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. 2021 Feb 17;413:125445. doi: 10.1016/j.jhazmat.2021.125445

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Fig. 4 — Box and whisker plots of NO₂ levels during weekdays (24-h average) for a given month at Grand Bend (rural), Kitchener (urban) and Toronto West (urban). Median values from these weekdays data were used to calculate percentage difference in NO₂ levels in 2020 relative to 2017–2019 as described in the text. Number below each data box corresponds to the calculated p-value. See text for details.