A new report from Ontario’s chief medical officer of health mining current scientific evidence finds that while living near wind turbine farms “may annoy some people,” it’s a stretch to blame the turbines for health problems.
“According to the scientific evidence, there isn’t any direct causal link between wind turbine noise and adverse health effects,” Dr. Arlene King said last week on the release of her report.
Although the report does offer some public relations advice for developers planning wind power projects in the future, it also adds the weight of the province’s health department against criticisms now levelled against various wind power developments.
Some people living near wind turbines have previously reported symptoms such as “dizziness, headaches and sleep disturbance,” the province said, but King’s report finds no evidence of a direct link to those from the giant spinning blades now dotting a number of rural Canadian horizons.
In Ontario, where over 690 wind turbines now operate, the minimum setback distance for a single turbine is 550 metres, and that increases with the number of turbines at a given site.
For example, a wind project with five turbines, each with a sound power level of 107 decibels (dB), must have its turbines set back at least 950 metres from the nearest receptor. The setback regulations are meant to limit sound at the nearest residence to no more than 40 dB.
According to the World Health Organization, King wrote, this 40-dB guideline is below the level at which effects on sleep and health occur. The province, in its release Thursday, noted 40 dB as “approximately the noise level experienced in a quiet office or library.”
“However,” King wrote in her report, “it is above the level at which complaints may occur.”
King notes a “key data gap” that could be dealt with in a future study: specifically, “sound measurements at residential areas around wind turbines and comparisons with sound levels around other rural and urban areas,” to see what the ambient noise levels are like in residential areas across Ontario, not just near wind farms.
A study of noise around wind farms as well as “other residential environments,” including monitoring for compliance with rules on noise levels, is an “important prerequisite to making an informed decision” on whether to pursue epidemiological studies looking at health outcomes, she wrote.
In drafting the report, King noted published papers in peer-reviewed scientific journals, and reviews by recognized health authorities such as the WHO, carry more weight in the assessment of health risks than “case studies and anecdotal reports.”
One of the main “anecdotal reports” was a group of published case studies of 38 people in 10 families in five countries in 2009 living near wind turbines and citing symptoms including dizziness, headaches and sleep disturbance.
That publication, by U.S. researcher Nina Pierpont, “suggested that the symptoms were related to wind turbine noise, particularly low frequency sounds and infrasound, but did not investigate the relationships between noise and symptoms,” King wrote.
“It should be noted that no conclusions on the health impact of wind turbines can be drawn from Pierpont’s work due to methodological limitations including small sample size, lack of exposure data, lack of controls and selection bias.”
Noting concerns raised about human exposure to “low-frequency sound” and “infrasound” from wind turbines, King again reported “no scientific evidence” of adverse health effects from such sound produced by the turbines.
“Low frequency sound and infrasound are everywhere in the environment,” King wrote. “They are emitted from natural sources (e.g., wind, rivers) and from artificial sources including road traffic, aircraft, and ventilation systems. The most common source of infrasound is vehicles.
“Under many conditions, low frequency sound below 40 Hz from wind turbines cannot be distinguished from environmental background noise from the wind itself.”
King noted one Portuguese research group which has proposed excessive long-term exposure to vibration from high levels of low-frequency sound and infrasound may cause “whole body system pathology” or “vibro-acoustic disease.”
However, King added, “this finding has not been recognized by the international medical and scientific community. This research group also hypothesized that a family living near wind turbines will develop vibro-acoustic disease from exposure to low frequency sound, but has not provided evidence to support this.”
King’s report lists other previous suggestions of possible health risks from turbines, such as:
- electromagnetic fields (EMFs), but notes wind turbines are “not considered a significant source of EMF exposure since emissions levels around wind farms are low.”
- shadow flicker, caused when the blades of a turbine rotate in sunny conditions, casting moving shadows on the ground that appear to flick on and off at high speeds. About three per cent of people with epilepsy are photosensitive, King noted, at flicker frequencies between five and 30 Hz., but “most industrial turbines rotate at a speed below these flicker frequencies.”
- ice throw, caused when ice forms on wind turbines and can be thrown or break loose and fall to the ground. “Sizeable ice fragments” have been reportedly found within 100 metres of a turbine, King wrote, suggesting turbines could be stopped during icy conditions to cut that risk.
- other structural hazards, such as turbine blade failure, in which the reported record for an entire blade to be flung from a turbine is 150 metres (and 500 metres for a chunk of a blade). Risks of turbine blade failure reported in a 2005 Dutch handbook range from one in 2,400 to one in 20,000 turbines per year, King wrote.
“Community engagement at the outset of planning for wind turbines is important and may alleviate health concerns about wind farms,” King wrote.
Also, she added, “concerns about fairness and equity may also influence attitudes towards wind farms and allegations about effects on health. These factors deserve greater attention in future developments.”