Biologist Arturo Massol and radiochemist Elba Díaz conducted an unpublished study in 2001 that showed vegetables and plants growing in the civilian area of Vieques were highly contaminated with heavy metals such as lead, cadmium and copper. Furthermore, they discovered that metal concentrations in edible crops were both substantially above the maximum levels set by the European Union Council and much higher than plants tested in mainland Puerto Rico. Chiles, pasture grasses, and squashes were affected more than plants with deeper root systems such as trees. This is consistent with the theory that heavy metals travel by air to civilian areas via the steady easterly trade winds that blow directly from the bombing zone.