Table 1. Maternal, paternal, and child characteristics by RF-EMF ^a .

	RF-EMF exposure from base stations, age 5				RF-EMF exposure from WiFi/cordless phones, age 5					mobile phone owernership at age 7
	Low	Medium	High	P-trend	both	WiFi no, CP yes	WiFi yes, CP no	neither	P-diff	no	yes	P-diff
Child characteristics
N	1094	919	237		1607	438	158	108		2223	108
Age (years)	7.4	7.4	7.4	0.68	7.4	7.4	7.3	7.5	0.03	7.4	7.6	<0.001
Sex (% girls)	50	47	52	0.94	50	46	46	44	0.24	48.6	49.1	0.928
Maternal characteristics
Age (years)	39.7	39.8	39.6	0.55	40	39.7	38.6	37.5	<0.001	39.8	38.6	0.006
Country of birth (% non Dutch)	17	23	19	0.01	16	25	20	44		19	36.1	<0.001
Educational level (%) high	74	69	77		78	62	65	46		73.5	41.7
medium	19	20	13		17	25	22	27		18.9	27.8
low	7	11	9	0.35	6	13	13	28	<0.001	7.7	30.6	<0.001
Paternal characteristics
Age (years)	42.2	42.6	42.7	0.13	42.3	43.3	41.1	41.9	0.000	42.4	42.2	0.775
Country of birth (% non Dutch)	21	25	24	0.10	18	32	31	51	<0.001	21.8	49.5	<0.001
Parental financial situation
A lot to spare	27	26	30		31	18	22	14		27.5	12
A little to spare	40	39	37		41	38	40	26		40.1	36.1
Just enough	22	23	20		18	30	26	43		21.7	29.6
To use or dip into the savings	5	5	7		6	5	3	6		4.9	8.3
To go into the red or into debt	6	7	6	0.64	5	9	10	12	<0.001	5.8	13.9	<0.001

^aValues are percentages for the categorical variables and arithmetic means for the continuous variables

CP: Cordless phone; P-diff = P-value for group differences based on chi-square or Kruskal-Wallis tests; P-trend = P-value for non-parametric test for trend