Disorders on two cattle farms highly unlikely to be due to wind turbines
Farmers from two cattle farms located near a wind farm in Loire-Atlantique have reported various problems with their animals, including a reduction in milk yield and quality, behavioural problems, and an increase in mortality. ANSES stresses that these particular situations require support measures. However, it has concluded that the disorders encountered are most likely unrelated to the presence of the wind turbines. The Agency recommends establishing a suitable comprehensive diagnostic protocol, in order to be able to act promptly in the event of disorders occurring in other farms close to wind turbines.
For several years now, two cattle farms in the Loire region have been reporting various disorders in their animals: high mortality, lameness, reduction in milk quality and quantity, udder inflammation, etc. The farmers believe that these problems began in 2012, following the construction and commissioning of a wind farm with eight turbines, located around 700 and 1500 metres respectively from each farm. Despite the numerous investigations carried out on both farms (veterinary and electrical audits, infrasound and vibration measurements, etc.), the problems have persisted. This led the Ministries of Ecology and Agriculture to ask ANSES to determine whether these disorders were attributable to the presence of wind turbines.
A scientific approach tailored to the physical agents generated by wind turbines
ANSES notes that despite the investigations carried out on the two farms, there was no rigorous and documented follow-up of the remedial actions and this very detrimental situation continues to weigh on the people and the farms. This calls for suitable support measures.
To carry out the scientific assessment, the expert group set up by ANSES began by identifying the various physical agents generated by wind turbines: audible and non-audible sound waves, electromagnetic fields located both at the level of the wind turbines and around the cables carrying the electricity, stray currents, and vibrations at ground level. They ruled out any visual discomfort caused by the wind turbines, as cattle's vision and perception of movement is much poorer than that of humans.
In the absence of a suitable method for answering the question posed, the experts developed a method for assessing the causality of the disorders, which was tailored to the physical agents involved, based on assessment practices used in toxicovigilance. This approach took several criteria into account: the animals' level of exposure to the physical agent in question, the proportion of this physical agent attributable to the wind turbines (as these were not the only possible source of the physical agents investigated), the timeline of events, the possibility that the disorders had other causes, and lastly the existence of data in the scientific literature indicating a link between the disorders observed and the presence of wind turbines.
For each disorder observed, therefore, the possibility that it was caused by one of the physical agents generated by the wind turbines was assessed. This assessment was conducted independently for each of the two farms.
Disorders highly unlikely to be attributable to wind turbines
The experts concluded that the causality of the wind turbines could be largely ruled out. Regarding comparative data, neither the information collected from around twenty of ANSES's counterparts across Europe – including countries where wind power is more developed – nor the literature review revealed any problems of this type.
Concerning the situation on the two farms for mastitis, the reduction in milk quantity and quality, the reproductive disorders and mortality, the expert appraisal report concluded that "regardless of the physical agent considered, the timeline of the disorders is incompatible with the periods when the wind farm was built and commissioned". For the other disorders, the levels of exposure to most physical agents were low and did not differ from those typically found on a farm. However, the experts did find an unusual level of exposure to stray currents in the buildings of both farms, which they believe is probably due to their electrical installations. In addition, other causes that were not investigated could be behind the disorders encountered, such as diseases, husbandry practices, etc.
The expert appraisal was complicated by the fragmented information and the fact that the events go back a long way in time. The Agency therefore recommends establishing a standardised assessment protocol in order to promptly deal with any similar situation encountered on a farm. This should allow the causes of the disorders to be investigated in a comprehensive non-targeted manner, integrating not only the physical agents but also the health and husbandry aspects. It will also have to ensure that any difficulties encountered by the farms can be traced.
A special case that cannot be generalised
The results obtained on these two farms cannot be extrapolated to other situations. Research and monitoring should be conducted to determine the potential impact of wind turbines on the health and welfare of farm animals. The experts recommend a case-control study comparing farms located near wind turbines with others that are not, or site-specific studies before and after the installation of wind turbines in the vicinity.
Furthermore, as few studies are available on the sensitivity of farm animals to physical agents, research on this topic should be stepped up.
Lastly, a centralised reporting system for adverse effects occurring after the installation of wind turbines could be set up, similar to the one that exists for reporting adverse effects of veterinary drugs.