“…wind-energy projects create negative impacts on human health and well-being, the impacts are experienced mainly by people living near wind turbines who are affected by noise and shadow flicker.” [1]
In addition to noise pollution wind turbines also have visual burdens. [2]
The health impact of visual burdens cannot be underestimated. An epidemiology study conducted by World Health Organization determined a “bad view out of window” increased the risk for depression by 40%. The same study also demonstrated disturbance by noise and sleep disturbance by noise increased the risk of depression 40%, and 100% respectively. [3] In addition to visual burdens wind turbines create noise pollution [4] which can cause annoyance, stress and sleep disturbance. [5], [6], [7], [8], [9] In light of these statistics it is expected that people may suffer adverse health effects from visual and noise impacts of wind turbines.
Rotating wind turbine blades interrupt the sunlight producing unavoidable flicker bright enough to pass through closed eyelids, and moving shadows cast by the blades on windows can affect illumination inside buildings. [10] This effect is commonly known as shadow flicker.
Wind turbine shadow flicker has the potential to induce photosensitive epilepsy seizures however the risk is low with large modern models and if proper planning is adhered to. [11], [12] Planning should ensure the flash frequency does not exceed three per second, and the shadows cast by one turbine on another should not have a cumulative flash rate exceeding three per second. [13]
Wind turbine shadow flicker induced adverse human health effects include annoyance and/or stress. [14], [15], [16], [17], [18]
Wind turbine noise including low frequency noise may also contribute to the overall annoyance.
“Wind turbine noise is easily perceived and annoying even at low A-weighted SPLs….Wind turbines are furthermore prominent objects whose rotational movement attracts the eye. Multimodal sensory effects or negative aesthetic response could enhance the risk of annoyance. Adverse reactions could possibly lead to stress-related symptoms due to prolonged physiological arousal and hindrance to psychophysiological restoration.” [19]
No generalized dose-response curves have yet been modeled for wind turbine shadow flicker primarily due to the lack of results of published field studies.
Further investigation into the effects of wind turbine stressors including shadow flicker is required to assist in the development authoritative guidelines designed mitigate potential adverse health effects. [20]
Shadow flicker is also a safety concern. For example it can cause vehicle driver distraction. [21]
Most jurisdictions do not have explicit regulations to protect people from the adverse health effects of shadow flicker. [22]
To mitigate risk to human health wind turbines should be sited to ensure people will not be adversely affected. For example in the northern hemisphere people located East-NE or WNW from the turbine must be protected from shadow flicker. [23]
Recommended shadow flicker setbacks for current wind turbine designs are 10 rotational diameters which would typically translate to approximately 1000 m. [24]
Greater setback distances may be required when wind turbines are sited on elevated ridges as the shadows can be cast over distances of several kilometres.
It is acknowledged that “…shadow flicker can be an issue both indoors and outdoors when the sun is low in the sky. Therefore, shadow flicker may be an issue in locations other than the home.” [25] Shadow flicker modelling must consider human exposure to shadow flicker outside a building.
Protection from wind turbine shadow flicker exposure must be engineered into the design of the wind turbine facility during the planning stage. [26], [27]
To ensure protection from adverse human health effects a shadow flicker study must be conducted during the planning stage of a wind turbine facility. The shadow flicker study should:
· Calculate shadow flicker based on the actual location of the wind turbines.
· Calculate shadow flicker exposure on the entire neighbouring properties and not just the “receptor (house)”.
· Calculate shadow flicker for both sun and moon induced flicker using conservative assumptions to ensure maximum protection against adverse human health effects and safety risks.
· Protect against photosensitive epilepsy by ensuring the flash frequency does not exceed three per second, and the shadows cast by one turbine on another do not have a cumulative flash rate exceeding three per second.
Conclusions: Wind Turbines and Shadow Flicker
Based on the best available science the following conclusions can be drawn.
· Wind turbines produce noise and visual burdens.
· Scientific research confirms visuals impacts can adversely affect human health.
· Wind turbine shadow flicker has the potential to induce photosensitive epilepsy seizures however the risk is low with large modern models and if proper planning is adhered to.
· Wind turbine shadow flicker induced adverse human health effects include annoyance and/or stress.
· No generalized dose-response curves have yet been modeled for wind turbine shadow flicker primarily due to the lack of results of published field studies.
· Protection from wind turbine shadow flicker exposure must be engineered into the design of the wind turbine facility during the planning stage.
[1] National Research Council (NRC). Environmental Impacts of Wind-Energy Projects, 2007 NRC, Washington, DC
[2] Energy, sustainable development and health.Background document for the Fourth Ministerial Conference on Environment and Health, 23-25 June 2004, Geneva.
[3] World Health Organization, Large analysis and review of European housing and health status (LARES) Preliminary overview, 2007
[4] Energy, sustainable development and health. Background document for the Fourth Ministerial Conference on Environment and Health, 23-25 June 2004, Geneva.
[5] W. David Colby, M.D et al., Wind Turbine Sound and Health Effects, An Expert Panel Review 2009, Prepared for American Wind Energy Association and Canadian Wind Energy Association
[6] Arlene King M.D., Ontario Ministry of Health and Long Term Care Memorandum, October 21, 2009,
[7] Copes, R. and K. Rideout. Wind Turbines and Health: A Review of Evidence. Ontario
Agency for Health Protection and Promotion 2009
[8] Pedersen et al., 2008,Project WINDFARMperception Visual and acoustic impact of wind turbine farms on residents
[9] Thorne et al, Noise Impact Assessment Report Waubra Wind Farm Mr & Mrs N Dean Report No 1537 – Rev 1 – July 2010
[10] Graham Harding, Wind Turbines, Flicker, And Photosensitive Epilepsy: Characterizing The Flashing That May Precipitate Seizures And Optimizing Guidelines To Prevent Them, 2008
[11] Smedley AR et al, Potential Of Wind Turbines To Elicit Seizures Under Various Meteorological Conditions., 2009
[12] Graham Harding, Wind Turbines, Flicker, And Photosensitive Epilepsy: Characterizing The Flashing That May Precipitate Seizures And Optimizing Guidelines To Prevent Them, 2008
[13] Ibid.
[14] National Research Council (NRC). Environmental Impacts of Wind-Energy Projects, 2007 NRC, Washington, DC
[15] Copes et al, Wind Turbines And Environmental Assessment, National Collaborating Centre for Environmental Health, June 23, 2009
[16] Copes, R. and K. Rideout. Wind Turbines and Health: A Review of Evidence. Ontario
Agency for Health Protection and Promotion 2009
[17] Minnesota Department of Health (MDH) 2009 Public Health Impacts of Wind Turbines
[18] Pedersen et al., 2008,Project WINDFARMperception Visual and acoustic impact of wind turbine farms on residents
[19] Pedersen Eja, Human Response To Wind Turbine Noise: Perception, Annoyance And Moderating Factors , May 23, 2007
[20] Copes et al, Wind Turbines And Environmental Assessment, National Collaborating Centre for Environmental Health, June 23, 2009
[21] Minnesota Department of Health (MDH) 2009 Public Health Impacts of Wind Turbines
[22] National Research Council (NRC). Environmental Impacts of Wind-Energy Projects, 2007 NRC, Washington, DC
[23] Verkuijlen E, Westra CA. (1984) Shadow hindrance by wind turbines. Proceedings of the European wind Energy Conference. October 1984, Hamburg, Germany.
[24] Minnesota Department of Health (MDH), Public Health Impacts of Wind Turbines, 2009
[25] Minnesota Department of Health (MDH) 2009 Public Health Impacts of Wind Turbines
[26] National Research Council (NRC). Environmental Impacts of Wind-Energy Projects, 2007 NRC, Washington, DC
[27] Minnesota Department of Health (MDH) 2009 Public Health Impacts of Wind Turbines
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