Table 3 Single pollution index grading standards (adapted from Wang et al.43).

From: Are heavy metals in urban garden soils linked to vulnerable populations? A case study from Guelph, Canada

Level

Single pollution index (Pi)

Degree of pollution

I

Pi ≤ 1

Non pollution

II

1 < Pi ≤ 2

Mild pollution

III

2 < Pi ≤ 3

Moderately polluted

IV

Pi > 3

Severe pollution

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