We anticipated that formal recycling would give rise to lower concentrations of the biomarkers, since the workers are only exposed for 8 h per day, in plants with process ventilation. Whereas informal workers are often both exposed when performing e-waste recycling and from contaminated soil, water, and locally produced food items (Grant et al., 2013). To further evaluate the concentrations of metals in both formal and informal e-waste recycling workers a multi-center study would be needed. Such a study should use the same sampling and analytical techniques, preferably described in an international recognized standard.