1 Executive summaryEnvironmental noise is an inevitable nuisance in the urban community. Despite efforts to restrict the exposure, noise constitutes an increasing problem, primarily as a consequence of continuous urbanization and transportation growth. The major contributor to the overall burden of environmental noise is traffic, primarily road-, railway- and aircraft traffic, but noise from neighbours, construction sites and industrial plants also contribute. Absence of quiet and restorative areas in the society affects our health and well-being. Annoyance, sleep disturbances, impaired communication, cognitive effects and physiological stress reactions are possible health impacts associated with an excess exposure to noise. There is also evidence of a long-term effect of traffic noise on the cardiovascular system, but many issues remain to be resolved in the risk assessment.With the aim of providing a scientific basis and guidance for future work on noise abatement in Sweden, we conducted a literature review of the current knowledge on health effects related to traffic and industrial noise, including annoyance, sleep disturbance, performance and learning and cardiovascular disease. Certain aspects concerning the exposure assessment techniques used in health risk assessments have also been reviewed. Furthermore, we aimed to identify important gaps in the knowledge and to summarize the main imminent research needs.Noise exposure can be assessed in different ways, commonly by measurements or modelling. In terms of modelling, national calculation models and indicators are often used, resulting in difficulties to compare the findings internationally. With the implementation of the European Environmental Noise Directive (END; 2002/49/EC), the Member States of the European Union (EU) are obliged to produce strategic noise maps for major roads, railways, airports, agglomerations and industries on a five-year basis. The END also proposed that common assessment methods should be established in order to ensure consistency of noise exposure data across Europe. Such methods are currently developed within the CNOSSOS-EU program and could, when fully developed, be valuable for estimations of population exposure. However, for the purposes of local action planning, urban planning and health risk assessments, the END maps need some refinements. For example, the maps should include noise levels <55 dB Lden and 50 dB Lnight and have a resolution of less than 5 dB. Equally important is to adapt the calculation models to local conditions; in Sweden, primarily with regard to temperature and the use of studded tyres. To assess the impact of noise on health, it is also important to improve the individual assessments of traffic noise exposure. For example, techniques should be developed to take into account noise from multiple sources, varying exposure during the day and exposure modifying factors, in particular acoustic insulation and access to a quiet side.Traffic noise is clearly related to annoyance. For a given equivalent noise level, aircraft noise generates a higher proportion annoyed residents than road traffic noise, which, in turn, generates a higher proportion annoyed residents than railway noise. For aircraft noise, an upward trend in annoyance has been seen which cannot fully be explained by methodological issues. Also, new findings suggest that annoyance related to railway noise may be higher than expected in areas with intense traffic or simultaneous ground-borne vibrations. These models thus need to be updated. Furthermore, exposure-response models for combined traffic noise are lacking and should be developed. Industrial noise has been found to be similarly or slightly more annoying than road traffic noise. But further studies are needed, in particular for annoyance relating to harbours and rail yards.Sleep disturbances are one of the most common complaints in noise exposed populations and have several short and long-term health consequences, such as tiredness, irritability and impaired cognitive functioning. Clear exposure-response associations exist between traffic noise and sleep disturbances, but data on industrial noise are lacking. Since the auditory system is always open, noise may activate our alertness system even during sleep, thereby affecting several endocrine, metabolic and immune functions. Physiological effects of noise during sleep, such as increases in blood pressure and heart rate, are seen from 35 dB LAmax, inside and awakenings occur from 42 dB LAmax, inside. However, established threshold levels, defined as sound levels at which certain effects are first observed, are lacking for several effects, including changes in stress hormones. Furthermore, there is a need for largescale longitudinal studies to demonstrate a causal pathway linking noise and disturbed sleep to long-term cardiovascular and metabolic effects.Traffic noise may disturb cognitive functioning, that is, how information is processed, retained and recalled, and thereby affect performance and learning. But much is still unknown regarding the mechanistic pathways. Most studies on traffic noise and cognitive functioning have concerned day-time noise at schools among children, showing effects primarily of aircraft noise on reading comprehension, memory and motivation. However, the overall evidence of cognitive effects among children is limited and no reliable studies exist among adults. Further longitudinal studies are therefore needed, for children as well as for adults, preferably differentiating the role of day- and night-time exposures.A recent review on the long-term effects of traffic noise on the cardiovascular system stated that the weight of evidence clearly supports a causal link. However, it was also concluded that many questions remain to be resolved, in particular with regard to the establishment of threshold levels and sourcespecific exposure-response associations. To some extent, the inconclusiveness is due to methodological problems, such as a lack of large-scale longitudinal studies and imprecise exposure characterisation. Efforts are also needed to disentangle the effects of noise and air pollution as well as to identify particularly vulnerable groups. Furthermore, there are also plausible biological pathways between traffic noise and metabolic outcomes which have not yet been investigated systematically and therefore warrant further attention. This review has identified a number of important gaps in the knowledge on health effects of environmental noise. To protect populations from harmful health effects of excess exposure to noise, further research in this area is urgently needed. Of particular interest is to study the long-term consequences of traffic noise-induced sleep loss and chronic stress on cardiovascular as well as metabolic outcomes. Synergistic effects between noise and air pollution should be prioritized. Additional studies are also needed on health effects of railway and industrial noise, as well as on combined exposures. Furthermore, identification and definition of particularly vulnerable individuals may assist in targeting preventive measures.