Table 3. Concentration of DDT residue in mg/kg of soil and mg/m² surface area in soil samples from wall and floor surfaces of houses and the environment among seven villages in Gilgel-Gibe area, southwestern Ethiopia.

Village group	Site of sample collection	N	Mean ± SD (mg/kg/soil)	Mean ± SD (mg/m2 surface)
‘Low risk’	Wall surface	22	36.87±90.75	0.21±0.56
‘High risk’	Wall surface	45	316.54±236.71	1.45±1.16
‘Low risk’	Floor surface	22	2.59±4.88	0.02±0.03
‘High risk’	Floor surface	38	60.86±72.17	0.30±0.32
Control	Wall surface	11	n/d	n/d
Control	Floor surface	11	n/d	n/d
‘Low risk’	Environment	21	n/d	n/d
‘High risk’	Environment	44	n/d	n/d
Control	Environment	11	n/d	n/d

n  =  number of soil samples; SD  =  standard deviation; n/d  =  not detected.