Illumination, lighting technologies, and indoor environmental quality

Indoor Air reached a milestone in the April 2014 issue: We published our 1000th article! Throughout the past quarter century, the pages of this journal have chronicled important advances for many aspects of indoor environmental quality (IEQ) and health. However, less than 1% of the articles published in this journal have been concerned with the influence of lighting technologies and illumination on IEQ and health. Many reasons may account for this weak level of attention. It is certainly not for lack of importance. Access to controllable light is a primary requirement for human development. Lighting technologies allow for the hours of productive and social activity to be extended from the daylight hours to the full period outside of sleep. Mills (2005) has estimated that two billion people worldwide rely on fuel-based lighting, because they lack reliable access to electricity. Generating light by means of incandescence at low flame temperatures, fuel-based lighting is inherently inefficient. An all-too-common result is poor quality light service obtained at relatively high cost. Furthermore, fuel combustion indoors for any purpose contributes to the degradation of indoor air quality. Lam et al. (2012a) recently reviewed the household use of kerosene and associated health hazards. Noting that kerosene-fueled lamps are potentially important contributors to air pollution exposure, they also commented on the sparseness of published data. Only four studies were identified that reported emission factors or microenvironmental concentrations of pollutants associated with kerosene lamp use, one of which was published in Indoor Air (Apple et al., 2010). Another study by Lam et al. (2012b) reported sufficiently high emission factors of black carbon particulate matter from kerosene lanterns to make a noteworthy contribution to radiative climate forcing in near-equatorial latitudes. Candles, the other major combustion-based lighting technology, are more widely used for decorative than for functional purposes. For the United States alone, estimated annual sales are $2 billion and utilize more than 40,000 tonnes of wax (http://www.candles.org/about_facts.html). One associated IEQ concern is exposure to lead from candles with metal-cored wicks (Nriagu and Kim, 2000). Another set of issues arises from the emissions of inorganic and carbonaceous particles formed during combustion (Pagels et al., 2009). Associated inhalation exposures may contribute to adverse health risks. Deposition of soot onto interior surfaces constitutes a long-term soiling risk for works of art and other cultural artifacts (Fine et al., 1999). A recent study of ultrafine particulate matter in Danish households identified candle use as a major source (Bekö et al., 2013). Previously, Afshari et al. (2005) had identified candle use as a particularly strong source of ultrafine particles among various household activities. Indoor lighting is a major end-use sector for electricity consumption. In the United States, an estimated 550 billion kWh/year of electricity is used for lighting in commercial (350 billion kWh/year) and residential (200 billion kWh/year) buildings (http://buildingsdatabook.eren.doe.gov/). Indirectly, this electricity use has consequences for air pollution emissions and exposure as, for example, about 40% of US electricity is generated by coal combustion, which remains a major source of atmospheric sulfur dioxide and sulfate particles. The high electricity use in this sector is also subject to considerable scrutiny, with strong efforts to reduce energy use through improved end-use efficiency. One of the changes underway is a shift from incandescent lighting toward more efficient technologies, including compact fluorescent lamps (CFL) and light-emitting diodes. The necessary presence of mercury, a neurotoxicant, in CFL bulbs raises an exposure and potential health concern in the event of accidental breakage indoors (Salthammer et al., 2012). More subtle influence of lighting technologies on IEQ arises from the heating of electric lamp bulb surfaces when they are used. When heated, household dust can emit volatile organic compounds and produce submicrometer particles (Pedersen et al., 2003). Mathiesen et al. (2004) found that heating indoor dust reduced its ability to stimulate a proinflammatory response in a cell culture. Lower bulb surface temperatures should accompany the transition to more efficacious lighting technologies. An important theme for many articles published in Indoor Air is how IEQ might influence performance in workplaces and in schools. However, until now, the relatively sparse research that assesses human response to lighting conditions in field settings has been published in other journals (e.g., Boyce et al., 2006). A few papers published in Indoor Air have explicitly considered how lighting influences occupant satisfaction (Frontczak et al., 2012; Newsham et al., 2008). Engvall et al. (2004) incorporated questions about illumination into a standard survey regarding indoor environmental quality in dwellings. A final theme to consider is the direct influence of photons on the chemical and microbiological characteristics of indoor environments. Carslaw (2007) presented a state-of-science numerical model of indoor reactive chemistry, which included many photolytic reactions. Her article highlighted the need for better knowledge on the spectral distribution of light indoors, a prerequisite to predicting photolytic reaction rates. Gligorovski and Weschler (2013) noted that the impacts on indoor photochemistry of lighting changes, from incandescent bulbs to CFLs and LEDs ‘have received almost no attention’. Of related interest, and not yet adequately studied, is whether ultraviolet germicidal irradiation, designed for control of airborne disease transmission (Linnes et al., 2014), might induce important indoor photochemistry. In contrast to the dearth of information on these subjects, a related topic has received substantial research attention: photocatalytic oxidation, including its application to control indoor volatile organic compounds (Mo et al., 2005, 2009). This editorial has presented a brief survey of the relationships among lighting, IEQ, and health. Relative to its importance and also to the scientific challenges, it remains a substantially understudied research space. Perhaps some creative and ambitious young scholars might be inspired to take up the challenge and dedicate their professional effort to help us better understand the manifold ways in which illumination and lighting technologies affect indoor environmental quality and health.