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PubMed2003

Soluble sunscreens fully protect E. coli from disinfection by electrohydraulic discharges.

We show that the ultraviolet radiation emitted, rather than the thermal/pressure shocks or the chemical species that are generated in these events, is the lethal agent that inactivates Escherichia coli colonies exposed to electrohydraulic discharges, EHD. Disinfection is completely suppressed in the presence of <100 mg L(-1) of 2,2'-dihydroxy-4,4'-dimethoxybenzophenone-5,5'-disulfonic acid, BP9, a commercial water-soluble sunscreen. Viable bacteria decay by logit kinetics with the number of EHD. The fact that the slopes of the logit plots depend inversely on BP9 concentration, and vanish above approximately 30 mg BP9 L(-1), is direct evidence that E. coli is exclusively sterilized by UV radiation in these experiments. Present LD50 photon doses are about 10(3) times larger than those required from low-power germicidal lamps, indicating that high-intensity radiation is able to further promote into inactive channels the lower excited state(s) of nucleic acids responsible for DNA damage. The present study confirms the existence of a significant trade-off between photon efficiency and radiative power in bacterial disinfection by UV light.

Benzophenones↗
PubMedDate not supplied

Adult leukemia and proximity-based surrogates for exposure to Pilgrim plant's nuclear emissions.

Possible associations between adult leukemia incidence and proximity-based surrogate measures of potential for exposure to radioactive emissions from the Pilgrim nuclear power plant in Plymouth, Massachusetts, were investigated. Included in this study were 105 nonchronic lymphocytic leukemia cases, diagnosed between 1978 and 1986 at age 13 y or older, that occurred in 22 towns near Pilgrim; population controls numbered 208. Residence within 4 mi (6.4 km) of Pilgrim during "high-emissions" years was related to case-control status (adjusted odds ratio [OR] = 3.88, 95% confidence interval [95% CI] = 0.81-10.64). A high "exposure" score (i.e., a value that accounted for downwind time) was also related to case-control status (OR = 3.46, 95% CI = 1.50-7.96). Some statistically significant dose-response trends were found. Cautious interpretation of associations is warranted in light of the low levels of reported emissions.

Adolescent↗
PubMed1987

A model to evaluate half-lives of PAHs naturally occurring on airborne particulate.

Constant decay of polycyclic aromatic hydrocarbons (PAHs) adsorbed onto airborne particulate collected in glass fibre filters and exposed to sunlight ranged from 1.8 to 4.4 X 10(-3) (min-1), corresponding respectively to a half-life of 100 and 425 min. Half-life of PAHs appeared to be positively correlated with filter loading. Experimental results showed that decay of PAHs adsorbed on airborne particulate was induced by two concomitant reactions; a photochemical reaction involving the outer layers of collected particulate, and a "dark" reaction that may occur in the inner layers. The constant decays of these two reactions were calculated using a simplified mathematical model. The authors suggest the use of this model to compare chemical stability of airborne PAHs exposed, during their permanence in the atmosphere, to different physical (light intensity, temperature, humidity) as well as chemical conditions (oxidant concentration, chemical composition of particulate).

Air Pollutants, Occupational↗
PubMed1989

[A study of the differentiation inducibility of cultured cells by environmental chemical substances].

The author conducted an experimental study of the cell differentiation inducibility of some environmental chemical substances which currently draw attention because of their influences on the human body, using an azaguanine-resistant PCC4 cell line, a clone derived from mouse teratocarcinoma OTT 6050. Cells in monolayer culture or suspension culture were exposed to the test substances and the survival and morphological changes of the cells were determined. It was extremely rare that embryonal carcinoma cells exposed and cultured in a monolayer showed differentiation in the control group, with the rate of both epithelial cell-like and fibroblast-like morphological changes being less than 1%. Cells cultured in normal medium following exposure and incubation in suspension culture showed various patterns of differentiation according to the type and concentration of the test substance. In the cell groups exposed to mono, di-methylformamide, fibroblast-like differentiation was observed most frequently, while little or no epithelial differentiation was seen. These findings were in contrast to those observed in the cell groups exposed to mono, di-methylacetamide. For dimethyl sulfoxide it is considered that there is a relatively limited range of optimal concentration for differentiation induction within the concentration range which is free from cell toxicity. Polybrene and diethylene glycol were proven to have low differentiation inducibility. As to the differentiation induction potency of extracts (tar) of granules in exhausts from light-duty (4 cylinder) and heavy-duty (6 cylinder) diesel engines, no concentration-response relation was seen for the differentiation inducibility of light-duty tar and no constant tendency was observed for heavy-duty tar.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants↗
PubMed2006

Gating a channel photomultiplier with a fast high-voltage switch: reduction of afterpulse rates in a laser-induced fluorescence instrument for measurement of atmospheric OH radical concentrations.

By employing a commercially available high-voltage switch in a time-gating circuit to drive a channel photomultiplier (CPM), the afterpulse rates are significantly reduced in the time window to collect fluorescence >200 ns after the pulsed laser excitation. The CPM, kept deactivated under normal conditions (normally off), is turned on immediately after the passage of the laser pulse by shifting the voltage applied to the photocathode by 150 V to collect the fluorescence. When the detection system is used as part of a laser-induced fluorescence instrument to measure atmospheric OH radicals with the photon-counting method, the background signal is reduced by more than a factor of 10 as compared with our previous case where a conventional dynode-gated photomultiplier tube (PMT) is used, while the sensitivity toward the fluorescence is almost unchanged. A detection limit as low as 2 x 10(5) radicals cm-3 or 0.008 parts per trillion by volume is achieved for OH, with an integration time of 1 min and a signal-to-noise ratio of 2, enabling sensitive detection of the important radical in the atmosphere. This system is a superior choice with higher sensitivity and cost effectiveness as compared with the gated PMITs utilizing a microchannel plate as an electron multiplier, and could also be used effectively in light detection and ranging (lidar) instruments, where a delayed scattering signal would be efficiently discriminated from afterpulses.

Air Pollutants↗
PubMed1999

A field comparison of inhalable and thoracic size selective sampling techniques.

We measured inhalable, thoracic, and so-called "total" wood dust exposure in British Columbia lumber mill workers. Particle-size selective sampling was conducted using the GSP and Seven hole inhalable samplers, the PEM thoracic sampler and the 37-mm closed-face cassette "total" sampler. All measurements were full-shift personal samples, obtained from randomly selected workers. We obtained intersampler comparison data for the following pairs of instruments: GSP and 37-mm sampler; GSP and seven-hole sampler (SHS); and PEM and 37-mm sampler. The intersampler measurement ratios were estimated as: GSP/37-mm sampler = 4.2; GSP/SHS = 1.7; and PEM/37-mm sampler = 1.6. The GSP/37-mm sampler ratio is consistent with previously reported findings, while PEM/37-mm sampler and GSP/SHS ratios were both larger than expected. We found that in all comparisons, the measurement ratio had significant variability that was greatest at low ambient dust concentrations. Although it was not possible to attribute the source of the variability to specific sampler types, we concluded that the GSP sampler might be susceptible to "projectile" particles not normally aspirated, and may be vulnerable to direct aspiration of dust from accidentally contacted surfaces. The PEM was designed for environmental monitoring, and it is possible that it is unsuited to the higher particulate concentrations found in some occupational settings. Disparities among inhalable sampling techniques such as that between GSP and SHS should be investigated further in light of the proposed adoption of the inhalable method as an industrial standard.

Air Pollutants, Occupational↗
PubMed1996

[The use of biological indices on environmental quality assessment].

The aquatic ecosystems quality can be evaluated through the analysis of physico-chemical and biological parameters. However, the biological parameters differ from the physico-chemical ones, having the advantage of providing information on the water quality concerning longer periods of time--specially if one considers sessil organisms--thus reflecting, in a better way, the general ecological conditions of the water body. It is necessary, though, that the taxonomic information be translated into simple numerical values (indices), in order to simplify its interpretation as well as providing subsidies for the elaboration of water quality criteria. Several numerical biological indices can be applied, some of them to specific communities, and others to the hole biological community of an aquatic environment. Three kinds of indices are more generally applied to evaluate the pollutant impacts on aquatic communities: biotic, diversity and community comparison indices. The biotic indices will measure the variation in terms of tolerance and relative sensitivity of the occurring organisms to a certain pollution condition; the diversity indices evaluate the effect of pollution in terms of the community structure; the community comparison indices (also named similarity or dissimilarity indices) establish the effects of pollutants on the community composition. It is important, for the numerical indices users, to know the limitations of each method, so that the interpretation of the values obtained may be made in the light of such limitations.

Animals↗
PubMed2002

Measurement of atmospheric NO2 concentrations in Antarctica with NO2 filter badge and tube.

Nitrogen dioxide (NO2) levels in Antarctica were monitored to determine background levels and distribution profile. The NO2 levels were higher than those reported from tropical remote areas. The NO2 concentrations gradually increased proceeding from the edge of the continent to the polar region, suggesting global pollutant transportation. To avoid artificial contamination of the data, a sled was used because motor vehicles discharge high levels of NO2. NO2 tubes and filter badges were selected as monitoring devices because of their convenience of transportation in Antarctica. They are small in size, light and easy-to-handle, and usually employed in personal NO2 exposure measurements. Because of severe Antarctica climate, the devices needed to be protected from the bitter cold. For that purpose, we designed an insulation container to shield the devices. The fixed NO2 monitoring site was Patriot Hill, located on the coast of the Weddell Sea. We also measured NO2 concentration along the expedition route from the fixed site to the South Pole, along with the 80 degrees west longitude. The survey periods were during November 1992 and January 1993. NO2 concentrations in Antarctica ranged from 1.0 to 2.8 ppb, which were relatively higher than previously reported background concentrations. The NO2 concentrations increased when nearing to the South Pole, supporting the theory that atmospheric circulation converges in the polar regions. This indicated that air pollutants discharged in populated regions were widely spread to isolated areas, like the South Pole.

Air Pollutants↗
PubMed2005

PCDD/Fs in Norwegian and U.K. soils: implications for sources and environmental cycling.

This paper presents data on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in a set of well-characterized, undisturbed surface (0-5 cm) and subsurface background soils from the U.K. and Norway. The soils have been used previously to investigate the latitudinal distribution, fractionation, cold condensation, and "hopping" of other classes of persistent organic pollutants (POPs). The mono- to octa-CDD/F homologues were quantified. Woodland soils contained higher concentrations (on a dry and soil organic matter (SOM)-basis) than grassland soils, consistent with previous studies. The absolute concentrations of all the PCDDs and most of the PCDFs significantly decreased with latitude, generally supporting the idea of a "southern source region" and a "remote/ receiving northern region". There was little evidence of "fractionation" and minimal influence of PCDD/F "hopping" on PCDD/F distribution. The %SOM content had a rather minor influence on soil PCDD/F composition. These findings contrast with the trends seen in these soils for hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Possible reasons for these differences are discussed and may include influences of/proximity to diffusive combustion sources and/ or sources of variable homologue emissions, formation/ conversion processes for PCDD/Fs in soils, or strong soil-PCDD/F partitioning. These soils, from regionally remote/ background locations in Europe contained between 0.2 and 78 pg sigmaTEQ/g DW. Some therefore exceed recommended levels of contamination for certain land uses by some European countries. These recommendations seem unrealistic and prohibitively restrictive in light of the dataset presented here.

Benzofurans↗
PubMed2001

Pollution-induced community tolerance (PICT) and seasonal variations in the sensitivity of phytoplankton to atrazine in nanocosms.

Algae communities exposed to a herbicide like atrazine (PS II inhibitor) are expected to be selected and to be more tolerant to the herbicide than unexposed communities (pollution-induced community tolerance, PICT). The PICT may be an ecotoxicological tool for detecting this selective action of chronic pollution, and this method has been applied to several toxicants in experimental systems and in field studies. But the detection of PICT with PS II inhibitors has sometimes been variable. This work was done to study the long-term effects of exposure to atrazine (10 microg/l) and the PICT responses of phytoplankton communities in repeated outdoor nanocosms. Phytoplankton communities were sampled in Lake Geneva at different periods of the year and the effects of atrazine were analysed by studying community structure, biomass and primary production, and by measuring tolerance to atrazine in a short-term physiological test based on 14C incorporation. We find that PICT is a sensitive method for measuring effects. Even atrazine concentrations causing little restructuring induced tolerance in most of our experiments. But the short- and long-term responses of phytoplankton to atrazine varied between experiments, probably due to the initial compositions of the communities and environmental factors associated with seasonal parameters. The selection and detection steps of PICT to atrazine thus vary greatly with environmental conditions and the physiological adaptations of algae to the herbicide. To monitor risk assessment in aquatic systems, PICT studies applied to algae, must be investigated in the light of seasonal contaminations and seasonal events and successions.

Adaptation, Physiological↗
PubMed2002

Photocatalytic degradation of pesticides and bio-molecules in water.

Two approaches are suggested for the acceleration of the photocatalytic oxidation of organic contaminants of water: acceleration by oxidants and photo-enhancement by dyes. These processes were examined with several substances: two widely applied herbicides, bromacil (a uracil) and metribuzin (a triazine), and three proteins, studied as models of biocontaminated waters. The effects of oxygen and hydrogen peroxide indicated two different reaction patterns of photo-oxidation of the herbicides. With metribuzin, oxygen had a pronounced effect on the rate of photo-oxidation, while the influence of hydrogen peroxide was quite moderate; with bromacil, oxygen had a limited effect on the rate of photo-oxidation, which however was considerably enhanced by hydrogen peroxide. Acceleration of the photo-catalytic oxidation of colourless refractory contaminants by photo-excited dye was observed. Both UV and visible light were required for the enhanced decomposition. The mechanism of the reaction seems to involve a combination of oxidation by hydroxyl radicals, via the hole-electron semiconductor route, with subsequent oxidation of photo-intermediates by singlet oxygen formed by dye sensitization. The TiO2-photocatalyzed oxidation of proteins (albumin, ovalbumin and gamma-globulin) showed the susceptibility of proteins to photocleavage and of the amino acids to photocatalytic degradation. Tyrosine was the most sensitive, while the degradation of the aliphatic amino acids Gly and Asp was slow.

Albumins↗
PubMed1992

Use of historical assessment for evaluation of process-based model projections of future environmental change: Lake acidification in the Adirondack mountains, New York, USA.

Because of the considerable uncertainties associated with modeling complex ecosystem processes, it is essential that every effort be made to test model performance prior to relying on model projections for assessment of future surface water chemical response to environmental perturbation. Unfortunately, long-term chemical data with which to validate model performance are seldom available. The authors present here an evaluation of historical acidification of lake waters in the northeastern United States, and compare historical changes in a set of lakes to hindcasts from the same watershed model (MAGIC) used to estimate future changes in response to acidic deposition. The historical analyses and comparisons with MAGIC model hindcasts and forecasts of acid-base response demonstrate that the acidic and low-ANC lakes in this region are responsive to strong acid inputs. However, the model estimates suggest lakewater chemistry is more responsive to atmospheric inputs of sulfur than do the estimates based on paleolimnological historical analyses. A 'weight-of-evidence approach' that incorporates all available sources of information regarding acid-base response provides a more reasonable estimate of future change than an approach based on model projections alone. The results of these analyses have important implications for predicting future surface water chemical change in response to acidic deposition, establishing critical loads of atmospheric pollutants, and other environmental assessment activities where natural variation often exceeds the trends under investigation (high noise-to-signal ratio). Under these conditions, it is particularly important to evaluate future model projections in light of historical trends data.

Journal Article↗
PubMed2001

Enhanced photo--catalytic activity of gold ion and gold modified.

The gold ion modified TiO2 was prepared by means of sol-gel whereas gold deposited TiO2 was prepared by means of photo-reduction. The physical properties were influenced significantly by the presence of gold ion or gold. The enhanced photo-activity of gold modified TiO2 was quantified in terms of methylene blue degradation. The presence of gold ion in TiO2 lattices or gold on TiO2 surface enhanced their photo-activity. The optimum molar content of gold ion doping and gold deposition all was 0.5%. The first-order rates constants of gold modified TiO2 was more than that of pure TiO2, and decreased by increasing the content of gold ion and gold when their contents were more than 0.5%. Gold ion doped in TiO2 lattices was more effective to enhance the photo-activity than gold on TiO2 surface. Moreover, the relationship between physical properties, chemical properties and photo-activity has been discussed.

Binding Sites↗
PubMed1987

[Lung cancer: recent epidemiologic data].

The prognosis of lung cancer is still very poor. However, during the last few years a favorable trend has been observed, consisting in the stabilization and even the decrease of incidence rate in Western countries. Besides, the sex-ratio shows a divergent trend, increasing in France and decreasing in the United States where lung cancer nowadays is the first cause of cancer deaths in women. The major risk factor, tobacco smoke, is now well established, qualitatively as well as quantitatively. Other air contaminants, occupational factors and air pollutants, have a lesser responsibility. The intervention of nutritional or genetic factors could explain why smokers are not equally susceptible to tobacco smoke. Screening for lung cancer is, and will be, reconsidered in the light of the results of prospective studies initiated 10 years ago under the auspices of the American Cancer Society.

Adult↗
PubMed1995

A positive, individually ventilated caging system: a local barrier system to protect both animals and personnel.

Most local barrier systems are designed primarily either to protect animals from airborne contamination (exclusion) or to ensure the safety of personnel (hazard containment). Few, other than isolators, are able to cope with the often conflicting demands to do both. The Positive Individually Ventilated system (PIV), which provides pressure adjustable, individual supply and exhaust ventilation to each cage has been tested with this in mind as well as the need to ensure that environmental conditions comply with the requirements of the Home Office Code of Practice (CoP). The results indicate that when compared with traditional open racking the system can reduce both the risk of animals becoming contaminated by airborne infection from the room and the risk of aeroallergens escaping from the cages into the room air. At the same time, environmental conditions within the cages are both less variable and less stressful to the occupants. Conditions of air temperature, relative humidity, ventilation rates, light intensity and (with appropriate air handling) sound levels, all comply with or are better than those required by the CoP. Even with the room air change rate set at only 8/h (8 ac/h) the air distribution system results in draught-free cage ventilation rates of around 50-120 ac/h. This means that with at least the PIV exhaust(s) linked directly into the air conditioning system of the building, the size of the latter and its associated running costs can be reduced by around 50%; this energy saving concept has been approved in principle by the Home Office. Additional benefits include the fact that bedding is kept much drier allowing further cost savings in bedding and associated labour costs. The system is thus beneficial to the animals in protecting them from airborne infection and other stresses. By providing a less variable environment it also helps to minimise the sort of interference with experiments which can arise from that source. Similarly, in accordance with the aims of 'The Control of Substances Hazardous to Health Regulations' (COSHH 1988) and the Health & Safety Executive (HSE 1990), by reducing dust levels in the room air, including allergens, it is also beneficial to the personnel working in the animal rooms.

Air Pollutants, Occupational↗
PubMed2005

Preparation and characterization of visible-light-active nitrogen-doped TiO2 photocatalyst.

A visible-light photocatalyst was prepared by calcination of the hydrolysis product of Ti(SO4)2 with ammonia as precipitator. The color of this photocatalyst was vivid yellow. It could absorb light under 550 nm wavelength. The crystal structure of anatase was characterized by XRD. The structure analysis result of X-ray fluorescence (XRF) shows that doped-nitrogen was presented in the sample. The photocatalytic activities were evaluated using methyl orange and phenol as model pollutants. The photocatalytic activities of samples were increasing gradually with calcination temperature from 400 degrees C to 700 degrees C under UV irradiation. It can be seen that the degradation of methyl orange follows zero-order kinetics. However, the calcination temperatures have no significant influence on the degradation of phenol under sunlight. The N-doped catalyst shows higher activity than the bare one under solar irradiation.

Catalysis↗
PubMed1988

Isolation of dinitropyrene in emission gas from a municipal incinerator and its formation by a photochemical reaction.

In a previous paper, direct-acting mutagenicity was reported in emission gas from incomplete municipal incineration using Salmonella typhimurium TA-98 and TA-100. This paper reports the detection of dinitropyrene (DNP) as a direct-acting mutagen using nitrogen selective gas chromatography. The gas-phase photochemical reaction of pyrene with nitrogen dioxide was examined in a quartz vessel with various reaction times and temperatures. 1-Nitropyrene (1-NP) was readily formed from pyrene in the absence of light irradiation and at low temperature, but DNP was not formed under similar conditions. DNP formation was catalyzed by nitric acid. The formation of DNP is dependent on light irradiation, temperature and HNO3 as catalyst. In a combustion source these factors affect the formation of DNP.

Air Pollutants↗
PubMed2000

Determination of optical parameters for light penetration in particulate materials and soils with diffuse reflectance (DR) spectroscopy.

The results of our investigations of particulate materials (aluminium oxide, quartz sand) and "real world" soils (a brown sand and a dark brown soil) using diffuse reflectance (DR) spectroscopy are presented. The findings are discussed within the framework of Kubelka-Munk (KM) theory as a simplified description of light propagation in highly turbid media. The relation between the KM and the Lambert-Beer (LB) treatment is outlined. The KM parameters determined were the scattering and absorption coefficients (S and K, respectively), and the light penetration depths, dp(KM). It was found that in the UV/VIS spectral range the scattering coefficients of the materials investigated vary by ca. one order of magnitude (S = 6-> 100 cm-1), whereas the absorption coefficients change by more than three orders of magnitude (K = < 1-> 1500 cm-1). The different absorption and scattering properties of the materials lead to strong variations in light penetration depths from the micron into the mm regime [dp(KM) = < 20-> 3500 microns].

Environmental Monitoring↗