Scientists See No Basis for Turbine 'Infrasound' Claims
Two reports challenge rationale for 1.25-mile wind farm buffer
January 30, 2011 | By Jim Dulzo
Great Lakes Bulletin News Service
|Farmers near McBain, Mich., have welcomed the Stony Corners wind farm’s 19 460-ft. turbines, each generating up to 1.8 million watts on breezy days.|
BENZIE COUNTY—At the Gail Windpower Project Expo, held recently at a county high school here, a sound meter measured the noise level of the event’s lively conversational din at 70 decibels.
That’s three times louder than Michigan State University Extension’s guidelines for siting wind turbines recommends—and five times louder than the noise that Duke Energy, the expo’s sponsor and Gail Windpower’s developer, says its proposed project would make.
But, as quiet as the company says it will make its proposed wind farm, some local residents are raising a ruckus against the 112-turbine project Duke wants to build in four townships along the Benzie-Manistee county line. The opponents say the farm, which Duke estimates would be a $360 million investment in 200 MW of clean energy, would be too noisy for their rural area.
They shrug off Duke’s promise of a 45-decible limit, even though it’s half as loud as MSUE’s 55-decibel guideline. (Loudness doubles every 10 decibels.) They claim there will be a far more serious problem from turbine sounds that nearby residents won’t even be able to hear: ultra-low-frequency “infrasound” waves.
The opponents claim that infrasound created by the 485-ft. turbines’ huge, rotating blades, gearboxes, and generators will cause unpleasant, even dangerous symptoms in nearby residents. And, they argue, because low-frequency sounds fade so slowly over distance, wind farms should be located 1.25 miles from residential property to protect their health.
Typically, turbine setbacks are 1,000 to 1,500 feet, and windpower advocates point out that mile-plus setbacks would drastically reduce, if not eliminate, future wind development throughout Michigan.
Two local groups opposed to the project, Citizens for Responsible Wind Development and the Arcadia Wind Study Group, base their push for mile-plus setbacks on a self-published book by New York pediatrician Nina Pierpont. She claims her “natural experiment” shows that wind turbine infrasound causes serious health problems, and that mile-plus setbacks are necessary.
Wind opponents nationwide now routinely use her claim to push for big, project-killing setbacks.
Dr. Pierpont’s theory, however, has little research other than her own to back it up, even though she has been promoting it aggressively since at least 2005.
In the past 13 months, her infrasound-based “wind turbine syndrome” theory has drawn strong criticism from two panels of acoustic scientists and medical doctors who formally investigated it. And a 40-year infrasound research veteran is urging policy makers to ignore unfounded worries about low-frequency sound and, instead, concentrate on protecting people from sounds they can actually hear.
A Struggle Over Setbacks
But the argument over setbacks seems likely to continue.
For example, Benzie and Manistee Counties' opposition groups persuaded Blaine and Pleasanton Township officials to impose, respectively, six-and-nine-month moratoria on turbine permitting in order to review their ordinances. Blaine Townships ordinance includes sound regulations, but does not deal specifically with infrasound. Now with the the moratoria in place township officials must decide how far turbines should be set back from residential homes or property lines.
The other two townships in the proposed windfarm's footprint, Arcadia and Joyfield have differing circumstances. Arcadia Township zoning has setback requirements that do not specifically address sound and that township is considering imposing a moratorium of their own. Joyfield Township has no zoning ordinance.
The answers produced by these and other local officials around Michigan grappling with proposed wind farms could determine whether more Michigan farmers are allowed to partner with companies like Duke to harvest and earn income from the wind blowing across their property. Those royalties, assigned via private, not public, contracts, are estimated by some who’ve seen Duke’s local leases at 12 to 15 thousand dollars per year, per turbine.
The setbacks could also affect budgets of hard-pressed local governments. Duke claims its project, if fully built and split equally between both counties, would add about $1.5 million to each county’s annual property tax levy—in Benzie’s case, a 4.4 percent increase over 2009 levels, based on numbers from the county assessor.
Unreasonable setbacks could also hamper the state’s emerging wind turbine manufacturing industry: Manufacturers like to be close to their markets, and 1.25-mile setbacks would cut Michigan’s turbine market. Recently, the Michigan Economic Development Corporation estimated that there are now 25 firms in Michigan making turbine parts.
MEDC also says there are about 900 other Michigan firms now involved in the design, engineering, machining, and other services related to making turbines, blades, and towers. One company, Merrill Technology Systems, in Saginaw, is manufacturing complete turbines with a radically different, more efficient design that is also quieter.
A Very Close Look
Pediatrician Pierpont makes her case for very large setbacks in Wind Turbine Syndrome: A Report on a Natural Experiment. But her effort has received criticism from wind advocates who point out that it has not been properly peer-reviewed and that her research methods are questionable. They point out that Dr. Pierpont’s research did not follow standard scientific methods including using a random sample population, control groups or an adequate sample size to reach its conclusion that turbines’ infrasound causes migraines, sleeplessness, dizziness, panic attacks, and other maladies.
Critics claim that her work amounts to what scientists call a “case set”—a quick, informal look at something that might be worth a larger, scientifically valid, follow-up study. Despite the doctor’s highly public advocacy and promotion of her idea over at least five years, further research on her claims still has not happened.
Not surprisingly, however, when Dr. Pierpont finally published her idea as a book in 2009, the American Wind Energy Association (AWEA) and the Canadian Wind Energy Association (CanWEA), two non-profit wind industry trade groups, realized that, given the traction her claims were gaining among anti-wind groups, they had to respond.
According to the organizations, when they could not find an independent organization willing to underwrite such a study, they paid for it themselves. AWEA and CanWEA assembled eight scientists and doctors to survey the available scientific literature on the known health effects of living near wind turbines.
Collectively, the eight have strong research or clinical experience in public health, otolaryngology, noise-induced hearing loss, balance and hearing disorders, clinical medicine, audiology, infrasound acoustics, industrial sound pathology, wind and turbine physics, and turbine sound measurement and siting.
Their review of 140 different studies and papers issued in 2009, largely from Europe, where wind farms are common and located quite close to residential areas, is called Wind Turbine Sound and Health Effects; An Expert Panel Review.
The panel points out that the environment and our bodies are awash in infrasound, much of it naturally occurring. It finds Dr. Pierpont’s list of maladies too poorly characterized to be medically useful. It finds a markedly stronger correlation between subjects’ claimed turbine syndrome symptoms and their initial attitudes toward turbines than between their symptoms and their level of exposure to turbine sounds.
Windpower opponents quickly attacked the industry funded findings as biased, something that Mike Klepinger, who formerly worked at Michigan State University Extension Service, where he wrote the agency’s wind turbine siting guidelines, says is not surprising.
“Of course, whenever you invite industry into a panel, the whole panel becomes suspect,” Mr. Klepinger said in an interview with Great Lakes Bulletin News Service. “They say, ‘It couldn’t possibly be operating scientifically.’ But you look at the who’s who on the [panel] list, and you kind of have to give the industry an A-plus for trying to make the panel objective.”
Their three major conclusions:
- “There is no evidence that the audible or sub-audible sounds emitted by wind turbines have any direct adverse physiological effects.
- “The ground-borne vibrations from wind turbines are too weak to be detected by, or to affect, humans.
- “The sounds emitted by wind turbines are not unique. There is no reason to believe, based on the levels and frequencies of the sounds and the panel’s experience with sound exposures in occupational settings, that sounds from wind turbines could plausibly have direct adverse health consequences.”
As the infrasound-powered pushback against wind development continued, the Chief Medical Officer of Health of Ontario, whose department was hearing from worried citizens as more companies began planning wind farms on that province’s windy plains, conducted another study.
A spokesman confirmed to the news service that his department received no financial support from AWEA or CanWEA, two major wind industry trade groups.
The report, The Potential Health Impacts of Wind Turbines, is less ambitious than the trade groups’ encyclopedic effort. Still, an unspecified list of public health officials from several Ontario public health departments considered 40 reports, papers, and studies—mostly medical and mostly peer reviewed. Released in May 2010, it concludes:
- “While some people living near wind turbines report symptoms such as dizziness, headaches, and sleep disturbance, the scientific evidence available to date does not demonstrate a direct causal link between wind turbine noise and adverse health effects.
- “The sound level from wind turbines at common residential setbacks is not sufficient to cause hearing impairment or other direct adverse health effects. However, some people might find it annoying. It has been suggested that annoyance may be a reaction to the characteristic “swishing” or fluctuating nature of wind turbine sound rather than to the intensity of sound.
- “Low frequency sound and infrasound from current-generation upwind model turbines are well below the pressure sound levels at which known health effects occur. Further, there is no scientific evidence to date that vibration from low frequency wind turbine noise causes adverse health effects.”
The doctors did urge more community engagement at the beginning of wind-farm planning, and more equity in wind royalty distribution. Both, they said, could affect attitudes toward such developments and allegations about health effects.
Predictable, one Canadian anti-wind group promptly labeled the independent Ontario health report a "sell-out.
But David Jensen, an Ontario health department spokesman, said that the general public received the report “quite well.” He shrugged off the harsh criticism.
“I think it is just that there are some people you will never convince,” he said.
Meanwhile, Dr. Geoffrey Loventhall, a 40-year veteran infrasound researcher, urges those still concerned about low-frequency sound to look at the problem differently.
In a recent study of his own, Dr. Loventhall, who’s published dozens of peer-reviewed papers, urged regulators to establish turbine setbacks that mitigate the problems caused by sounds that people actually can hear.
“It is the ‘swish’ noise on which attention should be focused,” he concluded in a paper published in Canadian Acoustic, a scientific journal, “in order to reduce it and to obtain a proper estimate of its effects.”
The scientist, whose years of infrasound research earned him a place on the wind industry panel and inclusion in the Canadian health department study, added that it would then be “the responsibility of legislators to fix the criterion [sound] levels.”
Dr. Leventhall currently consults for a wind turbine developer and, according to his curriculum vita, now specializes in “active attenuation of noise’’—the audible kind.