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# Why pro-wind studies often use a 10 km radius

Last week I was reading of an Australian study, by a Professor Gary Wittert, which had shown sleeping pill usage for those living near wind turbines was no greater than the general population . The study compared those living within 10 km of turbines with those living more than 10 km away. There have been similar studies with property values using a 5 mile or 10 km radius that showed property values are not affected by wind turbines. Had you ever thought why they pick a 10 km radius?

Consider this graphic. It shows 1 km bands with the calculated area for each band shown in blue.

Let’s keep it easy and assume that households are evenly distributed and there is one household for every 10 square kilometers.

So, within 2 km (the two innermost bands) of the turbine, the area is 3.1 + 9.4 km² (=12.5 km²) which would represent 1.2 households.

Now let’s consider the two outermost (9 km and 10 km) bands. The area of these bands is 53.4 + 59.7 km² (=113.1 km²) which represents 11.3 households. So the outermost bands have about TEN TIMES the number of households of those living within 2 km, making sure that the contribution of the inner bands is diluted, swamped, covered up or however else you would describe it.

Or consider if you live within 2 km of a turbine. The outer bands of those living from 2–10 km from the turbine adds up to 301.6 km², which would represent 30.1 households – which is 24 TIMES the number of households within 2 km.

No wonder your voice is being “drowned out”. The bigger the circle, the more “dilution” occurs.

Add this to the list of things where “size matters”, and next time you see a study like this, consider the radius and area that was chosen. The choice of the circle size plays a major role in the result obtained and speaks volumes about the motivation of the author.

by Alec Salt, Professor, Department of Otolaryngology, Washington University School of Medicine
via Wind Concerns Ontario [1]