Infrasound and Low Frequency

III.           Wind turbine health impacts: A review of current literature

In May of 2008 the Chatham-Kent Public Health Unit was asked to prepare a report on the possible health effects of wind turbines near residences and public properties. This report reviewed a variety of published literature and correspondence with health officials.

Wind Power and Health

Wind power use has dramatically increased in recent years because it has no emissions, waste products, or harmful pollutants. One modern wind turbine will save over 4,000 tones of carbon dioxide emissions annually. Renewable energy is now a necessary investment to combat the impacts of global warming. Chatham-Kent plans to support the development of wind energy, but like any new technology needs to be reviewed for the well being of the public.

Human Health Impacts versus Human Safety

Health impacts are defined as an immediate effect of a program, policy, or process on health. Health impact assessments are conducted to determine whether these impacts are positive or negative for the population. Human safety is defined as a judgment of the acceptability of risk, and risk, in turn, as a measure of the probability and severity of harm to humans. A thing is safe if its risks are judged to be acceptable. The Workplace Safety and Insurance Board of Ontario identify five health hazards. They are chemical agents of any form, physical agents that are forms of energy or force, biological agents including microorganisms, ergonomic hazards, and stress hazards. This report will cover the potential health and safety issues of turbine blade and structural failure, icing issues in northern climates, sound emissions and noise concerns, shadow flicker, and construction injuries. Other issues such as aesthetic issues, wildlife concerns, and aviation navigation are beyond the scope of this report.

Turbine Blade and Structural Failure

To date, there is no recorded evidence of injury to the public caused by a wind turbine. All modern wind turbines must meet strict engineering standards and wind turbine blades are now designed so that they can stand hurricane force winds. The only recorded cases of injury occurred in construction workers and only when operating instructions were not abided by. The four recorded cases of turbine blade failure in Ontario occurred because of lightning strikes at which point the turbine was shut down for repairs. Currently, minimum setbacks in Canada for wind turbines are one blade length plus 10 meters. The Chatham-Kent setback of 600 meters from any residential or institutional zone is more then ample.

Icing Issues in Northern Climates

There is a potential for injury from ice build up on wind turbines. This can occur in two ways: ice throw during operation or ice shed when the turbine is off or idling. For injury to occur the following several conditions must exist simultaneously: a sustained weather condition conducive to icing, ice dislodging from the turbine or blade, ice pieces are large enough to remain intact through the air, and the ice manages to travel past the stated guidelines and someone is in that path. With a setback distance of 300 meters for buildings, 200 for vehicles, and 300 for individuals on the ground, the potential number of ice strikes to buildings is 1/500,000 years, vehicles 1/260,000 years, and 1/137,500,000 years for individuals on the ground. An injury occurring from ice build up on a turbine is most likely to happen to a construction worker when the turbine is idle. 

Sound and Noise Concerns

Wind turbine noise comes from both mechanical operations and aerodynamic sources. It is impossible to create a noiseless wind turbine. However, the effect of infrasound and turbine noise has been studied and there is no empirical evidence that this noise harms the human ear. Noise is measured in decibels (dB), but environmental noise is adjusted to include the sensitivity of the human ear. At over 300 meters the audible sound created by wind turbines is 35-45 dB, while wind on its own can be as loud as 35 dB. Downwind rotor placement used to account for a large portion of the noise emitted, but most turbines are now upwind models.  While noise and sound can be annoying, the audible noise created by a wind turbine, constructed at the approved setback distance does not pose a health impact concern. Infrasound, which is inaudible sound, is generated by wind turbines, but not at a level (especially with required setbacks) that is harmful to human health.

Shadow Flicker

Shadow flicker occurs when the sun is located behind a wind turbine, creating moving shadows. The frequency at which shadow flicker occurs is below the levels that are known to trigger epilepsy symptoms. However, shadow flicker from any source has been shown to negatively impact a bout 5% of people with epilepsy. When required setbacks are enforced, shadow flicker should not be of any concern other than it may be irritating.

Construction Injuries

Wind farms adhere to Canadian health and safety standards. Human injury has been known only to occur when guidelines were not adhered to.

Recommendations

The recommendation section for this report contains a table discussing health and safety along with suggested mitigation activities.

Chatham-Kent Public Health Unit. (2008). The Health Impact of Wind Turbines: A Review of the Current White, Grey, and Published Literature. Chatham, ON. Chatham-Kent Municipal Council. Retrieved from: http://wind-works.org/articles/large_turbines.html#Noise,%20Health%20&%20Safety