Over the decade, the wind energy sector has expanded significantly. Canada is now the fifth-largest global market for the installation of wind turbines. With this demand, however, come concerns that the presence of wind turbines may pose a public health risk.
In response, Health Canada asked the Council of Canadian Academies to convene a panel of Canadian and international experts from various fields, including occupational health and engineering. The panel examined the state of scientific evidence and where there may be a link to an adverse health effects, using a two-step methodological process. The resulting report, Understanding the Evidence: Wind Turbine Noise provides an important foundation of information that will be of value for the public, policy and decision makers, and industry.
Tee Guidotti, Fulbright Visiting Chair, Institute for Science, Society and Policy at the University of Ottawa, is Chair of the Expert Panel that conducted an in-depth assessment and produced the report, Understanding the Evidence: Wind Turbine Noise. He discusses the Panel’s findings in the Q and A below:
Wind turbines are not new; why is there still a lack of scientific certainty about health effects?
Simply put, it wasn’t a burning issue before. In the past, wind turbines were largely individual, low-wattage installations supplying small or remote areas. Today we have much larger turbines that operate at higher energy levels, and which are more concentrated near populated areas. So the public concern has grown and researchers are now responding to the proliferation of wind turbines, the change in technology and the questions that are being asked by the public.
What do wind turbines sound like?
If you were to stand directly under one, you might hear a kind of thumping noise that varies in intensity as the rotor goes through its cycle. This sound is emitted at all frequencies, i.e. high and low pitch. If you were a bit further away, the higher-pitched sounds would be dampened by structures such as houses, trees and the ground, so you would only hear lower pitches.
At its peak, the noise is on the order of the background noise from wind, or similar to the traffic on a not-very-busy street. It goes down from there; within a kilometre, you probably would not hear it at all.
What health effects did the Expert Panel examine?
We generated a list of 32 potential health outcomes that had been expressed in the scientific literature, in reports by government agencies or citizen groups, in the press, or in briefs filed as part of legal actions. We cast a very wide net in order to be responsive to what people were expressing as concerns, and the list really spans the entire spectrum of the human body. We looked at annoyance, sleep disturbance, hearing loss, cardiovascular disease, diabetes, joint pain, headaches, nausea, dizziness and many other disorders and symptoms.
What did the Expert Panel find?
We found that the evidence is strongest for annoyance. The World Health Organization defines health as not merely the absence of disease, but a state of physical, mental and social well-being. In that sense, annoyance can be considered a health effect, and there is evidence that wind turbine noise leads to annoyance.
There is limited evidence for sleep disturbance. This finding was based on a series of studies that had designs which were not particularly strong, for example, they used questionnaires rather than physiological indicators. They also had relatively small sample sizes and provided results that were not entirely consistent. Therefore, the evidence for sleep disturbance is limited.
We can say conclusively that hearing loss is not related to wind turbine noise, nor would it be expected to be, given the sound energy levels involved.
For all other health outcomes, we found that the scientific evidence was inadequate to make an association with wind turbine noise.
What did the Panel mean by inadequate?
It does raise the question: are we not seeing an association because the amount of work that has been done is inadequate to show an effect that might be there, or is it that the evidence is limited, but indicates that there is probably no effect? This is an inherent limitation of this kind of work, and we can’t really provide an answer. All we can say is that when you look at the literature, we’re not seeing sufficient evidence for those effects.
What are the key knowledge gaps that need further investigation?
The major gap is to determine whether the outcomes for which there is strong evidence (annoyance) or even weak evidence (sleep disturbance) are associated with stress. For example, it is possible that sleep disturbance, if it is in fact present, might result in stress that could mediate a series of downstream health effects, such as cardiovascular disease. But at this point, we’re not seeing evidence for that.
At the end of the day what do we need to know?
There is a literature that addresses the concerns about health effects due to wind turbine noise. It is not complete or extensive enough to address all conceivable issues. However, it can give us a hint as to what may be there: annoyance and possibly sleep disturbance, though the evidence is limited. Just as important, it can give us a hint as to what is probably not there.
I would note that if there were effects that were intense or prevalent, we would likely be seeing more evidence for them.