However, reading the evidence review I tend to come to somewhat different conclusions. It looks to me, without going to each of the evidence documents cited in the review, to be a classic case of mixing up absence of evidence with evidence of absence. As far as I could see much of the evidence was surrogate - supporting the idea that low intensity noise (below 40dB) is known not to cause hearing damage, therefore, since wind turbines are not very loud that there couldn't be any adverse health effects. It also suggests that the main problem may be annoyance which has been found to be increased if wind turbines are visible to the person being assessed and also to suggest that people who are stressed or anxious about their health are more likely to be annoyed by the noise from wind turbines. People who object to the visual presence of wind turbines have also been found to be more likely to complain of annoyance regarding wind turbine noise.
None of this seems to be addressing the direct question: does wind turbine noise cause adverse health effects? A lack of evidence in this case of adverse health effects seems to be the result of a lack of well designed studies in this area, and not because the studies that have been done have found no adverse health effects. Studies of the noise levels of wind turbines, or factors predicting annoyance experienced as a result of wind turbine noise, are not evidence either for or against the possibility of adverse health outcomes.
Indeed, the possibility that the problems may be caused by the low frequency of the sound - at the borderline of audibility for human hearing (around 20Hz) is discussed in the evidence review. However these are dismissed again on primarily theoretical grounds. Wind turbine design is apparently able to rule out the production of infrasound (though of course as it is inaudible, this cannot be verified by any lay person visiting a wind farm and would have to be confirmed via specialised acoustic and engineering equipment). The evidence review casts serious doubts on the claims of one researcher who has described a cluster of symptoms she calls "Wind Turbine Syndrome". The thrust of the review's criticism is that none of the research has been published in peer-reviewed journals. This criticism is somewhat undermined by the lack of peer-reviewed evidence the review cites to support its conclusions and points more to the overall lack of evidence in this area.
A further problem with this rapid review is it does not appear to have any named authors, so that the expertise of those producing the review cannot be ascertained. It has no methodology, so the reader cannot be certain whether important evidence has been omitted from the review, and it does not make any critical appraisal of the evidence included in the review, to allow the reader to judge the likely validity of the evidence. These are all essential and well accepted principles of evidence-based research and practice. Without these elements the usefulness of the evidence review is questionable.
Given these factors the strength of findings in the review is surprising. Experienced systematic reviewers and health technology analysts are well aware of the need for evidence products to be produced in a timely manner to be of use to policy makers. However, rapid does not need to imply "quick and dirty" and it seems unlikely that this review was that. But given the potential perception of low quality, it is even more important for the methods of the rapid review to be included in the published summary. This review, rather than relying on established and validated review research methodology, seems to rely instead on the authority of the author organisation and of other public institutions whose reports are cited as evidence including the Chatham-Kent Public Health Unit of Canada, the Australian Wind Energy Association, the American and Canadian Wind Energy Associations and Health and Environment departments in Australia, Canada and the UK.
For a contentious issue such as this, it is disappointing that we cannot determine whether the evidence review can be relied on to increase certainty about this issue. This leaves the way open for continued community debate and division.
The evidence review ends with what is in essence a red herring:
"The health effects of many forms of renewable energy generation, such as wind farms, have not been assessed to the same extent as those from traditional sources. However, renewable energy generation is associated with few adverse health effects compared with the well documented health burdens of polluting forms of electricity generation (Markandya & Wilkinson, 2007)."
However, the review did not at any point set out to compare the possible health effects of renewable energy generation such as wind turbines to other more polluting forms of electricity generation. This statement has no place in this evidence review and seems to be designed to reframe the issue and divert attention away from the fact there is a paucity of evidence about the health effects of living near wind farms.
Based on the evidence in the review (and given its methodological limitations) I think a better conclusion would be:
there is insufficient evidence about the health effects of wind turbine noise to either rule in or rule out adverse health effects
- there is evidence that wind turbines produce low intensity sound (less than 40dB). Such low intensity sound is not associated with noise induced or other hearing impairment
- the report claims that wind turbines do not produce infrasound (i.e. low frequency sound at the threshold of audibility for humans). There is unclear evidence about the health effects of exposure to infrasound.
- there is some evidence that noise from wind turbines causes annoyance. The link between annoyance caused by noise from wind turbines and other health effects is unclear from the evidence in this review
- this review did not consider evidence which may have been relevant about the effect of noise exposure generally on health (for example evidence from people living in heavily trafficked areas or near airports)