Table 3. Summary OR and 95% CI of ELF-EMF exposure and female breast cancer risk.

Group	Study number	OR	95% CI	P **	I 2
All studies*	23	1.07	1.02–1.13	0.03	39%
Exposure modes
blanket exposure	8	1.03	0.95–1.12	0.27	21%
occupational exposure*	7	1.08	1.00–1.15	0.24	25%
residential exposure	5	1.09	0.97–1.22	0.83	0%
multiple exposure	2	1.35	0.97–1.89	0.02	82%
ER status
ER+*	7	1.11	1.03–1.20	0.85	0%
ER–	7	0.96	0.84–1.10	0.54	0%
Menopausal status
Premenopausal*	9	1.11	1.00–1.23	0.24	22%
Postmenopausal	9	1.02	0.95–1.09	0.60	0%

*P<0.05;

**P value of heterogeneity.