Wind turbine noise Frequently Asked Questions

Does this study demonstrate that a relationship exists between sound exposure from wind turbines and negative impacts on health and well-being?

No evidence was found to support a link between exposure to wind turbine noise and any of the self-reported or measured health endpoints examined. However, the study did demonstrate a relationship between increasing levels of wind turbine noise and annoyance towards several features (including noise, vibration, shadow flicker, and the aircraft warning lights on top of the turbines) associated with wind turbines.

The findings of this study provide a more complete overall assessment of the potential impacts that exposure to wind turbines may have on human health. In this study, both self-reported responses from a questionnaire and physical health measures were assessed.

It is important to note that the findings from this study do not provide definitive answers on their own and must be considered in the context of a broader evidence base. It is also important to note that the study does not permit any conclusions about causality (a direct cause and effect) between wind turbine noise and health impacts.

Does Health Canada's study reveal any information to those who are concerned their symptoms are related to levels of low frequency noise and infrasound associated with the turbines?

Some individuals in the study did report illness; a fact that was supported by their physical measures. However, these individuals were randomly distributed across the sample (residences were located at distances between 250 metres and 10  kilometres from the wind turbines) and no association could be found between increasing levels of wind turbine noise and health effects.

The levels of low frequency noise and infrasound were found to be below levels that would be expected to result in harm to human health. These findings were further supported by the results of the self-reported questionnaire.

How can my symptoms be associated with "wind turbine noise annoyance" yet not be associated with the wind turbines themselves?

A small percentage of people surveyed reported being highly annoyed by wind turbine noise.

Although some showed health conditions consistent with annoyance (such as high blood pressure, migraines, headaches), this does not mean that annoyance is necessarily causing these conditions as other factors may also be contributing to the health conditions observed. Furthermore, these health conditions cannot be linked directly to the wind turbines due to the respondents' varying distances from the turbines and from their varying exposure to different levels of noise.

Many of the same health conditions were found in people who reported being annoyed by road traffic noise. In some cases, these health conditions may have pre-dated the installation of the wind turbines.

Why did Health Canada release its results as "preliminary" and not wait until completion of peer-review in the scientific literature?

Under the Statistics Act, Statistics Canada has established the Official Release Policy which ensures that information is protected until its official release. The notification appeared on November 6, 2014 in The Daily, Statistics Canada's official release vehicle and the key means through which the Agency provides data users with equitable access to newly released information. Consistent with standard practice for a data set of high public interest, Health Canada released a summary of results concurrent with the Statistics Canada posting. The summary of results of the study underwent peer-review, prior to release, with members of the Wind Turbine Noise Study Expert Committee, a multidisciplinary team comprised of experts in areas including, but not limited to, noise, clinical medicine, health assessment, sleep, statistical analysis and epidemiology, including internationally recognized authorities in the required fields.  Results were released as "preliminary" in acknowledgement of the process that must ensue with respect to peer-review for publication in the scientific literature. Representatives of organizations identified as having interests in the subject area were contacted and briefed on results immediately following the announcement including representatives from the provinces and territories, other federal government Departments, Wind Concerns Ontario, the Council of the Chief Medical Officers of Health, and the Canadian wind energy industry.

Why did Health Canada not include individuals who may have abandoned their homes?

The number of residences considered out of scope for the sample was consistent with numbers predicted by Statistics Canada for a rural environment. Of the 434 out of scope addresses, 138 of these were identified as vacant for unknown reasons and were found to be randomly distributed across all distances studied in both provinces. Health Canada has no way of knowing the reasons for such vacancies. Had investigators deliberately sought out individuals who may have abandoned their homes, the study integrity would have been compromised as the sample would no longer be considered random. Health Canada's Wind Turbine Noise and Health Study was a population-level study designed to investigate a response in a large sample.

What measures has Health Canada taken to ensure rigour in the design and methodology?

Health Canada's study design underwent rigorous peer-review prior to finalization. In addition to the review of the study methodology by the Wind Turbine Noise Expert Committee and the external Science Advisory Board of Health Canada, the design was shared with the World Health Organization's Noise Committee for review and comment as well as with international experts at relevant conferences such as Inter-Noise 2012. The Department further undertook an open and transparent process to consult publically on the study design and engaged key affected stakeholders in the process, including advocacy groups, wind industry officials and external subject matter experts. The design methodology, as well as names and areas of expertise of the members of the research design committee, were published on the Health Canada website for a 60-day public comment period in July 2012. This consultation resulted in over 950 submissions of comments; a summary of comments and Health Canada responses are available on the Health Canada website. The final study methodology was reviewed and approved by the Public Health Agency of Canada/Health Canada Research Ethics Board in March 2013.

Why are there two different names for the Study?

The official Statistics Canada title of this study is the  Community Noise and Health Study. Upon visiting the homes, Statistics Canada introduced the study as the Community Noise and Health Study and individuals were told both the questionnaire and the study were being carried out to look at community noise and health. This approach was taken in order to reduce bias within the survey sample at the time of data collection. Health Canada refers to this study as the Wind Turbine Noise and Health Study. The full text of the questionnaire can be viewed on the  Statistics Canada Website.

What specific communities were included in the study and why?

The communities targeted in the study were selected randomly from communities situated near wind turbine installations where there were sufficient homes within 10km of a wind turbine installation to make up an adequate sample size. The areas included in this study were selected from southern Ontario and PEI. In order to protect the confidentiality of the participants in the study, the specific communities are not provided.

Why are no children included in the study?

A primary objective of the study was to assess the potential impacts that WTN had on measured sleep. Sleep patterns among children are very different from those of adults, making it difficult to identify potential impacts that might be due to WTN exposure. Furthermore, the questionnaire in the study included questions that would not be suitable for a minor to respond to.

Why was only 1 person per household interviewed for this study?

Experts in survey design expressed concern with interviewing multiple residents from the same household. The responses to questions from 2 individuals living in the same house may not be truly independent, as they are likely to be related to each other, thereby introducing the possibility of influence or bias.

Were the substations that are located on wind farms studied?

Substations were not included in the study because they were not present at every wind farm studied and, when they were present, it was not possible to isolate the substation sound from other environmental and wind turbine sounds.

Why did Health Canada not include an analysis of property values?

In designing the study there needed to be a balance between adding content to the questionnaire and risking a reduced participation rate as the questionnaire became excessively lengthy. An analysis of property values was outside the scope of the study, which was focused on the potential impact that wind turbine noise exposure had on health and well-being. Reviews published recently provide a thorough assessment of property values in areas located in proximity to wind turbine installations.

What does cortisol measured in someone's hair represent?

Cortisol is a hormone produced by the body and is often called a "stress hormone" because the levels of cortisol typically increase when people are exposed to stressors. Cortisol has been shown to accumulate in the hair shaft as hair grows over time. Hair grows at a rate of about 1cm per month and therefore the amount of cortisol in, for example, a 3 cm sample of hair gives a relative indication of how much cortisol the body produced in the previous 3 months. This makes hair cortisol particularly useful when studying the potential health effects associated with long term exposure to stressors e.g., wind turbine noise.

Why have respondents been asked about only a limited number of chronic diseases?

Expert committee members were consulted with regard to the chronic diseases that were included in the questionnaire. Prevalence of some diseases and/or symptoms is so low in the general population that Health Canada would not be able to detect any associations. A review of the literature was undertaken to identify the incidence of specific chronic diseases in the general population.

Some of the questions posed were unrelated to wind turbine noise and could be considered offensive to participants. Why were such questions asked?

It was important to apply standardized valid questionnaires where available in the measurement of endpoints being assessed. The WHOQOL-Bref, Pittsburgh Sleep Quality Index and the Perceived Stress Scale provide measures of quality of life, sleep and stress, respectively and have been widely used in social science contexts. A requirement when using these questionnaires is that their content is not to be changed in order to maintain their validity and facilitate comparisons between studies. The full text of the questionnaire can be viewed on the  Statistics Canada Website.

What was the rationale for measuring sound at some locations but not all?

This study included short term field measurements indoors and outdoors at several homes and near the base of the turbines. The purpose of these measurements was both observational and to acquire enough data to support the modelling used to calculate the A-weighted values used in the study. This objective was satisfied with the amount of measures taken.

Why did Health Canada take noise measurements in the summer when there is very little wind?

It is true that wind is, on average, lower during the summer months compared to other times of the year. In order to minimise awareness bias, noise measurements in any given community only began after Statistics Canada had completed the in-home interview. This meant that noise measurements began in June 2013 and continued through October 2013. Some of the field measurements needed to be carried out during the summer months simply due to the timing of the collection period. Taking measures during summer months simply meant that it sometimes took longer to acquire enough data (waiting for windy periods). It is important to note that field measurements were taken only to the extent that enough data was collected to validate the calculated A-weighted values used in the study. This objective was met.

What is the difference between high and low frequencies and different weighted decibels?

Scientists that study the community response to noise typically measure different sounds levels with a unit called the A-weighted decibel (dBA). The A-weighting reflects how people respond to the loudness of common sounds; that is, it places less importance on the frequencies that the ear is less sensitive to. For most community noise sources, this is an acceptable practice, but when a source contains a significant amount of low frequencies, an A-weighted filter may not fully reflect the intrusiveness or the effect that the sound may have (e.g. annoyance). In these cases, the use a C-weighted filter (dBC) may be more appropriate because it is similar to the A-weighting except that it includes more of the contribution from the lower frequencies than the A-weighted filter. For additional information on noise, please refer to the Primer on Noise.

Do the results of this study apply to all wind farms in Canada?

The particular communities in the study were not randomly selected from all potential communities in Canada and therefore the results of the study may not be generalized to all wind farms in Canada. Conclusions about the study results are restricted to the sample that made up the study.

How will Health Canada use the study results?

Health Canada will not make any recommendations on the basis of results obtained. Results may not be generalized beyond the sample studied. Health Canada will consider the results of this study, together with the existing body of scientific evidence, when providing advice on the health impacts of environmental noise. Health Canada will also continue to review any new scientific literature that becomes available.

The results of this study will also support decision-makers in the development of decisions, advice and policies related to wind power development proposals, installations and operations. These results will be shared with the provinces and territories and will contribute to the global knowledge on wind turbine noise and health but will not provide definitive answers on their own.

How many wind turbine models were included in your study?

13 industrial wind turbine models were assessed in the study; all were 3 bladed, with hub heights between 60m and 80m and output capacities ranging from 660kw to 3MW.

How much did this study cost?

The initial budget for the study was $1.8 M over three years. As a consequence of changes related to the public consultation, with respect to a more extensive questionnaire and low frequency noise in particular, and adjustments that were required in the field, the final cost of the Study was approximately $2.1 M.

Can people receive the results of noise measurements taken in their house or outside their house?

Home owners may request a summary of the results of noise measurements taken at their property. It is important to keep in mind that these measurements were taken for research purposes only and are not intended to be used to support or refute any noise limits that may exist.

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