TOKYO: Wind-power generation is expected to be a clean, green energy source, but an environmental issue may have surfaced in Japan, as infrasonic waves caused by windmills are suspected of causing health problems.

Mr Shinjuro Kondo, 76, of Higashi-Izucho in Shizuoka prefecture, reported such symptoms as "stiff shoulders, headaches, insomnia, hand tremors... since February last year, soon after the test operation of windmills started".

The neighbourhood is 350m from a group of 10 windmills.

Over a fifth of the 100 residents report similar physical disorders and say these abate when the windmills stop because of mechanical troubles and other reasons.

Infrasonic waves generated by the windmills' rotors are thus a suspect. The sound waves oscillate once to 20 times a second, a frequency too low to be heard by human ears.

Similar complaints have been made in Aichi, Ehime and Hyogo prefectures. But no research has been published mapping the link between infrasonic noise and human health.

Still, windmill operators are concerned. One said: "When we measure sounds from the windmills, no numerical differences are found from the measurement of sounds in the natural environment."

In 2004, the Environment Ministry set guidelines for local governments on dealing with problems caused by infrasonic noise.

The guidelines were issued mainly because of reports of symptoms at factories and construction sites caused by infrasonic noise at the frequency of 20Hz to 200Hz.

Infrasonic noise from windmills is not covered by the guidelines, as its frequency is lower.

Dr Fumitaka Shiomi, who has studied infrasonic-noise problems for 30 years, said: "There is health damage caused by infrasonic noise. Unless measures are taken immediately, a serious problem will occur."

The Environment Ministry is asking local governments to collect complaints. Wind-power generation also poses a danger to birds, which are often struck by the spinning vanes.

- YOMIURI SHIMBUN/ASIA NEWS NETWORK