many of the regular cotton balls are bleached with chlorine. you dont want to use that stuff because a byproduct from the bleaching is dioxin.
all organic cotton ive seen is bleached with hydrogen peroxide, a naturally occurring disinfectant. our bodies even make H2O2 to prevent infection. neutrophils produce it to defend against toxins, parasites, bacteria, viruses.
i wouldnt be too concerned about it. just stick with organic cotton. stay away from the regular, low price cotton balls.