Analysis of the Epidemiology and Related Evidence on Health Effects of Wind Turbines on Local Residents
July 3, 2010 by Carl V. Phillips, MPP PhD
This important document prepared by Dr. Carl V. Phillips MPP, PhD, was submitted to the Wisconsin Public Service Commission as testimony on whether turbine noise is having an adverse effect on human health.
A summary of the main conclusions of my expert opinion, based on my knowledge of epidemiology and scientific methods, and my reading of the available studies and reports, is as follows:
• There is ample scientific evidence to conclude that wind turbines cause serious health problems for some people living nearby. Some of the most compelling evidence in support of this has been somewhat overlooked in previous analyses, including that the existing evidence fits what is known as the case-crossover study design, one of the most useful studies in epidemiology, and the revealed preference (observed behavior) data of people leaving their homes, etc., which provides objective measures of what would otherwise be subjective phenomena. In general, this is an exposure-disease combination where causation can be inferred from a smaller number of less formal observations than is possible for cases such as chemical exposure and cancer risk.
• The reported health effects, including insomnia, loss of concentration, anxiety, and general psychological distress are as real as physical ailments, and are part of accepted modern definitions of individual and public health. While such ailments are sometimes more difficult to study, they probably account for more of the total burden of morbidity in Western countries than do strictly physical diseases. It is true that there is no bright line between these diseases and less intense similar problems that would not usually be called a disease, this is a case for taking the less intense versions of the problems more seriously in making policy decisions, not to ignore the serious diseases.
• Existing evidence is not sufficient to make several important quantifications, including what portion of the population is susceptible to the health effects from particular exposures, how much total health impact wind turbines have, and the magnitude of exposure needed to cause substantial risk of important health effects. However, these are questions that could be answered if some resources were devoted to finding the answer. It is not necessary to proceed with siting so that more data can accumulate, since there is enough data now if it were gathered and analyzed.
• The reports that claim that there is no evidence of health effects are based on a very simplistic understanding of epidemiology and self-serving definitions of what does not count as evidence. Though those reports probably seem convincing prima facie, they do not represent proper scientific reasoning, and in some cases the conclusions of those reports do not even match their own analysis.
Important editor's note: The last page of Dr. Phillips document, which contained references to his work, was omitted. He has provided us with the missing information as follows:
Roberts M, Roberts J. Evaluation of the scientific literature on the health effects associated with wind turbines and low frequency sound. Exponent Inc. Prepared for Wisconsin Public Service Commission Docket No. 6630-CE-302 (the identity of the actual client for whom this was prepared is not disclosed in the document). October 2009.
Waye K. Effects of low-frequency noise on sleep. Noise and Health 6(23):87-91, 2004.
Dr. Phillips will post any other errata at this link as the need arises.
phillips WI filed expert report.pdf (206.07 kB)
WISCONSIN DEPARTMENT OF HEALTH AGAIN SAYS NO TO REQUEST FOR LOCAL STUDY OF HEALTH IMPACTS OF LARGE WIND TURBINES.
State of Wisconsin Department of Health Services
DIVISION OF PUBLIC HEALTH
Dear Mr. Marion:
Thank you for your July 12,letter to Secretary Karen E. Timberlake regarding the possible health effects of wind turbine noise.
Secretary Timberlake has asked me to respond to you on her behalf, and I welcome the opportunity to do so.
In your letter of May l3,you asked for confirmation of the Division of Public Health's views regarding the health effects of wind turbine noise.
You shared additional information with us, and requested that the Division of Public Health (DPH) conduct a formal epidemiological study of the health effects of wind turbine noise in Wisconsin.
The presentation 'Wind Turbines, a Brief Health Overview" by Dr. Jevon McFadden to the Wisconsin Wind Siting Council on May 17,2010, was not a statement about the position of the Wisconsin Division of Public Health.
DPH recognizes that wind turbines create certain exposures; audible sound, low-frequency sound, infrasound and vibration, and shadow flicker.
Certain ranges of intensity or frequency of audible sound, low frequency sound, vibration, and flicker have been associated with some objectively-verifiable human health conditions.
Our review of the scientific literature indicates, exposure levels measured from eontemporary wind turbines at current setback distances do not reach those associated with objective physical conditions, such as hearing loss, high blood pressure, or flicker-induced epilepsy.
Your letter also cites information that many symptoms are reported by some who live near wind turbines. This information is difficult to interpret for a few reasons.
First, symptoms such as sleep disturbance and headache are common, and caused by a wide variety of conditions.
For example, sleep disturbance is a common problem in the general population, and may also be a sign of an underlying medical disorder.
The same is true for symptoms like nausea, headache, problems with equilibrium, and others mentioned in your letter.
Neither individuals, nor investigators should assume that they originate from exposure to wind turbines.
Persistent symptoms, or those that interfere with daily functions, should be evaluated by a medical professional.
Second, as your letter describes, some people experience annoyance at wind turbines, and annoyance has been associated with some of the symptoms you cite.
Unfortunately, we cannot know which may be responsible for the other.
Annoyance is a psychological reaction with a wide range of individual variability and is influenced by multiple personal and situational factors.
Annoyance, per se, is not considered a physical or mental health disorder, but it may influence perception or interpretation.of health-related complaints (or introduce "bias," in scientific terminology).
This makes it very difficult to objectively assess whether or not reported symptoms are indicative of actual physical conditions caused by exposures from wind turbines.
DPH staff previously reviewed the five reports you referenced in your letter.
They also reviewed over 150 reports from the scientifiennd medical literature (published and unpublished) pertinent to the issue of wind turbines and health.
DPH has also taken time to listen to, and respond to concerns voiced by local residents, municipalities, and local health department officials from across the State of Wisconsin.
We have discussed this issue with colleagues at UW School of Medicine and Public Health, the Minnesota and Maine state health departments, and the Centers for Disease Control and Prevention.
From this, we conclude that current scientific evidence is not sufficient to support a conclusion that contemporary wind turbines cause adverse health outcomes to those living nearby.
This is different from saying that future evidence about harms may not emerge, or that wind turbines will not change over time, or that annoyance and other quality-of-life considerations are irrelevant.
DPH does not endorse a specific setback distance or noise threshold level relating to wind turbines.
Nevertheless, in keeping with standard public health practice, DPH favors a conservative approach to setbacks and noise limits that provides adequate protections to those who live or work near wind turbines.
These will help minimize local impacts on quality of life and serve as a buffer against possible unrecognized health effects.
Current draft siting rules limit noise exposures from wind turbines to very modest levels, and we anticipate that the final siting rules will, at the very least, be equally protective.
For this reason, we do not believe there is a compelling reason to perform an epidemiologic investigation in
To the extent that gaps remain in current science, DPH favors continued investigations to help advance knowledge and guide future policy development.
The value of these studies will depend on the degree to which subjective corpplaints can be compared with
objective clinical and environmental measurements.
However, complex clinical studies requiring coordination of acoustical engineering efforts with clinical assessments are outside the scope of standard public health investigations.
As additional scientific evidence becomes available, DPH will continue to appraise its relative strength, credibility, and applicability to the issue of wind turbine development in Wisconsin.
As is the case with any major deve[opment undertaking in the State of Wisconsin, it is important that we continue to look for ways to maximize positive impacts and minimize negative impacts to residents.
To the extent that these impacts fall into the public health realm, DPH will continue to seek data and information to guide public policy on this matter.
Wisconsin Department of Health Services
Division of Public Health
Siting of wind turbines with respect to noise emissions and their health and welfare effects on humans
July 6, 2010 by Richard D. Horonjeff
This report, prepared by Acoustics and Noise Control expert Richard D. Horonjeff, explains how turbine noise differs from other types of noises within a community. The information was submitted to the Wisconsin Public Service Commission. An excerpt of the report is provided below. The full report can be accessed by clicking on one of the links at the bottom of this page.
The nature of wind turbine noise compared with other noise sources heard in residential communities
Different sound sources vary in their sound level, frequency content and temporal character. These differences are most easily described by example. First, there are steady state noise sources. A good example would be an active highway. The sound level at a listener location away from the highway may vary somewhat from moment to moment, but by small amounts. But by and large human observers perceive highway sound as near constant in amplitude.
Second, there are transient sources. These are sources present only for brief periods of time. Good examples are passing trains or aircraft. These sources rise gradually in amplitude as they approach the listener and then decay as they depart.
A third class of sound source is the impulsive one. These sources can be repetitive or random in nature. Repetitive impulse sources would be jackhammers and pile drivers. The basic difference between the two examples is the rate at which the impulses occur. A random impulsive source would be the operations in a machine shop where hammering or metal fabrication takes place. In all of these examples any one impulse lasts for only a very small fraction of a second, and the onset and offset of the impulse is very rapid.
Finally, we come to the wind turbine source. Unlike any of the previous sources described, it is neither steady state in the classic sense, nor is it transient, nor is it impulsive. Instead, it produces a distinctive broadband "swoosh-boom" sound4 with each passing blade of the turbine. Each whoosh effectively modulates the sound level, with a more gradual onset than an impulsive sound, and a less gradual one than the transient sources I mentioned. For the typical three-bladed turbine in the 1-megawatt output range the blade passage rate is nominally one per second. One can sound out the observed sound in the typical second-counting style... "whoosh" one thousand, "whoosh" two thousand, "whoosh" three thousand, and so on. So long as the wind is blowing at sufficient speed to drive the turbine the sound will be generate for lengthy periods of time without interruption.
The hours of operation of wind turbines are not dictated by diurnal patterns of human activity like many other anthropogenic sources. They are able to operate when wind conditions are favorable, day or night. This means they may become a factor during both waking and sleeping hours.
The repetitive sound character is unique and unlike any other source found in residential communities. As such it is easily identifiable. It does not blend in to other background sources that are continuous in nature.
Wind turbine noise is most prevalent in rural areas. By their very nature, large-scale wind turbine installations require vast areas of open land. Hence, any potential sound masking effect from urban and suburban sources is unlikely to be present. This means that their sound will be audible at lower levels in the rural environment. It further means that rural noise standards should be applied to these installations as opposed to suburban or urban ones where nighttime sound levels, for example, can be 15 to 20 decibels higher.
HorojeffReportFinal.pdf (275.71 kB)