Occupational health and safety considerations in lighting

¶ … Risk and Hazard Factors of Bright Blue Light

The public is constantly being inundated by advertising that states that the intensity and range of colors offered by lamps that replicate sunshine and daylight are necessary for best vision and visual health. Simultaneously, the public is admonished by those in the medical field to wear blue-blocking, UV-protective sunglasses outdoors. This has necessarily left questions which need answered concerning these matters in relation to whom the public should believe and how light can damage the retinas of the individual as well as what the differences are between fluorescent, halogen, neodymium, and regular incandescent light bulbs.

The aim of the following proposal for research is to examine the risk and hazard factors of bright blue light in the workplace and to further compare the use of green light in the work place and examine the safety issues relating to green light use.

OBJECTIVES

The objective of this research is to examine the hazards and risks associated with the use of blue light in the work place and the various factors such as aging that result in different effects for different individuals who are exposed to bright blue light. As well, this work will examine the use of green light in the workplace and the safety issues relating to the use of green light. This work intends to examine as well the fact that blue light marketers inform the public that lamps with 'enhanced' UV will ensure better health.

HYPOTHESIS

The hypothesis of this work is one which holds that green light is safer for use in the workplace than blue light and seeks to answer the question of why the public is continually informed that blue light or UV light when is enhanced serves to enhance the health of the individual.

RATIONALE

This study intends to sort through the plethora of conflicting information in this area of study and to attempt to determine the facts associated with blue lighting safety in the workplace and to make a comparison of green lighting use in regards to safety and health issues.

METHODOLOGY

The methodology of this study is one of a qualitative nature and will be conducted through an extensive review of literature in this area of study. This study is therefore, interpretive in nature is a study that will be conducted through a synthesis of the research findings in this area of study.

LITERATURE REVIEW

The work of Lack, Bramwell, Wright and Kemp entitled: "Morning Blue Light Can Advance the Melatonin Rhythm in Mild Delayed Sleep Phase Syndrome" reports an investigation into the "effectiveness of morning blue light in advancing the sleep and melatonin rhythm of individuals with mild delayed sleep phase syndrome." (2007) the study was conducted through random allocation of the participants (n=18) to a light or control group. Reported is a gradually advance of wake-up times to 06:00 hours over the course of a week. The blue light group is stated to have shown "significant 2.53-h advance of dim light melatonin onset, compared to no change in the control group. However, neither group had a significant advance of sleep times following treatment." (Lack, Bramwell, Wright, and Kemp, 2007)

Sunnex Biotechnologies reports, in the work entitled: "Risk Factors of Blue and Bright Light Therapy" that photoretinitis, also known as "light-induced photochemical damage to the eye, is related to the 'blue light hazard' a term which begins to suggest why the prospect of blue light therapy dramatically raises the risk of light-induced retinal damage from light therapy." (2008) it is stated that there are commercial standards used for assessing the "acute risk to photoreceptor cells from high intensity white light sources for a 'standard observer', but individual susceptibility to blue light damage is so variable that these standards cannot presume to eliminate a person's risk of acute damage from a blue light therapy device, let alone the long-term risk that repeated exposure may contribute towards the development of age-related macular degeneration (AMD) to which these standards do not apply." (Sunnex Biotechnologies, 2008) Additionally stated is that "the image of a light source on a small area of the retina with the intensity necessary to be chronobiologically effective may cause a hazard to the retina, even if the same number of photons diffused over a larger portion of the retina do not." (Sunnex Biotechnologies, 2008) the factors identified as those which provide indication as to why blue light therapy presents a "significant, inestimable risk to the retina not accounted for by commercial assessments of blue light hazard" are those as follows: (1) the variability of individual susceptibility to AMD, as well as to the variability of the transmissibility of blue light through the eye to the retina; the susceptibility for AMD varies greatly with the individual, and the conditions by which normal retinal deterioration from aging becomes the pathological deterioration known as AMD are not yet established. Contributing to the variability of susceptibility amongst individuals are genetic factors such as skin color, macular pigment density, lifestyle factors such as the amount of fat, lutein, antioxidant vitamins and zinc in the diet, history of smoking, outdoor activity, and other environmental factors such as previous levels of light exposure." (Sunnex Biotechnologies, 2008) There is stated to be a problem in the determination of the intensity of blue light that would be necessary for effective therapy. Stated is: "The proportion of blue light reaching the eye that is transmitted to the retina is highly variable from one individual to another." (Sunnex Biotechnologies, 2008) the yellowing of the lens of the eye, which is related to aging and resulting in a change in the lens, cornea and vitreous "...substantially decrease the amount of blue wavelengths reaching the retina by middle age." (Sunnex Biotechnologies, 2008) This means there would be a need for a substantial increase in the intensity of blue light for effective treatment n older people. However, it is noted that as one advances in age the blue light absorbing macular pigment which provides protection to the small region of the retina experiences a decrease. As well, the MP density is greatly variable among individuals and is related to the individual's genetic, history of light exposure and factors related to individual lifestyle. MP density is also determined by the diet of the individuals and experiences variability daily. Due to these reasons: "...it would be impossible to calibrate a level of blue light that is both effective and safe for a wide range of individuals. Higher levels of exposure to blue light would be necessary to stimulate chronobiologically significant pathways in individuals in whom the ocular media prevents most blue light wavelengths from reaching the retina. But a blue light therapy device that provided sufficient intensity for effective stimulation of this middle-aged or older individual whose ocular media screens our most of the blue light could pose a significant risk of creating photo-oxidative damage in a person who has high transmissibility of blue light, such a younger adult or a person who has had cataract surgery, or a person is pre-disposed to retinal disease." (Sunnex Biotechnologies, 2008) (2) Risks of blue light therapy in the elderly, a target group for light therapy: The older population is one causing the most concern in relation to blue light hazard and risk with particular concern related to Oxidative damage in the "non-replicating photoreceptor cells because they are exceptionally rich in polyunsaturated fatty acids and lipoproteins that are highly susceptible to oxidative damage and exist in an environment that is very favorable to the generation of reactive oxygen species (ROS) from the high levels of oxygen and light energy. (Sunnex Biotechnologies, 2008); (3) Additional blue light hazard due to the timing of light therapy: Light therapy is believed to be effective only during the subjective night, when melatonin levels are high. Studies show that the retina is much more sensitive to photic damage when serum melatonin levels are high. Furthermore, light therapy is often used upon awakening, when the eye is still dark-adapted. The dark-adapted eye is much more sensitive to photic damage than the eye that has previously been exposed to bright light for extended periods of time; (Sunnex Biotechnologies, 2008) (4) Additional blue light hazard potentially contributed by other medical treatments: Some applications for which light therapy is used increase the risk of retinal damage. For example, some studies suggest that light therapy can enhance and hasten the response to antidepressant medication. However, antidepressants are photosensitizing, as are many other medications, including: a) diuretics, a problem for treating geriatric chronobiological and sleep disorders b) some antibiotics, a problem for anyone who develops a bacterial infection while on light therapy c) non-steroidal anti-inflammatory drugs (NSAIDs) d) some neuroleptics; e) Heart medications and other commonly used medications and popular herbal treatments. There are additional medical factors that may increase risk of progressive ocular diseases such as AMD, including the removal of cataracts; (Sunnex Biotechnologies, 2008) and (5) Blue light therapy subverts protective mechanisms against the blue light hazard: A therapy lamp must be in the field of vision. Even though users of light therapy are often advised not to look directly at the light source, the mechanisms of the eye focus incoming light onto the macula, the small region of the retina where vision takes place, and where age-related macular degeneration occurs. Since blue light wavelength make up only a small percentage of the light in white light, any form of light therapy using a high proportion of blue light therefore risks subverting a variety of defensive mechanisms that protect the retina against blue light hazard. These defensive mechanisms include the anatomical positioning and structure of eye and its surrounding features, as well as human posture, which makes it awkward for humans to gaze upwards for long periods of time. Sunnex Biotechnologies, 2008)

The work of David H. Sliney entitled: "Ocular Hazards of Light" presented at the International Lighting in Controlled Environments Workshop states the following risks and hazards to the eye due to lighting: (1) Ultraviolet photochemical injury to cornea (photokeratitis) and lens (cataract) stated at 180mn to 400 nm; (2) thermal injury to the retina of the eye (400nm to 1400nm); (3) blue-light photochemical injury to the retina of the eye (principally 400nm to 550 nm; unless aphakic, 310 to 550 nm); (4) near infrared thermal hazards to the eye lens (approximately 800 nm to 3000 nm); and (5) thermal injury to the eye cornea (approximately 1400 nm to 1mm). (1994) Sliney states that the primary "retinal hazard" due to bright light sources is "photoretinitis, e.g., solar retinitis with an accompanying scotoma which results from staring at the sun." (1994) Sliny states that it is only recently that it has become clear that "photoretinitis results from "a photochemical injury mechanism following exposure of the retina to shorter wavelengths in the visible spectrum, i.e., violet and blue light."(1994) Sliny states that it has been show conclusively that an intense exposure to short-wavelength light, or 'blue light' can cause retinal injury. Sliny specifically states: "The product of the dose-rate and the exposure duration always must result in the same exposure dose (in joules-per-square centimeter at the retina) to produce a threshold injury. Blue-light retinal injury (photoretinitis) can result from viewing either an extremely bright light for a short time, or a less bright light for longer exposure periods. This characteristic of photochemical injury mechanisms is termed reciprocity and helps to distinguish these effects from thermal burns, where heat conduction requires a very intense exposure within seconds to cause a retinal coagulation; otherwise, surrounding tissue conducts the heat away from the retinal image. Injury thresholds for acute injury in experimental animals for both corneal and retinal effects have been corroborated for the human eye from accident data. Occupational safety limits for exposure to UVR and bright light are based upon this knowledge. As with any photochemical injury mechanism, one must consider the action spectrum, which describes the relative effectiveness of different wavelengths in causing a photobiological effect. The action spectrum for photochemical retinal injury peaks at approximately 440 nm." (1994)

Calculation of retinal exposure is also addressed in Sliny's work who states that the knowledge "of the optical parameters of the human eye and from radiometric parameters of a light source" enables the calculation of "irradiances (dose rates) at the retina. (1994) Sliny states that there are two sets of light-measurement quantities and units in the endeavor to define light exposure of the retina: (1) radiometric; and (2) photometric. (1994) Specifically, Sliny states: "Radiometric quantities such as radiance -- used to describe the "brightness" of a source [in W/cm2 sr] and irradiance -- used to describe the irradiance level on a surface [in W/cm2] are particularly useful for hazard analysis. Radiance and luminance are particularly valuable because these quantities describe the source and do not vary with distance. Photometric quantities such as luminance (brightness in cd/cm2 as perceived by a human "standard observer") and illuminance in lux (the "light" falling on a surface) indicate light levels spectrally weighted by the standard photometric visibility curve which peaks at 550 nm for the human eye (Figure 1). To quantify a photochemical effect it is not sufficient to specify the number of photons-per-square-centimeter (photon flux) or the irradiance (W/cm2) since the efficiency of the effect will be highly dependent on wavelength. Generally, shorter-wavelength, higher-energy photons are more efficient." (1994) Sliny goes on to state: "Unfortunately, since the spectral distributions of different light sources vary widely, there is no simple conversion factor between photometric (either photopic or scotopic) and radiometric quantities. This conversion may vary from 15 to 50 lumens/watt (1m/W) for an incandescent source to about 100 1m/W for the sun or a xenon arc, to perhaps 300 to 400 lm/W for a fluorescent source (Sliney and Wolbarsht, 1980; as cited in Sliny, 1994)

The work of Wu (2004) entitled: "Blue Light Induced Retinal Damage" states that there is a high damage potential for "visible, non-coherent blue light" and that green light "in sharp contrast does not induce lesions." The work of Wenzel, Grimm and Iseli (2003) relate that photochemical retinal damage "are exceed within one minute for nine out of ten combinations" when the spectrum and energy of light are measured. The work of Biesen, et al. entitled: "Endoiollumination During Vitrectomy and Phototoxicity Thresholds" relates is has been shown that "intense exposure to shorter wavelengths in the visible spectrum, i.e. violet and blue light...can cause retinal injury." This work related that it has been shown that reduction of the risk of photochemical injury to the retina can be greatly reduced through filtering out the short-wavelengths of light.

Sunnex Biotechnologies has produced a 'GreenLIGHT' System which uses a low-intensity narrow spectrum technology. Sunnex reports having conducted studies that show that "intensities between 5,000 and 10,000 lux of white light are most successful in shifting the human body clock to align it with a night work schedule." (2008) it is stated however, that "this high intensity of white light is not practical in the workplace, and may be harmful to the eye." (Sunnex Biotechnologies GreenLIGHT System, 2008) the GreenLIGHT system is stated to be safe for the individual's eye and makes provision of a "non-UV light source that filters out the harmful wavelengths of visible light, the blue rays, contained in white and full-spectrum lighting." (Sunnex Biotechnologies GreenLIGHT System, 2008) the elimination of the 'blue light hazard' "eliminates the risk of eye damage inherent from repetitious exposure to bright or blue light." (Sunnex Biotechnologies GreenLIGHT System, 2008) GreenLIGHT is a system that has been patented by Sunnex Biotechnologies.

Okudaira, Kripe, and Webster (1983) conducted a study and reported it in the work entitled: "Naturalistic Studies of Human Light Exposure." In this study which included 10 volunteers, who, for twenty-four hours "wore an apparatus that recorded their exposure to light at eye level and at the wrist" with activity being recorded at the heard, both wrists and one ankle findings are stated which relate that "Illuminations at the eye level and wrist were correlated 0.76 while eye-level illumination was correlated 0.25, 0.44, 0.39, and 0.44 with head wrists and ankles respectively,: Conclusions of the study state: "Because human biologic rhythms are probably well synchronized only by illumination approaching daylight intensities, inadequate illumination could be a source of sleep disturbance, chronobiologic disorders, or depression." (Okudaira, Kripe, and Webster, 1983)