Children who live within 600m of a high voltage power line (132 kV, 275 kV, 400 kV) at birth are more likely to develop leukemia. No difference between downwind and upwind distances. Draper et al, 2005. https://europepmc.org/articles/pmc558197
Since breathing in ionized particles was proposed by Fews, 1999, as a possible mechanism for how power lines might affect human health, the sameness of the upwind vs downwind results make this hypothesis less likely, at least in regard to leukemia. https://europepmc.org/abstract/med/10622258