Table 2.

Spearman correlation coefficient matrix for Mn and Ni concentrations in water and hair, age, sex, length of residence and smoking years (only in Sotkamo) in the black shale and reference areas of Sotkamo and Kaavi

Sotkamo black shale area (n = 45)	Mn in water	Mn in hair	Ni in water	Ni in hair
Mn in water	1
Mn in hair	0.569**	1
Ni in water	− 0.045	− 0.143	1
Ni in hair	0.249	0.432**	0.337*	1
Age	0.042	0.012	0.083	− 0.042
Sex	− 0.044	− 0.243	0.114	0.127
Length of residence	− 0.115	− 0.022	− 0.216	− 0.172
Smoking years (n = 19)	0.199	− 0.045	0.381	− 0.046

Sotkamo reference area (n = 17)	Mn in water	Mn in hair	Ni in water	Ni in hair
Mn in water	1
Mn in hair	0.450	1
Ni in water	− 0.272	− .630**	1
Ni in hair	− .682**	− 0.007	0.204	1
Age	0.046	− 0.193	0.461	− 0.151
Sex	0.252	0.105	0.119	0.132
Length of residence	− .515*	− 0.255	0.085	0.251

Kaavi Black shale area (n = 19)	Mn in water	Mn in hair	Ni in water	Ni in hair
Mn in water	1
Mn in hair	0.452	1
Ni in water	0.157	0.384	1
Ni in hair	0.110	.577**	0.686**	1
Age	0.106	0.186	-0.142	-0.157
Sex	0.250	0.259	0.441	-0.020
Length of residence	0.053	0.091	0.084	-0.096

Kaavi reference area (n = 11)	Mn in water	Mn in hair	Ni in water	Ni in hair
Mn in water	1
Mn in hair	0.856**	1
Ni in water	0.115	0.124	1
Ni in hair	0.366	0.409	0.494	1
Age	− 0.546	− 0.223	0.161	− 0.082
Sex	0.087	− 0.058	− 0.087	0
Length of residence	− 0.129	− 0.085	0.08	− 0.456

**Significant at the 0.01 level (2-tailed). *Significant at the 0.05 level (2-tailed).