. 2013 Sep 2;68(1):29–36. doi: 10.1136/jech-2013-202722

Table 1.

Asturias INfancia y Medio Ambiente (INMA) cohort characteristics and estimated pollution levels

	NO₂						Benzene
	N	Mean	SD	Minimum	Maximum	p Value*	N	Mean	SD	Minimum	Maximum	p Value*
Residential zone
Town centre	356	25.01	5.40	8.30	39.06	<0.001	356	2.43	1.29	0.34	7.91	<0.001
Residential zone	35	18.91	7.10	8.08	30.52		35	2.13	1.36	0.47	5.58
Countryside	39	14.94	6.61	7.56	35.82		39	1.34	1.08	0.04	4.26
Residential building age
<5	94	22.14	6.17	9.09	38.27	0.001	94	2.65	1.53	0.51	6.76	0.109
5–14	67	22.67	7.14	9.56	37.89		67	2.44	1.41	0.04	5.76
15–29	66	24.79	5.75	8.30	39.06		66	2.20	1.24	0.34	7.91
>29	160	24.68	6.03	7.56	37.30		160	2.13	1.11	0.19	5.97
Missings	43						43
Participant's age
<25	21	21.48	7.54	8.30	32.95	0.503	21	1.84	1.21	0.34	5.76	0.055
25–29	117	23.61	6.20	8.68	36.88		117	2.10	1.12	0.45	5.80
30–34	183	23.98	6.45	8.30	38.27		183	2.37	1.36	0.05	6.76
35+	109	23.36	6.68	7.56	39.06		109	2.51	1.42	0.04	7.91
Country of birth
Spain	413	23.57	6.42	7.56	39.06	0.409	413	2.31	1.33	0.04	7.91	0.893
Other	17	24.42	8.37	8.08	36.88	0.409	17	2.18	0.89	0.97	4.83	0.893
Education
Primary	80	23.29	6.24	8.30	34.58	0.793	80	2.26	1.21	0.34	5.76	0.117
Secondary	194	23.49	6.88	7.56	38.27		194	2.19	1.31	0.19	7.91
University	156	23.90	6.16	8.08	39.06		156	2.47	1.36	0.04	6.76
Social class (SC, mother)
SCI+II	92	23.96	6.18	8.05	39.06	0.949	92	2.45	1.28	0.45	5.32	0.026
SCIII	90	23.02	7.26	7.56	34.50		90	2.06	1.38	0.04	7.91
SCIV+V	247	23.67	6.34	8.30	38.27		247	2.33	1.30	0.19	6.76
Missings	1						1
Working status (third term)
Yes	106	24.43	6.18	8.68	37.89	0.132	106	2.43	1.25	0.04	5.97	0.126
No	298	23.33	6.59	7.56	39.06		298	2.27	1.33	0.05	7.91
Missings	26						26
Parity
Primiparous	262	23.83	6.35	8.05	39.06	0.524	262	2.36	1.29	0.34	6.76	0.175
Multiparous	168	23.24	6.73	7.56	37.78	0.524	168	2.22	1.36	0.04	7.91	0.175
Smoking
Never smoking	204	23.09	6.54	7.56	38.27	0.196	204	2.30	1.28	0.04	5.97	0.022
No smoking during pregnancy	129	24.67	5.94	10.24	39.06		129	2.47	1.40	0.05	7.91
Smoking but not after 12th week	2	27.13	0.37	26.87	27.39		2	4.18	0.18	4.05	4.31
Smoking after 12th week	69	23.12	7.23	8.30	37.78		69	1.98	1.15	0.34	5.76
Missings	26						26
Season of last menstruation
Winter	122	22.72	6.04	8.30	36.88	0.014	122	2.27	1.31	0.38	5.80	0.108
Spring	95	24.04	6.89	8.52	39.06		95	2.55	1.39	0.19	6.76
Summer	93	24.99	6.36	8.46	37.78		93	2.11	1.31	0.05	7.91
Autumn	120	23.07	6.61	7.56	38.27		120	2.30	1.25	0.04	5.97

*Kruskal-Wallis or Mann-Whitney test.