Table 5.

Comparison of the concentrations of six heavy metals in rice grain (mg kg⁻¹) in this research with the data from some previous studies.

	Cd (mg kg−1)	Pb (mg kg−1)	Ni (mg kg−1)	Cr (mg kg−1)	Zn (mg kg−1)	Cu (mg kg−1)
Data (n = 86)
Max	1.094	0.483	14.55	1.34	58.67	6.75
Min	0.028	0.048	0.28	0.05	19.22	2.33
Median	0.233	0.175	1.14	0.38	29.64	4.17
Statistics
Mean	0.163	0.148	0.88	0.31	27.67	4.04
SD	0.206	0.094	1.57	0.25	7.89	0.91
CV	88.1%	53.5%	137.8%	66.9%	26.6%	21.8%
References
Guidelines a	0.2	0.2	–b	1.0	–	–
Exceeding	34%	30%	–	6%	–	–
Mean values and range of other areas
Zhejiang Provincec (n = 248)	0.037	0.060	–	–	–	–
	LOD-0.112	0.005–0.220	–	–	–	–
Wenling (n = 219)	0.132	–	0.223	–	17.4	2.46
	0.011–2.50	–	0.014–0.959	–	10.3–31.4	0.580–5.05
Changshu (n = 155)	0.019	0.171	–	0.292	19.1	3.84
	LOD-0.201	LOD-0.957	–	0.024–0.742	9.10–28.3	0.87–7.77

^aChinese national standards for food safety limit of pollutants in food (GB 2762-2017).

^bThe threshold value is not defined.

^cHuang et al.⁴³.

^dLi et al.²¹.

^eHang et al.³⁵.