From first hand experience, I know that noise pollution is another key issue. If certain as of yet unknown conditions are met, then the turbines produce large amounts of noise which can be problematic for self explanatory reasons. Even if these circumstances are not met, they do still emit a sound at an audible level - especially if the turbines are working at higher capacity.
Although I've heard very little about this, there have been events of collapsing wind turbines - this mainly occurs to the larger models due to more weight being placed upon their structure. An article related to this can be found here.
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