Are windmills that are located within a half-mile of residents harmful to human health? This is one of the questions at the heart of the AES Na Pua Makani wind farm controversy, along with the equally important questions of environmental harm and social justice the project raises.

AES claims that there will be no effects based upon the conclusions of the Kahuku project’s environmental impact study (EIS). However, after reading the EIS as well as a number of the studies used in the EIS, it seems that there is no definitive answer to that question.

The studies generally agree that there are “no harmful effects on human health,” but add the caveat, “if the windmills are sited correctly.” The studies, however, never define exactly what “sited correctly” means. Rules regarding setback distance and other conditions are usually left up to local jurisdictions to determine on a case-by-case basis. Only two states have set standards for setback distances (Wyoming and Wisconsin), and both, as well as most European countries, require greater setbacks than that of the windmills of Na Pua Makani.

In this particular case, the difficulty coming to a conclusion about the effects of windmills on human health is that none of the studies researched the effects of windmills that have been located this close to human habitation. Most studies measure the effects on humans living within a one-half to 2-mile radius, so there is just no solid information that would tell us what the effects are when a windmill is less than a half-mile away. For instance, one of the principal studies used for the project’s EIS was Colby et al. (2009), and the data used for that study was based on people living within 1.5 miles of the turbines.

It would have been expected that the studies would have looked at effects at a greater variety of distances from the windmills, perhaps every half-mile, so that there would be more data on which to base decisions. The very reason for this may be that even those studying the effects did not consider that anyone would propose building such large windmills so close to homes and schools.

Even if you accept the studies’ conclusions that wind farms (“properly sited”) do not cause any direct health problems, many studies report that wind farms may be likely factors of indirect health problems caused by stress arising from any of the wind farm’s effects.

For instance, the noise of the wind mills is often likened to that of light traffic, but studies of light traffic noise show it can cause health-affecting stress in 8-10% of the population. Most of us support alternative energy, but are we really willing to sacrifice the mental and/or physical health of a significant percentage of the residents of Kahuku in its name?

A windmill built too close will generate excessive and/or persistent background noise, flicker from sunlight passing through the spinning blades, electromagnetic radiation, and infrasound (sound below the level human ears detect).

Perhaps, as AES claims, there will be no detrimental health effects from these if Na Pua Makani is built — but what if there are? The science doesn’t tell us definitively. Are the people of Kahuku to be the human guinea pigs for the next study?

A basic concept of international law and trade and environmental agreements is the Precautionary Principle, which states that if the scientific evidence is inconclusive, it is always better to err on the side of human health and the environment. Shouldn’t the people of Kahuku be given that consideration?

Michael Richards, of Kaneohe, is executive director of Science Camps of America, a Hawaii-based nonprofit that provides informal, hands-on science learning opportunities for youth.