Table 3 The concentrations of metals in different studies and WHO standards in (µg/g)

WHO (2002)

350

300

0.5

0.5

5.5

100

[40]

Iran(by Razzagh and et al., 2015)

2.03–6.8

-

0.08–0.12

-

-

-

[15]

Ethiopia (by Gebru and et al., 2015)

0.65–0.93

0.13–0.23

0.03–0.1

0.02–0.03

-

-

[36]

Kenea (Erene 2012)

1.01-2,1

0.07–0.24

0.01–0.05

0.01–0.05

-

-

[5]

Ethiopia (Shibru 2014)

-

0.085–0.133

0.152–0.201

0.07–0.222

-

[33]

Nigerea(EzehErnesti and et al., 2018)

-

-

0.175

0.088

-

6.67

[34]

Ethiopia (Wolde and et al., 2018)

1.92–4.22

ND-0.468

ND

ND-0.69

ND-0.885

1.20–4.33

[37]

Ethiopia (Ashenafi 2018)

0.062–0.33

0.027–0.0697

-

-

0.0693–0.815

-

[14]

Turky(Tuba and et al., 2015)

0.48

0.15

-

-

0.187

-

[25]

Ethiopia 2018 study (present study)

1.97–2.04

1.92-2

ND

0.025–0.031

0.83–1.01

0.25–0.45