Table 2. H3K4me3 in nickel smelting and office workers with different lengths of service (nmol/mg prot).

Groups	working years (20 individuals per group)
	0–4.99	5–9.99	10–14.99	15–19.99	20–24.99	25–19.99	30+	Total	rs	P
Smelting	37.71±1.13	44.26±1.22	36.23±1.11	45.15±1.58	49.90±1.09	42.52±2.01	52.98±1.52	47.24±20.85	0.267	0.001*
Office	13.60±1.54	16.28±1.31	20.09±1.60	20.70±1.51	23.34±1.36	25.79±1.28	31.19±1.11	22.65±8.81	0.608	0.000*
t’	10.320	11.372	6.514	5.015	12.995	3.167	4.427	12.859
P	0.000*	0.000*	0.000*	0.000*	0.000*	0.000*	0.000*	0.000*

Note: *P < 0.05 was here considered statistically significant.