Table 2 Showing limits of selected heavy metals in drinking water, waste water, soils and vegetables as recommended by WHO, Kenya, China, USA EPA, World Bank, and India (CPCB).

Organization /Country	The variable whose standards were reviewed	Recommended limits for the studied heavy metals (ppm)
Organization /Country	The variable whose standards were reviewed	Hg	Cd	Pb	Cr (hexavalent)	Tl	Ni
WHO	Drinking water⁵⁷	0.006	0.005	0.01	0.1	NG	0.07
	Waste water (effluents)^16,20	0.001⁹	0.003	0.01	0.05	NG	0.02
	Soils (for agriculture)¹⁵	–0.08¹⁰	0.003	0.1	0.1	NG	0.05
	Plants (Vegetables)⁵⁸	0.1	0.02	0.1–0.3	1.3	NG	10
China (Chinese Ministry of Health; and The National Standards)	Drinking water²⁶	0.0001	0.005	0.01	0.05	0.0001	0.03
	Waste water (effluents)⁵⁹	0.005	0.03	1.0	0.5	NG	1.0
	Soils (for agriculture)^60,61	0.3–1.0	0.3–0.6	80	150–300	NG	40–60
	Plants (vegetables)^62,63,64,65	0.01	0.05–0.2	0.1–0.3	0.5–1.0	NG	1.0
Kenya (NEMA and KEBS)	Drinking Water^66,67	0.02	0.01	0.05	NG	NG	NG
	Waste water (effluents)⁶⁶	0.005	0.01	0.01	0.05	NG	0.3
	Public sewers⁶⁶	0.05	0.5	1.0	0.05	NG	3.0
	Soils (for agriculture)	NG	NG	NG	NG	NG	NG
	Plants (Vegetables)⁶⁸	0.01	0.05	0.3	NG	NG	NG
US EPA	Drinking Water^69,70	0.002	0.005	0.05	0.1 (total Cr)	0.013	0.02
	^aSWQS limit level⁷¹	0.002⁷²	0.009	8.5	0.08	6.3	8.3
	Water reclaimed from effluent for irrigation⁷³	NG	0.01	5.0	0.1	NG	0.2
	Waste water (effluents)⁷⁴	0.00003	0.01	0.006	0.05	NG	0.2
	Soils (for a garden)⁷⁵	1.0	0.48	200	11	NG	72
	Plants (Vegetables)⁷⁶	0.015	0.2	0.3⁷⁷	2.3⁷⁷	NG	NG
World Bank	Waste water (effluents)⁷⁸	0.01	0.1	0.1	0.5 (total Cr)	NG	0.5¹⁰
India CPCB	Inland surface water⁷⁹	0.01	2.0	0.1	0.1	NG	3.0
India CPCB	Public sewers⁷⁹	0.01	1.0	1.0	2.0	NG	3.0

^aSWQS stands for Surface Water Quality Standards; The references for the recommended limits (ppm) are shown in superscript; ppm implies mg/kg or mg/L; NG stands for Not Given.

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