Light-emitting diodes (LEDs) have been used to provide illumination in industrial and commercial environments. LEDs are also used in TVs, computers, smart phones, and tablets. Although the light emitted by most LEDs appears white, LEDs have peak emission in the blue light range (400-490 nm). The accumulating experimental evidence has indicated that exposure to blue light can affect many physiologic functions, and it can be used to treat circadian and sleep dysfunctions. However, blue light can also induce photoreceptor damage. Thus, it is important to consider the spectral output of LED-based light sources to minimize the danger that may be associated with blue light exposure. In this review, we summarize the current knowledge of the effects of blue light on the regulation of physiologic functions and the possible effects of blue light exposure on ocular health.

/pdf/effects-of-blue-light-on-the-circadian-system-and-eye-37qaaosmxg.pdf

Effects of Blue Light on the Circadian System and Eye Physiology

http://www.reticare.com/imagenes/documents/18.-Behar-Cohen-2011.pdf

Light-emitting diodes (LED) for domestic lighting: any risks for the eye?

Removal of rhodamine B using iron-pillared bentonite.

Background
Helicobacter pylori colonizes the mucus layer of the human stomach and may cause peptic ulcer and adenocarcinoma. Novel antimicrobial approaches are sought due to the occurrence of antibiotic resistance and consequent treatment failure. We report here that H. pylori is susceptible to inactivation by blue light.

Study Design/Materials and Methods
A controlled, prospective, blinded, trial of endoscopically delivered blue light to eradicate H. pylori in regions of the gastric antrum, in 10 patients between the ages of 21 and 80 who tested positive for H. pylori. Light (405 nm) (40 J/cm2) was delivered to a 1-cm diameter spot in the gastric antrum via optical fiber passed through the endoscope and weighed biopsies were taken from treated and control spots and colonies quantitatively cultured.

Results
Blue light killed 5 logs of bacteria in vitro. The mean reduction in H. pylori colonies per gram tissue between treated and control spots was 91% (7.4±4.8×106 vs. 8.1±1.9×107, two-tailed P<0.0001). Some patients had reductions approaching 99%. No differences were observed on histological examination of light-treated and control gastric tissue.

Conclusion
Blue light phototherapy may represent a novel approach to eradication of H. pylori, particularly, in patients who have failed standard antibiotic treatment. © 2005 Wiley-Liss, Inc.

/pdf/helicobacter-pylori-in-patients-can-be-killed-by-visible-2cwmey21sd.pdf

Helicobacter pylori in patients can be killed by visible light

Neglecting health effects from indoor pollutant emissions and exposure, as currently done in Life Cycle Assessment (LCA), may result in product or process optimizations at the expense of workers' or consumers' health. To close this gap, methods for considering indoor exposure to chemicals are needed to complement the methods for outdoor human exposure assessment already in use. This paper summarizes the work of an international expert group on the integration of human indoor and outdoor exposure in LCA, within the UNEP/ SETAC Life Cycle Initiative. A new methodological framework is proposed for a general procedure to include human-health effects from indoor exposure in LCA. Exposure models from occupational hygiene and household indoor air quality studies and practices are critically reviewed and recommendations are provided on the appropriateness of various model alternatives in the context of LCA. A single-compartment box model is recommended for use as a default in LCA, enabling one to screen occupational and household exposures consistent with the existing models to assess outdoor emission in a multimedia environment. An initial set of model parameter values was collected. The comparison between indoor and outdoor human exposure per unit of emission shows that for many pollutants, intake per unit of indoor emission may be several orders of magnitude higher than for outdoor emissions. It is concluded that indoor exposure should be routinely addressed within LCA.

/pdf/integrating-human-indoor-air-pollutant-exposure-within-life-50dlwrtdyk.pdf

Integrating Human Indoor Air Pollutant Exposure within Life Cycle Impact Assessment

Infrared Spectrophotometry (IR) is now widely used to determine crystalline silica in industrial dust samples. Though the IR method has many advantages when dealing with respirable dust samples, some serious analytical errors are often caused by interference minerals contamination. These minerals have a characteristic absorption band corresponding in position to the analytical peak for crystalline silica. In this paper, six typical interference minerals (Kaolinite, Mullite, Muscovite, Pyrophyllite, Montmorillonite and Amorphous silica) were pre-size controlled to respirable range and their infrared spectra were measured by means of an FT-IR with the well-known potassium bromide tablet technique. The effects of these interference minerals on the Japanese OEL or the administrative control level for respirable dust which depend on the silica content were calculated and expressed in figures. The measured absorption coefficients of the interference minerals and quartz were 1.36-6.98 Abs/mg and 24.46 Abs/mg, respectively. The absorption band height ratios of each interference minerals were also measured. Then the efficiency and applicability of two spectrum correction methods for the interference minerals, absorbance ratio method and difference spectrum method were examined by using artificially mixed samples (standard interference mineral + standard quartz). By comparing the quantifying results for the mixture samples, it was revealed that the interfered spectra were almost corrected successfully when using the difference spectrum method, whereas correction by the absorbance ratio method resulted in apparent negative errors. Furthermore, the difference spectrum method was proven to be superior to the absorbance ratio method in applicability.

/pdf/determining-of-crystalline-silica-in-respirable-dust-samples-2438y4wd61.pdf

Determining of Crystalline Silica in Respirable Dust Samples by Infrared Spectrophotometry in the Presence of Interferences

Visible light of short wavelength (blue light) may cause a photochemical injury to the retina, called photoretinitis or blue-light hazard. In this study, various light sources were evaluated for blue-light hazard. These sources include the sun, the arc associated with arc welding and plasma cutting, molten steel, iron and glass, the interior of furnaces, the arc or envelope of discharge lamps, the filament or envelope of incandescent lamps, the envelope of fluorescent lamps and light-emitting diodes. The spectral radiance of each light source was measured, and blue-light effective radiance and the corresponding permissible exposure time per day were calculated in accordance with the ACGIH (American Conference of Governmental Industrial Hygienists) standard. The sun, arc welding, plasma cutting and the arc of discharge lamps were found to have extremely high effective radiances with corresponding permissible exposure times of only 0.6-40 s, suggesting that viewing these light sources is very hazardous to the retina. Other light sources were found to have low effective radiances under the study conditions and would pose no hazard, at least for short exposure times.

Evaluation of blue-light hazards from various light sources.

The arcs associated with arc welding emit high levels of ultraviolet radiation (UVR), and this often causes acute injuries in the workplace, particularly photokeratoconjunctivitis. It is important to know the level of UVR emitted by arc welding under various conditions, as this information will help in evaluating potential UVR hazards in welding workplaces and taking protective measures against it. In this study, the ACGIH effective irradiance for UVR was measured experimentally for CO2 arc welding in order to evaluate its UVR hazards. A welding robot was used in the experiment in order to realize reproducible and consistent welding operations. The effective irradiance at 1 m from the arc was in the range 0.28-7.85 W/m 2 (28-785 |xW/cm 2 ) under the study conditions. The corresponding permissible exposure time per day is only 4-100 s, suggesting that UVR from CO2 arc welding is actually hazardous for the eye and skin. It was found that the effective irradiance is inversely proportional to the square of the distance from the arc, is strongly dependent on the direction of emission from the arc with a maximum at 50-60° from the plate surface, and tends to increase with welding current. © 2001 British Occupational Hygiene Society. Published by Elsevier Science Ltd. All rights reserved

Ultraviolet Radiation Emitted by CO2 Arc Welding

Concentrations of fumes, ozone (O3), carbon monoxide (CO), nitric oxide (NO), manganese (Mn) and total and hexavalent chromium (Cr) as well as size distribution of fumes were measured at a point corresponding to the welder's breathing zone during CO2-arc welding, using a welding robot and three kinds of wires. Concentrations of fumes, O3, CO, Mn and total-Cr were found to exceed their corresponding occupational exposure limit (OEL) values, while the concentrations of NO and Cr(VI) were below those OEL levels. Airborne concentration of Mn exceeded its OEL value, and the Mn content was 8 times higher in welding fumes than in the wire. Using an additive equation of OEL and exposure concentration of each hazardous component, health risk in welders with combined exposure to welding fumes and gases was assessed as 18.6 to 46.0 times of OEL, which exceeded the unity. This finding suggests that effective protection of welders from the exposure can be attained by use of the supplied-air respirator or combined use of a dust respirator and a local exhaust system.

Laboratory measurement of hazardous fumes and gases at a point corresponding to breathing zone of welder during a CO2 arc welding.

Objectives The objective was to quantify the blue-light hazard from CO(2) arc welding of mild steel. Methods The spectral radiance of arcs in CO(2) arc welding of mild steel was measured for solid and flux-cored wires at welding currents of 120-480 A. Effective blue-light radiance and the maximum acceptable exposure duration were calculated from the spectral radiance using their definitions in American Conference of Governmental Industrial Hygienists guidelines. Results The effective blue-light radiance ranged from 22.9 to 213.1 Wcm(-2)sr(-1). The corresponding maximum acceptable exposure duration was only 0.47-4.36 s, meaning that the total daily exposure to the welding arc without eye protection should not exceed this duration. Conclusions It is very hazardous to view the arcs in CO(2) arc welding of mild steel. Welders and their helpers should use appropriate eye protectors in these arc-welding operations. Also, they should avoid direct light exposure when starting an arc-welding operation.

/pdf/blue-light-hazard-from-co2-arc-welding-of-mild-steel-1in32ybatl.pdf

Jun Ojima

Papers

Determining of Crystalline Silica in Respirable Dust Samples by Infrared Spectrophotometry in the Presence of Interferences

Evaluation of blue-light hazards from various light sources.

Ultraviolet Radiation Emitted by CO2 Arc Welding

Laboratory measurement of hazardous fumes and gases at a point corresponding to breathing zone of welder during a CO2 arc welding.

Blue-light hazard from CO2 arc welding of mild steel