no interactions (P less than .10) between sex and response to ardacin. Average daily gain increased (P less than .05) and DM conversion decreased (P less than .01) with increasing levels of ardacin supplementation. At the 33 mg/kg level of supplementation, ADG and DM conversion were improved 10.6 and 5.6%, respectively. Four Holstein steers (344 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on characteristics of digestion. There were cubic effects of ardacin on ruminal starch digestion (P less than .05), microbial N synthesis (MNS, P less than .10), and microbial efficiency (MNEFF, grams of MNS/kilogram of OM fermented). For the 16.5 and 33 mg/kg levels of supplementation, ruminal starch digestion was increased 4.9%, and MNS and MNEFF were decreased 12.9 and 15.6%, respectively. Postruminal and total tract digestion of N increased linearly (P less than .10) with ardacin supplementation. Total tract digestion of OM, ADF, and starch were not affected (P greater than .10). Ardacin did not influence (P greater than .10) ruminal pH or molar VFA proportions. It is concluded that supplementation of a finishing diet with 33 mg ardacin/kg will enhance ADG and DM conversion of feedlot steers and heifers.

Aminoglycosides↗
PubMed1996

The sea to air bacteria transfer from the coastal waters.

Bacteria transfer from the water into the air may play an important role in bioaerosol cycle. Bubbles raising through the water column collect bacteria but also other suspended material and transport them towards water surface. When the bubble burst at the water surface collected material are skimmed off the bubble to become highly enriched in jet and film drops. After ejection airborne droplets can evaporate and as small droplets can be transported even to remote locations. Such a stream of aerosol droplets may carry stream of bacteria scavenged from the water column. The fate of bacteria in the air may possibly depend on the environmental conditions like intensity of sunlight or ambient air humidity. In addition the wind speed might be responsible for both wave/bubble mediated production of marine originated droplets and their transport in the atmosphere. The evidences that bacteria are transferred from the breaking waves, in particular in the coastal zone, were observed during several field experiments conducted in 1994 and 1995 over the Gulf of Gdansk and the Baltic Sea coast. Enhanced sea to air bacteria transfer were noticed over the polluted waters where in addition gas supersaturations in the water were recorded. Further laboratory investigations of bacteria scavenge via bubbles produced by single capillary and by plume of bubbles produced by ceramic stone indicated high enrichment within both mesophile and psychrophile bacteria categories.

Aerosols↗
PubMed2001

Nitrate in polluted mountainous catchments with Mediterranean climates.

The mountains of southern California receive some of the highest rates of nitrogen (N) deposition in the world (approximately 40 kg ha(-1) year(-1)). These high rates of deposition have translated into consistently high levels of nitrate (NO3-) in some streams of the San Bernardino Mountains. However, not all streams are exhibiting these high levels of NO3-. Perennial streams have high NO3- concentrations (approximately 200 micromoles l(-1)) while ephemeral streams do not (approximately 20 micromoles l(-1)). This difference points to groundwater as the source of the NO3- observed in streams. Furthermore, the evidence indicates a differential impact of N deposition on terrestrial and aquatic systems in Mediterranean climates, with aquatic systems being impacted more quickly. The primary reason for this difference involves the asynchrony between the time that atmospheric deposition occurs (summer), the time period of maximum soil NO3- availability and leaching (winter), and the time of maximum plant N demand (spring). Our results indicate that semiarid Mediterranean climate systems behave differently from more humid systems in that, because of this asynchrony, aquatic systems may not be indicative of changes in terrestrial ecosystem response. These differences lead us to the conclusion that the extrapolation of impacts from humid to Mediterranean climates is problematic and the concept of N saturation may need to be revisited for semiarid and seasonally dry systems.

Climate↗
PubMed2002

Micromechanical measurement of active sites on silicon nitride using surface free energy variation.

We have investigated chemical reactions between adsorbed water and active sites on a silicon nitride surface as a function of temperature and relative humidity using microcantilevers. Effects that might produce a change in the response of the microcantilever, such as a mass adsorption, surface tension of the adsorbed water, and changes in thermal conductivity, were systematically investigated. It is shown that the judicious choice of experimental conditions could make these effects essentially inconsequential in comparison with the instrument response produced by the change in free surface energy of the microcantilever due to the chemical reactions. Using this method, the variation in free surface energy when changing from dry to high humidity conditions was found and the number of active sites that reacted was estimated. This method may be extended to other problems for use in determining surface free energy change and thus the density of reactant sites under different conditions of interest.

Journal Article↗
PubMed1987

The effect of temperature and humidity levels in a protective mask on user acceptability during exercise.

Subjective and physiological responses were obtained from six subjects wearing a ventilated face mask while exercising (3.8 met) for 15 min on a bicycle ergometer. Different combinations of ambient air temperatures (7 degrees, 16 degrees, 25 degrees C) and mask air temperatures (22 degrees, 27 degrees, 33 degrees C) were studied together with two different air humidities inside the mask (61% and 86% RH). Control experiments were performed without the mask at the same ambient temperatures. Skin temperatures, heart rates and skin wettedness were monitored during exercise. The subject's acceptance of the mask and thermal environment, thermal sensation, sensations of discomfort, sweating and skin wettedness, and their judgment of the work of breathing were assessed at the end of the 15 min exercise period. The acceptance of both the ambient thermal environment and of the thermal microclimate in the mask primarily was determined by the ambient air temperature, but it was influenced by the air temperature and humidity inside the mask. At ambient temperatures of 7 degrees C and 25 degrees C, the acceptance of the thermal work conditions decreased. In the warm environment a mask air temperature less than or equal to 27 degrees C was 100% acceptable and increased the acceptance of thermal environment. In the cool environment, a mask air temperature greater than or equal to 27 degrees C was 100% acceptable. The humidity content of the mask air was only important when the mask air was warm. Warm humid air significantly decreased acceptance of the mask conditions.

Adult↗
PubMed2003

The influence of water vapour on the determination of glutaraldehyde vapour concentrations using an electrochemical fuel cell sensor.

The effects of relative humidity (40-90% RH) and varying glutaraldehyde vapour concentrations (< 0.1 ppm) on the response of an electrochemical fuel cell sensor have been investigated over time (0-400 s). These studies have identified changes in the response of the fuel cell with time after sampling. In particular, it has been found that the maximum cell output for water vapour occurs ca. 10 s after sampling whilst the response to glutaraldehyde occurs much later (> 100 s). For mixtures containing different ratios of water and glutaraldehyde vapours, the time taken to reach maximum fuel cell response varies between 10 and 100 s, depending on the ratio of the two vapours. For instance, glutaraldehyde vapour containing higher % RH has been found to result in shorter times to reach maximum fuel cell response. A comparison was made between measuring glutaraldehyde vapour concentrations in the presence of water vapour at the maximum fuel cell response and also at a fixed interval (240 s) after sampling. Such a comparison resulted in a reduction in the standard error from 36% to 5% for a glutaraldehyde vapour sample (0.023 ppm) measured at different values of relative humidity (40 to 80%). Examination of the effect of the sample volume (30-60 ml) on the response of the fuel cell shows, as expected, an approximate doubling of the fuel cell response. Optimisation of the fuel cell measurement parameters to measure a 60 ml sample leads to a lowering of the limit of detection from 0.083 ppm (for data taken at the maximum cell response) to 0.017 ppm for data measured 240 s after sampling. In the light of recent reductions in the legal limits for exposure to glutaraldehyde, this has important implications for the measurement of glutaraldehyde vapour in the workplace.

Disinfectants↗
PubMed2003

Dynamic responses to acute heat stress between 34 degrees C and 38.5 degrees C, and characteristics of heat stress response in mice.

We focused on dynamic responses to acute heat stress between 34 degrees C and 38.5 degrees C. Physiological and neuroendocrinological changes between 34 degrees C and 38.5 degrees C were studied in mice. The influence of humid conditions, 85% relative humidity (RH), on these changes was also investigated. Rectal temperatures increased above 34 degrees C and hematocrit levels increased at 38.5 degrees C 85% RH for 60 min. Food consumption and body weight gains decreased after a daily 60 min exposure to 34, 37 and 38.5 degrees C for 2 weeks. The corticosterone and vasopressin levels in the blood, and catecholamine and serotonin metabolite levels in the hypothalamus were not changed at 34 degrees C, but increased when above 37 degrees C for 60 min. Above 37 degrees C, these physiological and neuroendocrinological changes were accelerated by humid conditions. These results indicated that food consumption and body weight gains decreased above 34 degrees C, and the neuroendocrinological changes, which were accelerated by humid conditions, were induced above 37 degrees C. In comparison with restraint and water immersion stress, heat stress at 37 degrees C 85% RH showed a slower increase in serum corticosterone levels, smaller changes in plasma dopamine and dihydroxyphenylacetic acid levels, and, after repeated exposure, larger decreases in food consumption and body weight gains. This study clarified the relationships between temperature and humidity conditions and physiological and neuroendocrinological changes, along with the characteristics of responses in acute heat stress.

Animals↗
PubMedDate not supplied

The influence of environmental parameters in electrostatic cell radon monitor response.

To better understand the influence of air parameters such as pressure, humidity and temperature on the counting efficiency of a radon monitor based on solid state silicon detectors and radon daughter electrostatic collection, a number of experimental and theoretical studies have been performed. This study has been carried out using a multiparameter acquisition system used to monitor radon, temperature, pressure and relative humidity. Results show that air humidity and temperature inside the cell influence radon daughter collection in a significant way. For the tested cell, a decrease of the 218Po counting efficiency vs. humidity and temperature increase was measured in the ranges from 10% to 90% and from 15 degrees C to 35 degrees C, respectively. These effects were also theoretically studied by using Monte-Carlo software, which takes into account electrostatic collection of radon daughters in the cell, by considering the recombination process as a function of climatic parameters. A satisfactory agreement was obtained between experimental measurements and theoretical calculations.

Journal Article↗
PubMed1984

Laboratory validation and field verification of a new passive air monitoring badge for sampling ethylene oxide in air.

A new diffusion colorimetric air monitoring badge for sampling ethylene oxide is described. The Du Pont Pro-Tek C-70 badge has been laboratory validated over the range of 4-375 ppm-hours (0.5-47 ppm on an 8-hour TWA) using standard spectrophotometer readout in 1 centimeter (10 mm) cells. The lower range can be extended to 2 ppm-hours (0.25 ppm) by using 4 cm (40 mm) cells. The badge has an overall sampling and analytical method accuracy of +/- 13.5%. It meets NIOSH accuracy criteria and has a mean coefficient of variation CVT = 0.059. The badge has no temperature, pressure, relative humidity or face velocity effects over practical ranges. The response time is adequate to sample peak concentrations over short time periods. The badge may be used to determine ambient formaldehyde levels if suspected to be present along with ethylene oxide. Badges are shown to agree very well with the industry accepted and proposed ASTM pump/charcoal tube method in three extensive plant field tests. Badges were more precise than the charcoal tube/pump method in all field tests conducted.

Air Pollutants, Occupational↗
PubMed1988

Sweating and cardiovascular responses of aged men to heat exposure.

In this study, 6 older and 10 younger Japanese men were exposed, while sitting, to 40 degrees C and 40% relative humidity for up to 130 min. All participants were heat unacclimatized. Physiological measurements included sweat responses, esophageal and skin temperatures, nonevaporative heat exchange, heart rate, cardiac output, blood pressure, forearm blood flow, and metabolic heat production. There was no significant difference in sweat rate or in onset of sweating between the older and younger men; however, esophageal temperature at the onset of sweating was greater in the older men. Changes in skin temperature, nonevaporative heat exchange, metabolic heat production, heart rate, and cardiac output were the same during heat exposure in both age groups. However, forearm blood flow before and after exposure to heat was significantly lower in the elderly group. These data suggest that the greater health risk posed to resting, yet healthy, aged men by hot environments is not a consequence of inadequate sweating but could be associated with retardation of the vasodilation reflex, which can prevent effective transfer of the body heat to its shell, thus resulting in greater heat storage.

Adult↗
PubMed2002

Detecting odorous materials in water using quartz crystal microbalance sensors.

Water drawn from rivers into purification plants must be checked for the presence of odorous materials because oil or organic-solvent contamination of the water may occur. If the detection of odorous materials in water is untimely or fails, the consequences can be serious. Therefore, the water must be checked continuously. We have developed a water-monitoring system that uses a highly sensitive electronic nose consisting of quartz crystal microbalance sensors to detect odorous materials in water. The nose is sensitive enough to detect petroleum hydrocarbons without water vapor at a low-ppb level. However, the nose is very sensitive to humidity and temperature. We have thus developed a method for accurately maintaining the humidity and temperature in the sensor cell. Experimental results show that the developed system can quickly detect contaminated water that was mixed with gasoline, kerosene, or benzene (concentration: several hundred ppb level), and we should be able to classify the pollutant by using pattern recognition of the dynamic sensor response.

Fresh Water↗
PubMed2004

On the use of porous materials to simulate evaporation in the human sweating process.

The specific properties of porous materials when wet, namely the cooling effect near the surface due to the heat extraction during water evaporation, were known and used by ancient civilisations. During human perspiration, the necessary heat for sweat evaporation is provided by the cutaneous surface, which induces a temperature drop similar to that observed in a wet porous material. The potential for using porous materials to simulate human perspiration was investigated in this work using different permanently saturated porous materials (plaster, white clay and red clay). The existence and duration of a constant drying rate was studied, as well its dependency on the surrounding conditions, namely temperature, moisture and velocity. We verified the existence of a period with constant drying rate for all the tested samples; this is evidence that a uniformly distributed humid layer is formed and stays on the external surface of the porous body. This represents a step forward in simulation of the sweating mechanism. All three tested porous materials showed very good reproducibility and good sensitivity in terms of the response of the evaporation rate to any variation of the relative humidity.

Aluminum Silicates↗